University of Huddersfield Repository
Unver, Ertu and Mavromihales, Mike
Design and Development of an interactive 3D CNC Computer Aided Learning Program
Original Citation
Unver, Ertu and Mavromihales, Mike (2001) Design and Development of an interactive 3D CNC Computer Aided Learning Program. In: 17th International Conference on CAD/CAM, Robotics and Factories of Future, 10-12 July 2001, Durban, South Africa.
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DESIGN AND DEVELOPMENT OF AN INTERACTIVE 3D CNC COMPUTER
AIDED LEARNING (CAL) PROGRAM
E Unver1, M Mavromihales2
1- School of Design Technology
2- School of Mechanical Engineering and Manufacturing Systems
University of Huddersfield, Queensgate, Huddersfield HD1 3DH, West Yorkshire, UK e.unver@https://www.doczj.com/doc/6e1116341.html,
KEYWORDS: Virtual Reality, Manufacturing Simulation, CNC, CAD/CAM ABSTRACT
The UK Government has committed itself to establishing the University for Industry (UFI), an umbrella organization which will create new markets for education and stimulate change in provision to take advantage of new learning methods.
In 1998, a partnership of organizations (universities, colleges and companies) led by The Virtual College submitted a project proposal under ADAPT-UFI to develop on-line and/or CD-based digital interactive teaching material - Multimedia Learning for Industry (MLI). The nine universities / colleges have collectively produced a bid document in which each put forward a project title with a budget of ￡100k. As part of the MLI project, and due to extensive internal knowledge of CAD/CAM and CNC machine tools, it was decided to develop a 3D interactive CNC training software program for technician and undergraduate level.
Although 3D CAD and CAM software is widely available for industry, this concentrates on producing part programs and machining. We are unaware of any 3D CNC software developed for college and university education that teaches the set-up of the machine parameters. This paper describes the development of a 3D interactive CAL program for training in CNC. It also briefly reviews trends and policy for Communication & Information Technology (C&IT) and CAL.
1. INTRODUCTION
Virtual reality or CNC simulation software can be constructed by using VRML tools with limited functionality or with full functionality using 3D CAD software or programming languages such as Visual Basic, C++ and Delphi. 3D models are created through 3D design software such as Solidworks, 3D Studio, Alias Wavefront, and ProEngineer. The creation of 3D data via a CAD package and then exporting the data as a Virtual Reality (VR) model provides the simplest way of modelling a virtual environment with required graphics features. However, this provides no dynamic simulation of the imported data. The data can not therefore be used with an internet browser with a relevant VRML player for interaction. It is possible however, to zoom rotate and perform other basic functions. Third party VRML programs or VR Application Programming Interface (API), Java or its Scripting language are used to make these 3D models interact. The VRML language specification contains a collection of commands for creating a variety of simple objects, vertices, faces and script which is the link used to generate appropriate motion.
Although creating a VR environment is much simpler than using a software development language to interact with 3D models, it still requires extensive learning of individual
toolkits and programming skills before the virtual world can be created and often results in a virtual environment with insufficient geometric accuracy[6,7].
Also using VRML language has other limitations:
It is necessary to use an Internet browser and VRML player
Interaction can be very slow depending on the VR file size
Interaction is also limited to certain movements and lighting effects
Another method of creating virtual simulation of the machining process is to use either high or low level programming languages such as C++ and manipulate the 3D data created by one of the 3D design packages. It is also possible to create the 3D model with the development software. Although this takes a lot longer than basic VR programming, it provides for a more flexible, robust and a faster method. In developing 3D software, programmers are faced with the choice of either developing their own 3D kernel or leasing a proprietary kernel.
This paper outlines the case for more effective use of C&IT in education and focuses on design and development of an efficient approach to constructing virtual manufacturing environments, compares 3D simulation methods, the pros and cons of used kernels and covers details of the developed 3D simulation program for CNC machining operations.
