IMPC

Metal Injection Moulding (MIM) is a process that has developed out of the conjunction between powder metallurgy and plastic injection moulding.

MIM has a wide area of applications which include watch cases, radial rotors, turbocharger rotors, automotive parts, surgical tweezers, gas manifolds, fuel nozzles and many others.

The MIM industry has been driven by reduction in production costs as compared to other methods and MIM has become a mature technique for the fabrication of small and difficult to machine parts with complex shapes. Figure 1 shows competing technologies and Figure 2 identifies the optimal application of MIM.

The MIM cycle

The MIM cycle begins with preparation of a feedstock by mixing together very fine metallic powder with a binder comprising waxes, polymers, lubricants and surfactants as shown in Figure 3. The resulting feedstock is then granulated.

An injection moulding machine is used to heat up the feedstock before injecting it into a mould cavity under pressure. The molten feedstock is allowed to cool, solidify and become what is known as a “green” part.

The binder components are then removed by the process of debinding and the brown moulding becomes a highly porous “brown” part. The brown part is sintered at elevated temperature and shrinks during the process typically to over 95% density.