外文翻译注塑模具自动装配造型

毕业设计(论文)外文资料翻译系部： 机械系工程系 专 业： 机械工程及自动化 姓 名： 学 号： 外文出处：The International Joumal Of Advanced Manufacturing Technology 附 件： 1.外文资料翻译译文；2.外文原文。指导教师评语：译文基本能表达原文思想，语句较流畅，条理较清晰，专业用语翻译基本准确，基本符合中文习惯，整体翻译质量一般。 签名： 年 月 日附件1：外文资料翻译译文注塑模具自动装配造型X. G. Ye, J. Y. H. Fuh and K. S. Lee机械和生产工程部，新加坡国立大学，新加坡注射模是一种由与塑料制品有关的和与制品无关的零部件两大部分组成的机械装置。本文提出了（有关）注射模装配造型的两个主要观点，即描述了在计算机上进行注射模装配以及确定装配中与制品无关的零部件的方向和位置的方法，提出了一个基于特征和面向对象的表达式以描述注射模等级装配关系，该论述要求并允许设计者除了考虑零部件的外观形状和位置外，还要明确知道什么部份最重要和为什么。因此，它为设计者进行装配设计（DFA）提供了一个机会。同样地，为了根据装配状态推断出装配体中装配对象的结构，一种简化的特征几何学方法也诞生了。在提出的表达式和简化特征几何学的基础上，进一步深入探讨了自动装配造型的方法。关键字：装配造型；基于特征；注射模；面向对象。1、简介注射成型是生产塑料模具产品最重要的工艺。需要用到的两种装备是：注射成型机和注射模。现在常用的注射成型机即所谓的通用机，在一定尺寸范围内，可以用于不同形状的各种塑料模型中，但注射模的设计就必须随塑料制品的变化而变化。模型的几何因素不同，它们的构造也就不同。注射模的主要任务是把塑料熔体制成塑料制品的最终形状，这个过程是由型芯、型腔、镶件、滑块等与塑料制品有关的零部件完成的，它们是直接构成塑料件形状及尺寸的各种零件，因此，这些零件称为成型零件。（在下文，制品指塑料模具制品，部件指注射模的零部件。）除了注射成型外，注射模还必须完成分配熔体、冷却，开模，传输、引导运动等任务，而完成这些任务的注射模组件在结构和形状上往往都是相似的，它们的结构和形状并不取决于塑料模具，而是取决于塑料制品。图1显示了注射模的结构组成。 成型零件的设计从塑料制品中分离了出来。近几年，CAD/CAM技术已经成功的应用到成型零件的设计上。成型零件的形状的自动化生成也引起了很多研究者的兴趣，不过很少有人在其上付诸实践，虽然它也象结构零件一样重要。现在，模具工业在应用计算机辅助设计系统设计成型零件和注射成型机时，遇到了两个主要困难。第一，在一个模具装置中，通常都包括有一百多个成型零部件，而这些零部件又相互联系，相互限制。对于设计者来说，确定好这些零部件的正确位置是很费时间的。第二，在很多时候，模具设计者已想象出工件的真实形状，例如螺丝，转盘和销钉，但是CAD系统只能用于另一种信息的操作。这就需要设计者将他们的想法转化成CAD系统能接受的信息(例如线，面或者实体等)。因此，为了解决这两个问题，很有必要发展一种用于注射模的自动装配成型系统。在此篇文章里，主要讲述了两个观点：即成型零部件和模具在计算机上的防真装配以及确定零部件在模具中的结构和位置。这篇文章概括了关于注塑成型的相关研究，并对注射成型机有一个完整的阐述。通过举例一个注射模的自动装配造型，提出一种简化的几何学符号法，用于确定注射模具零部件的结构和位置。2、相关研究在各种领域的研究中，装配造型已成为一门学科，就像运动学、人工智能学、模拟几何学一样。Libardi作了一个关于装配造型的调查。据称，很多研究人员已经开始用图表分析模型会议拓扑。在这个图里，各个元件由节点组成的，再将这些点依次连接成线段。然而这些变化矩阵并没有紧紧的连在一起，这将严重影响整体的结构，即，当其中某一部分移动了，其他部分并不能做出相应的移动。Lee and Gossard开发了一种新的系统，支持包含更多的关于零部件的基本信息的一种分级的装配数据结构，就像在各元件间的“装配特征”。变化矩阵自动从实际的线段间的联系得到，但是这个分级的拓扑模型只能有效地代表“部分”的关系。自动判别装配组件的结构意味着设计者可避免直接指定变化的矩阵，而且，当它的参考零部件的尺寸和位置被修改的时候，它的位置也将随之改变。现在有三种技术可以推断组件在模具中的位置和结构：反复数值技术,象征代数学技术，以及象征几何学技术。Lee and Gossard提出一项从空间关系计算每个组成元件的位置和方向的反复数值技术。他们的理论由三步组成：产生条件方程式，降低方程式数量，解答方程式。方程式有：16个满足未知条件的方程式，18个满足已知条件的方程式，6个满足各个矩阵的方程式以及另外的两个满足旋转元件的方程式。通常方程式的数量超过变量的数量时，应该想办法去除多余的方程式。牛顿迭代法常用来解决这种方程式。不过这种方法存在两种缺点：第一，它太依赖初始解；第二：反复的数值技术在解决空间内不能分清不同的根。因此，在一个完全的空间关系问题上，有可能解出来的结果在数学理论上有效，但实际上却是行不通的。Ambler和Popplestone提议分别计算每个零部件的旋转量和转变量以确定它们之间的空间关系，而解出的每个零部件的6个变量(3个转变量和3旋转量)要和它们的空间关系一致。这种方法要求大量的编程和计算，才能用可解的形式重写有关的方程式。此外，它不能保证每次都能求出结果，特别是当方程式不能被以可解答的形式重写时。为了能确定出满足一套几何学限制条件的刚体的位置与方向，Kramer开发了一种特征几何学方法。通过产生一连串满足逐渐增长的限制条件的动作推断其几何特征，这样将减少物体的自由度数。Kramer使用的基本参考实体称为一个标识，由一个点和两正交轴构成。标识间的7个限制条件（coincident, in-line, in-plane, parallelFz,offsetFz, offsetFx and helical)都被定了义。对于一个包括独立元件、相互约束的标识和不变的标识的问题来说，可以用动作分析法来解决问题，它将一步一步地最后求出物体的最终的几何构造。在确定物体构造的每一个阶段，自由度分析将决定什么动作能提供满足限制物体未加限制部位的自由度。然后计算该动作怎样能进一步降低物体的自由度数。在每个阶段的最后，给隐喻的装配计划加上合适的一步。根据Shah和Rogers的分析，Kramer的理论代表了注射模具最显著的发展，他的特征几何学方法能解出全部的限制条件。和反复的数值技术相比，他的这种方法更具吸引力。不过要实行这种方法，需要大量的编程。现在虽然已有很多研究者开始研究注射成型机，但仍很少有学者将注意力放在注射模设计上。Kruth开发了一个注射模的设计支援系统。这个系统通过高级的模具对象(零部件和特征)支持注射模的成型设计。因为系统是在AUTOCAD的基础上设计的，因此它只适于线和简单的实体模型操作。3、注射模装配概述主要讲述了关于注射模自动装配造型的两个方面：注射模在电脑上的防真装配和确定结构零件在装配中的位置和方向。在这个部分，我们基于特征和面向对象论述了注射模装配。注射模在电脑上的防真装配包含着注射模零部件在结构上和空间上的联系。这种防真必须支持所有给定零部件的装配、在相互关联的零部件间进行变动以及整体上的操作。而且防真装配也必须满足设计者的下列要求：1） 支持能表达出模具设计者实体造型想象的高级对象。2）成型防真应该有象现实一样的操作功能，就如装入和干扰检查。为了满足这些要求，可用一个基于特征和面向对象的分级模型来代替注射模。这样便将模型分成许多部分，反过来由多段模型和独立部分组成。因此，一个分级的模型最适合于描述各组成部分之间的结构关系。一级表明一个装配顺序，另外，一个分级的模型还能说明一个部分相对于另一个部分的确定位置。与直观的固体模型操作相比，面向特征设计允许设计者在抽象上进行操作。它可以通过一最小套参数快速列出模型的特征、尺寸以及其方位。此外，由于特征模型的数据结构在几何实体上的联系，设计者更容易更改设计。如果没有这些特征，设计者在构造固体模型几何特征时就必须考虑到所有需要的细节。而且面向特征的防真为设计者提供了更高级的成型对象。例如，模具设计者想象出一个浇口的实体形状，电脑就能将这个浇口造型出来。面向对象造型法是一种参照实物的概念去设计模型的新思维方式。基本的图素是能够将数据库和单一图素的动作联系起来的对象。面向对象的造型对理解问题并且设计程序和数据库是很有用的。此外，面向对象的装配体呈现方式使得“子”对象能继承其“父”对象的信息变得更容易。