Protection of Electrical System
All electrical systems have the common purpose of providing electrical energy to the utilization equipment as safely and reliably as is economically feasible .The utilization equipment then converts the electrical energy to other forms, such as mechanical, light, and heat energy .The design of the electrical energy to transmit the electrical energy to the utilization equipment must focus on two basic requirements. First, the system must be adequate to deliver to each piece of equipment the necessary energy on a continuous basis under normal conditions. Second, the system must be designed to minimize power outages and damage in the event that abnormal conditions occur on the system. The following is a list of abnormal conditions that can occur on a system and for which corrective action should be taken:
1.Overloads
2.Short circuits
3.Under voltage
4.Single phasing of three phase systems
5.Over-voltages and transient surges
6.Incorrect synchronizing of frequencies
7.Incorrect phase sequence
8.Reverse power flow
Next in order of priorities is the desirability of keeping damage to the electrical equipment to the absolute minimum so that normal operation can resume as quickly as possible .Finally it makes economic sense, especially with large system can continue to operate normally .This requirement for the least amount of shutdown of the system involves coordination of the protective devices.
The protective device has two major functions:(1) to detect an abnormal condition on that portion of the system that it is protecting and (2) to automatically and safely disconnect the faulted portion from the balance of the system .Protective devices such as fuses and most low-voltage circuit breakers combine both the detection unit and the disconnecting means in the one unit. Other types of protective
devices separate the two functions. For example, medium-and high-voltage circuit breakers normally only perform the disconnecting function. They must be used in conjunction with separate protective relays that detect the abnormal conditions and then initiate the tripping of the circuit breaker. It must be emphasized again that protective devices cannot prevent faults from occurring on the system, but can only minimize their effects.
Protective devices are rated for the following:
1.Maximum continuous voltage: This is the maximum voltage that can be continuously applied to the device without eventually causing the insulation to fail.
2.Maximum continuous current: This is the maximum load current that the device can carry continuously without the contacts or other current-carrying parts overheating.
3.Interrupting rating: This is the maximum current that the device can safely interrupt at the specified voltage.
4.Short-time current ratings:
(a)Momentary: This is the maximum rms current that the device can withstand with regard to mechanical stressing. The maximum stressing occur one half-cycle after the fault starts. This rating is necessary to ensure that the device is not physically damaged before it can operate to disconnect the faulted part of the system.
(b) Specified time: This is the maximum rms current that the device can withstand for a specified time 0.5% with regard to thermal stressing .In the case of breakers, it is sometimes necessary under severe short circuits to delay their opening for a very short period of time in order to coordinate with other devices .This rating is necessary to ensure that the breaker is not damaged by heat before it can operate to disconnect the faulted part of the system.
Protective Relaying
Protective relaying is that area of power system design concerned with minimizing service interruption and limiting damage to equipment when failures occur. The function of protective relaying is to cause the prompt removal of a
defective element from a power system .The defective element may have a short circuit or it may be operating in an abnormal manner. Protective relaying systems are designed to detect such failures or abnormal conditions quickly (commensurate with system requirements) and to open a minimum of circuit breakers to isolate the defective element. The effect of quick isolate is threefold: (1) it minimizes or prevents damage to the defective element, thus reducing the time and expense of repairs and permitting quicker restoration of the element to service; (2) it minimizes the power system; and (3) it. maximizes the power that can be transferred on power system. The second and third points are of particular significance because they indicate the important role protective relaying plays in assuring maximum service reliability and in system design. The power that can be transmitted across system without the loss of synchronism is the function of fault clearing times. It is apparent that fast fault clearing times permit a higher power transfer than longer clearing times. High-speed clearing of faults can often provide a means for achieving higher power transfers and thereby defer investment in additional transmission facilities.
