© 2015 Smithers Information Ltd. T/1 Gummi Fasern Kunststoffe, 67, No. 10, 2014, pp. 640–644 Robust process control for rubber injection moulding with use of systematic simulations and improved material data M. Fasching 1 , G. Berger 2 , W. Friesenbichler 2 , P. Filz 3 , and B. Helbich 3* 1 Polymer Competence Center Leoben GmbH, Austria 2 University of Leoben, Austria 3 Simcon kunststofftechnische Software GmbH, Würselen, Germany Selected from International Polymer Science and Technology, 41, No. 11, 2014, reference GK 14/10/640; transl. serial no. 17208 Translated by M. Grange SUMMARY The heating phase is by far the most time-consuming part of rubber injection moulding. The determination of a suitable curing time is difficult despite extensive injection moulding trials, since in many cases the quality of a part, such as its degree of vulcanisation which is often visually detectable only where there is significant undercure (Figure 1a), cannot be assessed without closer examination (Figure 1b). Systematic injection moulding simulation with Varimos presents an effective solution because the Varimos methodology allows virtual detection of the impacts of process parameters and their interactions, as well as visualisation of e.g. impending undercure (Figure 1c). It therefore enables part, mould and process to be optimised automatically to the desired quality criteria. As a result, it is possible not only to save valuable machine time, which would otherwise be taken up for process development, but also to define the processing window more precisely and thus to improve the economic efficiency of the process while at the same time ensuring the necessary process stability. This was successfully investigated and demonstrated using a thick-walled test piece during the RubSim project at the Polymer Competence Center Leoben GmbH in collaboration with the Injection Moulding of Polymers Group of the University of Leoben and the industrial partners SKF Sealing Solutions Austria GmbH, Engel Austria GmbH, Simcon kunststofftechnische Software GmbH and Dr. Gierth Ingenieurgesellschaft mbH. INTRODUCTION For injection moulded thermoplastics, the Varimos optimisation system from Simcon kunststofftechnische Software GmbH is already a recognised software tool for the automatic optimisation of part, mould and process [1-4]. While the main focus in the injection moulding of thermoplastics is on the dimensional stability of the moulded parts and how this is affected by mould compensation, temperature control and process conditions, the most important parameter in rubber injection moulding in terms of obtaining the desired component quality is to achieve a defined degree of cure, which should be distributed as homogeneously as possible over the cross-section of the moulding. Within the RubSim project, the existing methodology has therefore been adapted for elastomer components with the aim of virtually modelling and optimising the response variables that can be obtained from an injection moulding simulation, such as component quality (degree of cure), process stability (incubation progress during the filling phase) and productivity. This was carried out at the Polymer Competence Center Leoben GmbH in collaboration with the Injection Moulding of Polymers Group of the University of Leoben and an industrial consortium consisting of SKF Sealing Solutions Austria GmbH, Engel Austria GmbH, Simcon kunststofftechnische Software GmbH, Germany and Dr. Gierth Ingenieurgesellschaft mbH, Germany.