Reaction Injection Moulding (RIM) is a process where a fast reacting PU (polyurethane) resin is low pressure injected into a mould. This process conveniently fits between Vacuum Casting and Thermoplastic Injection Moulding in the prototyping / manufacturing chain. This is a cold injection process that does not require pre-heating of moulds or post curing of castings. Larger sized components can be produced and several moulds can be cast consecutively, leading to quicker production times. Automotive Case Study.

Tools are made from Silicone, Resin, Model Board or Aluminium, and can yield anything from 50 up to 1000+. This process is mainly used for larger and simpler parts with a typical wall thickness of 2-3mm+.

As with vacuum casting, a wide range of production simulant materials are available, offering a wide range of properties; rigid or flexible; solid or foamed, with a density as low as 40 kg/m³. Rigid self-skinning materials, where the surfaces are hard and solid enclosing a foam core, can be moulded to produce lightweight but rigid components.