模具毕业设计外文翻译

Die Life of cold stamping die and mprovementsOverview of stamping dieStamping Die - Stamping in the cold, the material (metal or non-metallic) processing into parts (or half) of a special technical equipment, called cold stamping die (commonly known as Die). Press - is at room temperature, using the die installed in the press to put pressure on the material to produce a separation or plastic deformation, and thus to obtain the necessary parts of a pressure processing method.Stamping die in the form of many, the general categories according to the following main features:1. According to the technical nature of(1) Die along the closed or open contour the material are derived from mold. If blanking die, punch die, cut off the mold, cut mode, cutting mode, split mode, etc..(2) bending mode to blank or blank sheet along a straight line (curved line) to bend, deform, and thus obtain a certain angle and shape of the workpiece in the mold.(3) The drawing die is made of the blank sheet opening hollow, or hollow pieces of further changes to the shape and size of the mold.(4) Die rough or semi-finished workpiece is convex according to plan, direct copy the shape of the die shape, the material itself, generate only local plastic deformation of the mold. Such as the bulging mode, reducing the die, expansion die, forming die rolling, flanging mold, plastic mold.2. According to the degree classification process combination(1) single process model in a press tour, just completed a die stamping process.(2) composite model is only one station, in a press tour, at the same station at the same time to complete more than two or two die stamping process.(3) Progressive Die (also known as the modulus of continuity) in the feeding direction, rough, with two or more of the station, at the press of a visit, work in different places on the completion of two or two successive Road over stamping die process.Chong called cold stamping die Die-wide.Cold stamping die is used in cold stamping die mold industry, and accessories required for high-performance structural ceramic materials, preparation methods, high-performance ceramic materials, molds and accessories from the zirconium oxide and yttrium aluminum powder increases, Pr element composition, Preparation is the solution of zirconia, yttria solution, praseodymium oxide solution, according to a certain percentage of alumina solution when mixed liquor, ammonium bicarbonate infusion, by co-precipitation synthesis of ceramic materials, molds and accessories needed for raw materials, reaction precipitate generated by the treatment, drying, calcining and accessories by high performance ceramic mold material superfine powder, and then after forming, sintering, finishing, they will have high-performance ceramic materials,molds and accessories. Advantages of this invention is the invention made of cold stamping dies and parts and long service life, the process does not appear in the press and its parts and stamping die bond generated the phenomenon of stamping surface is smooth, no glitches, can replace traditional high-speed steel, tungsten steel.Die with the main partsDie stamping tools is the main process equipment, stamping rely on the relative movement under the mold completed. Processing time because the upper and lower mold between the constant division and, if continued operation of the fingers of workers to enter or remain in the mold closed, there will certainly pose a serious threat to their personal safety.(A) of the mold main parts, function and safety requirements1. Working parts is a direct punch to blank forming the working parts, therefore, it is the key to mold parts. Punch not only sophisticated and complex, it should meet the following requirements:(1) be of sufficient strength, can not be broken or destroyed during stamping.(2) should be appropriate to its material and heat treatment requirements, to prevent too high hardness and brittle fracture.2. Positioning parts positioning part is to determine the location of the parts installed blank, there are pins (board), gauge pin (plate), lead is sold, guide plate, knife set from the side, side pressure etc.. Design should be considered when positioning parts easy to operate and should not have had orientation, location to facilitate observation, preferably in the forward position, contouring to correct the pin location and positioning.3. Binder, unloading and discharging parts binder components are blank holder, binder board. Blank holder pressure can drawing blank holder force, thereby preventing billets under the action of the tangential pressure arch formed folds. The role of pressure plate to prevent movement and bounce blank. Top of the device, discharge board's role is to facilitate the pieces and clean up waste. Them by the spring, rubber and equipment, putting on the air-cushion support, can move up and down, knocking out pieces of the design should have enough top output, movement to the limited spaces. Stripper plate area should be minimized or closed position in the operating groove milling out empty-handed. Exposure of the stripper plate should have protection around the plate, to prevent finger inserted into or foreign objects inside, exposed surface edges should be blunt down.4. Guide parts and guide sleeve guide pin is the most widely used part of a guide. Its role is to ensure punch the punching clearance when accurate match. Therefore, the guide posts, guide cover the gap should be less than the blanking clearance. Guide Post located next mold base, to ensure that the stroke bottom dead center, the lead column in the template on the face over the top for at least 5 to 10 mm. Guide columns should be arranged far away from the module and the pressure plate in the area, so the operator's arms do not get to take over the lead column material.5. Supporting and clamping the upper and lower parts which includes templates, die handle,fixed plate punch, plate, stopper, etc..Up and down the template is the basis of the cold die parts, other parts are respectively fixed at the top. Template plane size, especially around the direction to be compatible with the workpiece, too large or too small are not conducive to action.Some molds (blanking, punching type mold) to the pieces of convenience, be set up under the mold plate. At this time the best and the template plate connected between the screw, the two plate thickness should be absolutely equal. Plate spacing out the pieces to be able to prevail, not too much, so as not to break the template.6. Fastening parts which includes screws, nuts, springs, pins, washers, etc., are generally used standard parts. Die more with the amount of standard parts, design choice and flexibility should be tightened to ensure the top out of the need to avoid exposure to the surface fastener operating position, the staff and impede operation to prevent bumps.Die with the development ofSince reform and opening, with the rapid development of the national economy, the market demand with the growing Die. In recent years, Die with the industry has been around 15% growth rate of the rapid development of industrial enterprises with ownership Die components also changed dramatically, in addition to the professional mold factory outside of state-owned, collective, joint ventures, wholly-owned and private has been a rapid development.As with the accelerating pace of international integration, the increasing competition in the market, it has been increasingly recognized product quality, cost, and new product development capacities. The cold die manufacturing is the most basic elements of the chain, one of the cold die manufacturing technology to measure a country's manufacturing sector has become an important symbol of the level, and largely determine the viability of enterprises.Die with enterprises to increase in recent years many technological advances for investment, technological progress will be seen as an important driving force for enterprise development. Some domestic enterprises have popularized the two-dimensional mold CAD, and gradually began to use UG, Pro / Engineer, I-DEAS, Euclid-IS and other international common software, individual manufacturers have also introduced Moldflow, C-Flow, DYNAFORM, Optris and MAGMASOFT etc. CAE software, and successfully applied in stamping die design.A car cover mold as the representative of a large stamping die manufacturing technology has made great progress, Dongfeng Motor Corporation mold factory, mold manufacturers such as FAW mold center has been able to produce some car cover mold. In addition, many research institutions and universities to carry out technology research and development of mold. After years of effort, in the mold CAD / CAE / CAM technology has made remarkable progress; in improving quality and reducing mold die design and manufacturing cycle, and so contributed. Although China Die with the industry over the past decade has made remarkable development, but in many ways compared with the industrialized countries there is still a large gap. Forexample, the precision machining equipment, processing equipment in Die with the relatively low proportion; CAD / CAE / CAM technology penetration is not high; many advanced mold technology not widely so, resulting in a considerable number of large, sophisticated, complex and long Die life with dependence on imports.With the continuous progress of science and technology, modern industrial production of increasingly complex and diverse, product performance and quality is ever increasing, thus the cold stamping technology put forward higher requirements. In order to adapt to the cold stamping technology industry needs, cold stamping technology itself also in innovation and development. cold stamping technology idea is to improve and expand as much as possible the advantages of the cold stamping process, to overcome its shortcomings. in the cold stamping technology development, should note the following aspects:(1) cold stamping technology process parameters should be properly identified and Die with the work of some of the shape and size, to improve the quality of stamping parts and shorten the new product production cycle should be in strengthening the metal forming the basis of theoretical studies, to metal forming theory to practice can produce a direction, and gradually establish a close connection with the actual production of the advanced process of calculation. abroad have begun to use plastic finite element method, automobile parts forming process of the stress and strain analysis and computer simulation to predict the forming part of a process plan on the possibilities and potential problems.(2) to accelerate product replacement, mold design to overcome the shortcomings of a long cycle. Should vigorously carry out computer-aided design and manufacture of molds (CAD / CAM) Research. In my country, paying particular attention to strengthening the multi-position progressive die CAD / CAM Technology.(3) to meet the needs of mass production, and reduce labor intensity. Should strengthen cold stamping of mechanized and automated, so that the average, small pieces of high-speed presses in a multi-position progressive die production, production reached a high degree of automation to further improve stamping productivity.(4) expand the scope of application of cold stamping production. So cold pressing both suitable for mass production, but also for small batch production; both the general accuracy of product production, but also can produce precision parts. Should pay attention to development such as fine blanking (especially thick material fine blanking), forming high-energy, soft mold forming, pressure and processing new superplastic forming process, but also promote the easy mode (soft mode and the low melting point alloy mold), Universal Hybrid model, the use of CNC punch press and other equipment.In addition, the performance improvement of sheet metal stamping, mold new material, die development of new processing methods should be further strengthened.Die with life and CountermeasuresDie with the life of the workpiece by punching out the number of terms. Many factors affect the life Die. There are die structure design, manufacture molds used in the punch and die materials, die quality and surface hardening heat treatment, precision die manufacturing parts and cold stamping materials selection. In addition, there are die installation, adjustment, use and maintenance.1. Die Design on Life(1) Layout design of layout methods and take the boundary value a great impact on the die life, too small to take the boundary value, often causing rapid wear and convex mold, die bite wounds on the. Starting from material savings, take the boundary value smaller the better, but take the edge is less than some value, the cut surface of the mold and the quality of life adversely. There will be left behind in the blanking die Q-gap were to produce spare parts glitch, or even damage the die edge, reduce die life. Therefore, consider increasing the material utilization of the same time, parts must yield, quality and life expectancy to determine the layout methods and take the boundary.(2) die structure prone to stress concentration on the cracking of the die structure, composite structure can be used or mosaic structure, and prestressed structure to enhance the mold life. (3) the impact of clearance when the gap is too small, compressed extrusion of interest, increased friction, increased wear, the wear side of aggravated discharge and push pieces after blanking time, materials and convex, the friction between die will cause wear and tear than the end edge on the side of the grinding much, but also easily lead to convex, concave mold temperature is high, the adsorption of metal debris in the side edge to form a metal tumor, so that male and female die chipping or expansion occurs crack phenomenon. Therefore, the gap is too small to Die Life very bad. Gap is too large will increase the punch and the die face the edge of the concentration of stress, resulting in a sharp increase in stress, so blade edge quickly lose angular yield deformation. Therefore, addition of blanking force, thereby enabling faster edge edge wear, reduce die life. But in order to reduce the male and female die wear, extending mold life, while ensuring quality of stamping pieces under the premise that larger space designed properly it is necessary.(4) Die-oriented structure of the life of a reliable guide for the working parts reduce wear, prevent male and female die bite wound is very effective. In particular, non-small-Q gap Q gap or Die, compound die and multi-position progressive die even more important. To improve the die life, must be based on processes and the demand of precision, the correct choice-oriented form and orientation accuracy, the choice should be higher than the accuracy-oriented convex, concave mold with precision.(5) the impact of cold stamping materials, cold stamping materials selected should meet the design requirements of workpieces and stamping process requirements, or easy to mold damage and reduce mold life. Poor surface quality of cold stamping, punching, cracking when the workpiece is also easy to scratch mold. Bad cold stamping plastic materials, deformation is small,easy to press when the workpiece rupture, but also easy to scratch mold. In addition, the material thickness tolerances shall comply with national standards. Die because of a certain thickness of material suitable for forming, bending, flanging, drawing die of the male and female die structure gap is directly determined by the thickness of the material. Therefore, uneven thickness, will result in waste generation and mold damage.2. Die Die Life ofDie Die Life of a mold material properties, chemical composition, structure, hardness and comprehensive reflection of metallurgical quality. Among them, the material properties and heat treatment affect the quality of the most obvious. Mold material properties on the impact of die life is great. If the same workpiece, using a different mold material of the bending test, the test results: The 9Mn2V material, the life of 5 million; with Crl2MoV nitriding, the life of up to 40 million. Therefore, the choice of materials, the batch size should be based on workpiece, rational use of mold materials. The hardness of the die parts to Die Life a great impact. But not the higher hardness, longer die life. This is because the hardness and strength, toughness and abrasion resistance are closely related. Some die demands of high hardness, long life. Such as the use of T10 steel dies, hardness 54 ~ 58HRC, only washed thousands of times a burr on the workpiece great. If the hardness to 60 ~ 64HRC, the grinding life of up to 2 to 3 million. However, if continue to improve hardness, fracture occurs earlier. Some die hardness should not be too high, as the die manufacturing using Crl2MoV 58 ~ 62HRC hardness, the general life of 2-3 million, invalid form of chipping and cracking, and if the hardness down to 54 ~ 58HRC, life expectancy increased to 5 ~ 60 000, but decreased to 50 ~ 53HRC hardness appears easy to blunt the die edge phenomenon. Thus, mold hardness must be based on material properties and failure modes may be. Should enable the hardness, strength, toughness and wear resistance, resistance to fatigue strength needed to achieve a particular stamping process the best match.3. The surface of the mold heat treatment to strengthen the quality and impact on lifeMold heat treatment the nature and quality of life of the mold a great impact. Practice shows that the die parts of the quenching distortion and cracking, early fracture during use, while the metallurgical and materials quality, forging quality, mold structure and process related, but related more to die of heat treatment. According to statistical analysis of failure causes of mold, heat treatment failure due to improper accounting for more than 50%. Practice shows that the mold material must be accompanied by high heat treatment process properly, can really play a material's potential. Parts surface hardening mold work purpose is to obtain the effect of external hard tough inside, so be hardness, wear resistance, toughness, good resistance to fatigue with. Many ways to die surface hardening, surface treatment technology of new technologies developed rapidly. In addition to Nitrocarburizing and ion nitride, boride, seepage niobium, vanadium permeability, hard chrome plated and spark strengthening, the chemical vapor deposition (CVD) and physical vapor deposition (PVD) has been gradually adopted. By CVD and PVD treatment, the mold surface covered with super-hard material, such as TiC, TiN, etc..High hardness, wear resistance, corrosion resistance, adhesion is very good, can improve the die life several times to several times.4. Manufacturing precision of the die parts of die lifePrecision die manufacturing and life in it in particular, mold surface roughness on the mold a great impact. If using Crl2MoV steel blanking die, if the surface roughness value R = 1.6 m, its life span is about 30,000. Such as polished by the precision, surface roughness value R = 0.4 m, life can be increased to 4-5 million. Therefore, the working parts of the mold surface, the general must go through grinding, grinding, polishing and other finishing and fine processing.5. Other aspects of the impact of die life(1) Press the accuracy is not high, but also easy to make die damage.(2) die in the press or not installed properly and the operator's technical level, on the tool life is also greatly affected.(3) dies in the custody and maintenance of good and bad, and the use of lubricant condition also affects mold life.6. ConclusionIn actual production, sheet metal dies for use, rare case of non-normal wear and tear. But when the die plate was found prone to irregular wear, we always study for the problems summarized. Because of a cold die, from the design, manufacture, assembly, commissioning and installation and use, all spent many hours, while the convex die, die material used, mostly high-quality alloy steel. Therefore, the die cost is relatively high. Therefore, in the production of understanding the factors that affect the die life and take the appropriate measures to guide the production of great practical significance.冷冲模具使用寿命的影响及对策冲压模具概述冲压模具--在冷冲压加工中，将材料（金属或非金属）加工成零件（或半成品）的一种特殊工艺装备，称为冷冲压模具（俗称冷冲模）。

