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Koder
(@koder)
Trusted Member
Deformed PEI sheet

After last print (ABS, large part, no raft) I have noticed a small deformation of the PEI sheet around perimeter of printed object:

It seems that some kind of bubbles formed between PEI and PCB; surface is also raised to the point that it significantly squashes first layer printed there. Is this is obviously caused by too good ABS adhesion to PEI while it was trying to warp up and I will try to print such parts on raft next time - but I'm worried about damage to PEI.

I have searched forum for this and found a number of posts on "PEI bubbling", which is supposedly normal and should go away on it's own in time, but with no photos to confirm that it is indeed the issue I'm experiencing.

What is there to be done? TIA.

Posted : 19/07/2017 9:25 am
Knickohr
(@knickohr)
Member Moderator
Re: Deformed PEI sheet

Ignorbit on 😉

Will disappear after a few prints.

Thomas

Posted : 19/07/2017 9:51 am
Koder
(@koder)
Trusted Member
Topic starter answered:
Re: Deformed PEI sheet

An update: the deformation indeed goes away after 2-3 prints. Just make sure to not print exactly same thing in exactly same place.

Posted : 20/07/2017 9:29 am
cyrille.p
(@cyrille-p)
Estimable Member
Re: Deformed PEI sheet

Yes once the PEI is heated for a new print, it seems to stick to the bed again.

My youtube channel about the Prusa I3 MK2 https://www.youtube.com/channel/UCz-zQZcKcvEDdd9C9hOKYWg

Posted : 20/07/2017 10:27 am
MrMik
(@mrmik)
Honorable Member
Re: Deformed PEI sheet

This is what you get with good print adhesion and medium warping forces. The higher the print bed temperature, the more the glue under the PEI sheet liquefies and form bubbles.

With large prints, good adhesion and somewhat warp-prone material (e.g. Polymaker PC Max), you can actually pull the PEI off the bed, or even warp the entire print bed.

I think you need to constantly move objects to different locations on the print bed to reduce wear of the PEI sheet glue layer. However, that leads to more use of the extreme x- and y- positions, and therefore more bending of the cables entering the extruder, with earlier cable breakages.

Posted : 20/07/2017 2:14 pm
Koder
(@koder)
Trusted Member
Topic starter answered:
Re: Deformed PEI sheet

I think you need to constantly move objects to different locations on the print bed to reduce wear of the PEI sheet glue layer. However, that leads to more use of the extreme x- and y- positions, and therefore more bending of the cables entering the extruder, with earlier cable breakages.
I currently work on project that covers practically whole print area, so moving to other locations is out of the question. Currently I'm using some brim - hopefully it will spread the force over larger region.

And yes, after 4 prints there is no deformation anymore.

Posted : 24/07/2017 6:50 pm
Jason Foss
(@jason-foss)
Eminent Member
Re: Deformed PEI sheet


I currently work on project that covers practically whole print area

Assuming the base isn't just a square, you might be able to get some additional mileage by arbitrarily rotating it

Posted : 24/07/2017 7:23 pm
Koder
(@koder)
Trusted Member
Topic starter answered:
Re: Deformed PEI sheet

Assuming the base isn't just a square, you might be able to get some additional mileage by arbitrarily rotating it

I have two orientations that works tops.

Posted : 24/07/2017 9:11 pm
Jason Foss
(@jason-foss)
Eminent Member
Re: Deformed PEI sheet


I have two orientations that works tops.

I mean, I bet you could print that vertically with some supports... Then you can shift and rotate to your heart's content.

lol

Posted : 24/07/2017 9:20 pm
Koder
(@koder)
Trusted Member
Topic starter answered:
Re: Deformed PEI sheet

I mean, I bet you could print that vertically with some supports... Then you can shift and rotate to your heart's content.
Thought crossed my mind, but model is 245x205x30, so I'm missing 5mm height-wise 🙂

And - it is one part of two-part print. I could probably slice it into thee parts, but it complicates things.

BTW, that's ABS.

Posted : 24/07/2017 9:25 pm
Jason Foss
(@jason-foss)
Eminent Member
Re: Deformed PEI sheet


Thought crossed my mind, but...

I could tell you were a true craftsman by the hand-cut dovetails along the bottom... :mrgreen:

Posted : 25/07/2017 10:35 pm
MrMik
(@mrmik)
Honorable Member
Re: Deformed PEI sheet

Has anyone tried if the elevated areas of the PEI sheet disappear faster when the bed is heated during printing, compared to standing around cold?

I assume it goes faster with a heated bed, which would make it feasible to heat the bed for a certain time between prints (after removing the print).

I tried 120C for 30min and the elevations reduced, I think. I have not figured out a good way to reliably measure it.

Posted : 25/07/2017 10:51 pm
Koder
(@koder)
Trusted Member
Topic starter answered:
Re: Deformed PEI sheet

Has anyone tried if the elevated areas of the PEI sheet disappear faster when the bed is heated during printing, compared to standing around cold?
I'm pretty sure it helps, but no hard measurements taken on my part. Another things that may help is putting a sheet of glass on heated bed (to help it flatten) or even just ironing it out; PTFE coating on iron should not stick to PEI - at leas not too much.

Posted : 25/07/2017 11:28 pm
Vertigo
(@vertigo)
Trusted Member
Re: Deformed PEI sheet


Thought crossed my mind, but model is 245x205x30, so I'm missing 5mm height-wise 🙂

Oh common, the solution is staring you in the face, you just dont want to see it: rotate the object ~45 degree around the X or Y axis. Add quite a bit of support columns. Move the support columns between prints. Taadaa, problem solved ;). Bonus: you can print slightly larger panels!

Posted : 25/07/2017 11:38 pm
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