I did some preliminary testing for injection molding a 1/3 inch thick part (disk shaped) from POM. I use a hot sprue bushing for direct injection. The surface finish is terrible. I suspect it is because the part shrinks a lot as it cools down so I have the hold pressure on for a long time and the POM that gets injected as the part shrinks moves the already cooled down skin along the mold surface. I hope that makes sense. Not sure if that is really what is going on, but it looks like it in my opinion.
Any suggestion how to get a good surface finish on that part? (BTW, I can't re-design the part, it needs to be that thick all the way through).
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