引言概述：在现代高等教育中，毕业设计（或称为毕业论文、学士论文等）是学生完成学业的重要环节。

而对于一些特定的专业，例如翻译专业，有时候还需要完成外文翻译这一项任务。

本文将探讨毕设外文翻译的意义和目的，以及为什么对翻译专业的学生而言这一任务极其重要。

正文内容：1.提高翻译能力和技巧外文翻译是一项对翻译专业学生而言十分重要的任务，通过进行外文翻译，学生们可以通过实践提高自己的翻译能力和技巧。

在这个过程中，他们可以学习如何处理不同类型的外文文本，熟悉不同领域的专业术语，并掌握一些常用的翻译技巧和策略。

2.扩展语言和文化知识毕设外文翻译要求学生们对翻译语言的相关知识和背景有一定的了解。

在进行翻译时，学生们需要遵循目标语言的语法规则，并确保所翻译的内容准确、清晰地传达源语言的意义。

通过这一过程，学生们可以进一步扩展自己的语言和文化知识，提高自己的跨文化沟通能力。

3.提供实践机会毕设外文翻译为学生们提供了一个实践的机会，让他们能够将在课堂上所学到的理论知识应用于实际操作中。

通过实践，学生们可以对所学知识的理解更加深入，同时也可以发现并解决实际翻译过程中的问题和挑战。

这对于学生们将来从事翻译工作时具备更好的实践能力和经验具有重要意义。

4.培养翻译专业素养毕设外文翻译要求学生们具备良好的翻译专业素养。

在进行翻译过程中，学生们需要保持专业的态度和责任心，严谨地对待每一个翻译任务。

他们需要学会如何进行翻译质量的评估和控制，以确保最终翻译稿的准确性和流畅性。

这一系列的要求和实践，可以帮助学生们培养出色的翻译专业素养。

5.提升自我学习和研究能力毕设外文翻译要求学生们进行广泛的文献阅读和研究，以便更好地理解所翻译的内容，并找到适当的翻译方法和策略。

在这个过程中，学生们需要培养自己的自主学习和研究能力，提高对学术和专业领域的敏感性，并能够独立思考和解决问题。

这将对学生们未来的学术研究和进一步的职业发展产生积极的影响。

总结：引言概述:毕业设计外文翻译（Thesis Translation）是指在毕业设计过程中，对相关外文文献进行翻译，并将其应用于研究中，以提供理论支持和参考。

1 工程概论1.1 工程专业1.2 工业和技术1.3 现代制造业工程专业1 工程行业是历史上最古老的行业之一。

如果没有在广阔工程领域中应用的那些技术，我们现在的文明绝不会前进。

第一位把岩石凿削成箭和矛的工具匠是现代机械工程师的鼻祖。

那些发现地球上的金属并找到冶炼和使用金属的方法的工匠们是采矿和冶金工程师的先祖。

那些发明了灌溉系统并建造了远古世纪非凡的建筑物的技师是他们那个时代的土木工程师。

2 工程一般被定义为理论科学的实际应用，例如物理和数学。

许多早期的工程设计分支不是基于科学而是经验信息，这些经验信息取决于观察和经历，而不是理论知识。

这是一个倾斜面实际应用的例子，虽然这个概念没有被确切的理解，但是它可以被量化或者数字化的表达出来。

3 从16、17世纪当代初期，量化就已经成为科学知识大爆炸的首要原因之一。

另外一个重要因素是实验法验证理论的发展。

量化包含了把来源于实验的数据和信息转变成确切的数学术语。

这更加强调了数学是现代工程学的语言。

4 从19世纪开始，它的结果的实际而科学的应用已经逐步上升。

机械工程师现在有精确的能力去计算来源于许多不同机构之间错综复杂的相互作用的机械优势。

他拥有能一起工作的既新型又强硬的材料和巨大的新能源。

工业革命开始于使用水和蒸汽一起工作。

从此使用电、汽油和其他能源作动力的机器变得如此广泛以至于它们承担了世界上很大比例的工作。

5 科学知识迅速膨胀的结果之一就是科学和工程专业的数量的增加。

到19世纪末不仅机械、土木、矿业、冶金工程被建立而且更新的化学和电气工程专业出现了。

这种膨胀现象一直持续到现在。

我们现在拥有了核能、石油、航天航空空间以及电气工程等。

每种工程领域之内都有细分。

6 例如，土木工程自身领域之内有如下细分：涉及永久性结构的建筑工程、涉及水或其他液体流动与控制系统的水利工程、涉及供水、净化、排水系统的研究的环境工程。

机械工程主要的细分是工业工程，它涉及的是错综复杂的机械系统，这些系统是工业上的，而非单独的机器。

机械设计毕业设计外文文献翻译中英文对照：塑料模具CAD集成技术毕业设计外文文献翻译毕业设计题目摇控器面板注塑模设计翻译题目The molding tool CAD gathers the technique专业机械设计制造及其自动化姓名班级机械A0731学号指导教师机械与材料工程学院二O一O年十一月[K.P. Rao and K. Sivaram: J. Mater. Proc. Technol., 1993, vol. 37, pp.295-318.]毕业论文(设计)外文翻译课题名称:塑料模具CAD集成技术内容提要:通过分析计算机辅助注射模设计和制造的各个环节中共享的技术和信息,本文揭示了注射模CAD的集成技术的根本内涵,并提出了它的研究热点和趋势。

引言模具CAD集成技术是一项重要的模具先进制造技术, 是一项用高技术改造模具传统技术的重要关键技术。

从六五计划开始,我国有许多模具企业采用CAD 技术, 特别是近年, CAD技术的应用越来越普遍和深入, 大大缩短了模具设计周期,提高了制模质量和复杂模具的制造能力。

然而, 由于许多企业对模具CAD集成技术认识不足, 投资带有盲目性, 不能很好地发挥作用,造成了很大的浪费。

本文就塑料模具CAD集成技术及其应用发表一些观点, 供大家参考。

1、塑料模具CAD集成技术塑料模具的制造, 包括塑料产品的造型设计、模具的结构设计及分析、模具的数控加工铣削、电加工、线切割等、抛光和配试模以及快速成形制造等。

各个环节所涉及的CAD单元技术有:造型和结构设计CAD、产品外形的快速反求RE、结构分析与优化设计CAE、辅助制造CAM、加工过程虚拟仿真SIMULATION、产品及模具的快速成形RP、辅助工艺过程CAPP和产品数据管理技术PDM等。

塑料模具CAD集成技术,? 就是把塑料模具制造过程所涉及的各项单元技术集成起来, 统一数据库和文件传输格式, 实现信息集成和数据资源共享, 从而大大缩短模具的设计制造周期, 提高制模质量。

毕业设计（论文）外文资料翻译及原文（2012届）题目电话机三维造型与注塑模具设计指导教师院系工学院班级学号姓名二〇一一年十二月六日【译文一】塑料注塑模具并行设计Assist.Prof.Dr. A. Y AYLA /Prof.Dr. Paş a YAYLA摘要塑料制品制造业近年迅速成长。

其中最受欢迎的制作过程是注塑塑料零件。

注塑模具的设计对产品质量和效率的产品加工非常重要。

模具公司想保持竞争优势,就必须缩短模具设计和制造的周期。

模具是工业的一个重要支持行业，在产品开发过程中作为一个重要产品设计师和制造商之间的联系。

产品开发经历了从传统的串行开发设计制造到有组织的并行设计和制造过程中,被认为是在非常早期的阶段的设计。

并行工程的概念(CE)不再是新的,但它仍然是适用于当今的相关环境。

团队合作精神、管理参与、总体设计过程和整合IT工具仍然是并行工程的本质。

CE过程的应用设计的注射过程包括同时考虑塑件设计、模具设计和注塑成型机的选择、生产调度和成本中尽快设计阶段。

介绍了注射模具的基本结构设计。

在该系统的基础上,模具设计公司分析注塑模具设计过程。

该注射模设计系统包括模具设计过程及模具知识管理。

最后的原则概述了塑料注射模并行工程过程并对其原理应用到设计。

关键词:塑料注射模设计、并行工程、计算机辅助工程、成型条件、塑料注塑、流动模拟1、简介注塑模具总是昂贵的,不幸的是没有模具就不可能生产模具制品。

每一个模具制造商都有他/她自己的方法来设计模具,有许多不同的设计与建造模具。

当然最关键的参数之一,要考虑到模具设计阶段是大量的计算、注射的方法,浇注的的方法、研究注射成型机容量和特点。

模具的成本、模具的质量和制件质量是分不开的在针对今天的计算机辅助充型模拟软件包能准确地预测任何部分充填模式环境中。

这允许快速模拟实习,帮助找到模具的最佳位置。

工程师可以在电脑上执行成型试验前完成零件设计。

工程师可以预测过程系统设计和加工窗口,并能获得信息累积所带来的影响,如部分过程变量影响性能、成本、外观等。

附录1 英文原文The molding tool CAD gathers the techniqueContents brief summary: Pass to analyze the calculator the assistance inject the mold design with make in the each link commonly shared of technique with information, this text announces to public to inject the mold CAD gathers technical and basic content, and the research heat that put forward it orders with trend.0, prefaceThe molding tool CAD gathers the technique is an important molding tool forerunner manufacturing technique, is the item reforms with the high technique traditional technical and important key in molding tool technique. From 6 5 plan beginning,Our country contain many molding tools business enterprise adoption CAD technique, especially recent years, the technical application in CAD is more and more widespread with thorough, shortened consumedly molding tool design period, Increases to make the mold quantity with the manufacturing ability that complicated molding tool.However, gather to the molding tool CAD because of many business enterprises technique cognition shortage, investment take the blindness, can't produce result nicely,Result in very big and wasted.This text gathers for the plastics molding tool CAD technique and its applications announce some standpoint, provide everybody consults.1, the plastics molding tool CAD gathers techniqueThe manufacturing of the plastics molding tool comtains the construction design of the shape design, molding tool and the number of the analysis, molding tools that include the plastics products control to process( I I , electricity process, the line incises etc.), throw the light with go together with to try the mold and take shape manufacturing etc. quickly.The each link a CAD for involving unit technique has: The shape design( CAD) with the construction, fast anti of the product shapebeg( RE), construction analysis with excellent turn the design( CAE), lend support to the manufacturing( CAM) and process the process conjecture imitate true( SIMULATION), product and molding tools take shape( RP) quickly, assistance craft process( CAPP) with product data management technique( PDM) etc..The plastics molding tool CAD gathers technique,Is to gather plastics molding tool manufacturing process a various units for involving technique get up, unify the database to deliver the format with the document, realize the information gather share with the data resources, from but shorten the design manufacturing period of the molding tool consumedly,Increases to make the mold quantity.2, the CAD design of the plastics product begs with fast anti of the shapeThe plastics molding tool that proceed the square one designs the manufacturing is the design of the EU a product.The traditional product design method is a design to product of three is conceive outline to use two I plane chart papers expresses to come out, marking clearly the craft and starting construction the method on the diagram paper,This kind of met hod comes to a decision the simple of a design sketch and can''ts control to make the quantity directly.The modern design method is a design establish the product directly on the computer of three the model of I ,According to the product three I models proceed the molding tool construction the design and excellent turn the design,Design according to the molding tool construction again three I models proceed to process to weave the distance and establishment crafts plan.This kind of method makes product model design, molding tool construction design, process to weave distance and technological designs regard a data as the foundation, realizing the data share, Can not only increases to design the efficiency quickly, but also can guarantee the quantity, decline low cost.The source of the computer EU a product model has three kinds of:Making use of the CAD system software proceeds the product model the designand make use of the real object measures fast anti in proceeding beg to set up the mold and make use of the standard format document of the other the system of CAD.Source method that aim at these three kinds of products model,Have studied every kind of technique now to the design efficiency that increases product model with quantity.The underneath further analyzes every kind of technical content with the characteristics.Making use of the CAD system software proceeds the product model design,Its technique includes primarily two is are several why the sketch draws, two the parameter of is turn the design of the sketch, three i entity shape design, three icharacteristic shape design, three the parameter of is turn the entity shape the design, three i curved face shape design, free shape in space design, the external appearance of the product exaggerates, product of dynamic advertise to design the etc..These softwareses contain many typical representatives.Two the software of is have: ME10, CADKEY, AUTOCAD, DHCAD, Genis, etc. of Sigraph; three the software of is have:UGII, PRO/ E, IDEAS, CATIA, etc. of EUCLID; free shape in product and advertise the software of the design have:Alias, etc. of CDRS.Two is are several why the sketch draws is to make use of the flat surface CAD software draw the spare parts sketch, then replace the handicraft painting with the calculator; but two the parameter of is turn,Then the calculator realizes the sketch changes the deal designs, making modification more convenient; threeishape designs is a true shape that the product that the arithmetic figure turn design, it expressed completely product,Can be further to designs for the molding tool, analysis with processes the mathematics model of the necessity of offering; the free shape in space design is the art of the product shape to design, making product been not only is a function product, but also art article.It is every kind of need that the external appearance of the product exaggerate that product of the result designs, making product more beautiful, the color can attractpeople more; the dynamic advertisement design of the product is a result that design to make to promote the advertisement directly the product,Proceed the market expansion.Making use of the real object measures fast anti of proceeding beg to set up mold is current investigative a little bit hot of a,It is an important technique that product imitate the type foundation go forward a line of the product modification designs.Its basic principle is to passes three coordinateses measure the machine, laser measure machine or electronicses copy the few ÒÇ to proceed to scan the diagraph to the real object,The data of large quantity that arithmetic figure turn that gets to measures the acquisition orders anti that send into the high class CAD software beg mold piece or appropriative anti beg the software inside, anti beg the software can read directly a data cluster,Combining can proceed the editor, filter, tidy up, beg the ¾« to a data cluster, row preface, part modification and reorganization, then automatic born curved face, It is end to acquire together the real object precision is consistent of or computer EU a product model that pass through reforms.This way can increases biggest new product design velocity.Current mature curved face anti beg to set up the mold software has: Surfacer,Cimatronrenge, etc. of Strim100.Make use of the standard format document of the other the system of CAD to set up the mold, this way than convenience.Because the world of the market turns with the technical development in the network of INTERNET,The CAD technique exchanges of the molding tool business enterprise with cooperate to have many pass the CAD document method proceed.Because the CAD system category is more, therefore documentary format must follow the international standard,Such as the DXF, IGES, STEP, VDA, etc. of STL.Pass to read standard format document to establish directly or establish the product model after modifying, since canquickly, deepen the customer and the exchanges of the molding tool factory house, Also can shorten the product the design the period.3, the CAD design of the molding tool and analysisThe CAD design of the molding tool, analysis,Include to divide the type, certain type C» according to the product model molding tool of proceeding the design with the type D¾ , molding tool structural and detailed design, the plastics ³a fills process analysis etc. a few aspects.Make use of the advanced characteristic shape software,such as PRO/ E, etc. of UGII, the very easily certain dividing the type,Born top and bottom mold C» with mold D¾, then the proceeding flows a way, sprinkle a people and cool