A protective relaying system is based on detecting fault conditions by continuously monitoring the power system variable such as current, voltage, power, frequency, and impedance. Measuring of currents and voltage is performed by instrument transformers of the potential type (PT) or current type (CT). Instrument transformers feed the measured variables to the relay system, which in return, upon detecting a fault, commands circuit breaker (CB) to disconnect the faulted section of the system.
An electric relaying system is divided into several protective zones for generators, transformers, buses, transmission and distribution circuits, and motors. The division is such that zones are given adequate protection while keeping service interruption to a minimum. It is to be noted that each zone is overlapped to avoid unprotected (blind) areas. The connections of current transformers achieve the overlapping. The general philosophy of relay application is divide the power system into zones that can be adequately protected by suitable protective equipment and can be disconnected from the power system in a minimum amount of time and with the
least effect on the remainder of the power system. The protective relaying provided for each zone is divided into two categories: (1) primary relaying and (2) backup relaying. Primary relaying is the first line of defense when failures occur, and is connected to trip only the protective relays will operate to trip all of the breakers within that zone. If a breaker is omitted between two adjacent elements, both elements will be disconnected for a failure in either one. This latter arrangement is illustrated by the unit generator-transformer connection in the power plant. On bulk power generating and transmission systems, primary protection is designed to operate at high speed for all faults. Slower protection may be used in less important system areas but, in general, any system area will benefit by the fastest possible primary relaying.
If the fault is not cleared by the primary protection, backup relaying operates to clear the fault from the system. In general, backup relaying disconnects a greater portion of the system to isolate the fault. Backup protection is provided for possible failure in the primary both relay backup as well as breaker backup. Ideally, the backup protection should be arranged so that anything that may cause the primary protection to fail will not also cause failure of the backup protection .Moreover, the backup protection must not operate until the primary protection has been given an opportunity to function. As a result, there is time delay associated with any backup operation. When a short circuit occurs, both the primary and the backup protection start to operate. If the primary protection clears the fault, the backup protection will reset without completing its function. If the fault is not cleared by the primary protection, the backup relaying will time out and trip the necessary breakers to clear the fault from the system.
There are two forms of backup protection in common use on power system. They are remote backup and local backup.
(1)Remote backup. In remote backup relaying, faults are cleared from the
system one station away from where the failure has occurred.
(2)Local backup. In local backup relaying, faults are cleared locally in the
same station where the failure has occurred. For faults on the protected
line, both the primary and the backup relays will operate to prepare
tripping the line breaker. Relay backup may be just as fast as the front line
relays. When either of these relays operates to initiate tripping of the line
breaker, it also energizes a timer to start the breaker backup function. If
the breaker fails to cleat the fault, the line relays will remain picked up,
permitting the timer to time out and trip the necessary other breaker on
the associated bus section.
Microcomputer-based Relaying
A new development in the field of power system protection is the use of computers (usually microcomputers) for relaying. Although computers provide the same protection as that supplied by conventional relays, there are some advantages to the use of computer-based relaying is much greater than for electromechanical devices. Computer-based relaying samples the values of the current, voltage, and other items covered in the protection scheme several times a second, and by use of A/D converters, change these analog values to digital form and then send them to the computer. In the event of a fault, the computer can calculate the fault’s current values and characteristics, and settings can be changed merely by reprogramming. Computer-based relaying are also capable of locating faults, checking features can be built in and sequence of events information can be downloaded to remote computers for fast analysis of relaying operations.
Computer-based relaying system consists of subsystems with well defined functions. Although a specific subsystem may be different in some of its details, these subsystems are most likely to be incorporated in its design in some form. The processor is the center of its organization. It is responsible for the execution of relaying programs, maintenance of various timing functions, and communicating with its peripheral equipment. The Random Access Memory (ROM) or Programmable Read Only Memory (PROM) is used to store the programs permanently. In some cases the programs may execute directly from the ROM if its read time is short enough. If this is not the case, the programs must be copied from the ROM into the PAM during an initialization stage, and then the real-time execution would take place
from the RAM. The Erasable PROM (EPROM) is needed for storing certain parameters (such as the relaying settings) which may be changed from time to time, but once it is set it must remain fixed even if the power supply to the computer is interrupted.