外文原文（复印件）Automated Assembly Modelling for Plastic Injection MouldsX. G. Ye, J. Y. H. Fuh and K. S. LeeDepartment of Mechanical and Production Engineering, National University of Singapore, SingaporeAn injection mould is a mechanical assembly that consists of product-dependent parts and product-independent parts. Thispaper addresses the two key issues of assembly modellingfor injection moulds, namely, representing an injection mouldassembly in a computer and determining the position andorientation of a product-independent part in an assembly. Afeature-based and object-oriented representation is proposedto represent the hierarchical assembly of injection moulds.This representation requires and permits a designer to thinkbeyond the mere shape of a part and state explicitly whatportions of a part are important and why. Thus, it providesan opportunity for designers to design for assembly (DFA). Asimplified symbolic geometric approach is also presented toinfer the configurations of assembly objects in an assemblyaccording to the mating conditions. Based on the proposedrepresentation and the simplified symbolic geometric approach,automatic assembly modelling is further discussed.Keywords: Assembly modelling; Feature-based; Injectionmoulds; Object-oriented1. IntroductionInjection moulding is the most important process for manufacturingplastic moulded products. The necessary equipment consistsof two main elements, the injection moulding machineand the injection mould. The injection moulding machines usedtoday are so-called universal machines, onto which variousmoulds for plastic parts with different geometries can bemounted, within certain dimension limits, but the injectionmould design has to change with plastic products. For differentmoulding geometries, different mould configurations are usuallynecessary. The primary task of an injection mould is to shapethe molten material into the final shape of the plastic product.This task is fulfilled by the cavity system that consists of core,cavity, inserts, and slider/lifter heads. The geometrical shapes and sizes of a cavity system are determined directly by theplastic moulded product, so all components of a cavity systemare called product-dependent parts. (Hereinafter, product refersto a plastic moulded product, part refers to the component ofan injection mould.) Besides the primary task of shaping theproduct, an injection mould has also to fulfil a number oftasks such as the distribution of melt, cooling the moltenmaterial, ejection of the moulded product, transmitting motion,guiding, and aligning the mould halves. The functional partsto fulfil these tasks are usually similar in structure and geometricalshape for different injection moulds. Their structuresand geometrical shapes are independent of the plastic mouldedproducts, but their sizes can be changed according to theplastic products. Therefore, it can be concluded that an injectionmould is actually a mechanical assembly that consists ofproduct-dependent parts and product-independent parts. Figure1 shows the assembly structure of an injection mould.The design of a product-dependent part is based on extractingthe geometry from the plastic product. In recent years,CAD/CAM technology has been successfully used to helpmould designers to design the product-dependent parts. The automatic generation of the geometrical shape for a productdependentpart from the plastic product has also attracted alot of research interest 1,2. However, little work has beencarried out on the assembly modelling of injection moulds,although it is as important as the design of product-dependentparts. The mould industry is facing the following two difficultieswhen use a CAD system to design product-independentparts and the whole assembly of an injection mould. First,there are usually around one hundred product-independent partsin a mould set, and these parts are associated with each otherwith different kinds of constraints. It is time-consuming