2.A CASE FOR (COMMUNICATION & INFORMATION TECHNOLOGIES) C&IT AND COMPUTER AIDED LEARNING (CAL) IN HIGHER EDUCATION Several reports [1,2,3] have recognised the use of C&IT as a means of improving long-term quality and flexibility of higher education and its management. In the short term, implementation requires investmen t in time, thought and resources. The Government?s White Paper on Higher Education recommends that all higher educational institutions should have in place a C&IT strategy. Although the UK enjoys a good IT infrastructure, the challenges lie in how to harness that infrastructure, together with high quality teaching materials and management, to meet the needs of students and others. Generally speaking, the use of new technologies for learning and teaching is still at a developmental stage. As has been recommended [2] and is expected, within the next 5 years all students will have their own desktop computer and certainly have open access to Networked Desktop Computers on campus. The extensive application of C&IT as part of the learning environment in inevitable.
Despite the potential of C&IT and some major national initiatives, there remains little widespread use of computer-based learning materials. This is partly due to a reluctance of some academics to use teaching materials created by others. The task of creating ones own CAL material can take considerable time. This can entail the redesign of programmes to integrate computer-based materials and the sorting through limited availability of good materials. Developing good teaching-based learning material is expensive. It therefore makes sound advice to develop materials and systems that can be used by large numbers of students.
Although it has been estimated that up to ten percent of expenditure in higher education goes to C&IT there is relatively little application in learning, teaching and assessment [2]. There is scope for much greater potential for CAL that in future will be driven partly by the impetus for enhanced quality of learning for students in an era of attenuated staff to student ratios.
Computer-based programmes, such as tutorials, simulations, exercises, learning tools and educational games can be highly interactive and provide activities that students need to develop their understanding of others? ideas and the articulation of their own.
As with the application of the program described in this paper, through using computer-based learning materials, students can receive immediate feedback to assist with learning
complex concepts. Through CAL students can often be provided with the opportunity to generate many exercises as a way of supplementing tutor-marked assignments for certain topics. In our application, students can avoid making costly errors that would be possible whilst learning (Computer Numerical Control) CNC programming on an expensive real machine tool. Students can repeat simulations as many times as necessary to enhance their understanding of the procedure and outcomes.
2.1 OTHER BENEFITS OF CAL
Other benefits of using CAL include:
Students can take greater control of their studying through the use of the technology. They can assess materials in their own time, set their own pace and explore materials as it suits them.
CAL can be used for computer-based text, graphics, animations and simple tests that students can use to develop understanding of certain subject matter. This can offer various levels of sophistication with high-end applications containing video or allowing the student to interact with simulations. The penetration of this relatively new technology into engineering teaching is low. Although a number of …off the shelf? programs are available for customisation to individual curriculum needs, the process is demanding on time. Some such commercially available programs include,
LearnOR
Question Mark
Blackboard
CVU
The nature of required customisation can be as that described in the proceeding sections.
Here a Kernel was used to produce the graphical interface required to generate a virtual
machine tool along with animation.
This forms only part of the CNC Part Programming process. The complete process is multi-facetted and will include a range of processes from graphical part definition in a detailed form, to component production and machine re-setting. To cover the entirety of the process using a combination of text and animation material, several programs and much customisation are required.
3. DEVELOPMENT OF INTERACTIVE 3D CNC SOFTWARE
3.1 THE USE OF KERNELS FOR 3D APPLICATIONS
Inside every 3D modelling application, there is a hidden engine called a geometric modelling kernel. The kernel consists of a library of core functions, designed to handle the details of creating and manipulating model geometry and topology. When a CAD user executes a command, the CAD software translates the command into a set of fundamental geometric calculations. These calculations are computed by the kernel, the result of which are passed back to the CAD application in preparation for output to the graphics engine for display. Kernels simplify the requirements of advanced maths necessary to develop a 3D design software [5].
Use of Kernels is not limited to CAD applications, indeed many other opportunities lie outside the boundaries of traditional CAD/CAM including such as applied to virtual reality, scientific modelling and laser scanning. Most traditional high-end systems have some kind of hybrid modelling capability. Hybrid solid modellers are an adaptation of the standard Boundary Representation (B-Rep) modeller that uses multiple data structures. For example, they can use 3D wireframe structure for rapid geometry creation and modification, B-Rep structures for geometric and topological integrity, facets for fast graphical display, and a history tree for greater ease in design modification. The
generally better known 3D kernels are Spatial Technology?s ACIS and Unigraphic?s Parasolid. Other Kernels include Ricoh?s DesignBase, Matra -Datavision?s Cas.cade, Thinkernel?s think3, Varimetrix Corporation?s UPG2, Solid Modelling Solutions?s Smlib and Lattice Technology?s Lattice Kernel. Owning or renting kernel technology is a business decision made by each application developer. If the application developer owns their kernel technology, the developer has control of the kernel technology without dependence on a third party, this leads to greater control over content and timing of new releases.
