计算机在模具设计中的应用-外文翻译本科学位.doc

毕业设计(论文)外文资料翻译

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外文出处：Michael Thielen.Plastics Pocket
Power Series,2001.
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附件1：外文资料翻译译文
计算机在模具设计中的应用
　　CAD一词有时用来指计算机辅助设计，有时用来指计算机辅助绘图，实际上，它既可表达上述两个概念之一，也可同时兼具这两个概念，设计人员有时会既用它设计又用它绘图。
　　CAD计算机辅助设计是指用计算机及外设简化设计过程、提高设计质量。CAD 计算机绘图是指用计算机和外设（如打印机、数字化仪）来产生设计过程的文件和图样,包括草图、加工图、零件清单及设计计算。
　　无论是计算机辅助设计还是辅助绘图，一套CAD 系统基本由三个部分组成：硬件，软件和用户。典型CAD 系统的硬件部分包括处理器、显示器、键盘、数字化仪和绘图仪；软件部分包括能实现设计和绘图功能的程序；用户指的是用这些软、硬件简化设计过程、提高设计质峨的设计人员。
　　图形显示是第一步，从而可将设计与计算机真正结合起来，接下来是用绘图仪画出图形。随着20 世纪60 年代早期数字化平板仪的发明，我们今天所知的CAD 硬件开始成型，很快计算机绘图软件随之得以发展。
　　早期的CAD 系统庞大、笨重且昂贵．因为太贵了，只有大公司才用得起．在20 世纪60 年代末，CAD 被认为有在模具设计中应用的潜力和意义但不实用的革新。但是，随着20 世纪70 年代硅芯片的引入，计算机开始在图形设计领域发挥作用。
　　硅晶片上的集成电路使得组装起来的计算机与电视机一样大小．。这种“迷你”小型机具有大型计算机的全部功能，但却小得多也相当便宜，很快又出现了更小的被称为微机的计算机。
　　20 世纪70 年代CAD 软硬件技术有了长足的发展，以至于在20 世纪80 年代初，研发与销售CAD 系统已成为一个飞速增长的产业。同时CAD 已由最初的新颖但不实用变成为今天的一项重要发明，到了1980 年，已有从微机、小型机到大型计算机用的多种CAD 系统。
计算机集成制造CIM 指与一个目标产品（这里以模具为例）设计和制造过程相关的所有部门的电子数据处理EDP 的集成，就信息技术而言，是联系计算机辅助设计CAD 、计算机辅助生产CAP 、计算机辅助制造CAM 、计算机辅助质量保证CAQ 和产品计划进度安排PPS （如图1 ）的纽带。这就意味着和产品有关的所有信息交换是连续无间断的，由集成电子数据处理计算机提供通讯链接。在CIM 结构模块中，CAM 占主导地位，借助CAM , 可将用CAD 研发的理论产品转化为真实有用的模具。
图1 实现CIM系统所用的CAD,CAP,CAM,CAQ和PPS
　　A ．计算机在注塑模具加工中的应用
　　CAM 的目标是：尽可能不用其他中间步骤（如不需要模型复制）就可生产出模具部件，也就是从计算机工作站开始加工操作。
实施CIM 意义上的CAM 所需的先决条件包括：CAD 、通讯接口、生产操作中转换产品信息所需的软件程序及硬件设备（如图2 所示）。
B . CAD 在制品图绘制中的应用
　　CAD 是指在显示器（电脑屏幕）上进行计算机辅助设计。先是设计人员（一般是产品设计人员）用计算机软件辅助绘制产品图，然后对产品，主要是其可视表面进行修改，直至其功能和外观设计都满足客户要求为止。

