Hot runners refine metal and ceramic injection moulding
Using plastics to create metal and ceramic parts
With the MIM and CIM processes, a metal or ceramic powder – in MIM, e.g. consisting of stainless steel or a titanium alloy – is mixed with a binding agent, often polyethylene (PE) or polyoxymethylene (POM), and a special wax, and then granulated. This mixture, called a "feedstock", can be processed with injection moulding like any conventional plastic material. The plastic is then removed from the moulding, the so-called "green part", by heating. After debinding, this component has a porous structure because of the removal of the plastic material and is called the "brown part". By sintering this brown part, the metals or ceramics are baked together to form a component with a homogeneous structure whose density and resistance does not differ from a conventionally manufactured steel or ceramic component. Thus, the advantages of, for example, a metal component, like high mechanical resistance and high conductivity, are combined with a relatively simple way of manufacturing.
Basically, conventional injection moulding machines can be used for CIM and MIM. But if manufacturers wish to employ these processes for a longer period, they should consider installing wear-resistant cylinders, screws and non-return valves because these components are submitted to increased abrasion from metals and, to an even higher extent, from ceramic powders.