It is important that the operating system supports and is compatible with the kernel. Most kernels are supported by Windows NT and Unix platforms such as Sun Solaris, SGI IRIX, IBM AIX, HP HP/UX.
3.2 CNC SIMULATION APPLICATIONS
There are numerous suppliers of CNC simulation software used for simulating the machining process and generating part programs that are post-processed into machine specific cutter paths. Such packages can usually import geometry such as 2D lines and text, surfaces and solid models. Many of these are standalone Computer Assisted Part Programming (CAPP) systems whilst others form part of a vendor?s suite of CAD/CAM applications. The former relies heavily on data translation through a neutral format such as IGES, DXF, STEP or a dedicated direct translator (which can be more reliable in data exchange, though less commonly found). In the latter transfer of geometrical data from CAD to CAM, using the vendor?s proprietary software should be a seamless process. Examples of the former (standalone CAPP programs) include, AlphaCAM by LICOM, PEPS by CAMTEK, MasterCAM. PTC, SDRC, Unigraphics Solutions, Dessault Systems amongst many other providers, supply turnkey systems with bundles of their own CAD/CAM software.
3.3 TRAINING STUDENTS IN COMPUTER NUMERICAL CONTROL (CNC) Prior to either becoming familiar with a CAPP application or using a CNC machine tool,
students should be familiar with certain basic concepts. These should include:
Dimensional co-ordinate system definition (X, Y and Z for both positive and negative directions) –
depending on machine tool configuration
Rotary and secondary axis definition (A, B,C and UVW), if applicable
Machine?s home position
- machine datum position
Workpiece co-ordinate system (c omponent?s zero datum)
Machine?s working envelope (maximum machining area)
The application of multiple tooling and the concept of tool offsets
Figure 1
Figure 1 shows a screen layout from a commercially available package of Virtual Reality (VR) and CNC software. This application is supplied by Denford Ltd who were collaborators during the development of our 3D CNC simulation machine control software. The example in figure 1 shows a screen …shot? CNC simulation of a desktop microrouter, a machine used in educational establishments for prototyping. This program includes a training module with limited VR interaction.
3.4 DEVELOPMENT OF THE APPLICATION CODE
How do you choose a programming language for power hungry applications such as CAD or visualisation? Visual Basic, Delphi, Java and C++ are programming languages used on windows platform for software development. Advantages and disadvantages are offered in using different programming languages for the same development work. Some programming languages will result in faster running of the developed application. It is generally recognised [4] that assembly language, or machine code provide for faster end results from the program. C++ is a popular programming language which may contain machine code and high level programming code. Other software such as Visual Basic may run slower. Java is also a popular language particularly for internet programming but needs to be used either with a browser or an interpreter. It therefore runs very much slower when compared to C++ programming language.
ACIS 3D Building Blox and Visual Basic Programming software has been used to develop our software. In this software the user can view, rotate, manipulate and carry out CNC simulation using relevant commands. The 3D models were created in Solidworks 3D design software and then converted to the ACIS *.sat format. Building Blox has enabled us to read the data from the 3D Modelling system, SolidWorks. Low spec hardware can be utilised for running the developed program.
Figure 2Figure 3
Beyond support for viewing, querying and manipulating ACIS 3D models, this reduced version of the ACIS kernel includes a basic set of model design features. While these won't help to build sophisticated CAD applications, they are good enough to build simple modelling applications, sketching, reading 3D data from other sources and parts recognition for programming. Other low cost application areas can include virtual product design, sales support, training, technical support and simulation.
3.5 SOFTWARE FEATURES AND FUNCTIONALITY
Figures 2 to 10 show screen …stills? of the developed software. Figures 2,3,4 and 5 show the designed CNC turning centre. The developed software allows us to zoom, rotate and split the screen into four whilst in either wireframe or shaded mode.
