Bumpy Print Sheet
Hello there!
I am a 3D print newbi and bought my first Mini recently. Since it was second hand I also bought a new Smooth PEI Print Sheet. I had six good prints on it, but after the last print (hexagonal shapes) the shapes left some imprints on the sheet and some slightly raised edges on the Print Sheet.
The print stopped for a few hours because I had to load new filament amd I was busy in between. Not sure if that had to do anything with it.
I added a photo of the Print Sheet.
Does anybody know why that happened and if the Print Sheet is still usable?
Thanks folks! 
This does happen sometimes with new smooth sheets. As long as you don't reprint in exactly the same spot (move the slice or use the other side) the bubbles will disappear as the plate is used, repeatedly reprinting the same part in the same place can make things worse and sometimes cause damage.
It is often a sign that whilst a print is adhering strongly to the sheet it is also attempting to warp ... the usual anti-warping procedures normally reduce the incidence.
Cheerio,
RE: Bumpy Print Sheet
As Diem said this is ok. Generally reheating the bed and leaving it hot for few minutes should help it to cure so it will look better - so this happens and cures during normal printig.
Just make sure not to print PETG in this print sheet type, because it sticks so well that some day it will fuse and you will damage the print sheet - so it is worth to plan to buy some other sheet for the PETG.
See my GitHub and printables.com for some 3d stuff that you may like.
RE: Bumpy Print Sheet
Thank you! I'll be watching the sheet.