off the pipe line of arrange etc..Made sure these designses data hereafter, then make use of the molding tool analysis software,Proceed such as the MOLDFLOW, CFLOW the plastics take shape the process analysis.According to the software of MOLDFOLW with it of the material, craft database of plentifulness, pass the importation take shape the craft parameter,Can the development imitate the true analysis plastics to inject in note EU mold C» the process flows the circumstance( the plastics with sprinkle a people more inject remits to flow the analysis of ÎAE ), analyze the temperature pressure variety circumstance and analyze to note EU a ²D remaining should dint etc.,According to analyze the circumstance to the rationality that check the molding tool construction, flow quantity problem etc. of the rationality, product of the appearance.For example whether the esse sprinkles to note the system not reasonable, appear to flow way with sprinkle a position size not appropriate,Can''t equilibrium alive with type C» ; whether to exsit product construction absurdity or molding tool constructions or not is not reasonable, appearing the product A dissatisfied( namely short shoot the phenomenon); whether to cool off asymmetry or not, the influence produces the efficiency with product quantity;Whether the esse notes the craft of EU wrong, appear the song of CI of the product transform etc..The molding tool passes the CAD the design with analyze, can dissolvemistake at design the stage, increase to try once the mold the success the rate.At plastics molding tool design with analyze to apply many new computer.aideds technique this stage, if the parameter turns technique, characteristic shape technique, database technique etc..There is many standards piece in the plastics molding tool, Turn such as the standard mold a parameter for outing organization, sprinkling noting system, cooling system...etc. can adopting basing on database managing the characteristic shape design method proceed the design or establish the standard a a, like this since can realize the data share,Can satisfy the customer again to the at any time modifying of the design, make the design analysis of the molding tool fast, accurate, efficiently.The parameter turns the characteristic shape can not only describe the product completely then several why sketch information,And can acquire accuracy, material and assemble etc. informations of the product, its a product for establishing model is a kind of apting to handle and can reflect design intention with process the model of the characteristic.Therefore,The parameter turns the characteristic shape technique is an one of the most important technique in process in manufacturing in molding tools.4, the technical application in CAM of the molding tool, process to imitate true and ml;I processing, line incising to process, electricity spark processing to wait.The technique of CAM rises in the type C» , type D¾ of the complicated molding tool and the I I of the electrodes process particularly more important function.Its main technique characteristics includes:(1) the O , ¾« processes the knife have the track excellent to turn the programming with the instruction of NC creation,(2) the knife has the category, characteristic to establish with the material ,(3) slicing the Ï÷ process the craft parameter to really settle,(4)The commonness slices the Ï÷ to slice with the high speed the characteristic that I process controls,(5) over slice the check with process the superficial accuracy control,(6)processing the computer entity of the process imitate the realistic I ,(7) The computer control number controls the technique of DNC and clusters of the machine bed control the technical and applied etc..Need the CAD specially in technical application in CAM three I product model data.More profession computer plait distance software,such as MASTERCAM, UNIMOD, etc. of CIMATRON, when the plait distance of many curved faces processes have the higher request to the curved face model of the product,Intend with the high accuracy of the curved face to match such as the directional consistency, curved face in U, V of the close together curved face, inclined rate in curved face continuous variety etc..In high class CAD/ the integral whole of CAM turn system,( such as UGII, PRO/ E)Because making use of the parameter turns the characteristic shape design with same database technique, making the type C of the product model data, molding tool have the track data to have got the inside contact with the type D¾ model data, knife, The modification knife of the product model has the track to also modify automatically.The molding tool processes the entity imitates the true technique more and more mature, also is more and more valued by people.It is mimicry machine bed that processing the entity imitate process the process on the computer, can keep the result that view reflect process,Can takes the gauge of directly quantity that after processing spare parts, can check the mistake that process.At check quantity that after processing spare parts, can at the computer is last to process behind of the entity model proceeds the aleatoric EE slices, Measure its size directly with the accuracy.Therefore, it can dissolve mistake at process the stage of craft plait distance design, reduce to repair after processing with return the work, increases consumedly the manufacturing efficiency of the molding tool with quantity.5, plastics product and its molding tools take shape the manufacturing quicklyPlastics product and its molding tools use the computer CAD techniquewdesignafter completing, can pass the fleetness take shape the technique make.This is the manufacturing technique of a kind of all new concept,It abandoned the traditional machine processes the method.Its take shape principle is three I CAD entity models are long.lost set up a series of a layer data of the thickness, make use of the laser take shape machine or others take shape the equipments read these datas,Increase the method technique with the material, pile up the each layer to take shape one by one in order.This technique calls the fleetness to take shape the technique automatically.( Rapid Prototype)It is also a CAD to gather the technical importance constitutes the part.The first pedestal takes shape the equipments quickly to bear in the United States a company in 1987, because of its characteristics is to has nothing to do with the complicated degree of the product of the manufacturing, bringing the manufacturing industry the enormous vibration.Henceforth decade,Take shape quickly the technique be flown to develop soon, the category of the equipments also piles up one after another,Turn from the material I the method can is divided into the laser with not the laser burns the knot method( SLS), solid surface layer shape method( SGC), layer a manufacturing method( LOM) and melt to sink to accumulate the method( FDM), district constituency glues the knot method( DSPC), laser spirit to sink to accumulate method( SALD) etc. mutually.Every kind of method characteristics is:The method of SLA is applied at the earliest stage of took shape the technique quickly, the early market occupied the bigger cent sum, but is narrow because of the material scope, the cost is higher, taking shape the piece was heat.proof and bore the burthen with applied color the ability low,The recent years was gradually replaced by the other method.The method of FDM because of taking shape the speed quick, the cost is low, get the good application in plastics product profession, because the size of the spare parts is small, accuracy bad, Also suffer certainly of restrict.The method of LOM because of adoption paper or isoutline edge that thin slice plastics, the cost is low, and the laser projects light upon each layer only, as a result take shape the speed quick,But the product surface quantity is bad.The method of SLS proceeds to burn the knot with the laser, adoptive material than wide, if the plastics,A¯ anticipates, porcelain and ceramics, metals etc. all can take shape, taking shape the piece is heat.proof and bear the burthen with apply color the ability stronger,Have the extensive and applied foreground.The other method also gets the application in some special kinds process.According to above take shape the method characteristics, take shape the technical function quickly to consist in primarily:The manufacturing useds for the design with the on trial product model, make to used for the small the molding tool that batch quantity produce to process with the special spare parts in small batch quantity.Take shape the product model of the technique manufacturing quickly in the aspects of material the ratio tradition processes the product model of the method manufacturing has the difference,But in shape and sizes almost complete similar, and there is certain machine strength, can make the function experiment, handles through surface at the same time, looking similar to true product,Can advertise the propaganda material.Take shape the molding tool of the technique manufacturing quickly,Is a soft material to take shape the mold( the mold of A¯ , wreath oxygen resin mold, ¹è rubber mold, low EU orders the metal alloy casts mold etc.) primarily to synthesize the hard type in material C mold with porcelain and ceramics or metals »ùs now.Hard mold in manufacturing the hour can take shape with the fleetness the spare parts makes the female die,Create first the soft mold between wreath oxygen resin mold or other material, sprinkle to note porcelain and ceramics or gypsum molds in soft mold, then sprinkle the steel of Öý steel mold; or sprinkle the admixture that note in soft mold chemistry contain steel powder glue knot,Proceed to burn to become the steel mold.Take shape the steel mold of the technique manufacturing quickly to process after needing further did to throw light etc., make into the small batch quantity produce of note the mold of EU .Because the molding tool sprinkles to note or burn the knot with the steel powder but, Material and common molding tool steel contain certain margin, therefore, the life span is shorter, cans make to manufacture on a trial basis product or small batch quantities produce.Moreover, taking shape the technique quickly can also manufacture the special spare parts,If make with the metallurgy powder legal system the metals electrode, nicety cast the legal system makes the copper electrode, ND mold legal system makes graphite electrode etc..Take shape the technique creation molding tool quickly to model the equipments with the product, all is STL to read CAD system creation or CLI etc. document format datas,Different document format data to the product accuracy of the creation contain bigger margin, therefore, study the system of CAD to take shape quickly the document format of the equipments output to have the very important meaning.6, the molding tool CAD gathers technical development trendA calculator for saying, molding tool CAD gathering technique is applying in molding tool making each link assistance technique on the ×U with each link information that realizes the technique gathers.Obviously,The information gathers unify with data the management is a key.The information of the product is to pierces through in the design, analyze, process, examine, assemble a stage,Fluency, solution data format that realizes each link information standardizes and the data maintenance is a point with future CAD that share to gather technique development.The system of PDM emergence is to resolve this problem brought the first light of day.It is molding tool business enterprise application CAD that the system of PDM puts into practice gather technical and important lesson.Design in molding toolmanufacturing aspect,The intelligence that imply the research, high speed that abundant expert''s knowledge turn molding tool CAD/ the system of CAM slices theI÷ processes and its plait distance etc. is a trend that future study the development.2 中文翻译塑料模具CAD集成技术内容提要：通过分析计算机辅助注射模设计和制造的各个环节中共享的技术和信息，本文揭示了注射模CAD的集成技术的根本内涵，并提出了它的研究热点和趋势。

