外文翻譯--注塑模具自動(dòng)裝配造型（英文）

1、Int J Adv Manuf Technol (2000) 16:739–747 ? 2000 Springer-Verlag London LimitedAutomated Assembly Modelling for Plastic Injection MouldsX. G. Ye, J. Y. H. Fuh and K. S. LeeDepartment of Mechanical and Production Engineer

2、ing, National University of Singapore, SingaporeAn injection mould is a mechanical assembly that consists of product-dependent parts and product-independent parts. This paper addresses the two key issues of assembly mode

3、lling for injection moulds, namely, representing an injection mould assembly in a computer and determining the position and orientation of a product-independent part in an assembly. A feature-based and object-oriented re

4、presentation is proposed to represent the hierarchical assembly of injection moulds. This representation requires and permits a designer to think beyond the mere shape of a part and state explicitly what portions of a pa

5、rt are important and why. Thus, it provides an opportunity for designers to design for assembly (DFA). A simplified symbolic geometric approach is also presented to infer the configurations of assembly objects in an asse

6、mbly according to the mating conditions. Based on the proposed representation and the simplified symbolic geometric approach, automatic assembly modelling is further discussed.Keywords: Assembly modelling; Feature-based;

7、 Injection moulds; Object-oriented1. IntroductionInjection moulding is the most important process for manufac- turing plastic moulded products. The necessary equipment con- sists of two main elements, the injection mould

8、ing machine and the injection mould. The injection moulding machines used today are so-called universal machines, onto which various moulds for plastic parts with different geometries can be mounted, within certain dimen

9、sion limits, but the injection mould design has to change with plastic products. For different moulding geometries, different mould configurations are usually necessary. The primary task of an injection mould is to shape

10、 the 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 shapesCorrespondence and offp

11、rint requests to: Dr Jerry Y. H. Fuh, Depart- ment of Mechanical and Production Engineering, National University of Singapore (NUS), 10 Kent Ridge Crescent, Singapore 119260. E-mail: mpefuhyh?nus.edu.sgand sizes of a cav

12、ity system are determined directly by the plastic moulded product, so all components of a cavity system are called product-dependent parts. (Hereinafter, product refers to a plastic moulded product, part refers to the co

13、mponent of an injection mould.) Besides the primary task of shaping the product, an injection mould has also to fulfil a number of tasks such as the distribution of melt, cooling the molten material, ejection of the moul

14、ded product, transmitting motion, guiding, and aligning the mould halves. The functional parts to fulfil these tasks are usually similar in structure and geo- metrical shape for different injection moulds. Their structur

15、es and geometrical shapes are independent of the plastic moulded products, but their sizes can be changed according to the plastic products. Therefore, it can be concluded that an injection mould is actually a mechanical

16、 assembly that consists of product-dependent parts and product-independent parts. Figure 1 shows the assembly structure of an injection mould. The design of a product-dependent part is based on extracting the geometry fr

17、om the plastic product. In recent years, CAD/CAM technology has been successfully used to help mould designers to design the product-dependent parts. The???????????????????????????????????????????????????????????????????

18、????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????? ?????????????????????????????????????????Fig. 1. Assembly structure of an injection mo

19、uld.Automated Assembly Modelling 741based on AutoCAD, it could only accommodate wire-frame and simple solid models.3. Representation of Injection Mould AssembliesThe two key issues of automated assembly modelling for inj

20、ection moulds are, representing a mould assembly in com- puters, and determining the position and orientation of a pro- duct-independent part in the assembly. In this section, we present an object-oriented and feature-ba

21、sed 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 constru

22、ction 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 meet the following requirements f

23、rom designers:1. It should be possible to have high-level objects ready to use while mould designers think on the level of real- world objects.2. The representation of assemblies should encapsulate oper- ational function

24、s to automate routine processes such as pocketing and interference checks.To meet these requirements, a feature-based and object-oriented hierarchical model is proposed to represent injection moulds. An assembly may be d

25、ivided 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 im

26、plies 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

27、 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

28、 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, desi

29、gners 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 fe

30、ature-based representation will provide high-level assembly objects for designers to use. For example, while mould designers think on the level of a real- world object, e.g. a counterbore hole, a feature object of a coun

31、terbore 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 con- cepts. The fundamental entity is the object, whi

32、ch combines both data structures and behaviour in a single entity. Object- oriented models are useful for understanding problems and designing programs and databases. In addition, the object-oriented representation of as

33、semblies makes it easy for a “child” object to inherit information from its “parent”. Figure 2 shows the feature-based and object-oriented hier- archical representation of an injection mould. The represen- tation is a hi

34、erarchical structure at multiple levels of abstraction, from low-level geometric entities (form feature) to high-level subassemblies. The items enclosed in the boxes represent “assembly objects” (SUBFAs, PARTs and FFs);

35、the solid lines represent “part-of” relation; and the dashed lines represent other relationships. Subassembly (SUBFA) consists of parts (PARTs). A part can be thought of as an “assembly” of form features (FFs). The repre

36、sentation combines the strengths of a feature-based geometric model with those of object-oriented models. It not only contains the “part-of” relations between the parent object and the child object, but also includes a r

37、icher set of structural relations and a group of operational functions for assembly objects. In Section 3.1, there is further discussion on the definition of an assembly object, and detailed relations between assembly ob

38、jects are presented in Section 3.2.3.1 Definition of Assembly ObjectsIn our work, an assembly object, O, is defined as a unique, identifiable entity in the following form:O = (Oid, A, M, R) (1)Where:Oid is a unique ident

39、ifier of an assembly object (O).A is a set of three-tuples, (t, a, v). Each a is called an attribute of O, associated with each attribute is a type, t, and a value, v.M is a set of tuples, (m, tc1, tc2, %, tcn, tc). Each

40、 element of M is a function that uniquely identifies a method. The symbol m represents a method name; and methods define operations on objects. The symbol tci (iFig. 2. Feature-based, object-oriented hierarchical represe