Robust Process Control for Rubber Injection Moulding with Use of Systematic Simulations and Improved Material Data

Abstract

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.