华南理工大学广州学院本科生毕业设计(论文）翻译英文原文名Review of Vibration Analysis Methods for Gearbox Diagnostics and Prognostics中文译名对变速箱振动分析的诊断和预测方法综述学院汽车工程学院专业班级车辆工程七班学生姓名刘嘉先学生学号201130085184指导教师李利平填写日期2015年3月15日英文原文版出处：Proceedings of the 54th Meeting of the Society for Machinery Failure Prevention Technology, Virginia Beach，V A, May 1-4，2000，p. 623-634译文成绩：指导教师(导师组长）签名：译文：简介特征提取技术在文献中有描述;然而，大多数人似乎掩盖所需的特定的预处理功能。

一些文件没有提供足够的细节重现他们的结果，并没有一个全面的比较传统的功能过渡齿轮箱数据。

常用术语,如“残差信号”,是指在不同的文件不同的技术.试图定义了状态维修社区中的常用术语和建立所需的特定的预处理加工特性。

本文的重点是对所使用的齿轮故障检测功能。

功能分为五个不同的组基于预处理的需要。

论文的第一部分将提供预处理流程的概述和其中每个特性计算的处理方案。

在下一节中，为特征提取技术描述，将更详细地讨论每一个功能。

最后一节将简要概述的宾夕法尼亚州立大学陆军研究实验室的CBM工具箱用于齿轮故障诊断。

特征提取概述许多类型的缺陷或损伤会增加机械振动水平。

这些振动水平，然后由加速度转换为电信号进行数据测量。

原则上,关于受监视的计算机的健康的信息被包含在这个振动签名。

因此，新的或当前振动签名可以与以前的签名进行比较,以确定该元件是否正常行为或显示故障的迹象。

在实践中，这种比较是不能奏效的。

由于大的变型中,签名的直接比较是困难的。

相反,一个涉及从所述振动署名数据特征提取更多有用的技术也可以使用。

附录A冲压中多工件的最佳排样摘要：在冲压生产中，生产成本受材料利用率影响最大，材料支出占整个生产成本的75%。

本文将介绍一种新的计算方法用于实现双工件在冲压排样设计中的最佳规划方法，以便提高材料利用率。

这种计算方法可以预示在带料中结构废料的位置及形状，以及工艺废料的位置和最佳宽度。

例如将两个相同的工件中的其中一个旋转180°,或是将两个不同的工件嵌套在一起。

这种计算方法适合与冲模设计CAE系统结合使用。

关键字：冲压，模具设计，最佳化，材料利用率，明可夫斯基和，设计工具绪论在冲压生产中，能够快速生产不同复杂程度的薄片金属零件，特别是在大产量的情况下，能够高强度生产。

生产过程效率高，其中材料成本占据整个冲压生产成本的75% [1]。

但材料不能被完全利用到零件上，因为零件不规则的外形必须被包含在带料内。

冲压生产的排样设计直接决定废料的大小。

很明显，使用最理想的排样设计对于提高公司的竞争力是至关重要的。

前期工作曾经, 带料排样设计问题需要通过手工来解决。

例如, 通过纸板模拟冲裁来获取一个好的排样方法。

通过计算机介绍的设计过程所得出的步骤。

也许首先要做出适合工件的矩形，然后将矩形顺序排放在带料上[2]。

这种方法适合不相互重叠的矩形[3]、拉深多边形[4, 5]、已知相互关联的外形[6]。

这种原理的方法具有一定局限性，尽管如此，在这种具有局限性下的设计中所产生较多的工艺废料不能被避免，这些额外损失的材料导致了设计方案无法达到最佳化。

增量旋转法是一种流行的排样设计方法[6-10, 16]。

具体实现方法为，将零件旋转一定的角度，例如2°，[7]，在设计中决定零件倾斜程度和带料宽度以及合适的材料利用率。

在不断重复这些步骤以后工件旋转量达到180º (由于对称)，然后从中选出最佳排样方法。

这种方法的缺点是，在一般情况下，最佳材料定位将降低旋转增量同时不能被找到。

尽管差别很小，但在大批量生产中每个零件所浪费的材料会累计进而导致较多材料损失。

毕业设计外文资料翻译学院：信息科学与工程学院专业：软件工程姓名： XXXXX学号： XXXXXXXXX外文出处： Think In Java (用外文写)附件： 1.外文资料翻译译文；2.外文原文。

附件1：外文资料翻译译文网络编程历史上的网络编程都倾向于困难、复杂，而且极易出错。

程序员必须掌握与网络有关的大量细节，有时甚至要对硬件有深刻的认识。

一般地，我们需要理解连网协议中不同的“层”（Layer）。

而且对于每个连网库，一般都包含了数量众多的函数，分别涉及信息块的连接、打包和拆包；这些块的来回运输；以及握手等等。

这是一项令人痛苦的工作。

但是，连网本身的概念并不是很难。

我们想获得位于其他地方某台机器上的信息，并把它们移到这儿；或者相反。

这与读写文件非常相似，只是文件存在于远程机器上，而且远程机器有权决定如何处理我们请求或者发送的数据。

Java最出色的一个地方就是它的“无痛苦连网”概念。

有关连网的基层细节已被尽可能地提取出去，并隐藏在JVM以及Java的本机安装系统里进行控制。

我们使用的编程模型是一个文件的模型；事实上，网络连接（一个“套接字”）已被封装到系统对象里，所以可象对其他数据流那样采用同样的方法调用。

除此以外，在我们处理另一个连网问题——同时控制多个网络连接——的时候，Java内建的多线程机制也是十分方便的。

本章将用一系列易懂的例子解释Java的连网支持。

15.1 机器的标识当然，为了分辨来自别处的一台机器，以及为了保证自己连接的是希望的那台机器，必须有一种机制能独一无二地标识出网络内的每台机器。

早期网络只解决了如何在本地网络环境中为机器提供唯一的名字。

但Java面向的是整个因特网，这要求用一种机制对来自世界各地的机器进行标识。

为达到这个目的，我们采用了IP（互联网地址）的概念。

IP以两种形式存在着：(1) 大家最熟悉的DNS（域名服务）形式。

我自己的域名是。

所以假定我在自己的域内有一台名为Opus的计算机，它的域名就可以是。

毕业设计(论文)外文资料翻译学院：机械工程专业：机械设计制造及其自动化姓名：学号：3082108330外文出处：Lecture Notes in Computer science (用外文写)附件： 1.外文资料翻译译文；2.外文原文。

注：请将该封面与附件装订成册。

附件1：外文资料翻译译文高速加工和现代模具制造一、概述1 目前模具制造的发展现状和趋势模具作为重要的工艺装备，在消费品、电器电子、汽车、飞机制造等工业部门中，占有举足轻重的地位。

工业产品零件粗加工的75%，精加工的50%及塑料零件的90%将由模具完成。

目前中国模具市场需求已达500亿元之规模。

汽车模具、特别是覆盖件模具年增长速度将超过20%；建材模具也迅速发展，各种异型材模具、墙面和地面模具成为模具的新增长点，今后几年塑料门窗和塑料排水管增长将超过30%；家电模具年增长速度将超过10%；IT业年均增长速度超过20%，对模具的需求占模具市场的20%。

2004年中国机床工具工业产值将继续增长。

我国模具制造市场潜力巨大。

根据资料统计，近年来，我国模具的年总产值达到30亿美元，进口超过10亿美元，出口超过1亿美元。

增长从1995年的25%增加到2005年的50%。

国外专家预言：亚洲在全球模具制造中占据的份额，将从1995年的25%增加至2005年的50%。

中国模具工业发展迅速，形成了华东和华南两人基地，并且逐渐扩大到其他省份。

（山东，安徽，四川) 1996年~2002年，模具制造业产值年平均增长14%, 2003年增长25%。

2003年我国模具产值为450亿人民币总产量位居世界第3，出口模具3.368亿美元，比上年增长33.5%。

但是，我国技术含量低的模具已供过于求，精密、复杂的高档模具很大部分依靠进口。

每年进口模具超过10亿美元。

出口超过1亿美元，精密模具精度要求在2~3u m，大型模具需要满足8000kN合模力注塑机的要求；小型模具需满足直径1mm 塑料管的要求。

南京理工大学紫金学院毕业设计（论文）外文资料翻译系：机械系专业：车辆工程专业姓名:宋磊春学号:070102234外文出处：EDU_E_CAT_VBA_FF_V5R9(用外文写)附件：1。

外文资料翻译译文；2.外文原文.附件1：外文资料翻译译文CATIA V5 的自动化CATIA V5的自动化和脚本：在NT 和Unix上：脚本允许你用宏指令以非常简单的方式计划CATIA。

CATIA 使用在MS –VBScript中(V5.x中在NT和UNIX3。

0 )的共用部分来使得在两个平台上运行相同的宏。

在NT 平台上：自动化允许CATIA像Word/Excel或者Visual Basic程序那样与其他外用分享目标。

ATIA 能使用Word/Excel对象就像Word/Excel能使用CATIA 对象。

在Unix 平台上:CATIA将来的版本将允许从Java分享它的对象。

这将提供在Unix 和NT 之间的一个完美兼容。

CATIA V5 自动化：介绍（仅限NT）自动化允许在几个进程之间的联系:CATIA V5 在NT 上：接口COM：Visual Basic 脚本(对宏来说)，Visual Basic 为应用（适合前:Word/Excel )，Visual Basic。

COM（零部件目标模型)是“微软“标准于几个应用程序之间的共享对象。

Automation 是一种“微软“技术,它使用一种解释环境中的COM对象。

ActiveX 组成部分是“微软“标准于几个应用程序之间的共享对象,即使在解释环境里。

OLE（对象的链接与嵌入）意思是资料可以在一个其他应用OLE的资料里连结并且可以被编辑的方法(在适当的位置编辑）.在VBScript,VBA和Visual Basic之间的差别：Visual Basic(VB）是全部的版本。

