外文翻译--注塑模具自动装配造型-模具设计(编辑修改稿)

外文翻译--注塑模具自动装配造型-模具设计(编辑修改稿)内容摘要：

difficultieswhen use a CAD system to design productindependentparts and the whole assembly of an injection mould. First,there are usually around one hundred productindependent partsin a mould set, and these parts are associated with each otherwith different kinds of constraints. It is timeconsuming forthe designer to orient and position the ponents in anassembly. Secondly, while mould designers, most of the time,think on the level of realworld objects, such as screws, plates,and pins, the CAD system uses a totally different level ofgeometrical objects. As a result, highlevel objectoriented ideashave to be translated to lowlevel 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 productindependent part and a mould assembly ina puter。 and determining the position and orientation of aponent 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 Research Assembly modelling has been the subject of research in diversefields, such as, kinematics, AI, and geometric modelling. Libardiet al. [3] piled a research review of assembly reported that many researchers had used graphstructures to model assembly topology. In this graph scheme,the ponents are represented by nodes, and transformationmatrices are attached to arcs. However, the transformation matrices are not coupled together, which seriously affects the transformation procedure, . 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 ponents. The transformation matrices are derived automatically from the associations of virtual links, but this hierarchical topology model represents only “partof” relations effectively. Automatically inferring the configuration of ponents in an assembly means that designers can avoid specifying the transformation matrices directly. Moreover, the position of a ponent will change whenever the size and position of its reference ponent are modified. There exist three techniques to infer the position and orientation of a ponent in the assembly: iterative numerical technique, symbolic algebraic technique, and symbolic geometric technique. Lee and Gossard [5] proposed an iterative numerical technique to pute the location and orientation of each ponent 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 Newton–Raphson 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 puting the req。