forthe designer to orient and position the components in anassembly. Secondly, while mould designers, most of the time,think on the level of real-world objects, such as screws, plates,and pins, the CAD system uses a totally different level ofgeometrical objects. As a result, high-level object-oriented ideashave to be translated to low-level CAD entities such as lines,surfaces, or solids. Therefore, it is necessary to develop anautomatic assembly modelling system for injection moulds tosolve these two problems. In this paper, we address the followingtwo key issues for automatic assembly modelling: representinga product-independent part and a mould assembly ina computer; and determining the position and orientation of acomponent part in an assembly.This paper gives a brief review of related research inassembly modelling, and presents an integrated representationfor the injection mould assembly. A simplified geometric symbolicmethod is proposed to determine the position and orientationof a part in the mould assembly. An example of automaticassembly modelling of an injection mould is illustrated. 2. Related ResearchAssembly modelling has been the subject of research in diversefields, such as, kinematics, AI, and geometric modelling. Libardiet al. 3 compiled a research review of assembly modelling.They reported that many researchers had used graphstructures to model assembly topology. In this graph scheme,the components are represented by nodes, and transformationmatrices are attached to arcs. However, the transformation matrices are not coupled together, which seriously affects the transformation procedure, i.e. if a subassembly is moved, all its constituent parts do not move correspondingly. Lee and Gossard 4 developed a system that supported a hierarchical assembly data structure containing more basic information about assemblies such as “mating feature” between the components. The transformation matrices are derived automatically from the associations of virtual links, but this hierarchical topology model represents only “part-of” relations effectively.Automatically inferring the configuration of components in an assembly means that designers can avoid specifying the transformation matrices directly. Moreover, the position of a component will change whenever the size and position of its reference component are modified. There exist three techniques to infer the position and orientation of a component in theassembly: iterative numerical technique, symbolic algebraic technique, and symbolic geometric technique. Lee and Gossard 5 proposed an iterative numerical technique to compute the location and orientation of each component from the spatial relationships. Their method consists of three steps: generation of the constraint equations, reducing the number of equations, and solving the equations. There are 16 equations for “against” condition, 18 equations for “fit” condition, 6 property equations for each matrix, and 2 additional equations for a rotational part. Usually the number of equations exceeds the number of variables, so a method must be devised to remove the redundant equations. The NewtonRaphson iteration algorithm is used to solve the equations. This technique has two disadvantages:first, the solution is heavily dependent on the initial solution; secondly, the iterative numerical technique cannot distinguish between different roots in the solution space. Therefore, it is possible, in a purely spatial relationship problem, that a mathematically valid, but physically unfeasible, solution can be obtained. Ambler and Popplestone 6 suggested a method of computing the required rotation and translation for each component to satisfy the spatial relationships between the components inan assembly. Six variables (three translations