它能产生独立的计划,它也能建立ActiveX 和服务器。

它可以被编辑。

VB中提供了一个补充文件名为“在线丛书“(VB的5。

毕业设计（论文）英文翻译课题名称系部材料工程系专业材料成型及控制工程班级学号姓名指导教师2 0 10年3 月 10日4 Sheet metal forming and blanking4.1 Principles of die manufacture4.1.1 Classification of diesIn metalforming,the geometry of the workpiece is established entirely or partially by the geometry of the die.In contrast to machining processes,ignificantly greater forces are necessary in forming.Due to the complexity of the parts,forming is often not carried out in a single operation.Depending on the geometry of the part,production is carried out in several operational steps via one or several production processes such as forming or blanking.One operation can also include several processes simultaneously(cf.Sect.2.1.4).During the design phase,the necessary manufacturing methods as well as the sequence and number of production steps are established in a processing plan(Fig.4.1.1).In this plan,the availability of machines,the planned production volumes of the part and other boundary conditions are taken into account.The aim is to minimize the number of dies to be used while keeping up a high level of operational reliability.The parts are greatly simplified right from their design stage by close collaboration between the Part Design and Production Departments in order to enable several forming and related blanking processes to be carried out in one forming station.Obviously,the more operations which are integrated into a single die,the more complex the structure of the die becomes.The consequences are higher costs,a decrease in output and a lower reliability.Fig.4.1.1 Production steps for the manufacture of an oil sumpTypes of diesThe type of die and the closely related transportation of the part between dies is determined in accordance with the forming procedure,the size of the part in question and the production volume of parts to be produced.The production of large sheet metal parts is carried out almost exclusively using single sets of dies.Typical parts can be found in automotive manufacture,the domestic appliance industry and radiator production.Suitable transfer systems,for example vacuum suction systems,allow the installation of double-action dies in a sufficiently large mounting area.In this way,for example,the right and left doors of a car can be formed jointly in one working stroke(cf.Fig.4.4.34).Large size single dies are installed in large presses.The transportation of the parts from one forming station to another is carried out mechanically.In a press line with single presses installed one behind the other,feeders or robots can be used(cf.Fig.4.4.20 to 4.4.22),whilst in large-panel transfer presses,systems equipped with gripper rails(cf.Fig.4.4.29)or crossbar suction systems(cf.Fig.4.4.34)are used to transfer the parts.Transfer dies are used for the production of high volumes of smaller and medium size parts(Fig.4.1.2).They consist of several single dies,which are mounted on a common base plate.The sheet metal is fed through mostly in blank form and also transported individually from die to die.If this part transportation is automated,the press is called a transfer press.The largest transfer dies are used together with single dies in large-panel transfer presses(cf.Fig.4.4.32).In progressive dies,also known as progressive blanking dies,sheet metal parts are blanked in several stages;generally speaking no actual forming operation takes place.The sheet metal is fed from a coil or in the form of metal ing an appropriate arrangement of the blanks within the available width of the sheet metal,an optimal material usage is ensured(cf.Fig.4.5.2 to 4.5.5). The workpiece remains fixed to the strip skeleton up until the laFig.4.1.2 Transfer die set for the production of an automatic transmission for an automotive application-st operation.The parts are transferred when the entire strip is shifted further in the work flow direction after the blanking operation.The length of the shift is equal to the center line spacing of the dies and it is also called the step width.Side shears,very precise feeding devices or pilot pins ensure feed-related part accuracy.In the final production operation,the finished part,i.e.the last part in the sequence,is disconnected from the skeleton.A field of application for progressive blanking tools is,for example,in the production of metal rotors or stator blanks for electric motors(cf.Fig.4.6.11 and 4.6.20).In progressive compound dies smaller formed parts are produced in several sequential operations.In contrast to progressive dies,not only blanking but also forming operations are performed.However, the workpiece also remains in the skeleton up to the last operation(Fig.4.1.3 and cf.Fig.4.7.2).Due to the height of the parts,the metal strip must be raised up,generally using lifting edges or similar lifting devices in order to allow the strip metal to be transported mechanically.Pressed metal parts which cannot be produced within a metal strip because of their geometrical dimensions are alternatively produced on transfer sets.Fig.4.1.3 Reinforcing part of a car produced in a strip by a compound die setNext to the dies already mentioned,a series of special dies are available for special individual applications.These dies are,as a rule,used separately.Special operations make it possible,however,for special dies to be integrated into an operational Sequence.Thus,for example,in flanging dies several metal parts can be joined together positively through the bending of certain metal sections(Fig.4.1.4and cf.Fig.2.1.34).During this operation reinforcing parts,glue or other components can be introduced.Other special dies locate special connecting elements directly into the press.Sorting and positioning elements,for example,bring stamping nuts synchronised with the press cycles into the correct position so that the punch heads can join them with the sheet metal part(Fig.4.1.5).If there is sufficient space available,forming and blanking operations can be carried out on the same die.Further examples include bending,collar-forming,stamping,fine blanking,wobble blanking and welding operations(cf.Fig.4.7.14 and4.7.15).Fig.4.1.4 A hemming dieFig.4.1.5 A pressed part with an integrated punched nut4.1.2 Die developmentTraditionally the business of die engineering has been influenced by the automotive industry.The following observations about the die development are mostly related to body panel die construction.Essential statements are,however,made in a fundamental context,so that they are applicable to all areas involved with the production of sheet-metal forming and blanking dies.Timing cycle for a mass produced car body panelUntil the end of the 1980s some car models were still being produced for six to eight years more or less unchanged or in slightly modified form.Today,however,production time cycles are set for only five years or less(Fig.4.1.6).Following the new different model policy,the demands ondie makers have also changed prehensive contracts of much greater scope such as Simultaneous Engineering(SE)contracts are becoming increasingly common.As a result,the die maker is often involved at the initial development phase of the metal part as well as in the planning phase for the production process.Therefore,a much broader involvement is established well before the actual die development is initiated.Fig.4.1.6 Time schedule for a mass produced car body panelThe timetable of an SE projectWithin the context of the production process for car body panels,only a minimal amount of time is allocated to allow for the manufacture of the dies.With large scale dies there is a run-up period of about 10 months in which design and die try-out are included.In complex SE projects,which have to be completed in 1.5 to 2 years,parallel tasks must be carried out.Furthermore,additional resources must be provided before and after delivery of the dies.These short periods call for pre-cise planning,specific know-how,available capacity and the use of the latest technological and communications systems.The timetable shows the individual activities during the manufacturing of the dies for the production of the sheet metal parts(Fig.4.1.7).The time phases for large scale dies are more or less similar so that this timetable can be considered to be valid in general.Data record and part drawingThe data record and the part drawing serve as the basis for all subsequent processing steps.They describe all the details of the parts to be produced. The information given in theFig.4.1.7 Timetable for an SE projectpart drawing includes: part identification,part numbering,sheet metal thickness,sheet metal quality,tolerances of the finished part etc.(cf.Fig.4.7.17).To avoid the production of physical models(master patterns),the CAD data should describe the geometry of the part completely by means of line,surface or volume models.As a general rule,high quality surface data with a completely filleted and closed surface geometry must be made available to all the participants in a project as early as possible.Process plan and draw developmentThe process plan,which means the operational sequence to be followed in the production of the sheet metal component,is developed from the data record of the finished part(cf.Fig.4.1.1).Already at this point in time,various boundary conditions must be taken into account:the sheet metal material,the press to be used,transfer of the parts into the press,the transportation of scrap materials,the undercuts as well as thesliding pin installations and their adjustment.The draw development,i.e.the computer aided design and layout of the blank holder area of the part in the first forming stage–if need bealso the second stage–,requires a process planner with considerable experience(Fig.4.1.8).In order to recognize and avoid problems in areas which are difficult to draw,it is necessary to manufacture a physical analysis model of the draw development.With this model,theforming conditions of the drawn part can be reviewed and final modifications introduced,which are eventually incorporated into the data record(Fig.4.1.9).This process is being replaced to some extent by intelligent simulation methods,throughwhich the potential defects of the formed component can be predicted and analysed interactively on the computer display.Die designAfter release of the process plan and draw development and the press,the design of the die can be started.As a rule,at this stage,the standards and manufacturing specifications required by the client must be considered.Thus,it is possible to obtain a unified die design and to consider the particular requests of the customer related to warehousing of standard,replacement and wear parts.Many dies need to be designed so that they can be installed in different types of presses.Dies are frequently installed both in a production press as well as in two different separate back-up presses.In this context,the layout of the die clamping elements,pressure pins and scrap disposal channels on different presses must be taken into account.Furthermore,it must be noted that drawing dies working in a single-action press may be installed in a double-action press(cf.Sect.3.1.3 and Fig.4.1.16).Fig.4.1.8 CAD data record for a draw developmentIn the design and sizing of the die,it is particularly important to consider the freedom of movement of the gripper rail and the crossbar transfer elements(cf.Sect.4.1.6).These describe the relative movements between the components of the press transfer system and the die components during a complete press working stroke.The lifting movement of the press slide,the opening and closing movements of the gripper rails and the lengthwise movement of the whole transfer are all superimposed.The dies are designed so that collisions are avoided and a minimum clearance of about 20 mm is set between all the moving parts.4 金属板料的成形及冲裁4. 模具制造原理4.1.1模具的分类在金属成形的过程中，工件的几何形状完全或部分建立在模具几何形状的基础上的。

外文原文Options for micro-holemakingAs in the macroscale-machining world, holemaking is one of the most— if not the most—frequently performed operations for micromachining. Many options exist for how those holes are created. Each has its advantages and limitations, depending on the required hole diameter and depth, workpiece material and equipment requirements. This article covers holemaking with through-coolant drills and those without coolant holes, plunge milling, microdrilling using sinker EDMs and laser drilling.Helpful HolesGetting coolant to the drill tip while the tool is cutting helps reduce the amount of heat at the tool/workpiece interface and evacuate chips regardless of hole diameter. Butthrough-coolant capability is especially helpful when deep-hole microdrilling because the tools are delicate and prone to failure when experiencing recutting of chips, chip packing and too much exposure to carbide’s worst enemy—heat.When applying flood coolant, the drill itself blocks access to the cutting action. “Somewhere about 3 to 5 diameters deep, the coolant has trouble getting down to the tip,” said Jeff Davis, vice president of engineering for Harvey Tool Co., Rowley, Mass. “It becomes wise to use a coolant-fed drill at that point.”In addition, flood coolant can cause more harm than good when microholemaking. “The pressure from the flood coolant can sometimes snap fragile drills as they enter the part,” Davis said.The toolmaker offers a line of through-coolant drills with diameters from 0.039" to 0.125" that are able to produce holes up to 12 diameters deep, as well as microdrills without coolant holes from 0.002" to 0.020".Having through-coolant capacity isn’t enough, though. Coolant needs to flow at a rate that enables it to clear the chips out of the hole. Davis recommends, at a minimum, 600 to 800 psi of coolant pressure. “It works much better if you have higher pressure than that,” he added.To prevent those tiny coolant holes from becoming clogged with debris, Davis also recommends a 5μm or finer coolant filter.Another recommendation is to machine a pilot, or guide, hole to prevent the tool from wandering on top of the workpiece and aid in producing a straight hole. When applying a pilot drill, it’s important to select one with an included angle on its point that’s equal t o or larger than the included angle on the through-coolant drill that follows. The pilot drill’sdiameter should also be slightly larger. For example, if the pilot drill has a 120° included angle and a smaller diameter than a through-coolant drill with a 140° included angle, “then you’re catching the coolant-fed drill’s corners and knocking those corners off,” Davis said, which damages the drill.Although not mandatory, pecking is a good practice when microdrilling deep holes. Davis suggests a pecking cycle that is 30 to 50 percent of the diameter per peck depth, depending on the workpiece material. This clears the chips, preventing them from packing in the flute valleys.Lubricious ChillTo further aid chip evacuation, Davis recommends applying an oil-based metalworking fluid instead of a waterbased coolant because oil provides greater lubricity. But if a shop prefers using coolant, the fluid should include EP (extreme pressure) additives to increase lubricity and minimize foaming. “If you’ve got a lot of foam,” Davis noted, “the chips aren’t being pulled out the way they are supposed to be.”He added that another way to enhance a tool’s slipperiness while extending its life is with a coating, such as titanium aluminum nitride. TiAlN has a high hardness and is an effective coating for reducing heat’s impact when drilling difficult-to-machine materials, like stainless steel.David Burton, general manager of Performance Micro Tool, Janesville, Wis., disagrees with the idea of coating microtools on the smalle r end of the spectrum. “Coatings on tools below 0.020" typically have a negative effect on every machining aspect, from the quality of the initial cut to tool life,” he said. That’s because coatings are not thin enough and negatively alter the rake and relief angles when applied to tiny tools.However, work continues on the development of thinner coatings, and Burton indicated that Performance Micro Tool, which produces microendmills and microrouters and resells microdrills, is working on a project with others to create a submicron-thickness coating. “We’re probably 6 months to 1 year from testing it in the market,” Burton said.The microdrills Performance offers are basically circuit-board drills, which are also effective for cutting metal. All the tools are without through-coolant capability. “I had a customer drill a 0.004"-dia. hole in stainless steel, and he was amazed he could do it with a circuit-board drill,” Burton noted, adding that pecking and running at a high spindle speed increase the drill’s effectiveness.The requirements for how fast microtools should rotate depend on the type of CNC machines a shop uses and the tool diameter, with higher speeds needed as the diameter decreases. (Note: The equation for cutting speed is sfm = tool diameter × 0.26 × spindlespeed.)Although relatively low, 5,000 rpm has been used successfully by Burton’s customers. “We recommend that our customers find the highest rpm at the lowest possible vibration—the sweet spot,” he said.In addition to minimizing vibration, a constant and adequate chip load is required to penetrate the workpiece while exerting low cutting forces and to allow the rake to remove the appropriate amount of material. If the drill takes too light of a chip load, the rake face wears quickly, becoming negative, and tool life suffers. This approach is often tempting when drilling with delicate tools.“If the customer decides he wants to baby the tool, he takes a lighter chip load,” Burton said, “and, typically, the cutting edge wears much quicker and creates a radius where the land of that radius is wider than the chip being cut. He ends up using it as a grinding tool, trying to bump material away.” For tools larger than 0.001", Burton considers a chip load under0.0001" to be “babying.” If the drill doesn’t snap, premature wear can result in abysmal tool life.Too much runout can also be destructive, but how much is debatable. Burton pointed out that Performance purposely designed a machine to have 0.0003" TIR to conduct in-house, worst-case milling scenarios, adding that the company is still able to mill a 0.004"-wide slot “day in and day out.”He added: “You would think with 0.0003" runout and a chip load a third that, say,0.0001" to 0.00015", the tool would break immediately because one flute would be taking the entire load and then the back end of the flute would be rubbing.When drilling, he indicated that up to 0.0003" TIR should be acceptable because once the drill is inside the hole, the cutting edges on the end of the drill continue cutting while the noncutting lands on the OD guide the tool in the same direction. Minimizing run out becomes more critical as the depth-to-diameter ratio increases. This is because the flutes are not able to absorb as much deflection as they become more engaged in the workpiece. Ultimately, too much runout causes the tool shank to orbit around the tool’s center while the tool tip is held steady, creating a stress point where the tool will eventually break.Taking a PlungeAlt hough standard microdrills aren’t generally available below 0.002", microendmills that can be used to “plunge” a hole are. “When people want to drill smaller than that, they use our endmills and are pretty successful,” Burton said. However, the holes can’t be very deep because the tools don’t have long aspect, or depth-to-diameter, ratios. Therefore, a 0.001"-dia. endmill might be able to only make a hole up to 0.020" deep whereas a drill of the same sizecan go deeper because it’s designed to place the loa d on its tip when drilling. This transfers the pressure into the shank, which absorbs it.Performance offers endmills as small as 5 microns (0.0002") but isn’t keen on increasing that line’s sales. “When people try to buy them, I very seriously try to tal k them out of it because we don’t like making them,” Burton said. Part of the problem with tools that small is the carbide grains not only need to be submicron in size but the size also needs to be consistent, in part because such a tool is comprised of fe wer grains. “The 5-micron endmill probably has 10 grains holding the core together,” Burton noted.He added that he has seen carbide powder containing 0.2-micron grains, which is about half the size of what’s commercially available, but it also contained grains measuring 0.5 and 0.6 microns. “It just doesn’t help to have small grains if they’re not uniform.”MicrovaporizationElectrical discharge machining using a sinker EDM is another micro-holemaking option. Unlike , which create small holes for threading wire through the workpiece when wire EDMing, EDMs for producing microholes are considerably more sophisticated, accurate and, of course, expensive.For producing deep microholes, a tube is applied as the electrode. For EDMing smaller but shallower holes, a solid electrode wire, or rod, is needed. “We try to use tubes as much as possible,” said Jeff Kiszonas, EDM product manager for Makino Inc., Auburn Hills, Mich. “But at some point, nobody can make a tube below a certain diameter.” He added that some suppliers offer tubes down to 0.003" in diameter for making holes as small as 0.0038". The tube’s flushing hole enables creating a hole with a high depth-to-diameter ratio and helps to evacuate debris from the bottom of the hole during machining.One such s inker EDM for producing holes as small as 0.00044" (11μm) is Makino’s Edge2 sinker EDM with fine-hole option. In Japan, the machine tool builder recently produced eight such holes in 2 minutes and 40 seconds through 0.0010"-thick tungsten carbide at the hole locations. The electrode was a silver-tungsten rod 0.00020" smaller than the hole being produced, to account for spark activity in the gap.When producing holes of that size, the rod, while rotating, is dressed with a charged EDM wire. The fine-hole option includes a W-axis attachment, which holds a die that guides the electrode, as well as a middle guide that prevents the electrode from bending or wobbling as it spins. With the option, the machine is appropriate for drilling hole diameters less than 0.005".Another sinker EDM for micro-holemaking is the Mitsubishi VA10 with a fine-hole jig attachment to chuck and guide the fine wire applied to erode the material. “It’s a standardEDM, but with that attachment fixed to the machine, we can do microhole d rilling,” said Dennis Powderly, sinker EDM product manager for MC Machinery Systems Inc., Wood Dale, Ill. He added that the EDM is also able to create holes down to 0.0004" using a wire that rotates at up to 2,000 rpm.Turn to TungstenEDMing is typically a slow process, and that holds true when it is used for microdrilling. “It’s very slow, and the finer the details, the slower it is,” said , president and owner of Optimation Inc. The Midvale, Utah, company builds Profile 24 Piezo EDMs for micromachining and also performs microEDMing on a contract-machining basis.Optimation produces tungsten electrodes using a reverse-polarity process and machines and ring-laps them to as small as 10μm in diameter with 0.000020" roundness. Applying a10μm-dia. electrode produces a hole about 10.5μm to 11μm in diameter, and blind-holes are possible with the company’s EDM. The workpiece thickness for the smallest holes is up to 0.002", and the thickness can be up to 0.04" for 50μm holes.After working with lasers and then with a former EDM builder to find a better way to produce precise microholes, Jorgensen decided the best approach was DIY. “We literally started with a clean sheet of paper and did all the electronics, all the software and the whole machine from scratch,” he said. Including the software, the machine costs in the neighborhood of $180,000 to $200,000.Much of the company’s contract work, which is provided at a shop rate of $100 per hour, involves microEDMing exotic metals, such as gold and platinum for X-ray apertures, stainless steel for optical applications and tantalum and tungsten for the electron-beam industry. Jorgensen said the process is also appropriate for EDMing partially electrically conductive materials, such as PCD.“The customer normally doesn’t care too much about the cost,” he said. “We’ve done parts where there’s $20,000 [in time and material] involved, and you can put the whole job underneath a fingernail. We do everything under a microscope.”Light CuttingBesides carbide and tungsten, light is an appropriate “tool material” formicro-holemaking. Although most laser drilling is performed in the infrared spectrum, the SuperPulse technology from The Ex One Co., Irwin, Pa., uses a green laser beam, said Randy Gilmore, the company’s director of laser technologies. Unlike the femtosecond variety, Super- Pulse is a nanosecond laser, and its green light operates at the 532-nanometer wavelength. The technology provides laser pulses of 4 to 5 nanoseconds in duration, and those pulses are sent in pairs with a delay of 50 to 100 nanoseconds between individual pulses. The benefits of this approach are twofold. “It greatly enhances material removal compared to other nanosecond lasers,” Gilmore said, “and greatly reduces the amount of thermal damagedon e to the workpiece material” because of the pulses’ short duration.The minimum diameter produced with the SuperPulse laser is 45 microns, but one of the most common applications is for producing 90μm to 110μm holes in diesel injector nozzles made of 1mm-t hick H series steel. Gilmore noted that those holes will need to be in the 50μm to 70μm range as emission standards tighten because smaller holes in injector nozzles atomize diesel fuel better for more efficient burning.In addition, the technology can produce negatively tapered holes, with a smaller entrance than exit diameter, to promote better fuel flow.Another common application is drilling holes in aircraft turbine blades for cooling. Although the turbine material might only be 1.5mm to 2mm thick, Gilmore explained that the holes are drilled at a 25° entry angle so the air, as it comes out of the holes, hugs the airfoil surface and drags the heat away. That means the hole traverses up to 5mm of material. “Temperature is everything in a turbine” he said, “because in an aircraft engine, the hotter you can run the turbine, the better the fuel economy and the more thrust you get.”To further enhance the technology’s competitiveness, Ex One developed apatent-pending material that is injected into a hollow-body component to block the laser beam and prevent back-wall strikes after it creates the needed hole. After laser machining, the end user removes the material without leaving remnants.“One of the bugaboos in getting lasers accepted in the diesel inject or community is that light has a nasty habit of continuing to travel until it meets another object,” Gilmore said. “In a diesel injector nozzle, that damages the interior surface of the opposite wall.”Although the $650,000 to $800,000 price for a Super- Pulse laser is higher than amicro-holemaking EDM, Gilmore noted that laser drilling doesn’t require electrodes. “A laser system is using light to make holes,” he said, “so it doesn’t have a consumable.”Depending on the application, mechanical drilling and plunge milling, EDMing and laser machining all have their place in the expanding micromachining universe. “People want more packed into smaller spaces,” said Makino’s Kiszonas.中文翻译微孔的加工方法正如宏观加工一样，在微观加工中孔的加工也许也是最常用的加工之一。