3.6 THE SIMULATION PROCESS
With reference to figure 2, using the created menu the user can select individual machine components that are part of the control process such as the door, chuck, turret, part catcher, and tool carousel (in CNC milling). The door offers options for either open or close and similarly the part catcher offers options for activation (on or off). If the user wishes to select the chuck as a device, the miscellaneous word address control codes M03 and M04 buttons can be selected for simulation of spindle rotation. The turret can be rotated for the selection of the appropriate tool. Whilst the turret is selected, the control codes G00 and G01 from the linear interpolation menu can be used to change the tool position in either rapid or feed rate mode. In figure 3 and 4, the part catcher and turret are selected and can be simulated with the menu provided. Figure 5 shows the turning centre in a four part screen format for shaded and wireframe viewing of the machine.
Figures 6 and 7 show a CNC milling centre. Another control menu is created to simulate and move the components of this machine with a similar format to that of the turning centre. Figures 8 and 9 show, a simplified display version of the CNC turning cutting process. This basic turning is a lot faster for tool movements. Users can view the operation from different angles such as top left, from the front or in perspective or simply maximising the size of the screen for the simulation. The control menu that is situated on the right can simulate G00 and G01 linear interpolation movements with specified feedrate. G02 clockwise and counter-clockwise simulation is incorporated within the software as are many other slide movement codes (G codes). The user has to enter the coordinates for the circular interpolation. If the wrong information is entered a Figure 5 Figure 4
Figure 7 Figure 6
warning is returned to the user for correction of the entered information. Current tool positional co-ordinate data can be seen at the bottom right corner of the screen. The spindle or slide (depending on which is applicable to the machine) can be sent to its home location. For visual effect a red arc is drawn where a circular movement of the tool is expected. The tool follows these co-ordinates.
Figures 9 and 10 show the basic CNC milling process. Similar to the basic turning process, the tool or table can be positioned using G00, G01 and G02. The tool positional co-ordinates here can also be shown at the bottom corner of the control menu.
Students are expected to learn the basic coordinate system and the functions used in CNC programming. Prior to using the real CNC machine, students are required to spend enough time with this software, by using it to simulate various functions. What is expected of them is to understand the basic functions of CNC and retain in their minds basic common control codes. Additional code is added to the interface offering the user the option of creating further basic prismatic objects such as a cube, cylinder or cone. Other features on offer to the user include the saving of specific screens once other 3D objects have been created or imported from other sources.
3.7 FUTURE DEVELOPMENTS OF THE SOFTWARE
More features are planned to be added to the CNC simulation software. This will include creating part programs direct from the machine motion simulation process, adding other ISO word address M & G codes for the simulation such as start and stop of coolant and incremental and absolute coordinate systems. The second phase of the project has started and this includes the use of the Parasolid kernel and Visual C++ programming language. We can therefore expect faster loading time for the models and also faster changes in Figure 9 Figure 8 Figure 10 Figure 11
display from shaded objects to wireframe representation or from single to multiple views and most importantly faster movements of graphics simulation.
The software has been designed for popular CNC machine configuration and operations as found in most shop floor environments. Adaptation of the software for other CNC processes such as Electro Discharge Machining (EDM), laser and other profile cutting, punch/press machines is possible.
4. CONCLUSIONS
Development of 3D CNC simulation software for specific machine tools associated with particular processes has been proven possible by the development of this CAL program. What has also been shown is that various machine components that are required to be part of the control process can also be simultaneously simulated. This will enable trainees at either undergraduate or technician level to be trained without the need to use real machines from the outset. This reduces the chances of costly errors. The advantages of using CNC simulation software also include:
?In industrial situations training can commence prior to the purchase or delivery of the machine therefore less time is spent at a later time when the machine is required to be productive.
?Provides for a more cost effective means of training groups of students where limited CNC machine tools are available. This is usually the case in educational institutions. Such software applications are in line with current trends in the development of CAL materials and as recommended in the Government?s white paper for the futu re use of C&IT in higher education.