and three rotations) for each component are solved to be consistent with the spatial relationships. This method requires a vast amount of programming and computation to rewrite related equations in a solvable format. Also, it does not guarantee a solution every time, especially when the equation cannot be rewrittenin solvable forms.Kramer 7 developed a symbolic geometric approach for determining the positions and orientations of rigid bodies that satisfy a set of geometric constraints. Reasoning about the geometric bodies is performed symbolically by generating a sequence of actions to satisfy each constraint incrementally, which results in the reduction of the objects available degrees of freedom (DOF). The fundamental reference entity used by Kramer is called a “marker”, that is a point and two orthogonal axes. Seven constraints (coincident, in-line, in-plane, parallelFz, offsetFz, offsetFx and helical) between markers are defined. For a problem involving a single object and constraints between markers on that body, and markers which have invariant attributes, action analysis 7 is used to obtain a solution. Action analysis decides the final configuration of a geometric object, step by step. At each step in solving the object configuration, degrees of freedom analysis decides what action will satisfy one of the bodys as yet unsatisfied constraints, given the available degrees of freedom. It then calculates how that action further reduces the bodys degrees of freedom. At the end of each step, one appropriate action is added to the metaphorical assembly plan. According to Shah and Rogers 8, Kramers work represents the most significant development for assembly modelling. This symbolic geometric approach can locate all solutions to constraint conditions, and is computationally attractive compared to an iterative technique, but to implement this method, a large amount of programming is required.Although many researchers have been actively involved inassembly modelling, little literature has been reported on featurebased assembly modelling for injection mould design.Kruth et al. 9 developed a design support system for aninjection mould. Their system supported the assembly designfor injection moulds through high-level functional mouldobjects (components and features). Because their system was based on AutoCAD, it could only accommodate wire-frameand simple solid models.3. Representation of Injection Mould AssembliesThe two key issues of automated assembly modelling for injection moulds are, representing a mould assembly in computers, and determining the position and orientation of a product- independent part in the assembly. In this section, we present an object-oriented and feature-based representation for assemblies of injection moulds.The representation of assemblies in a computer involves structural and spatial relationships between individual parts. Such a representation must support the construction of an assembly from all the given parts, changes in the relative positioning of parts, and manipulation of the assembly as a whole. Moreover, the representations of assemblies must meetthe following requirements from designers:1. It should be possible to have high-level objects ready to use while mould designers think on the level of realworldobjects.2. The representation of assemblies should encapsulate operational functions to automate routine processes such as pocketing and interference checks. To meet these requirements, a feature-based and object-orientedhierarchical model is proposed to represent injection moulds. An assembly may be divided into subassemblies, which in turn consists of subassemblies and/or individual components. Thus, a hierarchical model is most appropriate for representing the structural relations between