【正文】 the design stage of the plastic parts in order to exploit the cost benefit of CAE. CAE makes it possible to replace traditional, sequential decisionmaking procedures with a concurrent design process, in which all parties can interact and share information, Figure 3. For plastic injection moulding, CAE and related design data provide an integrated environment that facilitates concurrent engineering for the design and manufacture of the part and mould, as well as material selection and simulation of optimal process control parameters.Qualitative expense parison associated with the part design changes is shown in Figure 4 , showing the fact that when design changes are done at an early stages on the puter screen, the cost associated with is an order of times lower than that if the part is in production. These modifications in plastic parts could arise fr om mould modifications, such as gate location, thickness changes, production delays, quality costs, machine setup times, or design change in plastic parts. Figure 4 Cost of design changes during part product development cycle (Rios , 2001) At the early design stage, part designers and moulders have to finalise part design based on their experiences with similar parts. However as the parts bee more plex, it gets rather difficult to predict processing and part performance without the use of CAE tools. Thus for even relatively plex parts, the use of CAE tools to prevent the late and expensive design changesand problems that can arise during and after injection. For the successful implementation of concurrent engineering, there must be buyin from everyone involved. 5. Case Study Figure 5 shows the initial CAD design of plastics part used for the sprinkler irrigation hydrant leg. One of the essential features of the part is that the part has to remain flat after injection。 any warping during the injection causes operating problems. Another important feature the plastic part has to have is a high bending stiffness. A number of feeders in different orientation were added to the part as shown in Figure 5b. These feeders should be designed in a way that it has to contribute the weight of the part as minimum as possible. Before the design of the mould, the flow analysis of the plastic part was carried out with Moldflow software to enable the selection of the best gate location Figure 6a. The figure indicates that the best point for the gate location is the middle feeder at the centre of the part. As the distortion and warpage of the part after injection was vital from the functionality point of view and it has to be kept at a minimum level, the same software was also utilised to yiled the warpage analysis. Figure 5 b shows the results implying the fact that the warpage well after injection remains within the predefined dimensional tolerances. 6. Conclusions In the plastic injection moulding, the CAD model of the plastic part obtained from mercial 3D programs could be used for the part performance and injection process analyses. With the aid of CEA technology and the use of concurrent engineering methodology, not only the injection mould can be designed and manufactured in a very short of period of time with a minimised cost but also all potential problems which may arise from part design, mould design and processing parameters could be eliminated at the very beginning of the mould design. These two tools help part designers and mould makers to develop a good product with a better delivery and faster tooling with less time and money. References 1. Smith P, Reinertsen D, The timetomarket race, In: Developing Products in Half the Time. New York, Van Nostrand Reinhold, pp. 3–13, 1991 J, The total product development organization. Proceedings of the Second Asia–Pacific Rapid Product Development Conference, Brisbane, 1996 R, Don’t stop after the prototype, Seventh International Conference on Rapid Prototyping, San Francisco, 1997 PF, “Chapter 3: Rapid Product Development” in Rapid Tooling: Technologies and Industrial Applications , Ed. Peter D. Hilton。 Paul F. Jacobs, Marcel Decker, 2000 RS, Chen, YM, and Lee, CZ, “Development of a concurrent mould design system: a knowledge based approach”, Computer Integrated Manufacturing Systems, 10(4), 287307, 1997 B., “Simultaneous Engineering”, Mechanical Engineering , , , , 1998 A, Gramann, PJ and Davis B, “Computer Aided Engineering in Compression Molding”, Composites Fabricators Association Annual Conference , Tampa Bay, 200