REFERENCES
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Inventory management Inventory Control On the so-called "inventory control", many people will interpret it as a "storage management", which is actually a big distortion. The traditional narrow view, mainly for warehouse inventory control of materials for inventory, data processing, storage, distribution, etc., through the implementation of anti-corrosion, temperature and humidity control means, to make the custody of the physical inventory to maintain optimum purposes. This is just a form of inventory control, or can be defined as the physical inventory control. How, then, from a broad perspective to understand inventory control? Inventory control should be related to the company's financial and operational objectives, in particular operating cash flow by optimizing the entire demand and supply chain management processes (DSCM), a reasonable set of ERP control strategy, and supported by appropriate information processing tools, tools to achieved in ensuring the timely delivery of the premise, as far as possible to reduce inventory levels, reducing inventory and obsolescence, the risk of devaluation. In this sense, the physical inventory control to achieve financial goals is just a means to control the entire inventory or just a necessary part; from the perspective of organizational functions, physical inventory control, warehouse management is mainly the responsibility of The broad inventory control is the demand and supply chain management, and the whole company's responsibility. Why until now many people's understanding of inventory control, limited physical inventory control? The following two reasons can not be ignored: First, our enterprises do not attach importance to inventory control. Especially those who benefit relatively good business, as long as there is money on the few people to consider the problem of inventory turnover. Inventory control is simply interpreted as warehouse management, unless the time to spend money, it may have been to see the inventory problem, and see the results are often very simple procurement to buy more, or did not do warehouse departments . Second, ERP misleading. Invoicing software is simple audacity to call it ERP, companies on their so-called ERP can reduce the number of inventory, inventory control, seems to rely on their small software can get. Even as SAP, BAAN ERP world, the field of
机械设计 摘要：机器是由机械装置和其它组件组成的。它是一种用来转换或传递能量的装置，例如：发动机、涡轮机、车辆、起重机、印刷机、洗衣机、照相机和摄影机等。许多原则和设计方法不但适用于机器的设计，也适用于非机器的设计。术语中的“机械装置设计”的含义要比“机械设计”的含义更为广泛一些，机械装置设计包括机械设计。在分析运动及设计结构时，要把产品外型以及以后的保养也要考虑在机械设计中。在机械工程领域中，以及其它工程领域中，所有这些都需要机械设备，比如：开关、凸轮、阀门、船舶以及搅拌机等。 关键词：设计流程设计规则机械设计 设计流程 设计开始之前就要想到机器的实际性，现存的机器需要在耐用性、效率、重量、速度，或者成本上得到改善。新的机器必需具有以前机器所能执行的功能。 在设计的初始阶段，应该允许设计人员充分发挥创造性，不要受到任何约束。即使产生了许多不切实际的想法，也会在设计的早期，即在绘制图纸之前被改正掉。只有这样，才不致于阻断创新的思路。通常,还要提出几套设计方案，然后加以比较。很有可能在这个计划最后决定中,使用了某些不在计划之内的一些设想。 一般的当外型特点和组件部分的尺寸特点分析得透彻时，就可以全面的设计和分析。接着还要客观的分析机器性能的优越性，以及它的安全、重量、耐用性，并且竞争力的成本也要考虑在分析结果之内。每一个至关重要的部分要优化它的比例和尺寸，同时也要保持与其它组成部分相协调。 也要选择原材料和处理原材料的方法。通过力学原理来分析和实现这些重要的特性，如那些静态反应的能量和摩擦力的最佳利用，像动力惯性、加速动力和能量；包括弹性材料的强度、应力和刚度等材料的物理特性，以及流体润滑和驱动器的流体力学。设计的过程是重复和合作的过程，无论是正式或非正式的进行，对设计者来说每个阶段都很重要。 最后，以图样为设计的标准，并建立将来的模型。如果它的测试是符合事先要
附：外文翻译 外文原文： Fundamentals of Mechanical Design Mechanical design means the design of things and systems of a mechanical nature—machines, products, structures, devices, and instruments. For the most part mechanical design utilizes mathematics, the materials sciences, and the engineering-mechanics sciences. The total design process is of interest to us. How does it begin? Does the engineer simply sit down at his desk with a blank sheet of paper? And, as he jots down some ideas, what happens next? What factors influence or control the decisions which have to be made? Finally, then, how does this design process end? Sometimes, but not always, design begins when an engineer recognizes a need and decides to do something about it. Recognition of the need and phrasing it in so many words often constitute a highly creative act because the need may be only a vague discontent, a feeling of uneasiness, of a sensing that something is not right. The need is usually not evident at all. For example, the need to do something about a food-packaging machine may be indicated by the noise level, by the variations in package weight, and by slight but perceptible variations in the quality of the packaging or wrap. There is a distinct difference between the statement of the need and the identification of the problem. Which follows this statement? The problem is more specific. If the need is for cleaner air, the