Differential shaft, also known as friction shaft. It is applied to the winding shaft of the slitting machine, and also used for the unwinding shaft in special occasions. The purpose is to use the principle of the slippage of each slip ring on the slip shaft, so that multiple rolls on the shaft can always maintain constant tension for winding and unwinding. The differential shaft has been widely used in plastic film (including electronics, capacitors, battery film, cling film, packaging, composite film); metal foil (copper foil, aluminum foil, etc.); paper rolls; slitting and winding of PVC film rolls . It is now being extended to other fields, other industries, and other special materials for cutting and winding.