1、快速成型与虚拟成型在产品设计和制造中的应用毕业课程设计外文文献翻译Rapid Prototyping Versus Virtual Prototyping in Product Design and ManufacturingC. K. Chua1, S. H. Teh1 and R. K. L. Gay2School of Mechanical & Production Engineering; and 2Gintic Institute of Manufacturing Technology, Nanyang Technological University, SingaporeAbstr
2、actRapid prototyping (RP) is the production of a physical model from a computer model without the need for any jig or fixture or numerically controlled (NC) programming. This technology has also been referred to as layer manufacturing, material deposit manufacturing, material addition manufacturing,
3、 solid freeform manufacturing and three-dimensional printing. In the last decade, a number of RP techniques has been developed. These techniques use different approaches or materials in producing prototypes and they give varying shrinkage, surface finish and accuracy. Virtual prototyping (VP) is the
4、 analysis and simulation carried out on a fully developed computer model, therefore performing the same tests as those on the physical prototypes. It is also sometimes referred to as computer-aided engineering (CAE) or engineering analysis simulation. This paper describes a comparative study of the
5、two prototyping technologies with respect to their relevance in product design and manufacture. The study investigates the suitability and effectiveness of both technologies in the various aspects of prototyping, which is part and parcel of an overall design and manufacturing cycle.Keywords: Product
6、 design; Rapid prototyping; Virtual prototyping1. IntroductionRapid prototyping (RP) is emerging as a key prototyping technology with its ability to produce even complicated parts virtually overnight. It enables product designers to shorten the product design and development process. The coming-of-a
7、ge of this technology is clearly reflected in the inclusion of a stereolithography (STL) file generator in most, if not all, CAD. systems today. The STL file is the de facto standard used by RP systems in the representation of the solid 3D CAD models.While RP is a relatively young technology, virtua
8、l prototyping (VP) has been in steady development since the 1970s in many guises. Virtual prototyping is taken to mean the testing and analysis of 3D solid models on computing platforms. Today, VP is often tightly integrated with CAD/CAM software and sometimes referred to as CAE packages. It provide
9、s the ability to test part behaviour in a simulated context without the need to manufacture the part first 1.2. Definitions of RP and VPRapid prototyping (RP) is a widely used term in engineering, particularly in the computer software industry where it was first coined to describe rapid software dev
10、elopment.This term has also been adopted by the manufacturing industry to characterise the construction of physical prototypes from a solid, powder, or liquid in a short period of time when compared to “traditional” subtractive machining methods. This technology has also been variously referred to a
11、s layer manufacturing, material deposit manufacturing, material addition manufacturing, solid freeform manufacturing and threedimensional printing 2.Virtual prototyping (VP) refers to the creation of a model in the computer, often referred to as CAD/CAM/CAE. Virtual or computational prototyping is g
12、enerally understood to be the construction models of products for the purpose of realistic graphical simulation 1. In this paper, VP will refer to thesimulation, virtual reality and manufacturing process design domains 3.Nevertheless, there are many areas where the distinction between RP and VP is b
13、lurred. As RP systems rely on CAD systems to generate the files needed to produce the prototype, it would seem that RP is a downstream process from VP in the product or part development cycle. Indeed, Pratts definition of VP reveals the fact that VP is a term which is loosely used in the prototyping
14、 community. As such, it would be appropriate to clearly define both RP and VP.Rapid prototyping will be taken to mean, as above, the production of a physical model from a computer model without the need of any jig or fixture or NC programming. This also includes other related processes and applicati
15、ons which use RP-produced objects, such as rapid tooling.Similarly, VP is defined as the subsequent manipulation of a solid CAD model as a substitute for a physical prototype for the purposes of simulation and analysis, and is not inclusive of the construction of the solid 3D model. VP includes the
16、following functions:1. Finite element analysis.2. Mechanical form, fit and interference checking.3. Mechanical simulation.4. Virtual reality applications.5. Cosmetic modelling.6. Assemblability.The relationships between RP and VP are shown in Fig. 1.Fig. 1. Classification of RP and VP3. Prototyping
