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.
Re: Deformed PEI sheet
Ignorbit on 😉
Will disappear after a few prints.
Thomas
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
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.
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.
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
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
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.
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... 
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.
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.
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!