1、Three-Dimensional Kernel Development for Injection Mould DesignToday, many software “plug-ins” have been developed on high-level 3D modelling platforms to facilitate processes such as FEM analysis, CAM, injection mould design, simulation and visualisation. Such an arrangement is advantageous in many
2、 ways. However, it is not without shortcomings. Ideally, these “plug-ins” could also be developed using low-level 3D kernels for higher flexibility and better portability. This paper examines the various issues and methodologies related to the development of such 3D-based applications. The emphasis
3、is placed on the software aspect. First, a methodology for the development of 3D-based applications is proposed. The idea is then implemented by developing an injection mould design application using a low-level 3D kernel called Parasolid. Based on design concepts used in an established mould design
4、 application, IMOLD, the development of a mould base design module is illustrated. An object-oriented programming language has been chosen for the development of the software on a Windows NT platform.1.IntroductionThree-dimensional CAD systems have increasingly been used to speed up the product real
5、isation process. One of the first steps involved in the automation of the product design process is the creation of the component parts in a 3D modelling application. The 3D model, upon creation, is called the digital master copy. This 3D digital model forms the key to a wide spectrum of process aut
6、omation.Creating the 3D digital model of component parts is only the very first step. There are several other secondary tasks that must to be done before the part can be manufactured. Such tasks include finite-element analysis, jigs and fixtures design, injection mould design, computer-aided manufac
7、turing, simulCorrespondence and ofprint requests to: K.-S. Lee, Department of Mechanical and Production Engineering, National University of Singapore, 119260 Singapore. E-mail: mpeleeksKnus.edu.sgation, and visualisation. Today, many application Plug-ins have been developed on high-level 3D modellin
8、g platforms to facilitate these secondary tasks. The 3D-modelling platform provides the plug-in software with a library of functions as well as an established user interface and style of programming. As a result, the development times for these plug-ins are significantly reduced.Such an arrangement
9、is advantageous in many ways. However, it has its shortcomings, especially in the long run. In order to develop a plug-in for established software, the developers must adhere to the many constraints imposed. There is a need to be consistent with the style of the parent software. The developers must
10、be able to achieve any functionality they need with only the set of library functions provided. Most end-users need both the parent software and the plug-in. In many cases, however, they may be more interested in using only the plug-in software. An example of such a situation is in injection mould d
11、esign. These users, however, must purchase the entire software package which includes many features and functions that they do not need. Such a large program is often very demanding on the hardware, which also means higher cost. The plug-in software is also very dependent on developments in the pare
12、nt software. Whenever a new version is updated for the parent software, the plug-in developers have to follow-up on the changes. These shortcomings may not exist if these applications were developed on a low-level platform. Ideally, these plug-ins could be developed using low-level 3D kernels for hi
13、gher flexibility and better portability. In many instances, such a move is both feasible and advantageous.Traditionally, injection mould design is carried out directly on a CAD system. The entire injection mould, consisting of perhaps hundreds of components, is modelled and assembled on CAD systems
14、such as AutoCAD, Pro/Engineer, and Unigraphics. As the injection mould design process is recursive, it is very time-consuming to re-model and re-assemble the design. In this aspect, 3D CAD systems such as Pro/Engineer and Unigraphics, which are feature-based, have a significant advantage over 2D CAD
15、 systems such as AutoCAD. To further speed up the injection mould design process, plug-ins were developed on these 3D systems to automate certain stages of the design process. Examples of such add-on applications include IMOLD (Intelligent Mold Design and Assembly Sys-Mold Designer (based on CADKEY)
16、 and Moldmaker (based on EUCLID). As each is based on a specific CAD system, there is no plug compatibility.In 1994, Mok and Cheung 1 presented work on the development of an injection mould design application based on Unigraphics. In 1997, Shah 2 proposed a 3-tier architecture for standardising communications between geometric modelling kernels and applications that require geometric modelling services. His objective is to achieve plug compatibility between 3D ap