The relaying inputs are currents and voltages -- or, to a lesser extent –digital signals indicating contact status. The analog signals must be converted to voltage signals suitable for conversion to digital form. The current and voltage signals obtained from current and volts. The current inputs must be converted to voltages by resistive shunts. As the normal current transformer secondary currents may be as high as hundreds of amperes, shunts of Digital Converter (ADC). An alternative arrangement would be to use an auxiliary current another function; that of providing electrical isolation between the main CT secondary and the computer input system. Since the digital computer can be programmed to perform several functions as long as it has the input and output signals needed for those functions. It is a simple matter to the relaying computer to do many other substation task, for example , measuring and monitoring flows and voltages in transformers and transmission lines, controlling the opening and closing of circuit breakers and switches, providing backup for other devices that have failed, are all functions that can be taken over by the relaying computer. With the program ability and communication capability, the computer-based relaying computer offers yet another possible advantage that is not easily realizable in a conventional system. This is the ability to change the relay characteristics (settings) as the system conditions warrant it. With reasonable prospects of having affordable computer-based relaying which can be dedicated to a single protection function, attention soon turned to the opportunities offered by computer-based relaying to integrate them into a substation, perhaps even a system-wide network. Integrated computer systems for substations which handle relaying, monitoring, and control tasks offer novel opportunities for improving overall system performance.
中英文资料翻译 原文： AUTOMATING THE CONTROL OF MODERN EQUIPMENT FOR STRAIGHTENING FLAT-ROLLED PRODUCTS The company Severstal’ completed the successful introduction of new in-line plate-straightening machines (PSMs) on its 2800 and 5000 mills in August 2003 [1, 2, 3]. The main design features of the machines are as follows: ●each machine is equipped with hydraulic hold-down mechanisms (to improve the dynamics and accuracy of the machine adjustments and more reliably maintain a constant gap); ●the machines have mechanisms to individually adjust each work roller with the aid of hydraulic cylinders (this broadens the range of straightening regimes that can be realized by providing a measure of control over the change in the curvature of the plate); ●each work roller is provided with its own adjustable drive (to eliminate rigid kinematic constraints between the spindles); ●the system of rollers of the PSM is enclosed in cassettes (to facilitate repairs and reduce roller replacement costs); ●the PSM has a system that can be used to adjust the machine from a nine-roller straightening scheme to a five- ●roller scheme in which the distance between the rollers is doubled (this is done to widen the range of plate thick-nesses that the machine can accomodate). Thus, the new straightening machine is a sophisticated multi-function system of mechanisms that includes a wide range of hydraulically and electrically driven components controlled by digital and analog signals. The entire complex of PSM mechanisms can be divided into two functional groups: the main group, which includes the mechanisms that partici-pate directly in the straightening operation (the hold-down mechanisms, the mechanisms that individually adjust the rollers,the mechanisms that adjust the components for different straightening regimes, the mechanism that moves the top roller of the feeder, and the main drive); the auxiliary group (which includes the cassette replacement mechanism, the
