Casting silicone rubber moulds for use in injection moulding - by injecting resin around model supported in chase, inverting mould and model above second chase and casting opposite half of mould

摘要

Moulds for injection moulding of complex or undercut shapes are made by supporting a model of the moulding in a suitable chase and then casting a self curing (silicone) elastomer into the chase to form a mould around the model. The mould together with the model is inverted above a second chase for casting the opposite half of the mould in a similar manner. The model is disengaged from the cavity and the two moulds are mounted in an injection moulding machine. Provides rapid and reliable production of moulds for mouldings for which conventional metal moulds would be uneconomic, i.e. for small quantities or for shapes difficult to disengage or eject. Esp. suitable for materials moulded using relatively low injection pressures, e.g. 2 kg/cm2 and reinforced by incorporating inserts made of twisted glass filaments bound within a glass fibre mesh or sheath.