图2 模具生产工序
对于那些外形决定产品性能的塑料制品，如汽车保险杠，产品设计并不仅限在屏幕上进行，其研制从投标过程就开始了，竞标的设计者们先把各自准备好的石膏模型展示给汽车制造的管理部门，由其从中选择一个，接着要对所选的石膏模型测取各种型值点，然后把这些数据传到CAD 系统中，至此，产品设计人员才可用这些数据在屏幕上开始设计。借助于软件程序，将离散的点云拟合成3 一D 曲面，尖角光滑过渡，反复拟合修整直至得到满意的结果。
　　接下来在屏幕上把产品的曲面数据经由加工程序转换成3 一D 原始模型，这样生成的原始模型就可置人表示整体汽车的立体模型中了。在该设计阶段，最初负责石膏模型设计的人员通常不会对模型做大的改动，做完最后的修改，设计才被认可核准。
　　此时的模型已完全数字化，也就是说，探针扫描原始模型表面，（获得的）数据被电子化储存。一旦生成这种形式的数据，产品设计就完成了。此时计算机软件可用计算机语言描述产品，可对其进行修改、复制，如果有合适的接口还可方便地与其他计算机系统进行数据交换。
　　C ．接口
　　产品设计一般由模具制造商的客户承担，如汽车生产厂商要进行产品的计算机辅助设计，负责模具制造的厂商要能接收其数据．这就要求二者使用相同的计算机系统，或者所用机器接口要相兼容，以便数据从客户端（如汽车生产商）传送给模具制造商，并且要保证数据能在汽车生产商的CAD 部门内顺利交换。
　　接口按操作规则可分为两大类：一类是直接偶合接口（系统特定接口）；另一类是带有前、后里处理单元的独立于系统的接口。
　　直接偶合接口：原则上讲，期望一个计算机系统能够提供和另一个计算机系统直接的数据交换必须有两个程序：其中一个从另外一台计算机系统读数据并转化为自己的系统格式，另一个用来转换自己的数据并写成其他电脑识别的格式，这就是直接偶合。
　　独立系统接口：市场上已经有独立于系统的接口，有了这些接口，CAD / CAM 软件系统和系统版本基本不依赖硬件及操作系统，这种接口也需要两个程序：
　　① 写程序能把其他系统的数据转换成与系统无关的标准形式，并以文件形式记录下来（即前置处理程序）。
　　② 读程序能读取与系统无关的标准文件，并转换为用户自身的格式（即后置处理程序）。利用这些程序，用户系统就能将数据传送到支持该接口标准的其他任何计算机系统中，常用的与系统无关的接口有以下几种：
　　VDAFS ，这种接口能精确转换曲线和曲面信息（三维几何）。但尺寸、文字、视图及其他二维图素无法通过VDAFS ( 1986 DIN 标准VDA / VDMA 66301 ）进行交换，要在德国和欧洲使用．
　　IGES 是最早使用的主要用于二维数据交换的接口之一，较新的IGES 版本也可用来转换三维信息。主要在美国使用。
　　SET 接口主要用于汽车和飞机工业上，只在法国使用。
　　尽管接口技术在不断发展，也经过了15 年的应用，数据丢失现象依然普遍存在。当数据传送出现这种情况时，图纸就会再次作为传递信息的媒介被使用。
　　当前努力的目标是将上述标准结合起来．形成一个通用系统（STEP ) ，这种系统可以兼容各种接口技术，从而实现所有产品数据的无缝转换连接。目前，STEP 仍处于研究阶段。
　　接口还为单个计算机系统提供通讯手段，如果没有正确的接口配笼，极有可能由于选错软件造成同一公司内的CAD 和CAM 部门之间没办法通讯，这样会造成接口处数据文件丢失，导致产品表征不完全。数据传输必定被完全终止，或者丢失的数据必须进人合适的计算机系统重新获得。
D ．软件
随着数据交换技术的兴起，市场上出现了一大批软件供应商，使得在一家公司选择应用软件差不多同彩票中奖一样困难。然而，在随后的发展中，只有少数软件系统可以通过合适的接妇建立自身和其他软件系统的联系，软件功能需求的满足由最终用户的目标决定。供应商提供的软件包或多或少地拥有用户友好的界面，有助于帮助用户完成特定的任务，如产品设计（CAD ）、生产规划（CAP ）、加工程序编制（CAM ）等。
　　知名的机械设计软件供应商有Altium , Autodesk , Cadkey , Hewlett 一Packard , Interg - raph , McS 和ziegler 一Informatics 。很明显选择哪种软件不能仅看其可以实现何种功能，还要重点考虑图形的表达、能否或该不该显示二维或三维图形、对硬件有无限制，可能用到的接口及软件价格等因素。
　　E . CAD 模其设计
　　一旦用户将设计好的制品通过合适的接口传给模具制造商，模具设计人员就可依据制品设计模具。设计人员决定模具尺寸、需不需要滑动部件（滑块、推杆）、冷却管道的布局和浇口位里等与制品几何形状相关的所有因素。模具设计的所有细节都被存储在计算机中，可随时被生产部门或计划调度部门调用。

