I e-mailed 3M to see if they have a reccommendation for a better adhesive sheet to use than the 465mp stuff for this application. The permanent fix might be to just permanently CA glue the sheet to the bed substrate.
Are yall following the bed removal temperature guide?
Clean Bed
ABS - 50
PLA - 45
HIPS - 50
Laywood - 45
Laybrick - 45
Gluestick - Gluestick is REQUIRED for these materials or they can bond to the PEI
T-Glase (PET) - 45
Fliexible Filament - 35
Nylon - 50
PolyCarbonate - 50
N-Vent - 50
You shouldn’t let ANY print cool down all the way before removing it (I learned the hard way and was corrected by support). If your print can’t be pried off chances are it’s cooling down too much and/or is squished too close to the bed.
You should have this as part of your ending script:
M140 S** ; turn bed to **c
Replacing ** with your needed temp. so for PLA it would read:
M140 S45 ; turn bed to 45c
Note that this will keep your bed on until you manually turn it off. This will greatly help save your PEI bed. It’s also a good idea to rotate parts around the build plate.
I set my nozzle height set so that ABS prints pop-off / releases at 55- 50C. You can hear the snap, crackle and pop of the object releasing at it cools from 65C. Sometimes they need a little help using the clam knife or similar flat tool to wedge between the PEI and object. My print bottoms are smooth with little to no striations from the extruded filament (use .2 Z-offset to get a completely smooth bottom). I don’t think you can get the nozzle height dialed in better than that…
Bed still bubbling. It’s a combination of fatigue and humidity affecting the adhesive. It might be a good idea to use strips of adhesive rather than a complete sheet. A bit of space between the adhesive strips may help changing humidity… And release of moisture.
Epoxy might be the best way to keep the PEI on the glass… But that’s permanent.
Do you have any info about removal temperatures for PETG?
I’ve found that I can print it onto room-temperature PEI and it holds well and comes off fairly easily. Without any glues, etc.
For larger parts that have a tendency to curl, raising the bed temp. to 35 or 40 keeps it stuck down nicely, but it still pops off pretty readily.
The very first thing I printed with PETG I printed at 240 extruder, 85 for the bed. That gave me the worst single “stuck part” problem I’ve EVER had with this printer. I ended up having to bring the bed up to 115C to soften the PETG enough to slowly pry/pull it off. I’d not seen the above info about needing to use glue stick.
So, any advice for the best bed temperatures for printing or removing PETG on bare PEI (no glue stick)? After my one experience with the bed at 85 during printing, I’m sticking to much lower bed temps, mostly no heating at all, and I’ve gone through nearly a kilogram of PETG without a problem with the PEI that way. [edited]
I used to experience bubbles like that when I first got my taz and they used PET sheets on their beds. I was having issues with the prints sticking to the bed and tearing of the pet also. So I ordered a 100$ printinz 12" taz build plate and clipped out to my bed. It worked ok, for about 3 prints, then nothing would stick, and I found myself back at square one. I did some research and came to PEI. When I went online to purchase some they apparently were having a shortage problem from the extreme demand that PEI recently fell into. So I went to amazon.com and the only reasonable thing I could find was a 12x24" x1/8" thick piece. I repeat I ordered 1/8 inch thick PEI. I scored it in the middle with a utility knife and square on both sides and snapped it into 2 pieces so I would have a spare (1 year later and still using first one!). then using double sided 3m, I stick it to the bed.
After using this for a year, I never have to worry about any filament coming loose, air bubbles are non-existent, no tearing/ripping, heat bed works same as with thinner PEI. Of course you still need to use a glue stick, but this stuff is indestructable!
Happy Printing,
Sun
I second Menissalt. I added this code to my end G-code after my 3rd bed replacement:
M190 R50 ; wait for bed to cool to ABS removal Temp
G1 X145 Y175 Z156 F1000 ; move to cooling positioning
M140 S50 ; turn bed temp to ABS removal temp
M84 ; steppers off
G4 S21600 ; Hold bed temp for 6 hours (hours*3600) S<time in seconds>
M140 S0 ;Shut off heated bed
The only two things that might change print to print. One is change the bed temp on lines 1 and 3 to the removal bed temp for whatever material you’re using. Second, I added a small line of code for the number of seconds the bed should wait before turning off. This is really just there as a safety measure if I leave the house for days on end and forget I had a print going so eventually it will shut off. The value for this is in seconds. This is useful if you know a print is going to finish about 3am and you’d like it to hold the bed temperature until at least 8am. I have mine set for 6-8 hours which works great if the print finishes right after I hit the sack.
I’ve also been trying better removal techniques than prying up on the corner of a thick part. If the part is taller, I hit it lightly on all sides with the blue end of the knife and that helps loosen most parts up nicely so that no prying is needed. So far after many prints the bed still looks new. Hopefully I’m onto something here. Hope this helps!
Jim
Suntorn I did not get the 1/8 thick stuff but thinner and the 3M adhesive tape/sheet ( Amazon.com ) and put it on my MakerGear M2 bed 3 months ago… not a problem so far.
I print PETG at 245/85 and just let the bed cool down to below 50C and the project comes off with very little effort. BUT my printer is in a cool room, usually 65 F or so.
Yeah thinner will work, but just as a guage I have 1/8" and I really like it, it’s like a sheet of glass. Use whatever works for you 
Curious to hear how the 1/8" PEI works long term. It was mentioned in the original PEI thread that thicker sheets had a tendency to curl after some use.
Thanks for the tip to score and bend!
I’ve been using the 1/8" thick PEI for over a year now, and I have no problems. Other than a few scratches from using a clam knife ( use a 1/2" wood chisel to slowly pry edges up instead) its it’s still flat as glass and in pristine shape.bubbles or rips!
Happy printing
Thanks for the feedback.
The 1/8" sheet sounds like a candidate for a “removable” PEI sheet option.
My pei surface has finally given up and nearly completely peeled up from the back. Nevermind bubbles there’s enough air trapped under the surface to climb Everest.
PEI does not really seem available over here in the UK. I want to go the 1/8" sheet route. Where do you lot get this stuff from, McMaster Carr? Also is the surface truly flat across the top?
I use a 1/32" sheet, but I looked at Amazon when I got my sheet/s.
I don’t believe the bubbling is due to part removal forces. My TAZ5 originally had only very minor bubbles, not enough to be an issue, which steadily got worse over time. And the bubbles appeared mostly near the corners, where nothing is being printed. Then the TAZ sat idle for about 6 months, and the bubbles got much worse over that time. Now they’re showing up the at the center of the bed and it’s so bad it’ll have to be replaced it. And my TAZ5 is only 10 months old 
Oh well, maybe it’s still under warranty.
I don’t think the 3M adhesion they use is very good. My sheet came about 40% off the bed on my T6 during a print, not during removal. Had normal tiny air bubbles before the print started. During the print, about 5 hours in, the edges directly around the part formed larger and larger bubbles until they hit the edge of the bed and then curled up. When I removed the PEI from the bed, it just came right off with barely any effort. There were like 2 quarter-sized places where the adhesion was sticking pretty well to the PEI/bed, but most of it came totally off without ease and only stuck to the bed. It was like removing yellow postit-notes and I was expecting more like gorilla glue. Here’s some pics: https://forum.lulzbot.com/t/adjustable-heat-bed-glass-mount/38/1