I recently purchased a Ender 3 S1 Pro, and although it is a great printer and definitely a huge step up from my old Anycubic Mega Pro, there have been many problems getting PLA to stick to the PEI build platform. I have tried getting the bed level perfect, scrubbing it with dish soap and wiping it down with isopropyl alcohol, nothing seemed to help. More than once a piece would simply pop off during printing. raising the temperature to promote adhesion made the prints start to warp. I'm a little lazy and I don't want to bother with any kind of glue stick, hair spray or anything like that.
Then I came across someone using polycarbonate as a build platform (Here). I got a panel, trimmed it down to size, roughed it up on one side with 80 grit sandpaper, and tried it. Adhesion is so much better and no warping. I have not needed to print with a brim so far. Prints stay adhered when the build platform cools, but it's thin enough to take off and flex to help remove them.
Since this solution works so well and is cheap (I paid $17 for my sheet, which is probably more than I should have), I would recommend it to people having troubles with adhesion with PLA. I'm probably going to stick with it, although I may get a G10 build platform if I try anything with PETG.
