Application of mathematical methods for the evaluation of gas injection technology - shaped parts
Helmut Ridder, Helmut Potente
Institut fuer Kunststofftechnik
Germany

Keywords: GAIM, classification, scale-up rules

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When gas-assisted injection molding is used, the experience gained in practice has shown that an unfavorable molded part design can lead to instabilities during the process. In many cases these production problems result from an insufficient design of the part as well as from a poorly designed GAIM process. In this paper a proceeding is shown explaining the influences of the geometry of a part on the desired production. This is realized by using a classification method. Using a criteria catalog listing the most important geometric requirements for a GAIM part, the so-called geometry-describing features of a molded part are recorded. These features are subsequently made available for further data processing. Cluster analysis was selected as the classification process, which belongs to the multivariate statistical processes. This analysis has the advantage of allowing the classification to be depicted in graphical terms through the compilation of a dendrogram which is compiled on the basis of the complete-linkage-cluster algorithm. The basic idea behind this classification is the assumption that similar molded parts display a similar degree of suitability for production by the GAIM process. On this basis, it is thus possible to transpose the geometry assessment drawn up for an individual molded part to other parts or to generalize it. Based on the results of the classification it is possible to predict the resulting gas bubble cross section as well as the required material-, geometry- and process parameters in an early stage of part design. This can be done by the help of scale-up rules. Later on it is made clear how an expert system for the specification of mould data or for the building up of an experience database can be established by using the classification system.