The 3D printer market is FULL of solutions for keeping prints stuck to the bed while printing, and for getting them free from the bed once complete. Of course, these two tasks are somewhat in opposition. The long and short of it is, any bed/material combination that sticks really well while printing is going to be harder to separate once finished, and any combination that comes done easily at the end risks a failed print in the middle.
The be-all end-all solution to this was supposed to be spring steel beds that can be removed and peeled off the finished print, but in all honesty, while these make life MUCH easier in certain cases, they’re simply not the easiest solution in most.
This is the EASIEST solution: sharpen a putty knife to a one-sided blade.
I sharpened mine with a belt sander to make quick work of it, but any sandpaper or knife sharpening stone would do. It doesn’t have to be fine, since it doesn’t have to be sharp. 100 grit with a 220 finish would probably be fine. Mine is sharp enough that I use it to open boxes sometimes, but I’ve never cut myself and I’d have to try kinda hard to do so. it’s like non-serrated edge of a steak knife sharp.
You’ll notice I rounded the corners as well. I did this by blending the sharp blade back into the not-sharp side around a radius, so there aren’t any sharp corners to catch a PEI sheet.
I also made the slightest second bevel by touching the back edge ever so quickly with the sharpening stone. This makes the edge slightly less sharp, and slightly higher relative to the original plane of metal. Mostly it protects the print bed a bit from scraping while still letting you get the blade edge under the print easily.
Overall, this tool works absolutely PERFECTLY for removing ANY print from ANY bed. Glass? No problem – since it’s sharp right up against the bed, you can easily slip it under your print and pop it right off. PEI? Same deal. Powder coated PEI? I use it on mine all the time when scraping the print off is quicker than removing the bed.
Back when I had a Prusa i3 Mk2s with a rigid PEI bed, I used this to remove a super-rigid 0.5kg ~35 square inch first layer block without any trouble at all, just by sliding the kinfe under progressively until enough had unzipped that the rest came free. The full damage to the bed was a little bit of bubbling in the sticker glue that went away. These days I pull the whole sheet off for prints like that, but not for anything less.
This is also the only way I know of to remove a TPU print from a fully isopropyl-clean PEI bed without ruining either of them – and I do regularly because it’s less trouble than washing with windex or putting down glue stick. I’ve never used glue stick.
And best of all, you can make one for about $5, probably even with materials you already have.