附件2：外文原文（复印件）
The computer in die design
The term CAD is alternately used to mean computer aided desing and computer dided drafting.Actually it can mean either one or both of these concepts,and the tool designed will have ccasion to in both forms.
CAD computer dided design means using the computer and peripheral devices t simplify and enhance the design process.CAD computer aided drafting means using the computer and peripheral devices to produce the documentation and graphics for the design process.This documentation usually includes such things as preliminary drawings,working drawings,parts lists,and design calculations.
A CAD system,whether taken to mean computer aided design system or computer aided drafting system,consists of three basic components:hardware,software,users.The hardware compoents of a typical CAD system include a processor,a system display,a keyboard,a disgitizer,and a piotter.The software component of a CAD system consists of the programs which allow it to perform desgn and drafting functions.The user is the tool designer who user the hardware and software to simplify and enhance the design process.
Graphics displays represented the frist real step toward bringing the worlds of tool design dad the computer together.The plotters depicted in Figure,represented the next step.With the advent of the digitizing tabiet in the early 1960’s,CAD hardware as we know it today began to takeshape.The development of computer graphics software follow soon after these hardware developments.
Early cad system were large,cumbersome,and expensive,in fact that only the largest companies could afford them.During the late 1960’s CADwas looked on as an interesting,but impractical novelty that had only limited potential in tool design applications.However,with the introduction of the silicon chip during the 1970’s,computers began to take their place in the world of tool design.
Intergratedcircuits on silion chips allowed full scale computed to be packaged in small consoles no larger than Tvsets.these”minicomputers”had dll of the characteristics of full scale computers,but they were smaller and considerably less expensive.Even smaller computers called microcomputers followed soon after.
The 1970’s saw continued advances in CAD hardware and software technology.So much that by the beginning of the advance in CAD system had become a growth industry.Also,CAD has been transformed form its status of impractical novelty to its new status s one of the most important inventions to date.By 1980,numerous CAD systems were available ranging in size form microcomputer systems to large minicomputer and mainframe system.
Computerintegrated manufacturing (CIM) represents integration of electronic data processing (EDP) into all departments associated with planning and production of an object (in this case,a mold):the linking of computeraided design (CAD),Computeraided production (CAP),conputeraided manufacturing (CAM),computeraided qualityassurance (CAQ)，production planning and schedulng (PPS)(see Fig 1) in terms of information technolgy.This means uninterrupted exchange of all information pertinent to a product.The communications link is provided by the integrated EDP computer.Major importantance ithin the CIM structure is assigned to CAM.Conversion of the theoretical priuct developed in CAD into the practical reality o mold occurs via CAM.

Fig.1 Linking of CAD.CAP.CAM.CAQand PPS to implement CIM
A.Use of Comoutes for Machining of an Injection Mold
The objective of CAM is to produce,f possible,sections of a mold without intermediate steps (e.g..,elimination of copy patterns),i.e.,by initidting machining operations from the computer workstation.
Prerequisites for CAM in the sense of CIM include CAD,the communications interface,and appropriate software and hardware for converting product information in the required production operations (see sequence diagram,Fig2).

Fig.2 Mold Producting Sequence
B.CAD for Part Construction
CAD means computeraided design on a monitor.The designer,initially the part designer,draw a product with the aid of the computer software.The part,primarily its visible surface,is modified until both function and appearance (design) of the part satisfy the requirements.
For plasic parts with character determining product properties,e.g. automobile bumper fascias,product design does not occur on the creen only.Product development takes place in a kink of bidding proces in which several stylists (designer)frist prepare plaster patterns,which are then presented to the management of the automotive manufacture in a competition.The management makes a selection and agrees on a design model.Next,measurements are taken at various points on the piaster pattern of the select model,and these data are transferred to the CAD system.Using these data,the part designer can now start designing the part on the screen.With the aid of software programs,the designerbegins to connect the individual points to form 3D surfaces.Sharp transitions are smoothed and the product design is refined until the desired result is achieved.
In a subsequent step,the work on the screen is converted into a 3D master pattern through creation of a machining program form the surface data of the part.The master partern thus produced can now be attached to a cubing model that representa the entire automobile.At this phase in the development of the product the stylist,who was originally responsible for the plastr pattern,will generally allow minor changes to be made.After hese final modifications are made,the design is approved.

