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Problem with the compression bowl

This topic contains 8 replies, has 5 voices, and was last updated by  Edson Hugler 1 year ago.

Ezequiel ezeturk

Problem with the compression bowl

15/08/2018 at 19:49

Hello Community! I need some help.I am producing bowl by compression and I am always having the same problem. The problem is that when I realize the demolding of the mold it is observed in the bowl air bubbles that do not give a good finish Perform 13 tests using PP modifying times (30 40 50 minutes), quantity of material (450 430 400 420 grams) and the result is the same in all products. In test number 10 verify and correct the parallelism of the upper and lower plate of the compressor. the last 3 tests came out the same. I attach the images of the last test in search of help 🙂

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29/08/2018 at 09:24

Hi, have you solved this problem yet?

I see you’re compressing outside your oven, at what temperature do you take the plastic out?

I think the particles might not be properly melted. Or its too cool by the time it rises to that level.

Try and polish your mould a little more also or use mould release.

25/09/2018 at 19:44

Like the previous response said, it seems like the plastic is not fully melted yet. Perhaps melt for longer? Or use higher temperature to make it flow easier?

Other thoughts:
* What is the size of plastic chunks that you are using? The larger they are, the more air pockets you will get
* Perhaps compress it slower? If you compress very rapidly, the mould might overflow before the air voids have time to fill?
* Perhaps design a mould that has a tighter seal to make it more difficult for excess plastic to escape. This would encourage it to fill voids rather than seep outside. Getting enough pressure might be a problem however – I suppose different sized car jacks and a solid mould/frame would solve this problem.

30/09/2018 at 02:47

Hi @dplasto @nickchomey thank you for your answer-I havent solved the problem yet im going to try what you told me.
I compress the plastic at 210°C and I use a mesh of 8 mm hole
I usually use pp and hdpe and the residence time is about 40 minutes and the plastic is all reade melted
Im going to polish and use some mould release
Thank you guys

23/02/2019 at 01:23

Hi! I am also having problem with the compression bowl! did you already solved the problem? My problem is that when I try to unmold it it always sticks to either one side or the other but I havent accomplished to unmold it. What mold realease are you guys using? Hope you guy can help me! and vice versa!

24/02/2019 at 04:29

Hello @ehugler !  Some things that I learned using the outside compression:
1.The mould of the bowl has to be very well polish. Used grinder disk.
2.PS(5)-PP(6)-And ohter (7) are the best plastic for this technique
3.Alignment and parallelism are important to avoid imperfection.
4. When you are compressing do it very slowly to avoid over flow
5. HDPE (for me) is the worst plastic for this technique many time stick in the bowl and other time make bubbles (Im still try to improve with this material because i have a lot of and the most beutifull bowls of colors are of hdpe)
6.The best mould realase is Mirror Glaze Meguiar`s and alternative i used silicone spray
7. If you mould need 350 gr you have to put 400 gr and never compress the mould to the end,  live 5 mm between the upper and lower  bowl
8. After compressing i wait 5 minutes and  decompress the mould and put to colling in a place with wind (the dilation of the plasticand the steel make easy to unmould

I wait your answer

24/02/2019 at 08:18

@ezeturk hi !

Have you ever managed to do compression without any use  of mould releaser or silicone spray?

we don’t use any of these & have 0 issue..


24/02/2019 at 16:23

Hi @imuh for PS and Other 7 I dont use mould realese. For PP i use a little bit  but you could avoid using.
For HDPE i need a lot of mould realese.
Do you have any suggestion ? MAybe you can share the variables of a typical compression like type of plastic (Example:cups), temperature, time,etc
Thank you for share your experience 🙂

25/02/2019 at 18:38

Thank you very much @ezeturk I’m gonna try with your tips and see how it goes. I’ll keep in touch!

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