Circuit breaker 断路器 Compressed air circuit breaker is a mechanical switch equipm ent, can be i 空气压缩断路器是一种机械开关设备，能够在n normal and special conditions breaking current (such as sho rt circuit cur 正常和特殊情况下开断电流（比如说短路电流）。 rent). For example, air circuit breaker, oil circuit breaker, interf erence circ 例如空气断路器、油断路器，干扰电路的导体uit conductor for the application of the safety and reliability o f the circuit 干扰电路的导体因该安全可靠的应用于其中， breaker, current in arc from is usually divided into the followin g grades: a 电流断路器按灭弧远离通常被分为如下等级：ir switch circuit breaker, oil circuit breaker, less oil circuit break er, compr 空气开关断路器、油断路器、少油断路器、压缩空essed air circuit breaker, a degaussing of isolating switch, six s ulfur hexaf
本科毕业设计 外文文献及译文 文献、资料题目：Designing Against Fire Of Building 文献、资料来源：国道数据库 文献、资料发表（出版）日期：2008.3.25 院（部）：土木工程学院 专业：土木工程 班级：土木辅修091 姓名：武建伟 学号：2008121008 指导教师：周学军、李相云 翻译日期： 20012.6.1
外文文献: Designing Against Fire Of Buliding John Lynch ABSTRACT: This paper considers the design of buildings for fire safety. It is found that fire and the associ- ated effects on buildings is significantly different to other forms of loading such as gravity live loads, wind and earthquakes and their respective effects on the building structure. Fire events are derived from the human activities within buildings or from the malfunction of mechanical and electrical equipment provided within buildings to achieve a serviceable environment. It is therefore possible to directly influence the rate of fire starts within buildings by changing human behaviour, improved maintenance and improved design of mechanical and electrical systems. Furthermore, should a fire develops, it is possible to directly influence the resulting fire severity by the incorporation of fire safety systems such as sprinklers and to provide measures within the building to enable safer egress from the building. The ability to influence the rate of fire starts and the resulting fire severity is unique to the consideration of fire within buildings since other loads such as wind and earthquakes are directly a function of nature. The possible approaches for designing a building for fire safety are presented using an example of a multi-storey building constructed over a railway line. The design of both the transfer structure supporting the building over the railway and the levels above the transfer structure are considered in the context of current regulatory requirements. The principles and assumptions associ- ated with various approaches are discussed. 1 INTRODUCTION Other papers presented in this series consider the design of buildings for gravity loads, wind and earthquakes.The design of buildings against such load effects is to a large extent covered by engineering based standards referenced by the building regulations. This is not the case, to nearly the same extent, in the
A convection-conduction model for analysis of the freeze-thaw conditions in the surrounding rock wall of a tunnel in permafrost regions HE Chunxiong( 何春雄 )， (State Key Laboratory of Frozen Soil Engineering, Lanzhou Institute of Glaciology and Geocryology, Chinese Academy of Sciences, Lanzhou 730000, China; Department of Applied Mathematics, South China University of Technology, Guangzhou 510640, China) WU Ziwang( 吴紫汪 )and ZHU Linnan( 朱林楠 ) (State key Laboratory of Frozen Soil Engineering, Lanzhou Institute of Glaciology and Geocryology Chinese Academy of Sciences, Lanzhou 730000, China) Received February 8, 1999 Abstract Based on the analyses of fundamental meteorological and hydrogeological conditions at the site of a tunnel in the cold regions, a combined convection-conduction model for air flow in the tunnel and temperature field in the surrounding has been constructed. Using the model, the air temperature distribution in the Xiluoqi No. 2 Tunnel has been simulated numerically. The simulated results are in agreement with the data observed. Then, based on the in situ conditions of sir temperature, atmospheric pressure, wind force, hydrogeology and engineering geology, the air-temperature relationship between the temperature on the surface of the tunnel wall and the air temperature at the entry and exit of the tunnel has been obtained, and the freeze-thaw conditions at the Dabanshan Tunnel which is now under construction is predicted. Keywords: tunnel in cold regions, convective heat exchange and conduction, freeze-thaw. A number of highway and railway tunnels have been constructed in the permafrost regions and their neighboring areas in China. Since the hydrological and thermal
