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It consists of a knowledge-based mould design system embedded in anInternet-based environment. Mould design generally in-volves complex and multi-related design problems and thuslacks a complete quantitative and structured approach.The present methodology has involved breaking down thecomplete 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 thevarious sub-problems. All design activities are organized inseven functional modules, namely, cavity layout design,feed design, cooling design, ejection design, mouldconstruction, mould base selection and standard compo-nents selection. These modules are used to generate thefunctional designs including cavity layout, feed design,cooling circuit, ejection devices, mould construction and toselect the standard mould base and ancillary componentsincluding register rings, guide bushes, guide pillars,fasteners, etc.5. The knowledge-based mould design systemThe knowledge-based part of the Internet-based moulddesign system is shown in Fig. 3. By using a coding systemas the mechanism of inference engine, the knowledge base is accessed from independent interactive programme,which aids the designer to select a number of recommendedsolutions to the particular functional design under con-sideration. The selection of the actual solutions and theirfinal development into a finished design is left to the moulddesigner so that their own intelligence and experience couldalso be incorporated with the total mould design. Thedetailed operations of the system are described as follows.Firstly, a remote user in the client side submits the plasticpart which may be drawn or retrieved from the partdrawing database and its requirements to the server side.Then an enquiry routine (block 5) selects which questionsto put forward by reviewing answers given about the partin terms of its geometry, dimensions, material, etc., andalso about the mould specifications in terms of number ofcavities, mould design features, etc. After the designeranswering all the questions, the system would create acoded description of the part and the mould. The use of thecode is two-fold. Firstly it is used to make reference to theexisting mould database and look for part codes identicalto or close to the existing part (block 6). If the search findsappropriate part(s) and their respective mould(s), then theycan be retrieved and reviewed whether they are suitable foruse. It is normally required to modify existing moulds totune them up to a different part but this can usually bedone fairly quickly using the system’s CAD facilities. Thesecond and main use of the code is to access the knowledgebase of the system. Within the next stage of the designprocedure, a functional design analysis is performed so thatthe methods related to the various functional designs canbe chosen (block 7). The methods file forms part of theknowledge base and it contains a long list of methods ofachieving the various functional designs of an injectionmould. Since only some of these methods are applicable tothe particular part under consideration, thus it is necessaryto filter out the possible list of methods to be posed to thedesigner for his selection. This task is now done by themethod screening routine (block 8) which uses the partcode to select the recommended list of methods. Oncemethod has been selected a code associated with eachchosen method would be generated. It is quite often thatone method has alternative mould features (hardwarearrangements). The code associated with the chosenmethod is then used to access and pose to the designerthe alternative mould features of the chosen method fromthe knowledge base of the alternative mould featuresthrough the mould feature screening routine (block 9). Byseparating the fundamental methods from their technicaldetails in the present procedure would guide the designer tofocus on basic methods before dealing with their imple-mentation. This logical approach would also speed up thedesign process by reducing the variety of choices. Whenparticular mould feature of chosen method has beenselected, a code associated with each mould feature wouldbe produced and is then used to access and prompt thedesigner to input information concerning inpidualdimensions, position and orientation from the knowledgebase of mould feature geometry through the autographicroutine. In the knowledge base of mould feature geometry,the detailed dimensions of the geometry of all the mouldfeatures are stored in terms of parameters. Once thegraphic information has been inputted, the geometry of thechosen mould feature would be drawn. Afterwards thedesigner then proceeds to the design of another functionaldesign through similar procedure as mentioned above.When all the functional designs have been completed, acomplete drawing would be generated. Finally all thedesigner has to do is to review and modify the moulddrawing if necessary.5.1. The coding systemThe code is a coded representation of all necessaryinformation about the plastic part such as shape, undercutfeatures, material and other specifications. In designing thecoding system considerations have been made to thecharacteristics of most injection moulded parts andmoulds. The design of injection moulds depends criticallyon the shape and features of the product. It is almostimpossible to develop a unique definition for all the shapesof plastic parts as their shapes can vary indefinitely.Nevertheless, in real life the shapes of a large percentage ofcommonly encountered plastic parts can be approximatedas either rectangular or circular. For example most of theplastic housings and casings are basically rectangular inshape; and most of the knobs, buckets and cups arebasically circular in shape. The Opitz system [19] which isthe popular classification system for mechanical parts, hasalso been referred to in developing part of the codingsystem.The code is pided into three sections and has a total of12 digits. The first section which describes the plastic partcontains the first four digits. The second section whichdescribes the relation between the part and the mouldincludes the fifth digit. The third section which describesthe mould contains the last seven digits.5.1.1. The first section: part descriptionThis section includes the first four digits. They representthe part class, part external shape, undercut features andmaterial class, respectively.5.1.1.1. Part class. The first digit distinguishes the part asa circular part or a non-circular part. There are sevennumeric positions for this digit as shown below.(1) Circular part with H/Dp0.5.(2) Circular part with 0.5oH/Do3.(3) Circular part with H/DX3.(4) Variational circular part.(5) Non-circular part with H/Dep0.5.(6) Non-circular part with 0.5oH/De o3.(7) Non-circular part with H/DeX3. (3) Insulated hot runner.(4) Hot manifold.5.1.3.5. Gating system. There are eight positions for the10th digit.(1) Sprue gate.(2) Edge gate.(3) Submarine gate.(4) Pinpoint gate.(5) Tab gate.(6) Fan gate.(7) Film gate.(8) Diaphragm gate.5.1.3.6. Cooling system. There are five positions for the11th digit.(1) With cooled cavity plates.(2) With cooled cores.(3) With cooled cavities.(4) With cooled cores and cavities.(5) Optimum cooling.5.1.3.7. Ejection system. There are four positions for the12th digit.(1) Ejector pins.(2) Stripper plate.(3) Ejector sleeves.(4) Air ejection.It can be seen that this coding system has catered forvery complicated parts. For example, a non-circular partwhich has varying cross-section along its entire height andboth external undercuts and internal undercuts/thread canbe coded by this system.
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