There are several differences between MIM and standard plastic molds. MIM thermal conductivity of the feed is several times higher than that of plastic, so the fluidity is worse. The shrinkage rate of MIM moulds is usually 15%~22%, which is much larger than that of plastic moulds, so it is more difficult to control embryogenic density and sintering size. Many companies make mistakes on this issue. In addition, metal powder is more destructive to the die than plastic. Above all, we need to make some changes in the design of MIM moulds:

A, Tool steel. High wear resistant heat treated steel should be selected.

B, Hot runner. The liquid hot runner is more stable than the electrothermal runner, and more uniform embryogenesis can be obtained, so the sintering deformation will be smaller.

C. Runner and rubber port. Because of the high shrinkage rate and the high thermal conductivity of the feed, the layout of the runner and the rubber port must be balanced, otherwise the shaping work after sintering will be more troublesome. Sometimes, it is even necessary to modify the dimension by CNC machining, which will increase the manufacturing costs.

D. The length of the feed head in the mould nozzle should be as short as possible, and the flow path of the feed should be shortened to reduce the heat loss.

E, Surface treatment of the die cavity. Blackprint is a common problem in MIM products. The treatment of die surface will improve it. In general, VDI18 discharge treatment is used in die processing.