编号：毕业设计(论文)外文翻译（译文）学院：机电工程学院专业：机械制造及其自动化学生姓名：学号：指导教师单位：姓名：职称：2014年 5 月26 日摘录巨大线束网络的塑料装饰构件集成的发现在汽车领域上是降低汽车重量的一个很有吸引力的方式。

当任何异物插入注射成型的部分，在聚合物中横截面的变化导致了缩痕是审美缺陷而不是塑料装饰是可以接受的组件。

在本文中，插入成型采用注射成型过程分量的方法来减少或消除缩痕线。

采用L9正交试验设计实验框架用来研究工艺参数的影响，部分的肋的几何形状，并在水槽的标记线本身存在的形成。

水槽深度被定义为在表面轮廓可以感觉到的剩余的偏转。

一个描述性的模拟研究提出在不同的肋的几何形状的观察水池深度标记的工艺参数、模具温度、熔体温度和包装的时间是不同的。

仿真结果表明，较高的模具温度可有效地最小化的下沉深度为所有的肋的几何形状，而熔体温度和包时间的影响取决于特定的肋的几何形状。

研究结果还表明，适当的组合肋的几何形状和工艺参数消除了水槽标记。

感谢我要感谢我的导师David C. Angstadt 博士的指导和在这个项目的整个过程中的信任和支持。

Angstadt 博士的不断的反馈和很高的期望，驱使我不断进取，完成这项工作。

我衷心感谢Mica Grujicic博士让我进入Moldflow。

特别感谢我的研究生同学Peiman Mosaddegh 和Celina Renner这项工作的过程中的无私帮助。

我还要感谢我的朋友Nitendra Nath，Gayatri Keskar，Sonia Ramnani，Shyam Panyam，Judhajit Roy 和Ajit Kanda的不断鼓励和帮助。

最后，我要感谢我的家人和朋友们所有的爱和关怀，如果没有这些的话，这项工作将是不完整的。

第一章引言汽车制造商正越来越多地用塑料解决方案来减轻重量。

最近的一项研究表明，塑料占了10%的汽车的总重量。

塑料在汽车从内部的保险杠到外部的门体都存在。

Development of Flexible Manufacturing System using Virtual Manufacturing ParadigmSung-Chung Kim* and Kyung-Hyun ChoiSchool of mechanical engineering, Chungbuk National University, Cheongju, South Korea,School of mechanical engineering, Cheju National University, Cheju, South KoreaABSTRACTThe importance of Virtual Manufacturing System is increasing in the area of developing new manufacturing processes, implementing automated workcells, designing plant facility layouts and workplace ergonomics. Virtual manufacturing system is a computer system that can generate the same information about manufacturing system structure, states, and behaviors as is observed in a real manufacturing. In this research, a virtual manufacturing system for flexible manufacturing cells (VFMC), (which is a useful tool for building Computer Integrated Manufacturing (CIM),) has been developed using object-oriented paradigm, and implemented with software QUEST/IGRIP. Three object models used in the system are the product model, the facility model, and the process model. The concrete behaviors of a flexible manufacturing cell are represented by the task-oriented description diagram, TID. An example simulation is executed to evaluate applicability of the developed models, and to prove the potential value of virtual manufacturing paradigm.Key Words : FMS, virtual manufacturing system, CIM, object-oriented paradigm, TIDRecent trends in manufacturing systems, such as the need for customized products by small batches and for fast product renewal rates, have been demanding new paradigms in manufacturing. Therefore, the modern manufacturing systems are needed to be adaptable, and have the capability to reconfigure or self configure their own structure. Flexible Manufacturing Cells (FMCs) are generally recognized as the best productivity tool for small to medium batch manufacturing, and are also basic unit to construct a shop floor which is an important leve for developing computer integrated manufacturing (CIM). However, due to its complexity, the modeling and operation methodology related to FMC should be verified before implementation.As one of approaches to these requirements, Virtual Manufacturing (VM) approach has been introduced, and known as a effective paradigm for generating a model of manufacturing systems and simulating manufacturing processes instead of their operations in the real world. VM pursues the informational equivalence with real manufacturing systems. Therefore, the concept of Virtual Manufacturing System is expected to provide dramatic benefits in reducing cycle times, manufacturing and production costs, and improving communications across global facilities to launch new products faster, improve productivity and reduce operations costs for existing product shop [1,2].With an object-oriented paradigm, computer-based technologies such as virtual prototyping and virtual factory are employed as a basic concept for developing the manufacturing processes, including the layout of the optimal facility, to produce products. Virtual prototyping is a process by which advanced computer simulation enables early evaluation of new products or machines concept without actually fabricating physical machines or products. Bodner, et al.,[3] concentrated on the decision problems associated with individual machines that assemble electronic components onto printed circuit boards (PCBs). Virtual factory is a realistic, highly visual, 3D graphical representation of an actual factory floor with the real world complexity linked to the production controlling system and the real factory. Virtual factories are increasingly used within manufacturing industries as representations of physical plants, for example, VirtualWork system for representation of shop floor factory[4].Despite its benefits and applicability, VM systems should deal with a number of models of various types and require a large amount of computation for simulating behavior of equipment on a shop floor. To cope with this complexity in manufacturing, it is necessary to introduce open system architecture of modeling and simulation for VM systems.In this paper, three models, which are product, device, and process models will be addressed. Especially processmodel for FMC will be emphasized using QUEST/IGRIP as an implementation issue. The open system architecture consists of well-formalized modules for modeling and simulation that have carefully decomposed functions and well-defined interface with other modules.2. Concept of virtual manufacturingVirtual Manufacturing System is a computer model that represents the precise and whole structure of manufacturing systems and simulates their physical and logical behavior in operation, as well as interacting with the real manufacturing system. Its concept is specified as the model of present or future manufacturing systems with all products, processes, and control data. Before information and control data are used in the real system, their verification is performed within virtual manufacturing environment. In addition, its status and information is fed back to the virtual system from the real system.Virtual environments will provide visualization technology for virtual manufacturing. The virtual prototype is an essential component in the virtual product life cycle, while the virtual factory caters for operations needed for fabricating products. Therefore, the developments in the area of virtual prototyping and virtual factory will enhance the capabilities of virtual manufacturing.The major benefit of a virtual manufacturing is that physical system components (such as equipment and materials) as well as conceptual system compvonents (e.g., process plans and equipment schedules) can be easily represented through the creation of virtual manufacturing entities that emulate their structure and function. These entities can be added to or removed from the virtual plant as necessary with minimal impact on other system data. The software entities of the virtual factory have a high correspondence with real system components, thereby lending validity to simulations carried out in the virtual system meant to aid decision-makers in the real system.For virtual manufacturing, three major paradigms have been proposed, such as Design- centered VM, Production-centered VM, and Control- centered VM. The design-centered VM provides an environment for designers to design products and to evaluate the manufacturability and affordability of products. The results of design-centered VM include the product model, cost estimate, and so forth. Thus, potential problems with the design can be identified and its merit can be estimated. In order to maintain the manufacturing proficiency without actual building products, production-centered VM provides an environment for generating process plans and production plans, for planning resource requirements (new equipment purchase, etc.), and for evaluating these plans. This can provide more accurate cost information and schedules for product delivery. By providing the capability to simulate actual production, control-centered VM offers the environment for engineers to evaluate new or revised product designs with respect to shop floor related activities.Control-centered VM provides information for optimizing manufacturing processes and improving manufacturing systems.The virtual manufacturing approach in this paper is close to Control-centered VM. Fig.1 illustrates the viewpoint of the functional model of the virtual flexible manufacturing cell. Since the activity Execute real manufacturing systems depicts a model of real factory, it possibly replaces real factory. All manufacturing processesexcept physical elements of virtual manufacturing, such as design, process planning, scheduling, are included in the activity Operation of Virtual factory. The activity Execute simulation for virtual factory is a separate simulation model of VM system. With this virtual factory, parameters (e.g, utilization, operation time, etc.,) associated with operating a flexible manufacturing cell are simulated. And these results can provide the possibility of controlling manufacturing processes and predicting potential problems in the real manufacturing.3. Object modeling for virtual flexible manufacturing cellsObject-oriented technology may provide a powerful representation and classification tools for a virtual flexible manufacturing cell. It may also provide a common platform for the information sharing between sub-modules, and provide a richer way to store/retrieve/modify information, knowledge and models and reuse them. In the context of an object oriented approach, a model is simply an abstraction, or a representation of an objects or process.VFMC requires a robust information infrastructure that comprises rich information models for products, processes and production systems. As shown in Fig. 2, three models, that is product model, facility model, and process model, are developed for virtual flexible manufacturing cells. A product model is a generic model used for representing all types of artifacts, which appear in the process of manufacturing. It represents target products, which include conceptual shape information as well as analysis module for a specification, productivity, and strength.A facility model contains information about machines consisted of a virtual flexible manufacturing cell. By using the model, innovative tooling and methods can be evaluated without the cost of physical machine prototypes and fixture mock-ups. A process model is used for representing all the physical processes that are required for representing product behavior andmanufacturing processes.3.1 Product modelA product model holds the process and product knowledge to ensure the correct fabrication of the product with sufficient quality. It acts as an information server to the other models in the VFMC. It also provides consistent and up-to-date information on the product lifecycle, user requirements, design, and process plan and bill of material. An instance of Class Part provides detailed information about a part to be fabricated in VFMC. Sub-classes like ProcessPlan, BOM, and NcCode, are aggregated into the class Part. Classes Process Plan and BOM manipulate information and data associated with process plans and bill of materials, respectively. Class NcCode deals with NC programs, which interacts with CAD/CAM systems. With incorporation with the facility model, this developed NC programs can be verified and checked for collisions and interference with any workpiece or tooling in the fixture. This can avoid costly machine crashes and reduce risk during initial equipment installation and produce launch. Furthermore, productivity can be improved by avoiding nonproductive time for program prove out on the machine tool and by using thesimulation environment to train operators of new machines.3.2 Facility mode lReal manufacturing cell may consist of NC machines, robots, conveyors, and sensory devices. The architecture of class corresponding to the real manufacturing cell is shown in Fig.3, and represents the factory model. In VFMC, characteristics of the factory model include a detailed representation of machine behavior over time, a structure to the model that can configure and reconfigure easily, and a realistic and three-dimensional animation of machine behavior over time. Virtual machines defined within this model may be used to estimate accurately the merit of a process plan, and, based on this evaluation, determine appropriate process conditions to improve (and even optimize) the plan. V irtual robot contributes to unload and load parts into/from machines, and is used to find optimal paths without any collisions. With virtual operation, the fidelity of the machining and robot utilizing time and cost estimates is expected to improve. In addition, accurate modeling will predict the quality of the machined part, which cannot be determined easily and reliably without producing several physical prototypes. This information is invaluable to both the designer and the process planner. Physical entities such as machines and workpieces have the explicit representation as 3-D models for their shapes, positions, and orientations. 3-D models are conveniently used for calculating, geometrical attributes, checking spatial relations, and displaying computer graphics.3.3 Process modelBy assigning a finite set of states to each device in a cell (idle, busy, failed, etc.), the process of cell control can be modeled as a process of matching specific state change events to specific cell control actions, decision algorithms, or scripts. With this model, cell processes are represented a Task Initiation Diagram (TID) using an object-oriented approach. The methodology behind developing TID regards the tasks to be performed by the cell or any of its constituent machines for being primal, and employs the multi-layered approach. Sensory signals indicating the change of state of machines are used to trigger or initiate tasks. A task may be simple and require a relatively short time to execute, or may be complex and lengthy.Formally, a Task Initiation Diagram (TID) is defined as the four-tuple TID=(T, SR, C, O). Task Initiation Diagrams are composed of two basic components: a set of Rest states SR and a set of tasks T. Tasks, in turn, are classified into three groups: the cell configuration dependant task (Td), the cell configuration independent task (Ti), and the cycle transit task (Tt). Cell configuration dependent tasks are those which require some coordination among cell components to carry out the task. For example, the task load a s in aRobot load a part to:aMill requires that the actions of aRobot and aMill be coordinated. Cell configuration independent tasks require only one cell component to perform the task. The task move To as in Robot move to:MachineName configuration independent one, because it is carried out by the Robot without interacting with other components. Tt tasks are used for the transition from one cycle to another, and thus derived automatically by the system in order to complete a production job. State SR indicates rest states where cell constituents must be wait for next task. This state is given at any instant by the collection of states of itsconstituents. These composite states are depicted in the Task Initiation Diagram by ellipses, e.g., R11/3 or M13/4. The last number of the symbols indicates how many individual states are required to determine this composite state.To complete the diagram, it is necessary to define the relationship between the states and the tasks. This can be done by specifying two functions connecting states to tasks: the condition functionC, and the output function O. The condition function C defines, for each task Ti, the set of states for task C(Ti). Some condition functions may use guiding parameters in addition to a set of states. As an example, C(Tt) uses a Remaining Processing Time (RPT) to cause transition to the desired state.The output function O defines for each Task Ti the set of output States for the transition O(Ti).The Operation Initiation Diagram (OID) is the second layer diagram of the Task Initiation Diagram (TID). In the same way of TID to represent the model, the Operation Initiation Diagram OID is defined as the four-tuple, OID(task)=(OP,Sv,C,O). The symbol OP defines set of operation required for a given task. The operation, OP, is categorized into two groups: guided operations OPg and unconditional operations OPu. A guided operation is one that requires an external trigger to start it. Unconditional operations are ones that start automatically on the onset of all the necessary states.The symbol Sv indicates the set of visit-state. The visit-state, Sv, indicates an interaction between two machines and hence requires coordination among them. The symbol of this state has the pattern R-M-- for the robot, as an example, the state RvMnm. The small letter v represents the visit-state of the robot associated with location, Mn represents a machine served by the robot, and m represents the index of one of the visit locations. During the completion of the task, the busy states are employed, and indicate transitional states between operations or two executions without interaction. They can be recognized from the robot state symbol, Rtn. The small letter t i ndicates the state of the robot associated with transition. These states are useful in avoiding collisions with obstacles. The condition operator C, defines the setof state and guiding conditions necessary for each operation OPi i.e. C(Opi). The output operator O, defines the set of states resulting from each operation OPi, i.e., O(OPi).4. Control architecture for VFMCCell operation involves tasks to be performed on single machines independent of others, and tasks that to require the cooperation of two or more machines. In cases where a task calls for the coordination of two or more machines, the cell controller has to be involved to ensure proper execution of that task. For tasks involving a single machine, the primary function of a controller is to schedule the start of the task, and waits for its completion to command the nest task. In order to accomplish these functions, the cell controller is designed as a hybrid structure of both hierarchical controller and decentralized controllers as shown in Fig. 3. The controller consists ofthree different layers. The Scheduler, the Decentralized Control layer, and the Virtual Device layer. In the figure, the p assing of information and message are indicated by arrows. The Scheduler is a core component that receives the states of all the machines in the VFMC from the Decentralized Control layer, and decides the appropriate next task. It then dispatches the next task to be executed to the Decentralized Control layer. It uses the process knowledge bases that contain the routine cell task rules that are generated from the TID. The Decentralized Control layer consists of virtual drivers for the virtual machine that mimic to physical machines. Their main role is to perform the harmonization and the cooperation between the cell components in order to carry out the task called for by the Scheduler layer. They provide a device independent interface to the actual cell components by translating the generic commands and error messages of the corresponding machine. The virtual driver in the layer communicator and pass messages with each other. A virtual driver send commands to the corresponding physical machine, and receives the state of that machine, through that Virtual Device in the Virtual Device layer.The lowermost layer of the controller consists of the Virtual Devices which monitor and continuously mirror, in real time, the state of the physical machine they represent. Each machine state is analyzed by its Virtual Device and reported to the corresponding Virtual holons as required. The Virtual Devices also serve as conduits for commands from the Virtual holons to the physical machines.5. ConclusionIn this study, the concept of virtual manufacturing is investigated, and three models, such as the product, the facility, and the process model, are developed for virtual flexible manufacturing cells. A product model is a generic model used for representing all types of parts, which appear in the process of manufacturing. A facility model contains information about machines consisted of a virtual flexible manufacturing cell. A process model is used for representing all the physical processes that are required for representing product behavior and manufacturing processes. The methodology behind developing VFMC is an object-oriented paradigm that provides a powerful representation a nd classification tools. For the implementation IGRIP/QUEST is used to model all 3D virtual machines involved models, and to simulate the whole factories where manufacturing events are concerned. The concrete behaviors of simulation are d escribed by the task-oriented description (TID). Also the result of simulation is demonstrated to prove the applicability of the virtual manufacturing paradigm. The potential of virtual manufacturing is to support manufacturability assessments and provide accurate cost, lead-time, and quality estimate is a major motivation forfurther research and development in this area.References1. Iwata, Kazuaki Virtual Manufacturing System as Advanced InformationInfrastructure for Integrating Manufacturing Resources and Activities, Annals of CIRP, V ol. 46, No. 1, pp. 399, 1997.2. Kimura Fumihito "Product and Process Modeling as a Kernel for VirtualManufacturing Environment," Annals of CIRP, V ol. 42, No. 1, pp. 147-151, 1993.3. Bodner, D., Park, J., Reveliotis, A., and McGinnis, F., Integration of structural and perfromance-oriented control in flexibleautomated manufacturing , Proceedings of 1999 IEEE/ASME International Conference on Advanced Intelligent Mechatronics, USA, pp.345-250, 1999.4. Onosato, M., and Iwata, K., Development of a Virtual manufacturing System by Integrating Product Models and Factory Models, Annals of the CIRP, V ol. 42, No.1, pp. 475-478, 1993.摘要虚拟制造系统的重要性是在新的制造业发展过程中逐渐凸显出来的，进行自动化操作、设计工厂设备的布局以及工作场所的人机工程学。

