The calibration of the raw panels is a refinement of the surface and is considered an important quality factor in panel production. In a calibration sanding machine, also known as a sanding line, the raw boards are sanded simultaneously from the top and bottom, so that smooth surfaces are created and the board has precisely the desired thickness. Calibration sanding machines for the production of wood-based panels are powerful devices due to their large working width and material removal. They often contain several calibration and fine sanding units for the upper and lower side of the board, in order to be able to produce the desired surface quality with regard to the feed speed.