components. A hierarchy implies a definite assembly sequence. In addition, a hierarchical model can provide an explicit representation of the dependency of the position of one part on another.Feature-based design 10 allows designers to work at a somewhat higher level of abstraction than that possible with the direct use of solid modellers. Geometric features are instanced, sized, and located quickly by the user by specifying a minimum set of parameters, while the feature modeller works out the details. Also, it is easy to make design changes because of the associativities between geometric entities maintained in the data structure of feature modellers. Without features, designers have to be concerned with all the details of geometric construction procedures required by solid modellers, and design changes have to be strictly specified for every entity affected by the change. Moreover, the feature-based representation will provide high-level assembly objects for designers to use. For example, while mould designers think on the level of a realworld object, e.g. a counterbore hole, a feature object of a counterbore hole will be ready in the computer for use.Object-oriented modelling 11,12 is a new way of thinking about problems using models organised around real-world concepts. The fundamental entity is the object, which combines both data structures and behaviour in a single entity. Objectoriented models are useful for understanding problems and designing programs and databases. In addition, the objectoriented representation of assemblies makes it easy for a “child” object to inherit information from its “parent”.References1. K. H. Shin and K. Lee, “Design of side cores of injection moulds from automatic detection of interference faces”, Journal of Design and Manufacturing, 3(3), pp. 225236, December 1993.2. Y. F. Zhang, K. S. Lee, Y. Wang, J. Y. H. Fuh and A. Y. C. Nee, “Automatic slider core creation for designing slider/lifter of injection moulds”, CIRP International Conference and Exhibition on Design and Production of Dies and Moulds, pp. 3338, Turkey, 1921 June 1997.3. E. C. Libardi, J. R. Dixon and M. K. Simmon, “Computer environments for design of mechanical assemblies: A research review”, Engineering with Computers, 3(3), pp. 121136, 1988.4. K. Lee and D. C. Gossard, “A hierarchical data structure for representing assemblies”, Computer-Aided Design, 17(1), pp. 15 19, January 1985.5. K. Lee and D. Gossard, “Inference of position of components in an assembly”, Computer-Aided Design, 17(1), pp. 2024, January1985.6. A. P. Ambler and R. J. Popplestone, “Inferring the positions of bodies from specified spatial relationships”, Artificial Intelligence, 6, pp. 157174, 1975.7. G. Kramer, Solving Geometric Constraint Systems: A Case Study in Kinematics, MIT Press, Cambridge, MA, 1992.8. J. J. Shah and M. T. Rogers, “Assembly modelling as an extension of feature-based design”, Research in Engineering Design, 5(3&4), pp. 218237, 1993.9. J. P. Kruth, R. Willems and D. Lecluse, “A design support system using high level mould objects”, CIRP International Conference and Exhibition on Design and Production of Dies and Moulds, pp. 3944, Turkey, 1921 June, 1997.10. J. J. Shah, “Assessment of feature technology”, Computer-Aided Design, 23(5), pp. 331343, June 1991.11. S. R. Gorti, A. Gupta, G. J. Kim, R. D. Sriram and A. Wong, “An objection-oriented representation for product and design process”, Computer-Aided Design, 30(7), pp. 489501, June 1998.12. J. Rumbaugh, M. Blaha, W. Premerlani, et al. Object-Oriented Modeling and Design, Prentice Hall, Englewood Cliffs, NJ, 1991.13. Unigraphics Essentials User Manual, Unigraphics Solution Co., Maryland Heights, MO, 1997.14. IMOLD homepage http:/www.eng.nus.edu.sg/imold, Manusoft Plastic Pte Ltd. Singapore.