4。2。 System architecture

Based on the practical mould design procedures and the issues to be considered in this stage, the architecture of an Internet-based intelligent  injection  mould design system is proposed as shown in Fig。 2。 It consists of a

User Layer

Network Layer

Business Logic Layer

Data & Knowledge Layer

Fig。 2。  Architecture of the Internet-based mould design   system。

knowledge-based mould design system embedded in an Internet-based environment。 Mould design generally in- volves complex and multi-related design problems and thus lacks a complete quantitative and  structured  approach。 The present methodology has involved breaking down the complete design problem into a number of sub-problems (functional designs, e。g。 feed system, cooling system, etc。) and developing a knowledge base of solutions for the various sub-problems。 All design activities are organized in seven functional modules, namely, cavity layout design, feed design, cooling design, ejection design, mould construction,  mould  base  selection  and  standard compo-

nents selection。 These modules are used to generate the functional designs including cavity layout, feed design, cooling circuit, ejection devices, mould construction and to select the standard mould base and ancillary components including register rings, guide bushes, guide pillars, fasteners, etc。

5。 The knowledge-based mould design  system

The knowledge-based part of the Internet-based mould design system is shown in Fig。 3。 By using a coding system as the mechanism of inference engine, the knowledge  base

Fig。 3。  The interactive design procedure of the KB   system。

is accessed from independent interactive  programme, which aids the designer to select a number of recommended solutions to the particular functional design under con- sideration。 The selection of the actual solutions and their final development into a finished design is left to the mould designer so that their own intelligence and experience could also be incorporated with the total mould design。 The detailed operations of the system are described as follows。 Firstly, a remote user in the client side submits the plastic part which may be drawn or retrieved from the part drawing database and its requirements to the server side。 Then an enquiry routine (block 5) selects which questions to put forward by reviewing answers given about the part in terms of its geometry, dimensions, material, etc。, and also about the mould specifications in terms of number of cavities, mould design features, etc。 After the designer answering all the questions, the system would create a coded description of the part and the mould。 The use of the code is two-fold。 Firstly it is used to make reference to the existing mould database and look for part codes identical to or close to the existing part (block 6)。 If the search finds appropriate part(s) and their respective mould(s), then they can be retrieved and reviewed whether they are suitable for use。 It is normally required to modify existing moulds to tune them up to a different part but this can usually be done fairly quickly using the system’s CAD facilities。 The second and main use of the code is to access the knowledge base of the system。 Within the next stage of the design procedure, a functional design analysis is performed so that the methods related to the various functional designs can be chosen (block 7)。 The methods file forms part of the knowledge base and it contains a long list of methods of achieving the various functional designs of an injection mould。 Since only some of these methods are applicable to the particular part under consideration, thus it is necessary to filter out the possible list of methods to be posed to the designer for his selection。 This task is now done by the method screening routine (block 8) which uses the part code to select the recommended list of methods。 Once method has been selected a code associated with each chosen method would be generated。 It is quite often that one method has alternative mould features (hardware arrangements)。 The code associated with the  chosen method is then used to  access  and  pose  to  the designer the alternative mould features of the chosen method from the knowledge base of the alternative mould features through the mould feature screening routine (block 9)。 By separating the fundamental methods from their technical details in the present procedure would guide the designer to focus on basic methods before dealing with their imple- mentation。 This logical approach would also speed up the design process by reducing the variety of choices。 When particular mould feature of chosen method has been selected, a code associated with each mould feature would be produced and is then used to access and prompt the designer to input information concerning inpidual dimensions, position  and orientation from the    knowledge