Brown Marks in MIM Machining Process

MIM process manufacture may understand that brown marks is a quite common defect in metal powder  injection molding process. This article is to discuss reasons for brown marks based on lastest experience of UnmannedAircraft parts machining project.

Phenomenon:
Finish product’s surface appear black and yellow stripes

Causes :
- mould or material temperature is too high
-stuck material  too long in pipe

-injection pressure is too high, shear heat
-location of mould vent groove is inappropriate or too small
- too fast speed of screw rotation, back pressure is too high
- additive with improper formula, poor thermal stability

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