The approved master pattern is now completely digitized,i.e.,a stylus scans the surface of the pattern,and part designer can complete the work.The software now describes the product in computer language.The design can be modified,duplicated,and exchanged freely with other computer systems as long as suitable interfaces are available.
C.Interfaces
Responsibility for part design is assumed almost entirely by the cutomer of the moldmakeer.A computer aide part design that originates form the customer (e.g.,automotive manufacturer) must be accessible to be company that will produce the mold.these require either the same computer system or a compatible computer interface so that the data can be transferred from the customer (automotive manufacturer) to the mold maker.It must also be possible to exchange data among the CAD department of the automotive manufacturer.
Interfaces can be grouped into two basic types (operating principle):frist,interfaces based on the direct couple principle (system specific interface);second,he system independent interface with paeand post paocesing units.
Direct Coupler Interface:In principle,a comouter system that is expected to priovide direct data exchang with any other computer system must have tow programs:one program that reads the data from the other computer and transfers it into own system,and another program that converts its data and writes it in the data frmat of the other computer.Such an interface is called a direct coupler.
System Independent Interface:Interfaces that are system independent have became established in the market.With these,CAD\CAM system and system versions are essentially independent of the hardware and operating system.Such an interface must contain two programs:
①A write program that converts elements from the other computer system to the system-independent standard and writes them to a file (preprocessing);
②A read program that reads the data which are in a system-independent format, and converts theminto the computer users own format (postporcessing).
By means of these programs, the users own system can transfer data to all other computer systems that support this interface standard. The following system-independent interfaces are in use:
VDAFS This interface readily converts representations of curves and surface without loss of accuracy (3-D geometries). Dimensions, text, views, and other 2-D drawing elements cannot be exchanged via VDAFS (1986 DIN Standard VDA/VDMA 66301). Use: Germany and Europe.
IGES This is one of the first useful data interfaces for exchange primarily 2-D formats. With more recent IGES versions, it is also possible to exchange 3-D information. Use:USA.
SET This interface is important in the automotive and aircraft industries (Airbus) in France but isnot used outside France.
Despite the continued development of interface systems and more than 15 years of application, data loss is still not uncommon. In many cases, such difficulties during data transfer mean that the drawing (part drawing) once again becomes the medium by which information (data) must be conveyed.
Current efforts aim to combine the above¡ªmentioned standards into a national system (Standard for the Exchanged of Product Model data, or STEP) and in this way unite development of the various interfaces in order to facilitate the seamless transfer of all product-defining data. At present, STEP is still in the development phase.
The interface also provides for communication between the individual computer systems. It is quite possible to have no connection between, for instance, the CAD and CAM departments within the same company because the wrong software was selected without the correct interface configuration. Data files can be lost at the:iiiterface in thus way so that the product is represented incompletely. In this case, data transfer must be terminated completely or the lost information must be reentered into the appopriate computer system.
D. Software
With the introduction of data processing, a flood of software suppliers appeared on the market so that the selection of software for use within a company almost began to resemble a lottery. In the course of further development, however, only a few systems have established themselves, and these can communicate with one another via appropriate interfaces. The requirements to be satisfied by the software result from the objectives of the end user. Suitable software packages are available from the suppliers in a more or less user-friendly form to help accomplish a specific task, depending on whether a product is to be designed (CAD), production is to be scheduled (CAP), or machining operations are to be programmed (CAM).
Well-known software supplies from the mechanical standpoint include Altium, Autodesk, Cadkey, Hewlett-Packard, Intergraph, MCS and Ziegler-Informatics. At the same time, it is obvious that selection of a system cannot be based on these functions alone. A critical evaluation requires consideration drawings need to be prepared, and whether 2-D or 3-D geometric data can or should be displayed, not to mention the hardware, possible interfaces (very important), and the system price
E. CAD Mold Design
As soon as the customer has transferred the part design to the moldmaker via the appropriate interface, the mold designer can design theiold around thepart. The designer determines the dimension (size) of the mold, - ,vhetler moving parts (slides, lifters) are require