problem might be that of reducing the dust discharge from power-plant stacks, or reducing the quantity of irritants from automotive exhausts. Definition of the problem must include all the specifications for the thing that is to be designed. The specifications are the input and output quantities, the characteristics of the space the thing must occupy and all the limitations on t hese quantities. We can regard the thing to be designed as something in a black box. In this case we must specify the inputs and outputs of the box together with their characteristics and limitations. The specifications define the cost, the number to be manufactured, the expected life, the range, the operating temperature, and the reliability. There are many implied specifications which result either from the designer's particular environment or from the nature of the problem itself. The manufacturing processes which are available, together with the facilities of a certain plant, constitute restrictions on a designer's freedom, and hence are a part of the implied specifications. A small plant, for instance, may not own cold-working machinery. Knowing this, the designer selects other metal-processing methods which can be performed in the plant. The labor skills available and the competitive situation also constitute implied specifications. After the problem has been defined and a set of written and implied specifications has been obtained, the next step in design is the synthesis of an optimum solution. Now synthesis cannot take place without both analysis and optimization because the system under design must be analyzed to determine whether the performance complies with the specifications. The design is an iterative process in which we proceed through several steps, evaluate the results, and then return to an earlier phase of the procedure. Thus we may synthesize several components of a system, analyze and optimize them, and return to synthesis to see what effect this has on the remaining parts of the system. Both analysis and optimization require that we construct or devise abstract models of the system which will admit some form of mathematical analysis. We call these models
外文翻译 英文原文 Belt Conveying Systems Development of driving system Among the methods of material conveying employed，belt conveyors play a very important part in the reliable carrying of material over long distances at competitive cost．Conveyor systems have become larger and more complex and drive systems have also been going through a process of evolution and will continue to do so．Nowadays，bigger belts require more power and have brought the need for larger individual drives as well as multiple drives such as 3 drives of 750 kW for one belt(this is the case for the conveyor drives in Chengzhuang Mine)．The ability to control drive acceleration torque is critical to belt conveyors’performance．An efficient drive system should be able to provide smooth，soft starts while maintaining belt tensions within the specified safe limits．For load sharing on multiple drives．torque and speed control are also important considerations in the drive system’s design. Due to the advances in conveyor drive control technology，at present many more reliable．Cost-effective and performance-driven conveyor drive systems covering a wide range of power are available for customers’ choices[1]. 1 Analysis on conveyor drive technologies 1．1 Direct drives Full-voltage starters．With a full-voltage starter design，the conveyor head shaft is direct-coupled to the motor through the gear drive．Direct full-voltage starters are adequate for relatively low-power, simple-profile conveyors．With direct fu11-voltage starters．no control is provided for various conveyor loads and．depending on the ratio between fu11-and no-1oad power requirements，empty starting times can be three or four times faster than full load．The maintenance-free starting system is simple，low-cost and very reliable．However, they cannot control starting torque and maximum stall torque；therefore．they are
