The influence of the mould material on the rheology and mechanical characteristics of hybrid injection moulds

When hybrid moulds are used for the production of injection moulds, mostly the mould designer and/or plastic processor ignore the implementation of multiple mould materials and its effect on the polymer processing and material characteristics. This effect of mould material selection for injection moulds is underestimated. When one selects a mould material with poor or good thermal behaviour, it results in slower or faster cooling down of the polymer with positive or negative influence on the rheology of the injected polymer. To analyse the effect of mould material on the rheology of polymers, a hybrid micro injection mould of a spiral flow part was designed in which the flow length has been analysed for several injection moulding parameters and mould materials. Both mould and polymer analyses resulted in a better understanding of the rheology during the injection moulding process of hybrid moulds. It also resulted in a better understanding of the needed mould design strategy for multiple material moulds related to rheology, specially for micro injection moulding. Conventionally, micro moulds use techniques such as inductive heating to optimise the rheology. The research has proven that appropriate mould material selection can eliminate the need of mould heating during the injection process.