MK3 Dual Sided PEI Steel Sheet Bubbles  

Re: MK3 Dual Sided PEI Steel Sheet Bubbles

Bubbles are normal.

Re: MK3 Dual Sided PEI Steel Sheet Bubbles

Hey there,

I too have these bubbles on my plate 🙂 (using the MK2.5 though).
Other than that as far as I know these occur mostly due to higher bed temperatures and the 3M adhesive softening at higher temps a bit. According to Prusa IIRC this will go away over time when heating the bed up to these temperatures and not using the spots where the bubbles formed for printing.

In my experience this happens mostly above 90°C bed temperature and good adhesion of the PEI sheet to the part you're printing (that has happend a lot on my MK2S too actually). The stronger the warping forces the more bubbles form. For me nylon caused the most issues IF I got it to stick 🙂

Further I do have to say that the adhesive on the spring steel sheets appears to not be able to take as much as on the old MK42 heatbed. Bubbles now form even at lower temps than 90°C, which I guess is what you're seeing. I presume this is to be traced back to the heat conductivity of spring steel over the PCB from the MK42. As far as I'm informed we'll have to deal with it until either the powder coated sheets are out and readily available or maybe 3M's adhesive is changed for more heat resistance (probaly the former).

Regards
-DerBierBaron

Re: MK3 Dual Sided PEI Steel Sheet Bubbles

Thanks DerBierBaron! I believe your reason is correct and it's nice to at least understand why this is happening, but I guess time will tell about the durability of the PEI 😉

Re: MK3 Dual Sided PEI Steel Sheet Bubbles

I got my 1st Mk3 in November and I am still printing on the same PEI sheet, the bubbles are normal and have not caused me any issues.

Re: MK3 Dual Sided PEI Steel Sheet Bubbles

As others have said bubbles are normal, however I would recommend to be a bit careful with taking printed parts of the surface. I.e. let it cool down and if it doesnt work by flexing the steel plate to maybe use a flat spatula or some liquids to help get the print of the steel plate.

Reason is, that in contrast to alfred, and even so I got the steel plate only since february I damaged it just two month later with PETG and a part which just would not "unstick" from the PEI/steel plate and therefore did take a little piece of PEI with it in the end.

Re: MK3 Dual Sided PEI Steel Sheet Bubbles

As alfred.w writes, this is normal when printing at higher temperatures. Have been printing only with PETG since December (same PEI plate) and the bobbles comes and go, depending on the size and stress from the printed part.
No visible marks on the printed part.

Re: MK3 Dual Sided PEI Steel Sheet Bubbles

I just started printed on my new MK3 (kit) with the dual sided PEI steel sheet. My first print was with PLA, but my second print was with PETG. I used the standard Slic3r Pursa PET settings and changed the print bed temperature to 85/85 from the default 85/90. I noticed after letting the print cool and then bending the steel plate and popped the part off, that there were small bubbles forming under the PEI sheet, especially where the part was. I looked on the other side of the steel sheet and see bubbles starting to form on that side but smaller.

See attached photo. My MK2s has never done this and I even have replaced the PEI sheet once. Is this expected to get worse? Is the PEI going to eventually rip off?

The bubbles are normal and according to joe p you should consider flipping the plate between prints so that the pei can return to flat if you have any raised areas. Part of the issue is trying to remove prints which the sprint steel is still hot. This loosens the adhesive and you end up with what you have there. alternating sides every print allows those deformations to smooth out.

Re: MK3 Dual Sided PEI Steel Sheet Bubbles

PETG Prints adhere very well.

as do TPU prints.

some folk use Windex, or similar window cleaner as a parting agent, to dull the adhesion strength.
some folk use adhesive. I have always found this approach to be messy... maybe I used too much glue, but it's spoiled the forst layer...

I used to use talcum powder, rubbed into the surface and rubbed off...this has worked well for me. but i keep misplacing the powder.
now I use forehead grease, as I always know where that is... and it works well

regards Joan

Re: MK3 Dual Sided PEI Steel Sheet Bubbles

Reason is, that in contrast to alfred, and even so I got the steel plate only since february I damaged it just two month later with PETG and a part which just would not "unstick" from the PEI/steel plate and therefore did take a little piece of PEI with it in the end.

You can now buy replacement PEI for your spring steel: https://shop.prusa3d.com/en/3d-printer-parts/228-replacement-pei-sheet-ultem.html

Re: MK3 Dual Sided PEI Steel Sheet Bubbles

Well it didn't take more than a couple prints in PETG. Especially if you print over the same spot on the steel sheet. I had a little piece pull off and now I am adjusting my slicing so I'm not in the center of the printer bed. Maybe I'll reserve the other side for lower-temperature stuff like PLA. 😡

Do we know how to replace one side of the steel sheet without destroying the PEI on the other side? I have replaced the PEI on my MK2 and it was not easy and I had to soak it in limones which most likely will get on the back side.