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mold and unmold
- This topic has 7 replies, 4 voices, and was last updated 2 years ago by
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Hello everybody,
Is there any of you that had any problems with the plastic injected into molds when it comes to unmold the object? We cannot figure out what we do wrong. It becomes quite difficult to unmold them. We are even thinking that maybe we should add some products to the mold or maybe look for some special paint. Any idea?
team defaratt
Hello @defarat
There are a couple things you can do to easily remove your plastic parts from the moulds:
#1: Make sure that the internal walls of your mould are as smooth as possible. If your mould has any type of texture, the molten plastic will adhere to them.
#2: Use a mould release agent: You can buy mould release in spray cans, or make your own with cooking oil. Here are some examples:
https://www.youtube.com/watch?v=kNtkwKo0-VU
https://www.hunker.com/13410940/diy-mold-release-agent
https://www.youtube.com/watch?v=krJ8qpT8cL4
@defarat, You can also drill a few ejector holes and punch it out with some pins – or make a thread and screw it out.
However, the walls need a slight angle to address exactly this problem. Also have a look at the more popular video about injection molding – explaining a little this problem.
@xxxolivierxxx, thanks for the feedback, but I do not see that we can use any of those solutions with metallic molds or at least this is what I could understand from the videos and info you have shared.
Thanks for the idea of the ejection pins, we may be trying them if we get a go to an aluminum mold which we are thinking of.
For what concern the pics I have just posted it is clear that one of the problems is due to the fact that the surface is not smooth enough. Lately we got some tests done very well ( with the new square mold): even if we have some difficulties to reach correct temperature in the tube, it seems that if we are able to fill the mold in one go and not to heat the mold itself too much the object comes out quite well (see last pics) and it gets unmold nicely.
From your first and second picture it looks like you are injecting through a small hole so your part is trapped in the top piece. Are you doing that to help remove the part from the bottom pieces? You could add some jack screws in the perimeter frame to help separate the stack.
Yeah, a little more grind and polish to smooth the surface would help as well.
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