附录2Integrated simulation of the injection molding process withstereolithography moldsAbstract Functional parts are needed for design verification testing, field trials, customer evaluation, and production planning. By eliminating multiple steps, the creation of the injection mold directly by a rapid prototyping (RP) process holds the best promise of reducing the time and cost needed to mold low-volume quantities of parts. The potential of this integration of injection molding with RP has been demonstrated many times. What is missing is the fundamental understanding of how the modifications to the mold material and RP manufacturing process impact both the mold design and the injection molding process. In addition, numerical simulation techniques have now become helpful tools of mold designers and process engineers for traditional injection molding. But all current simulation packages for conventional injection molding are no longer applicable to this new type of injection molds, mainly because the property of the mold material changes greatly. In this paper, an integrated approach to accomplish a numerical simulation of injection molding into rapid-prototyped molds is established and a corresponding simulation system is developed. Comparisons with experimental results are employed for verification, which show that the present scheme is well suited to handle RP fabricated stereolithography (SL) molds.Keywords Injection molding Numerical simulation Rapid prototyping1 IntroductionIn injection molding, the polymer melt at high temperature is injected into the mold under high pressure [1]. Thus, the mold material needs to have thermal and mechanical properties capable of withstanding the temperatures and pressures of the molding cycle. The focus of many studies has been to create theinjection mold directly by a rapid prototyping (RP) process. By eliminating multiple steps, this method of tooling holds the best promise of reducing the time and cost needed to create low-volume quantities of parts in a production material. The potential of integrating injection molding with RP technologies has been demonstrated many times. The properties of RP molds are very different from those of traditional metal molds. The key differences are the properties of thermal conductivity and elastic modulus (rigidity). For example, the polymers used in RP-fabricated stereolithography (SL) molds have a thermal conductivity that is less than onethousandth that of an aluminum tool. In using RP technologies to create molds, the entire mold design and injection-molding process parameters need to be modified and optimized from traditional methodologies due to the completely different tool material. However, there is still not a fundamen tal understanding of how the modifications t o the mold tooling method and material impact both the mold design and the injection molding process parameters. One cannot obtain reasonable results by simply changing a few material properties in current models. Also, using traditional approaches when making actual parts may be generating sub-optimal results. So there is a dire need to study the interaction between the rapid tooling (RT) process and material and injection molding, so as to establish the mold design criteria and techniques for an RT-oriented injection molding process.In addition, computer simulation is an effective approach for predicting the quality of molded parts. Commercially available simulation packages of the traditional injection molding process have now become routine tools of the mold designer and process engineer [2]. Unfortunately, current simulation programs for conventional injection molding are no longer applicable to RP molds, because of the dramatically dissimilar tool material. For instance, in using the existing simulation software with aluminum and SL molds and comparing with experimental results, though the simulation values of part distortion are reasonable for the aluminum mold, results are unacceptable, with the error exceeding 50%. The distortion during injection molding is due to shrinkage and warpage of the plastic part, as well as the mold. For ordinarily molds, the main factor is the shrinkage and warpage of the plastic part, which is modeled accurately in current simulations. But for RP molds, the distortion of the mold has potentially more influence, which have been neglected in current models. For instance, [3] used a simple three-step simulation process to consider the mold distortion, which had too much deviation.In this paper, based on the above analysis, a new simulation system for RP molds is developed. The proposed system focuses on predicting part distortion, which is dominating defect in RP-molded parts. The developed simulation can be applied as an evaluation tool for RP mold design and process optimization. Our simula tion system is verified by an experimental example.Although many materials are available for use in RP technologies, we concentrate on using stereolithography (SL), the original RP technology, to create polymer molds. The SL process uses photopolymer and laser energy to build a part layer by layer. Using SL takes advantage of both the commercial dominance of SL in the RP industry and the subsequent expertise base that has been developed for creating accurate, high-quality parts. Until recently, SL was primarily used to create physical models for visual inspection and form-fit studies with very limited func-tional applications. However, the newer generation stereolithographic photopolymers have improved dimensional, mechanical and thermal properties making it possible to use them for actual functional molds.2 Integrated simulation of the molding process2.1 MethodologyIn order to simulate the use of an SL mold in the injection molding process, an iterative method is proposed. Different software modules have been developed and used to accomplish this task. The main assumption is that temperature and load boundary conditions cause significant distortions in the SL mold. The simulation steps are as follows:1The part geometry is modeled as a solid model, which is translated to a file readable by the flow analysis package.2Simulate the mold-filling process of the melt into a pho topolymer mold, which will output the resulting temperature and pressure profiles.3Structural analysis is then performed on the photopolymer mold model using the thermal and load boundary conditions obtained from the previous step, which calculates the distortion that the mold undergo during the injection process.4If the distortion of the mold converges, move to the next step. Otherwise, the distorted mold cavity is then modeled (changes in the dimensions of the cavity after distortion), and returns to the second step to simulate the melt injection into the distorted mold.5The shrinkage and warpage simulation of the injection molded part is then applied, which calculates the final distor tions of the molded part.In above simulation flow, there are three basic simulation mod ules.2. 2 Filling simulation of the melt2.2.1 Mathematical modelingIn order to simulate the use of an SL mold in the injection molding process, an iterative method is proposed. Different software modules have been developed and used to accomplish this task. The main assumption is that temperature and load boundary conditions cause significant distortions in the SL mold. The simulation steps are as follows:1. The part geometry is modeled as a solid model, which is translated to a file readable by the flow analysis package.2. Simulate the mold-filling process of the melt into a photopolymer mold, which will output the resulting temperature and pressure profiles.3. Structural analysis is then performed on the photopolymer mold model using the thermal and load boundary conditions obtained from the previous step, which calculates the distortion that the mold undergo during the injection process.4. If the distortion of the mold converges, move to the next step. Otherwise, the distorted mold cavity is then modeled (changes in the dimensions of the cavity after distortion), and returns to the second step to simulate the melt injection into the distorted mold.5. The shrinkage and warpage simulation of the injection molded part is then applied, which calculates the final distortions of the molded part.In above simulation flow, there are three basic simulation modules.2.2 Filling simulation of the melt2.2.1 Mathematical modelingComputer simulation techniques have had success in predicting filling behavior in extremely complicated geometries. However, most of the current numerical implementation is based on a hybrid finite-element/finite-difference solution with the middleplane model. The application process of simulation packages based on this model is illustrated in Fig. 2-1. However, unlike the surface/solid model in mold-design CAD systems, the so-called middle-plane (as shown in Fig. 2-1b) is an imaginary arbitrary planar geometry at the middle of the cavity in the gap-wise direction, which should bring about great inconvenience in applications. For example, surface models are commonly used in current RP systems (generally STL file format), so secondary modeling is unavoidable when using simulation packages because the models in the RP and simulation systems are different. Considering these defects, the surface model of the cavity is introduced as datum planes in the simulation, instead of the middle-plane.According to the previous investigations [4–6], fillinggoverning equations for the flow and temperature field can be written as:where x, y are the planar coordinates in the middle-plane, and z is the gap-wise coordinate; u, v,w are the velocity components in the x, y, z directions; u, v are the average whole-gap thicknesses; and η, ρ,CP (T), K(T) represent viscosity, density, specific heat and thermal conductivity of polymer melt, respectively.Fig.2-1 a–d. Schematic procedure of the simulation with middle-plane model. a The 3-D surface model b The middle-plane model c The meshed middle-plane model d The display of the simulation result In addition, boundary conditions in the gap-wise direction can be defined as:where TW is the constant wall temperature (shown in Fig. 2a).Combining Eqs. 1–4 with Eqs. 5–6, it follows that the distributions of the u, v, T, P at z coordinates should be symmetrical, with the mirror axis being z = 0, and consequently the u, v averaged in half-gap thickness is equal to that averaged in wholegap thickness. Based on this characteristic, we can divide the whole cavity into two equal parts in the gap-wise direction, as described by Part I and Part II in Fig. 2b. At the same time, triangular finite elements are generated in the surface(s) of the cavity (at z = 0 in Fig. 2b), instead of the middle-plane (at z = 0 in Fig. 2a). Accordingly, finite-difference increments in the gapwise direction are employed only in the inside of the surface(s) (wall to middle/center-line), which, in Fig. 2b, means from z = 0 to z = b. This is single-sided instead of two-sided with respect to the middle-plane (i.e. from the middle-line to two walls). In addition, the coordinate system is changed from Fig. 2a to Fig. 2b to alter the finite-element/finite-difference scheme, as shown in Fig. 2b. With the above adjustment, governing equations are still Eqs. 1–4. However, the original boundary conditions inthe gapwise direction are rewritten as:Meanwhile, additional boundary conditions must be employed at z = b in order to keep the flows at the juncture of the two parts at the same section coordinate [7]:where subscripts I, II represent the parameters of Part I and Part II, respectively, and Cm-I and Cm-II indicate the moving free melt-fronts of the surfaces of the divided two parts in the filling stage.It should be noted that, unlike conditions Eqs. 7 and 8, ensuring conditions Eqs. 9 and 10 are upheld in numerical implementations becomes more difficult due to the following reasons:1. The surfaces at the same section have been meshed respectively, which leads to a distinctive pattern of finite elements at the same section. Thus, an interpolation operation should be employed for u, v, T, P during the comparison between the two parts at the juncture.2. Because the two parts have respective flow fields with respect to the nodes at point A and point C (as shown in Fig. 2b) at the same section, it is possible to have either both filled or one filled (and one empty). These two cases should be handled separately, averaging the operation for the former, whereas assigning operation for the latter.3. It follows that a small difference between the melt-fronts is permissible. That allowance can be implemented by time allowance control or preferable location allowance control of the melt-front nodes.4. The boundaries of the flow field expand by each melt-front advancement, so it is necessary to check the condition Eq. 10 after each change in the melt-front.5. In view of above-mentioned analysis, the physical parameters at the nodes of the same section should be compared and adjusted, so the information describing finite elements of the same section should be prepared before simulation, that is, the matching operation among the elements should be preformed.Fig. 2a,b. Illustrative of boundary conditions in the gap-wise direction a of the middle-plane model b of thesurface model2.2.2 Numerical implementationPressure field. In modeling viscosity η, which is a function of shear rate, temperature and pressure of melt, the shear-thinning behavior can be well represented by a cross-type model such as:where n corresponds to the power-law index, and τ∗ characterizes the shear stress level of the transition region between the Newtonian and power-law asymptotic limits. In terms of an Arrhenius-type temperature sensitivity and exponential pressure dependence, η0(T, P) can be represented with reasonable accuracy as follows:Equations 11 and 12 constitute a five-constant (n, τ∗, B, Tb, β) representation for viscosity. The shear rate for viscosity calculation is obtained by:Based on the above, we can infer the following filling pressure equation from the governing Eqs. 1–4:where S is calculated by S = b0/(b−z)2η d z. Applying the Galerkin method, the pressure finite-element equation is deduced as:where l_ traverses all elements, including node N, and where I and j represent the local node number in element l_ corresponding to the node number N and N_ in the whole, respectively. The D(l_) ij is calculated as follows:where A(l_) represents triangular finite elements, and L(l_) i is the pressure trial function in finite elements.Temperature field. To determine the temperature profile across the gap, each triangular finite element at the surface is further divided into NZ layers for the finite-difference grid.The left item of the energy equation (Eq. 4) can be expressed as:where TN, j,t represents the temperature of the j layer of node N at time t.The heat conduction item is calculated by:where l traverses all elements, including node N, and i and j represent the local node number in element l corresponding to the node number N and N_ in the whole, respectively.The heat convection item is calculated by:For viscous heat, it follows that:Substituting Eqs. 17–20 into the energy equation (Eq. 4), the temperature equation becomes:2.3 Structural analysis of the moldThe purpose of structural analysis is to predict the deformation occurring in the photopolymer mold due to the thermal and mechanical loads of the filling process. This model is based on a three-dimensional thermoelastic boundary element method (BEM). The BEM is ideally suited for this application because only the deformation of the mold surfaces is of interest. Moreover, the BEM has an advantage over other techniques in that computing effort is not wasted on calculating deformation within the mold.The stresses resulting from the process loads are well within the elastic range of the mold material. Therefore, the mold deformation model is based on a thermoelastic formulation. The thermal and mechanical properties of the mold are assumed to be isotropic and temperature independent.Although the process is cyclic, time-averaged values of temperature and heat flux are used for calculating the mold deformation. Typically, transient temperature variations within a mold have been restricted to regions local to the cavity surface and the nozzle tip [8]. The transients decay sharply with distance from the cavity surface and generally little variation is observed beyond distances as small as 2.5 mm. This suggests that the contribution from the transients to the deformation at the mold block interface is small, and therefore it is reasonable to neglect the transient effects. The steady state temperature field satisfies Laplace’s equation 2T = 0 and the time-averaged boundary conditions. The boundary conditions on the mold surfaces are described in detail by Tang et al. [9]. As for the mechanical boundary conditions, the cavity surface is subjected to the melt pressure, the surfaces of the mold connected to the worktable are fixed in space, and other external surfaces are assumed to be stress free.The derivation of the thermoelastic boundary integral formulation is well known [10]. It is given by:where uk, pk and T are the displacement, traction and temperature,α, ν represent the thermal expansion coefficient and Poisson’s ratio of the material, and r = |y−x|. clk(x) is the surfacecoefficient which depends on the local geometry at x, the orientation of the coordinate frame and Poisson’s ratio for the domain [11]. The fundamental displacement ˜ulk at a point y in the xk direction, in a three-dimensional infinite isotropic elastic domain, results from a unit load concentrated at a point x acting in the xl direction and is of the form:where δlk is the Kronecker delta function and μ is the shear modulus of the mold material.The fundamental traction ˜plk , measured at the point y on a surface with unit normal n, is:Discretizing the surface of the mold into a total of N elements transforms Eq. 22 to:where Γn refers to the n th surface element on the domain.Substituting the appropriate linear shape functions into Eq. 25, the linear boundary element formulation for the mold deformation model is obtained. The equation is applied at each node on the discretized mold surface, thus giving a system of 3N linear equations, where N is the total number of nodes. Each node has eight associated quantities: three components of displacement, three components of traction, a temperature and a heat flux. The steady state thermal model supplies temperature and flux values as known quantities for each node, and of the remaining six quantities, three must be specified. Moreover, the displacement values specified at a certain number of nodes must eliminate the possibility of a rigid-body motion or rigid-body rotation to ensure a non-singular system of equations. The resulting system of equations is assembled into a integrated matrix, which is solved with an iterative solver.2.4 Shrinkage and warpage simulation of the molded partInternal stresses in injection-molded components are the principal cause of shrinkage and warpage. These residual stresses are mainly frozen-in thermal stresses due to inhomogeneous cooling, when surface layers stiffen sooner than the core region, as in free quenching. Based onthe assumption of the linear thermo-elastic and linear thermo-viscoelastic compressible behavior of the polymeric materials, shrinkage and warpage are obtained implicitly using displacement formulations, and the governing equations can be solved numerically using a finite element method.With the basic assumptions of injection molding [12], the components of stress and strain are given by:The deviatoric components of stress and strain, respectively, are given byUsing a similar approach developed by Lee and Rogers [13] for predicting the residual stresses in the tempering of glass, an integral form of the viscoelastic constitutive relationships is used, and the in-plane stresses can be related to the strains by the following equation:Where G1 is the relaxation shear modulus of the material. The dilatational stresses can be related to the strain as follows:Where K is the relaxation bulk modulus of the material, and the definition of α and Θ is: If α(t) = α0, applying Eq. 27 to Eq. 29 results in:Similarly, applying Eq. 31 to Eq. 28 and eliminating strain εxx(z, t) results in:Employing a Laplace transform to Eq. 32, the auxiliary modulus R(ξ) is given by:Using the above constitutive equation (Eq. 33) and simplified forms of the stresses and strains in the mold, the formulation of the residual stress of the injection molded part during the cooling stage is obtain by:Equation 34 can be solved through the application of trapezoidal quadrature. Due to the rapid initial change in the material time, a quasi-numerical procedure is employed for evaluating the integral item. The auxiliary modulus is evaluated numerically by the trapezoidal rule.For warpage analysis, nodal displacements and curvatures for shell elements are expressed as:where [k] is the element stiffness matrix, [Be] is the derivative operator matrix, {d} is the displacements, and {re} is the element load vector which can be evaluated by:The use of a full three-dimensional FEM analysis can achieve accurate warpage results, however, it is cumbersome when the shape of the part is very complicated. In this paper, a twodimensional FEM method, based on shell theory, was used because most injection-molded parts have a sheet-like geometry in which the thickness is much smaller than the other dimensions of the part. Therefore, the part can be regarded as an assembly of flat elements to predict warpage. Each three-node shell element is a combination of a constant strain triangular element (CST) and a discrete Kirchhoff triangular element (DKT), as shown in Fig. 3. Thus, the warpage can be separated into plane-stretching deformation of the CST and plate-bending deformation of the DKT, and correspondingly, the element stiffness matrix to describe warpage can also be divided into the stretching-stiffness matrix and bending-stiffness matrix.Fig. 3a–c. Deformation decomposition of shell element in the local coordinate system. a In-plane stretchingelement b Plate-bending element c Shell element3 Experimental validationTo assess the usefulness of the proposed model and developed program, verification is important. The distortions obtained from the simulation model are compared to the ones from SL injection molding experiments whose data is presented in the literature [8]. A common injection molded part with the dimensions of 36×36×6 mm is considered in the experiment, as shown in Fig. 4. The thickness dimensions of the thin walls and rib are both 1.5 mm; and polypropylene was used as the injection material. The injection machine was a production level ARGURY Hydronica 320-210-750 with the following process parameters: a melt temperature of 250 ◦C; an ambient temperature of 30 ◦C; an injection pressure of 13.79 MPa; an injection time of 3 s; and a cooling time of 48 s. The SL material used, Dupont SOMOSTM 6110 resin, has the ability to resist temperatures of up to 300 ◦C temperatures. As mentioned above, thermal conductivity of the mold is a major factor that differentiates between an SL and a traditional mold. Poor heat transfer in the mold would produce a non-uniform temperature distribution, thus causing warpage that distorts the completed parts. For an SL mold, a longer cycle time would be expected. The method of using a thin shell SL mold backed with a higher thermal conductivity metal (aluminum) was selected to increase thermal conductivity of the SL mold.Fig. 4. Experimental cavity modelFig. 5. A comparison of the distortion variation in the X direction for different thermal conductivity; where “Experimental”, “present”, “three-step”, and “conventional” mean the results of the experimental, the presented simulation, the three-step simulation process and the conventional injection molding simulation, respectively.Fig. 6. Comparison of the distortion variation in the Y direction for different thermal conductivitiesFig. 7. Comparison of the distortion variation in the Z direction for different thermal conductivitiesFig. 8. Comparison of the twist variation for different thermal conductivities For this part, distortion includes the displacements in three directions and the twist (the difference in angle between two initially parallel edges). The validation results are shown in Fig.5 to Fig. 8. These figures also include the distortion values predicted by conventional injection molding simulation and the three-step model reported in [3].4 ConclusionsIn this paper, an integrated model to accomplish the numerical simulation of injection molding into rapid-prototyped molds is established and a corresponding simulation system is developed. For verification, an experiment is also carried out with an RPfabricated SL mold.It is seen that a conventional simulation using current injection molding software breaks down for a photopolymer mold. It is assumed that this is due to the distortion in the mold caused by the temperature and load conditions of injection. The three-step approach also has much deviation. The developed model gives results closer to experimental.Improvement in thermal conductivity of the photopolymer significantly increases part quality. Since the effect of temperature seems to be more dominant than that of pressure (load), an improvement in the thermal conductivity of the photopolymer can improve the part quality significantly.Rapid Prototyping (RP) is a technology makes it possible to manufacture prototypes quickly and inexpensively, regardless of their complexity. Rapid Tooling (RT) is the next step in RP’s steady progress and much work is being done to obtain more accurate tools to define the parameters of the process. Existing simulation tools can not provide the researcher with a useful means of studying relative changes. An integrated model, such as the one presented in this paper, is necessary to obtain accurate predictions of the actual quality of final parts. In the future, we expect to see this work expanded to develop simulations program for injection into RP molds manufactured by other RT processes.References1. Wang KK (1980) System approach to injection molding process. Polym-Plast Technol Eng 14(1):75–93.2. Shelesh-Nezhad K, Siores E (1997) Intelligent system for plastic injection molding process design. J Mater Process Technol 63(1–3):458–462.3. Aluru R, Keefe M, Advani S (2001) Simulation of injection molding into rapid-prototyped molds. Rapid Prototyping J 7(1):42–51.4. Shen SF (1984) Simulation of polymeric flows in the injection molding process. Int J Numer Methods Fluids 4(2):171–184.5. Agassant JF, Alles H, Philipon S, Vincent M (1988) Experimental and theoretical study of the injection molding of thermoplastic materials. Polym Eng Sci 28(7):460–468.6. Chiang HH, Hieber CA, Wang KK (1991) A unified simulation of the filling and post-filling stages in injection molding. Part I: formulation. Polym Eng Sci 31(2):116–124.7. Zhou H, Li D (2001) A numerical simulation of the filling stage in injection molding based on a surface model. Adv Polym Technol 20(2):125–131.8. Himasekhar K, Lottey J, Wang KK (1992) CAE of mold cooling in injection molding using a three-dimensional numerical simulation. J EngInd Trans ASME 114(2):213–221.9. Tang LQ, Pochiraju K, Chassapis C, Manoochehri S (1998) Computeraided optimization approach for the design of injection mold cooling systems. J Mech Des, Trans ASME 120(2):165–174.10. Rizzo FJ, Shippy DJ (1977) An advanced boundary integral equation method for three-dimensional thermoelasticity. Int J Numer Methods Eng 11:1753–1768.11. Hartmann F (1980) Computing the C-matrix in non-smooth boundary points. In: New developments in boundary element methods, CML Publications, Southampton, pp 367–379.12. Chen X, Lama YC, Li DQ (2000) Analysis of thermal residual stress in plastic injection molding. J Mater Process Technol 101(1):275–280.13. Lee EH, Rogers TG (1960) Solution of viscoelastic stress analysis problems using measured creep or relaxation function. J Appl Mech 30(1):127–134.14. Li Y (1997) Studies in direct tooling using stereolithography. Dissertation, University of Delaware, Newark, DE..。

