This comes from the official "Documentation" that was posted earlier: Cleaning the print bed surface The Robo R2 print bed surface is a sheet of PEI. Make sure to clean it with a damp cloth to ensure your print sticks to its surface. After 4-6 months of use, you may need to retexture this sheet if you see that your prints are not sticking to it. To do this, simply grab some 2000 grit sandpaper and lightly sand the surface, afterwards cleaning it off with a damp cloth. Ensure that the print sheet is laid completely flat on the build platform, and that it is flush and level across the surface. If you would like, you can order more R2 print beds at www.robo3d.com. When removing and replacing the entire print bed, double check that its magnets align with the magnets on the platform to ensure it is seated correctly and plug in the power cord in the back of the bed. Build platforms that aren’t seated correctly will result in failed prints.