INJECTION-MOLDING MADE TRANSPARENT - NEW DEVELOPMENTS IN-PROCESS SIMULATION

The application of simulation programs in the design of injection moulds has gained increasing importance in conjunction with the introduction of CAE techniques (computer aided engineering). In the analysis of the increasingly complex special processes that have been developed in injection moulding simulation calculations, in particular, are becoming an indispensable part of mould design. For this reason, particular value is placed in the current paper on presenting new developments and extensions of the programs to describe the special problems encountered in injection moulding. The first section deals with the extension of the filling simulation. First of all, a refinement of the model describing the 2-component process is presented. The penetration behaviour of the core component into the skin component is described by means of a phenomenological formulation. The coefficients of this formulation can be determined on an approximate basis from the MFI values of the individual components. Following this, ways of calculating the gas-assisted injection moulding process are presented. The calculations are compared with practical results. Next, a means of calculating the topography of welding lines is explained. The results of a calculation of this type are of key importance for analysing weld line strength. In the case of critical materials such as LCPs (liquid crystal polymers) or fibre-filled materials, it is possible to obtain information on the quality of a component using this method. Injection-compression moulding is a special process frequently used for producing extremely thin-walled components or components with highly differing wall thicknesses. The simulation programs have thus been extended in order to describe the mould filling phase for this process as well. Initial results that have been obtained are presented. In the final section of the paper, details are given of developments on the calculation of shrinkage and warpage behaviour in injection moulded parts. The shrinkage and warpage of moulded parts represents one of the most frequent problems in practice. Using the simulation program presented, it is possible to analyse the influence of individual parameters on these variables. Adjustments have also been made to improve the computation model and to make it possible to describe moulded parts with a layered structure (2-component, GID) or with anisotropic properties (orientation). The facilities offered by the program are subsequently presented using the layout of a part encountered in practice.