Ever had the problem of print just not sticking to a PEI 3D printer bed? I sure have…
Thankfully, taking care of the printbed or even fully restoring one isn’t hard!
So I’ve run into the issue on pretty much all of my PEI-equipped 3D printers, where, after a while, prints just start refusing to stick well. So I tried adding glue stick or 3DLac, which again, is one of those stupid products that tries to be unique by having a name that is spelled wrong, but is supposed to be pronounced like the real thing, which works in forums but is pointless in spoken language -- but I digress. The bed on this MK2 is already freshened up, and parts stick like crazy. Yes, that’s a chisel, and yes, if you’re not careful, you’re going to mess up your bed even more with this. But let’s check out what it takes to get a PEI bed working as good as new again and how to keep it that way.
Depending on how much you’ve mistreated your PEI surface, you’re going to need a few different things. For a basic cleanse, you’ll need warm water and some sort of alcohol, I use denatured ethanol. If you want to go deeper and completely reset the surface, you’ll also need a stronger solvent like Acetone, Ethyl Acetate aka nail polish remover might also work. And for the finishing touch, some medium to fine steel wool, this is the only part that will actually remove material from the PEI sheet, so don’t use a super coarse pot scrubber, but the regular steel wool removes so little material that you’re more likely going to rip the PEI before you actually start wearing it through. Also, if you treat the bed well and clean it regularly, you’ll rarely need any abrasive at all.
Because I have various substances on here, I’m going to start with the least aggressive solvent, water. Either use warm water or preheat the heated bed and, of course, don’t forget to unplug the printer after that. The water softens and dissolves any PVA-based adhesive like glue stick etc. It needs to soak a bit, so I’m taking a paper towel and using that to keep the water spread out. As with any of the solvents, make sure it stays on the bed only and doesn’t drip down into bearings and electronics. After a minute or so, most of the glue stick and similar materials will have softened and you can start wiping them off. Make sure you get as much of it off and take a few passes if necessary.
Next up, acetone, this will dissolve most polymer-based coatings and take off any grease that might still be on there. Technically, you should be wearing the proper gloves, by the way. PEI, Kapton etc are typically not dissolved by acetone, so you’re not damaging the bed surface here. Again, take a few passes until there’s nothing coming off of the PEI surface anymore. And next up, steel wool. This actually does two things: First off, it takes off a tiny bit off of the top, exposing some fresh PEI, and it also roughens up the surface a bit, so, in theory, you get a bit more surface area for printed parts to stick to. I don’t know which one has the greater effect, but I do know that it works. And you don’t have to scrub super hard here, it’s more of a peeling than a complete surface grind.
Now, what I’ve found to work best here is to always use denatured alcohol right before every print -- in this case, obviously, it takes away all the dust and particles and grease you might have gotten onto the bed, but since PEI is relatively sensitive even to just fingerprints, quickly wiping it down before every single 3D print is what I’ve found to give optimum adhesion, and for some reason, using acetone instead to wipe the bed down before a print doesn’t quite give you the same results.
Now, you do have to be careful when removing the parts, because you can get them to stick extremely well. Prusa’s standard PEI is on 0.175mm thick, aka 175 microns, which isn’t a lot. Especially flexibles and polyesters, so PETG etc like to really bond to the surface, so print the first layer a bit cooler if you’re afraid to rip a chunk out of the PEI sheet. I do sorta speak out of experience here.
My favorite approach is to use that wood chisel, flat against the bed to get as many of the of the corners to lift, and then using a spatula, if necessary, to get the rest of the print unstuck from the bed. 3D Prima actually sell PEI sheets up 2mm thick, which should be able to take a substantial amount of abuse before giving up. And you can like, literally sand it down if you ever have to. I’ve tried in the past to patch in little spots with glue stick where I had ripped the PEI, which was better than nothing and allowed me to keep using the PEI sheet for longer than i should have, of course, sooner or later it just has has to go, but replacing it is a huge pain since the 3M adhesive sticks incredibly well to both the PEI and the surface you stick it onto, so it’s best to keep it usable as long as you can.
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