英语毕业论文引用和参考文献格式 英语专业毕业论文引用和参考文献格式采用APA格式及规范。 一、文中夹注格式 英语学位论文引用别人的观点、方法、言论必须注明出处，注明出处时使用括号夹注的方法（一般不使用脚注或者尾注），且一般应在正文后面的参考文献中列出。关于夹注，采用APA格式。 （一）引用整篇文献的观点 引用整篇文献（即全书或全文）观点时有两种情况： 1.作者的姓氏在正文中没有出现，如：CharlotteandEmilyBrontewerepolaropposites,notonlyintheirpersonalitiesbutinthe irsourcesofinspirationforwriting(Taylor,1990). 2.作者的姓氏已在正文同一句中出现，如：TaylorclaimsthatCharlotteandEmilyBrontewerepolaropposites,notonlyintheirperso nalitiesbutintheirsourcesofinspirationforwriting(1990). 3.如果作者的姓氏和文献出版年份均已在正文同一句中出现，按APA的规范不需使用括号夹注，如： Ina1990article,TaylorclaimsthatCharlotteandEmilyBrontewerepolaropposites,noto nlyintheirpersonalitiesbutintheirsourcesofinspirationforwriting. 4.在英文撰写的论文中引用中文着作或者期刊，括号夹注中只需用汉语拼音标明作者的姓氏，不得使用汉字，如：(Zhang,2005) （二）引用文献中具体观点或文字 引用文献中某一具体观点或文字时必须注明该观点或者该段文字出现的页码出版年份，没有页码是文献引用不规范的表现。 1.引用一位作者的文献 （1）引用内容在一页内，如： EmilyBronte“expressedincreasinghostilityfortheworldofhumanrelationships,whet hersexualorsocial”(Taylor,1988：11). （2）引用内容在多页上，如： Newmark(1988：39-40)notesthreecharacteristicallyexpressivetext-types:(a)seriousimaginativel iterature注意在这些例子中引文超过一页时的页码标记方法：APA的规范是(1988,。 假若作者的姓氏已在正文同一句中出现，则不需要在括号夹注中重复，如：TaylorwritesthatEmilyBronte“expressedincreasinghostilityfortheworldofhumanre lationships,whethersexualorsocial”(1988：11).
(文档含英文原文和中文翻译) 中英文资料外文翻译 Fundamentals Of Machinery Design This introductory chapter is a general survey of machinery design．First it presents the definition and major role of machinery design，the relationship between machinery
and its components．Then it gives an overview of machinery design as a fundamental course and outlines a general procedure of machinery design followed by all the engineers．Finally, it lists the contents of the course and the primary goals to be achieved． 1．1 The role of machinery design Machinery design is to formulate all engineering plan．Engineering in essence is to utilize the existing resources and natural law to benefit humanity．As a major segment of engineerin，machinery design involves a range of disciplines in materials，mechanics，heat，flow，control，electronics and production．Although many high technologies are computerized and automated，and are rapidly merged into Our daily life，machines are indispensable for various special work that is difficult or impracticable to be carried out by human．Moreover，machinery can significantly improve efficiency and quality of production，which is crucial in current competitive global market． In the modern industrialized world，the wealth and living standards of a nation are closely linked with their capabilities to design and manufacture engineering products．It can be claimed that the advancement of machinery design and manufacturing can remarkable promote the overall level of a country’s industrialization．Those nations，who do not perform well in design and manufacture fields，are not competitive in world markets．It is evident that several countries that used to be leaders in the design and manufacturing sectors until the l 960s and the 1 970s had，by the l990s，slipped back and lost their leadership．On the contrary, our Country is rapidly picking up her position in manufacturing industry since the l 9 80s and is playing a more and more vital role in the global market．To accelerate such an industrializing process of our country, highly skilled design engineers having extensive knowledge and expertise are needed．That is why the course of machinery design is of great significance for students of engineering． The course of machinery design is considerable different from those background subjects in science and mathematics．For many students，it is perhaps one of their basic professional engineering courses concerned with obtaining solutions to practical problem s．Definitely these solutions must clearly represent an understanding of the underlying science，usually such an understanding may not be sufficient，empirical knowledge or engineering judgement has to be also involved．Furthermore，due to be professional nature of this subject，most design problems may not have one right solution．Nevertheless it is achievable to determine a better design from all feasible solutions． 1．2 Machinery and components A state-of-the-art machine may encompass all or part of mechanical，electrical，control，sensor，monitoring and lubricating sub—systems．In
Manufacturing Engineering and Technology—Machining Serope kalpakjian；Steven R.Schmid 机械工业出版社2004年3月第1版 20.9 MACHINABILITY The machinability of a material usually defined in terms of four factors: 1、Surface finish and integrity of the machined part; 2、Tool life obtained; 3、Force and power requirements; 4、Chip control. Thus, good machinability good surface finish and integrity, long tool life, and low force And power requirements. As for chip control, long and thin (stringy) cured chips, if not broken up, can severely interfere with the cutting operation by becoming entangled in the cutting zone. Because of the complex nature of cutting operations, it is difficult to establish relationships that quantitatively define the machinability of a material. In manufacturing plants, tool life and surface roughness are generally considered to be the most important factors in machinability. Although not used much any more, approximate machinability ratings are available in the example below. 