原文：《Modelling the dynamics of the tilt-casting process and the effect of the mould design on the casting quality》H. Wang a,G. Djambazov a, K.A. Pericleous a, R.A. Harding b, M. Wickins bCentre for Numerical Modelling and Process Analysis, University of Greenwich, London SE10 9LS, UK b IRC in Materials Processing, University of Birmingham, Birmingham, B15 2TT, UAbstractAll titanium alloys are highly reactive in the molten condition and so are usually melted in a water-cooled copper crucible to avoid contamination using processes such as Induction Skull Melting (ISM). These provide only limited superheat which, coupled with the surface turbulence inherent in most conventional mould filling processes, results in entrainment defects such as bubbles in the castings. To overcome these problems, a novel tilt-casting process has been developed in which the mould is attached directly to the ISM crucible holding the melt and the two are then rotated together to achieve a tranquil transfer of the metal into the mould. From the modelling point of view, this process involves complex three-phase flow, heat transfer and solidification. In this paper, the development of a numerical model of the tilt-casting process is presented featuring several novel algorithm developments introduced into a general CFD package (PHYSICA) to model the complex dynamic interaction of the liquid metal and melting atmosphere. These developments relate to the front tracking and heat transfer representations and to a casting-specific adaptation of the turbulence model to account for an advancing solid front. Calculations have been performed for a 0.4 m long turbine blade cast in a titanium aluminide alloy using different mould designs. It is shown that the feeder/basin configuration has a crucial influence on the casting quality. The computational results are validated against actual castings and are used to support an experimental programme. Although fluid flow and heat transfer are inseparable in a casting, the emphasis in this paper will be on the fluid dynamics of mould filling and its influence on cast quality rather than heat transfer and solidification which has been reported elsewhere.KeywordsTilt-casting; Mould design; 3-D computational model; Casting process；1. IntroductionThe casting process is already many centuries old, yet many researchers are still devoted to its study. Net shape casting is very attractive from the cost point of view compared to alternative component manufacturing methods such as forging or machining. However, reproducible qualityis still an issue; the elimination of defects and control of microstructure drive research. Casting involves first the filling of the mould and subsequently the solidification of the melt. From the numerical modelling point of view, this simple sequence results in a very complex three-phase problem to simulate. A range of interactions of physical phenomena are involved including free surface fluid flow as the mould fills, heterogeneous heat transfer from the metal to the mould, solidification of the molten metal as it cools, and the development of residual stresses and deformation of the solidified component.In industry there are many variants of the casting process such as sand casting, investment casting, gravity, and low and high pressure die casting. In this study, the investment casting process, also called lost-wax casting, has been investigated. One of the advantages of this process is that it is capable of producing (near) net shape parts, which is particularly important for geometrically complex and difficult-to-machine components. This process starts with making a ceramic mould which involves three main steps: injecting wax into a die to make a replica of the component and attaching this to a pouring basin and running system; building a ceramic shell by the application of several layers of a ceramic slurry and ceramic stucco to the wax assembly; de-waxing and mould firing. The pouring of the casting is performed either simply under gravity (no control), or using a rapid centrifugal action [1] (danger of macro-segregation plus highly turbulent filling), or by suction as in counter-gravity casting (e.g. the Hitchiner process[2]), or by tilt-casting. In this study, tilt-casting was chosen in an attempt to achieve tranquil mould filling. Tilt-casting was patented in 1919 by Durville [3] and has been successfully used with sand castings[4] and aluminium die castings[5]. In the IMPRESS project [6], a novel process has been proposed and successfully developed to combine Induction Skull Melting (ISM) of reactive alloys with tilt-casting[7], [8], [9] and [10], with a particular application to the production of turbine blades in titanium aluminidealloys. As shown in Fig. 1, this is carried out inside a vacuum chamber and the mould is pre-heated in situ to avoid misruns (incomplete mould filling due to premature solidification) and mould cracking due to thermal shock.Tilt-casting process: (a) experimental equipment; (b) schematic view of the ISM crucible and mould, showing the domed shape acquired by the molten metal; (c) different stages of mould filling showing the progressive replacement of gas by the metal.The component(s) to be cast are attached to a pouring basin which also doubles as a source of metal to feed the solidification shrinkage. The components are angled on the basin to promote the progressive uni-directional flow of metal into the mould. As the metal enters the mould it displaces the gas and an escape route has to be included in the design so that the two counter-flowing streams are not mixed leading to bubbles trapped in the metal. Vents are also used to enable any trapped gas to escape. The ‘feeder’ used to connect the mould to the crucible is normally in any casting the last portion of metal to solidify, so supplying metal to the mould to counter the effects of solidification shrinkage. In tilt-casting, the feeder is also the conduit for the tranquil flow of metal into the mould and also for the unhindered escape of gas. For this reason, the fluid dynamics of the mould feeder interface merit detailed study.As well as the mould/feeder design, the production of castings involves several other key parameters, such as the metal pouring temperature, initial mould temperature, selective mould insulation and the tilt cycle timing. All these parameters have an influence on the eventual quality of the casting leading to a very large matrix of experiments. Modelling (once validated) is crucial in reducing the amount of physical experiments required. As mentioned above, the mathematical models are complex due to the fact that this is a three-phase problem with two rapidly developing phase fronts (liquid/gas and solid/liquid). In this paper, a 3-D computational model is used to simulate the tilt-casting process and to investigate the effect of the design of the basin/feeder on the flow dynamics during mould filling and eventually on casting quality.2. Experimental descriptionDetails of the experimental setup have been published elsewhere [11], but for completeness a summary description is given here. Fig. 1a shows an overall view of the equipment used to perform the casting. The Induction Skull Melting (ISM) copper crucible is installed inside a vacuum chamber. To enable rotation, it is attached to a co-axial power feed, which also allows cooling water containing ethylene glycol to be supplied to the ISM crucible and the induction coil. The coil supplies a maximum of 8 kA at a frequency of ∼6 kHz. The crucible wall is segmented, so that the induction field penetrates through the slots (by inducing eddy currents into each finger segment) to melt the charge and at the same time repel the liquid metal away from the side wall to minimise the loss of superheat. A billet of TiAl alloy is loaded into the crucible before clamping on the ceramic shell mould. The mould is surrounded by a low thermal mass split-mould heater. After evacuating the vacuum chamber, the mould is heated to the required temperature (1200 °C maximum) and the vessel back-filled with argon to a partial pressure of 20 kPa prior to melting. This pressure significantly reduces the evaporative loss of the volatile aluminium contained in the alloy. The power applied to the induction coil is increased according to a pre-determined power vs. time schedule so that a reproducible final metal temperature is achieved. At the end of melting (7–8 min), the mould heater is opened and moved away. The induction melting power is rampeddown and, simultaneously, the ISM crucible and mould are rotated by 180° using a programmable controller to transfer the metal into the mould. The mould containing the casting is held vertically as the metal solidifies and cools down.3. Mathematical model3.1. Fluid flow equationsThe modelling of the castingprocess has involved a number of complex computational techniques since there are a range of physical interactions to account for: free surface fluid flow, turbulence, heat transfer and solidification, and so on. The fluid flow dynamics of the molten metal and the gas filling the rest of the space are governed by the Navier–Stokes equations, and a 3D model is used to solve the incompressible time-dependent flow:(1)(2)where u is the fluid velocity vector; ρ is the density; μ is the fluid viscosity; Su is a source term which contains body forces (such as gravitational force, a resistive force (Darcy term) [12]) and the influence of boundaries. There is a sharp, rapidly evolving, property interface separating metal and gas regions in these equations as explained below.3.2. Free surface: counter diffusion method (CDM)One of the difficulties of the simulation arises from the fact that two fluid media are present during filling: liquid metal and resident gas and their density ratio is as high as 10,000:1. Not only does the fluid flow problem need to be solved over the domain, but the model also has to track the evolution of the interface of the two media with time. A scalar fluid marker Φ was introduced to represent the metal volume fraction in a control volume and used to track the interface of the two fluids, called the Scalar Equation Algorithm (SEA) by Pericleous et al. [14]. In a gas cell, Φ = 0; in a metal cell, Φ = 1; for a partially filled cell Φ takes on an intermediate value which the interface of the two media crosses through. The dynamics of the interface are governed by the advection equation:(3)The interface then represents a moving property discontinuity in the domain, which has to be handled carefully to avoid numerical smearing. As in [14], an accurate explicit time stepping scheme such as that by Van Leer [15] may be used to prevent smearing. However, the scheme is then limited to extremely small time steps for stability, leading to very lengthy computations. To overcome this problem, a new tracking method, the counter diffusion method (CDM) [11] and [16], was developed as a corrective mechanism to counter this ‘numerical diffusion’. Thisdiscretizes the free surface equation in a stable, fully implicit scheme which makes the computations an order of magnitude faster. The implementation assumes that an interface-normal counter diffusion flux can be defined for each internal face of the computational mesh and applied with opposite signs to elements straddling the interface as source terms for the marker variable. The equation for the flux per unit area F can be written as:(4)where C is a scaling factor, a free parameter in CDM allowing the strength of the counter diffusion action to be adjusted, and n is the unit normal vector to the face in the mesh. Of the two cells either side of the face, the one w ith the lower value of the marker ΦD becomes the donor cell while the ‘richer’ cell ΦA is the acceptor (in order to achieve the counter diffusion action). The proposed formula makes the counter diffusion action self-limiting as it is reduced to zero where the donor approaches zero (gas) and where the acceptor reaches unity (liquid). In this form, the adjustment remains conservative. Quantitative validation of CDM against other VOF type techniques is given in a later section of the paper for accuracy and efficiency.3.3. Heat transfer and solidificationHeat transfer takes place between the metal, mould and gas, and between cold and hot metal regions as the mould filling is carried out. The heat flow is computed by a transient energy conservation equation:(5)where T is the temperature; k is the thermal conductivity; cp is the specific heat (properties can be functions of the local temperature or other variables); ST is the source term which represents viscous dissipation, boundary heat transfer and latent heat contributions when a phase change occurs. For the latter, a new marker variable fL is used to represent the liquid fraction of the metal with (1 − fL) being the volume fraction of solidified metal. V oller et al. [13] used a non-linear temperature function to calculate the liquid fraction. In this study, the liquid fraction is assumed to be a linear function of the metal temperature:(6)TL is the liquidus temperature and TS is the solidus temperature.3.4. LVEL turbulence model (applied to solid moving boundaries)Even at low filling speeds, the Reynolds number is such that the flow is turbulent. The LVEL method of Spalding [17] is chosen to compute the turbulence because of its mixing-length simplicity and robustness. LVEL is an abbreviation of a distance from the nearest wall (L) and the local velocity (VEL). The approximate wall distance is solved by the Eqs. (7) and (8):(7)∇·(∇W)=-1where W is an auxiliary variable in the regions occupied by the moving fluid with boundary conditions W = 0 on all solid walls.(8)This distance and the local velocity are used in the calculation of the local Reynolds number from which the local value of the turbulent viscosity νt is obtained using a universal non-dimensional velocity profile away from the wall. The effective turbulent viscosity is then computed from the following equation:(9)where κ = 0.417 is the von Karman constant, E = 8.6 is the logarithmic law constant [17] and u+ is determined implicitly from the local Reynolds number Reloc = uL/ν with the magnitude of the local velocity u and the laminar kinematic viscosity ν[17]. The LVEL method was extended to moving solid boundaries and in particular to solidifying regions by setting W = 0 in every region that is no longer fluid and then solving Eqs. (7) and (8) at each time step.In simulating the tilt-casting process, the geometry is kept stationary and the gravitational force vector is rotated to numerically model the tilt instead of varying the coordinates of the geometry. The rotating gravitational force vector appears in the source term of Eq. (1) for the tilt-casting process. A mathematical expression relating the tilting speed to the tilting angle θ has been used. Since θ is a function of time, the variable rotation speed is adjustable to achieve tranquil filling. This technique neglects rotational forces within the fluid (centrifugal, Coriolis) since they are negligible at the slow rotation rates encountered in tilt-casting. Finally, the numerical model of the tilt-casting process and the new algorithm developments were implemented in the general CFD package (PHYSICA).4. Description of simulations4.1. Geometry, mould design and computational meshThe casting is a generic 0.4 m-long turbine blade typical of that used in an Industrial Gas Turbine. Fig. 2 shows three mould designs which comprise the blade, a feeder/basin and a cylindrical crucible. Fig. 2a incorporates a separate cube-shaped feeder that partially links the root of the blade and the basin. Fig. 2b is a variant in which the plane of the blade is rotated through 90°. In both cases, the computational mesh contains 31,535 elements and 38,718 points. Six vents are located on the platform and the shroud of the blade, as seen in Fig. 2a and b. Fig. 2c is an optimised design where the feeder and basin are combined to provide a smooth connection between the blade and the crucible. Two vents are located in the last areas to be filled to help entrapped gas to escape from the mould. Mesh of the crucible-mould assembly for the three casesinvestigated.The mesh for the last case contains 30,185 elements and 37,680 vertices. As in all the cases presented, numerical accuracy depends on mesh fineness and also the degree of orthogonality. To ensure a mostly orthogonal mesh the various components of the assembly were created separately using a structured body-fitted mesh generator and then joined using a mixture of hexahedral and tetrahedral cells. The mesh was refined as necessary in thin sections (such as the blade itself or the shroud and base plates), but not necessarily to be fine enough to resolve boundary layer details. For this reason the LVEL turbulence model was used rather than a more usual two-equation model of turbulence that relies on accurate wall function representation. The practical necessity to run in parallel with the experimental programme also limited the size of the mesh used. As with all free surface tracking algorithms, the minimum cell size determines the time step size for the stable simulations. Although the CDM method is implicit, allowing the time step to exceed the cell CFL limit, accuracy is then affected. With these restrictions, turnaround time for a complete tilt-casting cycle was possible within 24 h.As stated earlier, the feeder is necessary to minimise the solidification shrinkage porosity in the blade root. Two alternative designs have been considered: a cubic feeder with a volume to cooling surface area ratio of 14.5 mm, and a cylindrical feeder designed with better consideration of fluid dynamics during mould filling and which had a slightly lower volume to area ratio of 13.8 mm.4.2. Initial and boundary conditionsThe choice of parameters for the calculations was based on the experiments [16]. The properties of the materials used in the calculations are listed in Table 1. The initial conditions (the same as in the trials) and boundary conditions of the calculations are shown in Table 2.Table 1.Properties of the materials in this study.Ti–46Al–8Ta alloy MouldDensity (kg/m3) 5000 2200Thermal conductivity (W/(m K)) 21.6 1.6Specific heat (J/(kg K)) 1000 1000Viscosity (kg/(m s)) 0.5 ×10−60.1Liquidus temperature (°C) 1612 –Solidus temperature (°C) 1537 –Latent heat (J/kg) 355,000 100,0004.3. Tilt cycleThe molten metal in the ISM crucible is poured via the basin/feeder into the mould by rotating the assembly. A parabolic programmed cycle [16] is employed to complete the castingprocess with a total filling time of 6 s. The carefully designed cycle includes a fast rotation speed at the early stage of the mould filling to transfer the molten metal into the basin/feeder, a subsequent deceleration to a nearly zero velocity to allow most of the metal to fill the mould horizontally and to avoid forming a back wave and surface turbulence, and then the rapid completion of the filling to reduce the heat loss to the mould wall.5. Computing requirementsThe results presented here have been obtained using an Inter (R) Xeon (R) CPU E5520 2.27 GHz, 23.9 GB of RAM. For a typical mesh of 30,000 finite volume cells, each full tilt-casting simulation (real time 6 s) took approximately 15 h and 1200 time steps to complete. The CDM algorithm uses a fixed time step of 0.005 s which is at least five times larger than that used in conventional methods such as Van Leer or Donor–Acceptor. Similar computations carried out with the alternative Donor–Acceptor algorithm took typically one week to complete.The speed of execution and stability of the CDM method does not necessarily compromise accuracy. This can be demonstrated in the classic collapsing column benchmark experiment of Martin and Moyce [18] shown schematically in Fig. 3. A rectangular water column with a height of 2 m and a width of 1 m is initially confined between two vertical walls in hydrostatic equilibrium. Air is present as the outer medium. Once the confining wall is removed, the water column collapses on to the plane y = 0 under gravity and spreads out along the x direction.Fig. 3. Configuration of water column collapsing experiment.View thumbnail images The experiment was designed specifically so that it could be modelled computationally in two dimensions. Therefore, a 2D domain was used meshed into 880 cells (40 × 22).The comparison between the numerical result with CDM, the Van Leer and the popular Donor–Acceptor algorithm against the experimental data is presented in Fig. 4, where the horizontal extent of the water front and the residual height of the water column are plotted as functions of elapsed time. It can be seen that there is generally good agreement between the numerical results and the experimental data. However, although the three numerical methods match each other perfectly, there is some disagreement against the experiment when the non-dimensional time t* is greater than 1.4. It is concluded that in terms of accuracy, CDM is at least as good as the alternative explicit techniques which have been in widespread use for many years.Fig. 4. Validation of the CDM method and comparisons of the CDM against Van Leer, and donor acceptor for (a) the front position and (b) the residual height of the collapsing water column experiment of Martin and Moyce [18].As mentioned above, a feature of the CDM method is that the discretization of the free surface equation is made in a stable, fully implicit scheme which makes the computations an order of magnitude faster. Table 3 presents a comparison of CDM against the other two methods investigated, in terms of the computational efficiency. It is shown that CDM can be applied with a bigger time step than the other methods since CDM it is not limited by the Courant–Friedrichs–Levy (CFL) criterion. Furthermore, due to greater numerical stability, the number of iterations per time step is also reduced which makes the CDM simulation even faster. The first two columns in the table show that the time step for CDM can be ten times bigger than the others. The running time with the Van Leer total variation diminishing (TVD) scheme is 1.3 times longer than with CDM for the same time step, but the Van Leer scheme suffers from interface smearing. The running time of the most popular scheme for casting simulations, the donor acceptor method, is almost four times longer than that with CDM when the same time step is used. CDM is up to eight times faster (16 s vs. 132 s as shown underlined in Table 3) when the optimal time step for CDM is used.Table 3. Comparisons of the efficiency of CDM with others numerical methods.Δt1 = 0.1 s Δt1 = 0.05 s Δt1 = 0.01 sMethodN t (s) N t (s) N t (s)Van Leer Error Exceeds CFL limit 10 47Donor Acceptor Error Exceeds CFL limit 40 132CDM 20 16 15 17 5 34Notes: Δt = time step; t = running time; N = average number of iterations per time step.6. Simulations – results and discussion6.1. Effect of mould orientationCalculations with two orientations (Fig. 2a and b) for the assembly with the cubic feeder have been performed. Fig. 5 shows the mould filling progression as iso-surface plots of the free surface marker, at Ф = 0.5, at a filling time of 3.2 s. It is seen that in a design without consideration for flow behaviour, the metal is thrown into the cubic feeder in both cases in a turbulent state, becauseof the sudden change in cross-section. At any given time during filling, more metal enters the cubic feeder and less enters the blade in orientation 2, Fig. 5b, compared with orientation 1, Fig. 5a, leading to a restricted exit path for the escaping gas. For both orientations, the sudden drop at the connection between the feeder and the root of the blade leads to jetting and turbulence at the point where the metal flows from the feeder into the blade cavity.Comparison of mould filling with two orientations in contour plots of the free surface marker Ф = 0.5 at the interface, time = 3.2 s for a cubic feeder: (a) orientation 1: mould oriented at 30° to tilt axis; (b) orientation 2: long axis of the root perpendicular to the tilt plane.A later stage in the filling process is presented in Fig. 6 for the same two orientations, with the blades now filled with metal. Although both orientations display the same problems of gas mixing and turbulence caused by the two sudden steps in the feeder, it seems that orientation 1 leads to less gas mixing than orientation 2. Fig. 7 shows the 0.4 m-long turbine blade castings produced by the process. There is surface evidence of porosity at the connection between the feeder and the root of the blade on the concave sides, and this is worse for orientation 2 than for orientation 1. Radiography indicates the internal extent of this porosity. Although several factors are responsible for its formation, including the presence of a hot spot leading to an isolated liquid pool during solidification and subsequent shrinkage, the presence of trapped gas is a major contributorComparison of mould filling with two orientations in contour plots of the free surface marker Ф = 0.5 at the interface, time = 5.2 s for a cubic feeder: (a) orientation 1: mould oriented at 30° to tilt axis; (b) orientation 2: long axis of the root perpendicular to the tilt plane.Comparisons of the experimental results with two orientations: (a) orientation 1: mould oriented at 30° to tilt axis; (b) orientation 2: root axis perpendicular to the tilt plane.6.2. Effect of the mould design: cubic vs. cylindrical feederIn the above discussion, it was shown that the orientation of the blade relative to the tilt axis in Fig.2 is important, and that the sudden changes in cross-section with a cubic feeder lead to turbulent mixing of gas and liquid metal. In the following section, the effect of the feeder design on casting quality will be studied comparing two mould designs: one with a cylindrical feeder (Fig. 2c) and the other with a cubic feeder with the preferred orientation (Fig. 2a).Fig. 8 shows a comparison of the instantaneous free surface location at a filling time of 3.0 s. As can be seen, the metal is smoothly entering the blade cavity in the case of the cylindrical feeder. In contrast the metal is thrown into the cubic feeder because of the sudden change in the cross-section. The sudden drop at the connection between the feeder and the root of the bladeleads to jetting and turbulence when the metal flows from the feeder into the blade cavity. The comparison also shows that the filling of the blade with the cylindrical feeder is faster than with the cubic feeder. This phenomenon is demonstrated in Fig. 9 as well.The comparison of the mould filling with the two designs of feeder: iso-surface plots of the free surface marker Ф = 0.5 at time = 3.0 s: (a) cube feeder; (b) cylindrical feeder.Comparison of the mould filling with the two feeders: contour plots with the free surface marker Ф = 0.5 at the interface, time = 4.6 s: (a) cubic feeder; (b) cylindrical feeder.9 shows the flow progress at a later stage of the mould filling (rotation time of 4.6 s) for the two competing designs. It can be seen that the design with the cylindrical feeder and with the vertical orientation of the blade provides a better gas escape route back to the crucible (in addition to gas escaping through the vents in the mould) than the design with the cubic feeder. There are two flow restrictions in the cubic feeder design: one is the connection between the basin and the feeder and the other is the connection between the feeder and the root of the blade, both leading to a step change in cross-section. This geometric feature of the assembly causes the gas to be easily trapped in the upper corner of the root.Fig. 10 highlights the velocity vector field as the metal enters the mould in the cubic feeder design, Fig. 2a. It is seen that the metal is pushed back from the root of the blade (zoomed). The metal and the gas re-circulate in the cavity of the root. This recirculation will result in mixing of gas with the metal which presents a high risk of forming casting defects such as bubblesFig. 10. The computed velocity field and iso-surface (free surface marker Ф = 0.5 at the interface) time = 3.1 s for the cubic feeder.The computed velocity field in Fig. 11a illustrates that the gas is trapped and gas recirculation takes place in the cube feeder although some gas in the aerofoil and in the platform is slowly evacuated by the vents at the platform of the blade (zoomed). Gas recirculation leads to gas–metal mixing. This introduces a high risk of the formation of gas bubbles which are then blocked inside the casting if the superheat is not high enough to allow them time to float up before the casting solidifies. In Fig. 11b, it is shown that the cross-section at the connection of the basin with the cubic feeder is fully blocked by the metal coming from the crucible at a certain moment during the mould filling. This is the reason that gas recirculation appears in the cube feeder and the root of the blade. For the cylindrical feeder, the gas evacuation path is clear (Fig. 11c and d) and there is no danger of the gas being trapped in the upper corner of the root, especially since a vent is located at the top of the platform (see Fig. 2). Comparison of the computed velocity field and iso-surface (free surface marker Ф = 0.5 at the interface) time = 4.8 s。