For reasons that I cannot fathom, some prints I did today on the Form 3+, in Grey V4, would absolutely, positively NOT release from the bed. I managed to get the parts off without damage, but the rafts were not moving.
After some communications with Customer Support, and reviewing posts on this here forum, I recovered the build plate nicely. Though I still don’t know why this run was different.
I used a wood chisel to pry and scrape the remaining material. I found that it works better than the supplied tool, but you need to be careful with it.
Then I proceeded to sand the plate with a random orbital sander and a 120 grit pad.
I own a 2" wide Craftsman wood chisel specifically for this task (also works to get stuff off my FDM printer’s build plate if it’s stuck on really good). The chisel is machined flat on one side, you just lay that side down on the build plate surface and lightly tap (I have a small jeweler’s hammer I use). If you don’t nick or bend the edge of the blade, it doesn’t (or barely) even scratch the surface. Worth having in your toolkit.
You do have to carefully brace the build plate to chisel it. You don’t want the chisel to slip off the build plate and chisel the hand you’re using to hold the build plate…
Technique originally developed for my Form1+, but translated nicely to the Form2. Haven’t had this problem yet with the Form3, though.
Putting the platform in the freezer might be another option. The CTE of the resin and aluminum platform is likely different enough that parts might pop off on their own, or at the least with minimal effort.