外文原文 Mechanical Design Abstract: A machine is a combination of mechanisms and other components which transforms, transmits. Examples are engines, turbines, vehicles, hoists, printing presses, washing machines, and movie cameras. Many of the principles and methods of design that apply to machines also apply to manufactured articles that are not true machines. The term "mechanical design" is used in a broader sense than "machine design" to include their design. the motion and structural aspects and the provisions for retention and enclosure are considerations in mechanical design. Applications occur in the field of mechanical engineering, and in other engineering fields as well, all of which require mechanical devices, such as switches, cams, valves, vessels, and mixers. Keywords: Mechanical Design mechanisms Design Process The Design Process Designing starts with a need real.Existing apparatus may need improvements in durability, efficiency, weight, speed, or cost. New apparatus may be needed to perform a function previously done by men, such as computation, assembly, or servicing. With the objective wholly or partly In the design preliminary stage, should allow to design the personnel fully to display the creativity, not each kind of restraint. Even if has had many impractical ideas, also can in the design early time, namely in front of the plan blueprint is corrected. Only then, only then does not send to stops up the innovation the mentality. Usually, must propose several sets of design proposals, then perform the comparison. Has the possibility very much in the plan which finally designated, has used certain not in plan some ideas which accepts. When the general shape and a few dimensions of the several components become
专业资料 学院： 专业：土木工程 姓名： 学号： 外文出处：Structural Systems to resist (用外文写) Lateral loads 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 抗侧向荷载的结构体系 常用的结构体系 若已测出荷载量达数千万磅重，那么在高层建筑设计中就没有多少可以进行极其复杂的构思余地了。确实，较好的高层建筑普遍具有构思简单、表现明晰的特点。 这并不是说没有进行宏观构思的余地。实际上，正是因为有了这种宏观的构思，新奇的高层建筑体系才得以发展，可能更重要的是：几年以前才出现的一些新概念在今天的技术中已经变得平常了。 如果忽略一些与建筑材料密切相关的概念不谈，高层建筑里最为常用的结构体系便可分为如下几类： 1.抗弯矩框架。 2.支撑框架，包括偏心支撑框架。 3.剪力墙，包括钢板剪力墙。 4.筒中框架。 5.筒中筒结构。 6.核心交互结构。 7. 框格体系或束筒体系。 特别是由于最近趋向于更复杂的建筑形式，同时也需要增加刚度以抵抗几力和地震力，大多数高层建筑都具有由框架、支撑构架、剪力墙和相关体系相结合而构成的体系。而且，就较高的建筑物而言，大多数都是由交互式构件组成三维陈列。 将这些构件结合起来的方法正是高层建筑设计方法的本质。其结合方式需要在考虑环境、功能和费用后再发展，以便提供促使建筑发展达到新高度的有效结构。这并
不是说富于想象力的结构设计就能够创造出伟大建筑。正相反，有许多例优美的建筑仅得到结构工程师适当的支持就被创造出来了，然而，如果没有天赋甚厚的建筑师的创造力的指导，那么，得以发展的就只能是好的结构，并非是伟大的建筑。无论如何，要想创造出高层建筑真正非凡的设计，两者都需要最好的。 虽然在文献中通常可以见到有关这七种体系的全面性讨论，但是在这里还值得进一步讨论。设计方法的本质贯穿于整个讨论。设计方法的本质贯穿于整个讨论中。 抗弯矩框架 抗弯矩框架也许是低，中高度的建筑中常用的体系，它具有线性水平构件和垂直构件在接头处基本刚接之特点。这种框架用作独立的体系，或者和其他体系结合起来使用，以便提供所需要水平荷载抵抗力。对于较高的高层建筑，可能会发现该本系不宜作为独立体系，这是因为在侧向力的作用下难以调动足够的刚度。 我们可以利用STRESS，STRUDL 或者其他大量合适的计算机程序进行结构分析。所谓的门架法分析或悬臂法分析在当今的技术中无一席之地，由于柱梁节点固有柔性，并且由于初步设计应该力求突出体系的弱点，所以在初析中使用框架的中心距尺寸设计是司空惯的。当然，在设计的后期阶段，实际地评价结点的变形很有必要。 支撑框架 支撑框架实际上刚度比抗弯矩框架强，在高层建筑中也得到更广泛的应用。这种体系以其结点处铰接或则接的线性水平构件、垂直构件和斜撑构件而具特色，它通常与其他体系共同用于较高的建筑，并且作为一种独立的体系用在低、中高度的建筑中。
毕业设计（论文） 外文文献翻译 文献、资料中文题目：供配电系统 文献、资料英文题目：POWER SUPPLY AND DISTRIBUTION SYSTEM 文献、资料来源： 文献、资料发表（出版）日期： 院（部）： 专业： 班级： 姓名： 学号： 指导教师： 翻译日期： 2017.02.14