17、in SingaporeTwo selected multi-national companies (one American and one French) based in Singapore with significant product development activities showed differing approaches to both RP and VP. Both use RP in their prototyping activities.The first company, B, placed more emphasis on virtual prototyp
18、ing. It manufactures telecommunications equipment such as pagers and handphones. It is moving all prototyping applications upstream, which is to move prototyping from RP to VP. At present, their RP models are used only for proof of concept and marketing purposes. Other prototyping activities are bei
19、ng carried out with VP.The second company, C, manufactures consumer electronics products such as television sets, video cassette recorders and telephones. It uses VP only as a tool to create a solid 3D model. From the solid 3D model, C generates the STL file needed to produce the RP prototype. Compa
20、ny C then uses the RP part as a master for silicone rubber moulds to produce a limited number of physical ABS (polyacrylonitrite butadienestyrene) prototypes for the various prototyping tests and simulation.Company B intends to move more prototyping to VP, rather than using physical models. Virtual
21、prototyping allows for improvements in reliability and quality as well as reducing costs. Manipulation of virtual prototypes makes it easier for B to implement design improvements compared to an iterative cycle using physical prototypes.Company B drafts the CAD models in Pro/ENGINEER, then uses Patr
22、an to pre-process the models. Static finite-element analysis (FEA) is carried out with ABAQUS Standard whereas dynamic scenarios are analysed with ABAQUS Explicit. ALIAS/Wavefront is used for cosmetic modelling when presenting different conceptual and actual designs.The bulk of the VP carried out by
23、 B uses FEA, which typically takes 46 weeks for a pager design. Of all the FEA carried out, the majority are concentrated on structural strength (static) analysis and drop test (dynamic) analysis. Vibration tests are occasionally carried out. Some cosmetic modelling is carried out, but usually only
24、for presentation purposes.Finite-element analysis is used to investigate the following problems:Relative comparison of different design options; to see how one design compares to another. Possible failure modes are:1. To evaluate a design change or design correction.2. To assess the possibility of f
25、ailure, based on past experience.3. To make some educated-guess correlation with physical testing.4. To try to identify what initiated a failure.According to B, the drawback of VP is that it cannot simulate process problems efficiently and effectively. The accuracy of FEA is also limited because of
26、the inconsistent behaviour ofmaterial. The amount of computing power also determines the accuracy of FEA.The application of RP is rather limited in B. The in-house laminated object manufacturing (LOM) RP system is used to produce design prototypes for proof of concept only, and notgeometrical protot
27、ypes. Company C uses RP heavily, but has very little VP. The parts produced using RP range from audio products to 29-in. television casings. Typically, it takes 1 year from the conception of the product to the sale of the product. Company C aims to prototype all (mostly plastic) parts by RP. A compa
28、rison between numerically controlled (NC) machining of prototypes from ABS against RP is shown in Table 1. Company C projected 50% savings using an in-house RP system versus an NC machining system.CAD models are created using I-DEAS. The .STL format is then created for production of the RP part. The
29、 main purpose of the RP parts is to verify the design. Rapid prototyping parts are used for the following functions:1. Form fitting.2. Ergonomics check.3. Proof of concept (to confirm design with industrialdesigners).4. Manufacturability (design for tooling, design for assemblability).5. Reliability
30、 check (whether part dislodges or breaks when force applied, especially snap-on covers).6. Kinematic check. Company C offers some insight into the limitations of VP, in that VP is unable to model:1. Tactile feeling (for buttons) not quantified; may be able to VP if able to quantify “pressing” force.
31、2. Assemblability (e.g. PCBs inserted at an angle, difficult to visualise).4. Case Study 1: Prototyping of a Telephone HandsetThis case study investigates the design verification, assembly, interference check and form fitting aspects of both the RP and VP model. The production ABS, RP and VP parts o
32、r models were evaluated in the above aspects. The RP system used here is the stereolithography apparatus (SLA). Both the ABS and RP parts are shown in Fig. 2. Inspection of the RP parts reveal that:1. The surface finish was much poorer than in the ABS part.2. Warpage was clearly evident (see Fig. 3).4.1 Design VerificationAs a true dimensional physical part, the RP model is able to give the designer a sense of size estimation. The judgement of a VP part can be erroneous because parts are often automatically sized to fit the viewing window. Another advantage
