Troubleshooting surface

[Ruben_Leys]

Hello,

We have a problem with the surface of a black product.
I think that the plastic is solidifies to fast.
Is it a sort of blushing or delamination?
See attachments.

Regards
Ruben

[JayDub]

If the part is cooling too fast – raise the mold temperature. The appearance issue could conceivably be gas trapping (seems like an odd location for it though) so check your venting. It could also be blooming of an additive on to the surface of the mold. Clean the cavity surface thoroughly and see if it goes away temporarily. I’m assuming that the material is dried properly.
More information would help.
What’s the material?
How big is the part?
What’s the mold temperature?
Is the problem consistent throughout the run?

[MTUHusky]

That tiger striping could be from flow hesitation for sure. The surrounding area seems to have some kind of texture to it, does the area with the tiger striping have texture to it as well? If so, then yes you could be getting delamination or "ghosting" from the mold surface texture. I would start with the flow hesitation, either raise mold temp, melt temp, fill speed or a combination of those things. If you cant process it out, I would start looking at the surface texture.

Husky

[rickbatey]

It looks like back fill to me caused by the melt fronts race tracking around the perimeter wall and trapping air in the part. The different flow directions create the defect. Higher melt and mold temp plus faster fill rate will help. You may even have to put flow helpers in the mold to eliminate the defect.
Rick