POWER SUPPLY AND DISTRIBUTION SYSTEM ABSTRACT The basic function of the electric power system is to transport the electric power towards customers. The l0kV electric distribution net is a key point that connects the power supply with the electricity using on the industry, business and daily-life. For the electric power, allcostumers expect to pay the lowest price for the highest reliability, but don't consider that it's self-contradictory in the co-existence of economy and reliable.To improve the reliability of the power supply network, we must increase the investment cost of the network construction But, if the cost that improve the reliability of the network construction, but the investment on this kind of construction would be worthless if the reducing loss is on the power-off is less than the increasing investment on improving the reliability .Thus we find out a balance point to make the most economic,between the investment and the loss by calculating the investment on power net and the loss brought from power-off. KEYWARDS：power supply and distribution,power distribution reliability，reactive compensation,load distribution
冲压模具成型外文翻译参考文献 (文档含中英文对照即英文原文和中文翻译) 4 Sheet metal forming and blanking 4.1 Principles of die manufacture 4.1.1 Classification of dies In 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
1、 外文原文 A: Fundamentals of Single-chip Microcomputer Th e si ng le -c hi p m ic ro co mp ut er i s t he c ul mi na ti on of both t h e de ve lo pm en t o f t he d ig it al co m pu te r an d th e i n te gr at ed c i rc ui t a rg ua bl y t h e to w m os t s ig ni f ic an t i nv en ti on s o f t he 20th c e nt ur y [1]. Th es e t ow ty pe s of ar ch it ec tu re a re fo un d i n s in g le -ch i p m i cr oc om pu te r. So m e em pl oy t he spl i t pr og ra m/da ta m e mo ry o f th e H a rv ar d ar ch it ect u re , sh ow n in Fi g.3-5A -1, o th ers fo ll ow t he p h il os op hy , wi del y a da pt ed f or ge n er al -p ur po se co m pu te rs a nd m i cr op ro ce ss o r s, o f ma ki ng n o log i ca l di st in ct ion be tw ee n p r og ra m an d d at a m e mo ry a s i n t he P r in ce to n ar ch ite c tu re , sh ow n i n F ig.3-5A-2. In g en er al te r ms a s in gl e -chi p m ic ro co mp ut er i s c h ar ac te ri ze d b y t h e i nc or po ra ti on o f a ll t he un it s of a co mp uter i n to a s in gl e d ev i ce , as s ho wn in Fi g3-5A -3. Fig.3-5A-1 A Harvard type Program memory Data memory CPU Input& Output unit memory CPU Input& Output unit
PA VEMENT PROBLEMS CAUSED BY COLLAPSIBLE SUBGRADES By Sandra L. Houston,1 Associate Member, ASCE (Reviewed by the Highway Division) ABSTRACT: Problem subgrade materials consisting of collapsible soils are com- mon in arid environments, which have climatic conditions and depositional and weathering processes favorable to their formation. Included herein is a discussion of predictive techniques that use commonly available laboratory equipment and testing methods for obtaining reliable estimates of the volume change for these problem soils. A method for predicting relevant stresses and corresponding collapse strains for typical pavement subgrades is presented. Relatively simple methods of evaluating potential volume change, based on results of familiar laboratory tests, are used. INTRODUCTION When a soil is given free access to water, it may decrease in volume, increase in volume, or do nothing. A soil that increases in volume is called a swelling or expansive soil, and a soil that decreases in volume is called a collapsible soil. The amount of volume change that occurs depends on the soil type and structure, the initial soil density, the imposed stress state, and the degree and extent of wetting. Subgrade materials comprised of soils that change volume upon wetting have caused distress to highways since the be- ginning of the professional practice and have cost many millions of dollars in roadway repairs. The prediction of the volume changes that may occur in the field is the first step in making an economic decision for dealing with these problem subgrade materials. Each project will have different design considerations, economic con- straints, and risk factors that will have to be taken into account. However, with a reliable method for making volume change predictions, the best design relative to the subgrade soils becomes a