Heated bed delaminate

Has anyone happend to see where there Lulzbot Mini Heated bed gets bubbles? Almost as if it is delaminating? My Mini just started to exhibit this. The spots started small but now are dime sized. It is beginning to affect the adhesion on the first layer. Thoughts and suggestions appreciated.

Mine is doing that too – gradually growing pockets under the PEI sheet. I’m down to the back right corner at this point. I’ve been thinking about taking an exacto, making a small slice, and squeezing out the air. If that doesn’t work, I guess I’ll be replacing the PEI sheet.

Edit – I tried it. The oldest one won’t stick back down, I think the sheet is deformed there. Some of the newer ones did deflate, but as the bed is heating up to print, they come back to some degree. I’m only printing at PLA temps right now, will be interesting to see if PLA temp has an effect, either positive or negative – I suppose it could melt the adhesive a little and get it to stick, or it’ll just make the bubbles re-inflate.

Try NOT to cut the plastic to remove the bubbles. The cuts will allow water, oils, and other things to degrade the adhesive and make it fail faster. The bubbles can be moisture in the adhesive getting vaporized and slowly separating the PEI sheet from the glass or the slow failure of the adhesive from the heat and pressure put on it by removal of the parts.

This is a known issue with the PEI surface. Call Lulzbot and they will replace the PEI sheet, glass and heater bed for you free of charge.

The root cause is the PEI material holds moisture. When they were assembling the sheets to the glass beds, there was moisture in the sheet. When the sheet is heated, the water turns to vapor causing the issue you see. New PEI sheets are baked to remove all moisture before assembling them to the glass.

E-mail Lulzbot and they should have a new assembly out to you in a few days. Then they will also ship you a return label to send the old bed back. Bed replacement takes about 10-15 minutes if you have the right allen wrench and a small zip tie and a set of wire cutters (for cutting the zip tie).


I’ve got this exact problem on my printer to the extent that the last part I printed ended up with a sizable dent underneath where the bubble sat.

I didn’t realize you could contact Lulzbot to get the whole assembly replaced & have already removed my current sheet, only for the adhesive layer to remain in place. I’m having to very slowly peel it off with my thumb nail. There are some new PEI sheets in the post for me already, any idea if the ones purchased through the store will have been baked too?

A couple of questions:

    • Has anyone got any advice for removing this adhesive?
  • Is there anything I should keep in mind when placing a new sheet on the glass?
    (besides the obvious ‘don’t break the glass’ & ‘try to make sure it’s on square’)


Instructions on replacing PEI

Thank you jim2386, I didn’t bother looking in the ohai kit as I didn’t think there would be instructions for replacing a sheet of plastic. Used some isopropyl alcohol & the stuff came straight off. Now I just need the new sheets to arrive.

If moisture is the problem, it shouldn’t take several weeks of use to develop, mine did. The instructions for replacing the PEI sheets yourself contain no info on baking the PEI sheet to remove moisture before applying it to the glass. It’s good that Lulzbot is replacing the entire bed when this problem surfaces, but the warranty is only a year.

I have same issue with bubble on PEI surface. Since I purchase the printer used, I replace the PEI with BuildTak. As long as do not stick hotend on the bed, BuildTak is a really sweet deal!

Random sources on the internet say PEI was introduced by GE in 1982, which makes me think that many of the basic patents on this material must have expired by now – whether that is true of the PEI sheets used on the Mini is not something I could easily discern, but I hope that it is so and since making film would be one of the earliest things likely done with the plastic, I’m optimistic about basic PEI film being patent-free by now. Buildtak claims to be “proprietary” and “patent pending”, and nothing on its site suggests it is using patents in a non-evil manner. I know this isn’t an important issue to everyone, but it is to me, which means I’ll have to avoid Buildtak.

(rant) The vast amount work that has gone into making consumer 3D printing a reality has been open source, both hardware and software. The consumer market only exists at all, because of all those who donated their time, money, experience, and inspiration to the world. Buildtak’s proprietary patent pending “contribution” to 3D printing is utterly insignificant in comparison – they wouldn’t even have a market to sell into without the technological contributions of others and their patent application shows a deep lack of insight into that fact. At least that’s my take.

I used lacquer thinner to help remove the one I did. Very flammable and don’t get on the heater underneath. I slopped on a small rag and dabbed on when needed.

Just got our replacement print bed from Aleph Objects. They sent a complete bed. Replacement was very straightforward - cut one zip tie and unplug the connectors. Took about 10 minutes, including boxing up the old one, to return. Very fast response from the company.

Thanks for the great service!

Jim Rasmussen