20.9.1 Machinability Of Steels Because steels are among the most important engineering materials (as noted in Chapter 5), their machinability has been studied extensively. The machinability of steels has been mainly improved by adding lead and sulfur to obtain so-called free-machining steels. Resulfurized and Rephosphorized steels. Sulfur in steels forms manganese sulfide inclusions (second-phase particles), which act as stress raisers in the primary shear zone. As a result, the chips produced break up easily and are small; this improves machinability. The size, shape, distribution, and concentration of these inclusions significantly influence machinability. Elements such as tellurium and selenium, which are both chemically similar to sulfur, act as inclusion modifiers in
Int J Interact Des Manuf(2011)5:103–117 DOI10.1007/s12008-011-0119-7 ORIGINAL PAPER Benchmarking of virtual reality performance in mechanics education Maura Mengoni·Michele Germani· Margherita Peruzzini Received:27April2011/Accepted:29April2011/Published online:27May2011 ?Springer-Verlag2011 Abstract The paper explores the potentialities of virtual reality(VR)to improve the learning process of mechanical product design.It is focused on the definition of a proper experimental VR-based set-up whose performance matches mechanical design learning purposes,such as assemblability and tolerances prescription.The method consists of two main activities:VR technologies benchmarking based on sensory feedback and evaluation of how VR tools impact on learning curves.In order to quantify the performance of the technol-ogy,an experimental protocol is de?ned and an testing plan is set.Evaluation parameters are divided into performance and usability metrics to distinguish between the cognitive and technical aspects of the learning process.The experi-mental VR-based set up is tested on students in mechanical engineering through the application of the protocol. Keywords Mechanical product design·Virtual reality·Experimental protocol·Learning curve· Mechanics education 1Introduction Modern society is dominated by continuous scienti?c and technical developments.Specialization has become one of the most important enablers for industrial improvement.As a result,nowadays education is more and more job-oriented and technical education is assuming greater importance.In this context both university and industry are collaborating to create high professional competencies.The?rst disseminates M.Mengoni(B)·M.Germani·M.Peruzzini Department of Mechanical Engineering, Polytechnic University of Marche, Via Brecce Bianche,60131Ancona,Italy e-mail:m.mengoni@univpm.it knowledge and innovative methods while the second pro-vides a practical background for general principles training. The main problem deals with the effort and time required to improve technical learning,while market competitiveness forces companies to demand young and high-quali?ed engi-neers in short time.Therefore,the entire educational process needs to be fast and ef?cient.Novel information technolo-gies(IT)and emerging virtual reality(VR)systems provide a possible answer to the above-mentioned questions.Some of the most important issues,in mechanical design?eld,are the investigation of such technologies potentialities and the evaluation of achievable bene?ts in terms of product design learning effectiveness and quality.While IT has been deeply explored in distance education,i.e.e-learning,VR still rep-resents a novelty. VR refers to an immersive environment that allows pow-erful visualization and direct manipulation of virtual objects. It is widely used for several engineering applications as it provides novel human computer interfaces to interact with digital mock-ups.The close connection between industry and education represents the starting point of this research. Instead of traditional teaching methods,virtual technolo-gies can simultaneously stimulate the senses of vision by providing stereoscopic imaging views and complex spatial effects,of touch,hearing and motion by respectively adopt-ing haptic,sound and motion devices.These can improve the learning process in respect with traditional teaching meth-ods and tools.The observation of students interpreting two-dimensional drawings highlighted several dif?culties:the impact evaluation of geometric and dimensional tolerances chains,the detection of functional and assembly errors,the recognition of right design solutions and the choice of the proper manufacturing operations.These limitations force tutors to seek for innovative technologies able to improve students’perception.