matter of economic comparison, and a much more rational design approach may be made. For example, typical techniques for dealing with expansive clays include: (1) In situ treatments with substances such as lime, cement, or fly-ash; (2) seepage barriers and/ or drainage systems; or (3) a computing of the serviceability loss and a mod- ification of the design to "accept" the anticipated expansion. In order to make the most economical decision, the amount of volume change (especially non- uniform volume change) must be accurately estimated, and the degree of road roughness evaluated from these data. Similarly, alternative design techniques are available for any roadway problem. The emphasis here will be placed on presenting economical and simple methods for: (1) Determining whether the subgrade materials are collapsible; and (2) estimating the amount of volume change that is likely to occur in the 'Asst. Prof., Ctr. for Advanced Res. in Transp., Arizona State Univ., Tempe, AZ 85287. Note. Discussion open until April 1, 1989. To extend the closing date one month,
The development of plastic mould China's industrial plastic moulds from the start to now, after more than half a century, there has been great development, mold levels have been greatly enhanced. Mould has been at large can produce 48-inch big-screen color TV Molded Case injection mold, 6.5 kg capacity washing machine full of plastic molds, as well as the overall car bumpers and dashboards, and other plastic mould precision plastic molds, the camera is capable of producing plastic mould , multi-cavity mold small modulus gear and molding mold. --Such as Tianjin and Yantai days Electrical Co., Ltd Polaris IK Co. manufactured multi-cavity mold VCD and DVD gear, the gear production of such size precision plastic parts, coaxial, beating requirements have reached a similar foreign the level of product, but also the application of the latest gear design software to correct contraction as a result of the molding profile error to the standard involute requirements. Production can only 0.08 mm thickness of a two-cavity mold and the air Cup difficulty of plastic doors and windows out of high modulus, and so on. Model cavity injection molding manufacturing accuracy of 0.02 to 0.05 mm, surface roughness Ra0.2 μ m, mold quality, and significantly increase life expectancy, non-hardening steel mould life up to 10~ 30 million, hardening steel form up to 50 ~ 10 million times, shorten the delivery time than before, but still higher than abroad,and the gap between a specific data table. Process, the multi-material plastic molding die, efficient multicolor injection mould, inserts exchange structure and core pulling Stripping the innovative design has also made great progress. Gas-assisted injection molding, the use of more mature technologies, such as Qingdao Hisense Co., Ltd., Tianjin factory communications and broadcasting companies, such as mold manufacturers succeeded in 29 ~ 34-inch TV thick-walled shell, as well as some parts on the use of gas-assisted mould technology Some manufacturers also use the C-MOLD gas-assisted software and achieved better results. Prescott, such as Shanghai, such as the new company will provide users with gas-assisted molding equipment and technology. Began promoting hot runner mold, and some plants use rate of more than 20 percent, the general heat-thermal hot runner, or device, a small number of units with the world's advanced level of rigorous hot runner-needle device, a small number of units with World advanced level of rigorous needle-hot runner mould. However, the use of hot runner overall rate of less than 10%, with overseas compared to 50 ~ 80%, the gap larger. In the manufacturing technology, CAD / CAM / CAE technology on the level of application of a new level to the enterprise for the production of household appliances representatives have introduced a considerable number of CAD / CAM systems, such as the United States EDS UG Ⅱ,