Notifications
Clear all

[Solved] Airid melting plastic  

 
SCC
 SCC
(@scc)
Member

My school just got the whole filament making setup and after grinding up some pla prints we put it in the airid to dry out the granules. I made sure to select pla like the paper says and followed all the steps given. We noticed that the pieces were clumping on the mixer arm, and were starting to melt to it. What's causing this?

Quote
Posted : 04/06/2020 6:57 pm
louis
(@louis)
Member Admin

Hello,

I am Louis Rinaldo, materials specialist at 3devo ; it is a pleasure to help you.
Thank you very much for reaching out to us and explaining your issue.

I am really sorry to see that your plastic started to clump to together inside the dryer.

After analyzing your case, I think it is possible that the particle shape facilitates this phenomenon :
- regrinds have a higher surface/volume ratio than pellets --> this increases the heat exchange and the 'clumping together'
- regrinds have a rougher shape which can increase the friction (and therefore unwanted heat generation)
It is also possible that the plastic, being recycled, has a degraded structure (compared to brand new virgin PLA). This lowers the energy needed to melt it.
One final factor, which may have a lesser influence, is that the plastic, having been printed before, might more amorphous, and therefore more prone to sticking at lower temperatures.

Those are potential causes. In order to fix the problem, I would recommend you to lower the drying set temperature, down to 60deg C. That would be a good starting point of experimentation.
Luckily, PLA is not extremely hygroscopic. It will undergo hydrolysis when being processed with water, but lower the drying temperature slightly should not have a significant influence on the results.

Can you please let me know how this goes ?
Please feel free to ask any quuestion, if my explanation is unclear.

Looking forward to hearing from you

Best regards,
Louis

ReplyQuote
Posted : 05/06/2020 3:20 pm
SCC
 SCC
(@scc)
Member

That fixed the melting problem we had. I assume it was because the regrind is more heat conductive like you said.  Thanks so much for the help!

ReplyQuote
Posted : 18/06/2020 4:07 pm
timo
 timo
(@timo)
Member Admin

@SCC, thanks for letting us know! If there is anything else, we would be glad to help!

Best regards,

Timo

ReplyQuote
Posted : 19/06/2020 10:59 am