Can you fix a warped, removeable build surface backing? I have an Ender 3 with a removeable build surface. The build surface backing has become warped - the center is at least 0.3 mm higher than the corners. I'm not sure what the material of this plate is - it's the part behind the BuildTak-clone surface that sits on the aluminum heat bed and is clipped to it. This makes it impossible to level the entire bed, and annoyingly tedious to level it enough just to use the center, since the paper method doesn't work at the corners. Can this be fixed, or do I need to source a replacement for it?
Yes. I rigged up the following setup with blue tape and clips and a pen for tensioning, used the nozzle (unheated) to hold the center down against the bed, and set the bed to 100 °C for about an hour. Afterwards the curvature was in the opposite direction and easily compensated by clips.