Has anyone tried leaving the PET on the glass and then bond the PEI to it with the transfer adhesive? I am reluctant to bond something directly to my glass, not knowing if I can get it off, since the heater mat is bonded to the glass.
If you use the 3M adhesive (486MP), it is pretty easy to remove the PEI.
In my case, I just pulled the PEI off (.040 thickness), and then with a razor blade scraper and some liquid WD-40, removed the adhesive. The glass is back to normal, ready for a new sheet of PEI.
Kenny
I ordered my stuff. I will be trying this out Wednesday!
pls let us know how it went, im also interested in printing with T-glase 
Yes I left my PET on there, had to raise my bed temp to about 95. Very little to no warp though 
Has anyone had to replace the PEI sheet yet?
I ended up attaching my 1/8" sheet to the glass with 5 strips of 3/4" tranfer tape. working very well. added a stack of m3 washers and a longer m3 bolt to the corner retainers to compensate for the aditional 1/8" height.
So far, I am having a bad time with this. I have a 0.0625 inch sheet from Amazon stuck to the bed with the recommended 3m tape. Running at 230 / 85 for ABS. One print stuck so hard I destroyed the parts trying to remove them. Since then, all builds have curled.
I see a variety of temps here, from cooler than 85 to 95 and maybe higher if I am not confusing my forum data 
. What is the consensus, should I try a higher bed temp? Should I scuff the bed with 2000 grit sand paper? Any suggestions?
I am not having the wonderful experience with this stuff I was hoping for. Boo. 
I’m sure sanding it will make it stick even more due to more surface area to stick to.
Try using some PAM… (hehe)
I’m runnning 85 for the bed, and 230 for the filliament here. Try increasing your bed gap slightly or dropping the temperature slightly. I usually remove the parts with a flat pry tool that happens to be a Cheese slicer. Have not had any problems with things not coming off with a bit of cooling and effort. Sorryit’s not working out as well for yours.
The larger parts I have been trying are cookie cutters. They have been warping up off the PEI. I think I will try scuffing the surface with 2000 grit. It sounds like that is a pretty common treatment.
I have varied the first layer squish following the part destruction episode. Currently I am back to my original set up which it a 0.005 gap with a 90% first layer thickness. This is the same set up that resulted in the parts sticking too tightly but now, they curl and warp.
I will let you know how it goes with a scuffed bed.
Are you all wiping the bed with alcohol or acetone?
Thanks.
I use 85 for the bed (ABS).
One thing I learned is to not squish the first layer. If you do, it will be difficult to remove the parts without scraping them off. When you scrape (or use sandpaper as you are thinking of doing), the parts become more difficult to remove. I ruined my first sheet because I over squished the first layer and all the scraping took its toll on the PEI.
You also need to let it cool before taking the parts off.
I haven’t had to use ABS Juice or Hairspray since using the PEI. ABS will still lift on the corners of long parts so Brim and round disks are still needed as they were before.
Kenny
My parts are curling off the bed now. Since I am squishing the first layer like I did before the PEI, it seems like I need a surface with more grip. Honestly, I am not sure what is going on. It doesn’t seem like my experience is matching up with most others on the net. Maybe I have some bum PEI.
I bought a sheet of .063 PEI from Zorro. I’ve just been holding the edges down with bulldog clips. (But I can’t use the bed leveling gcode, because it runs into the clips.) So far it has worked well for some parts with X and Y dimensions close to each other. But for longer parts I also got some end lifting, and parts that are bowed.
I also bought a sheet of BuildTak. This is the best bed surface I’ve used yet. You have to get the nozzle clearance just right, and that’s more clearance than I’ve used with other surfaces. If you’re too close to the bed, it will be nearly impossible to remove the part without damaging the BuildTak. I have some scuff marks in mine, but I haven’t cut it yet.
For a removal tool, I used my bench grinder to put an edge on the rounded end of the Lulzbot clam knife. I ground it from one side only, and then I touched up the grinding a bit with a file. (If you do this, you’ll need your quenching water. Quench constantly while grinding or the blade will burn.) I have learned to put the ground side down at just the correct angle so the edge goes under the part but not into the bed surface.
I just printed 2 Z top drive pieces for the Taz 4 conversion, and they are both flat. Earlier attempts on PEI were bowed. the parts stick extremely well to the BuildTak. I’m getting better at setting the nozzle height just right, and in removing the part.
So far I have only printed ABS on the BuildTak.
At $20 per sheet, I doubt I ever try Buildtak. I will just stick with the stock PET sheets if the PEI doesn’t work out…
This is an example of the problem I am facing. This part is roughly 4 x 3 inches. I cleaned the bed thoroughly with acetone and alcohol before printing this one. It is not curling as bad as the part I tried previously, which was a little larger than this one.
Yes it is pricey, but we have yet to find out how long the BuildTak will last, compared to PET. So far, with some scuffs but no gashes, it seems more durable than PET, as my previous PET sheets had gashes by this time. I’m hoping to compare the long-term cost rather than the initial purchase cost.
After sanding with 2500 grit paper and vigorously cleaning the bed with acetone and isopropyl alcohol I have had three successful warp free builds. I will keep my fingers crossed!
I have had many many successful warp free prints since installing the 1/8" thick PSI sheet.
I have carefully leveled the bed. With the exception for the bowing of the x axis in the center the bed is very level. I split the difference between the center and edge with the sides being a bit high and the center a bit low. This has resulted in the best first layer adhesion and repatable over and over. Haven’t had to re-level Only problem I have had with prints is an occasional extruder stall.
I have printed 16h full plate prints for the lite arm bot which is all long thin flat pieces. Had one piece where the end lift slightly but this was after that part had finished printing. By the time the bed cooled for removal of the parts, that part had flattened back down and was perfectly flat.
The last week has been the best repeatable printing of ABS I have experienced since putchasing the TAZ 3.1
The PEI upgrade alonng with teh Z lead screw upgrade is producing very high quality repeatable printing.
Only a couple more sues to over come on teh road to perfection. I have a 3 layer band showing up at a random position one time on a print same geode and it will show up different layers. 3 layers of slight blobbing visible on the sides of the print. very slight but a visible imperfection. The randomness of the position makes it a bit hard to pin down but it is minor and has not affected the functionality of the prints. More of an anoyance.
The other is the dim horizontal holes vs vertical holes and as far as I can tell, its an inherent problem to FFF printing and has to do with extrusion width etc. This can be worked around by cheating the vertical holes slightly larger in the model.
I have some BuildTak here but have not had a reason to try it once I got the PEI sheet installed and the machine dialed in. Until l I have a failure or damage to the PEI, I think the BuildTak will stay in its package.
My only regret with the PEI is the time waiting for the plate to cool and reheat between prints
I have been able to remove the parts after the bed cools about 10 degrees C on these last three builds. I just wiped with isopropyl and heated 'er up again.
So I have now ran about 20 prints through my machine with the new PEI sheet installed using the 3M adhesive on amazon. At first the bonding sucked. I was left scratching my head. Everyone seems to think this stuff is gold. The PLA stuck to it great but ABS would lift on any parts more than a few hours long. I have numerous parts I make that are 12+ hours. I started messing with the Z height setting at got it better dialed in but not perfect. I then started using acetone to clean the surface and that helped a little more. I finally mixed a little ABS into the acetone. Not nearly as much as my acetone “slurry”. That seems to have done the trick. My prints seem to stick well and for many hours now. I also got a new 3/16" tempered glass bed. I got sick of cracking the thin glass bed that comes with the machine. No cracks or issues since the install. I am very happy now with the 3/16" plate with the .03" PEI sheet combo. They seem to be working great.