[ukvacuumformer]

Hi Everyone,

Would anyone know what these marks are in the plastic surface.I have tried ABS HIPS and PVC,it is like a line in the plastic,if you run your finger over them you can feel a bump you can see in the picture its like a crease mark....i do understand some of the vacumm forming process bt don't know why this is happening.My mold is hot using 1.5mm plastic.I have cut a section out and It looks like the plastic goes thinner at the point of the bump..i know about chill marks and air entrapment but have tried allsorts to stop this happening but still no joy.....ive polished the mold(my mold is cast epoxy resin with metal powder)..then roughed it up on the surface to avoid air entrapment.. drilled more evacuation holes where I can..any advice would be greatly received.I'm using a professional Formech vacuum former by the way not a DIY one.

This is also happening on the other vac formed part(not pictured)which is basically a dome like the top of a motorcycle helmet and there is a large bump/mark running across the dome.

I think I understand why this is happening..i believe the plastic is not flowing correctly but I don't know how to remedy it.

[mkc2]

I had the same thing happen to one mold but I just blow the ABS up into a bubble then vacuum pull it, gets most of it out and most of the time there's none.

[ukvacuumformer]

Cheers for the answer looks like I need to be blowing more air into the sheet then before I vacuum down...Thanks