1. In the traditional system of screw extruder, screw is driven by DC motors. The screw is directly driven by the gear box in direcrt drive; in the case of indirect transmission, it is pushed by the belt and disk drives. There are some shortcomings of traditional DC motor itself, for example, the brush of DC motor must be replaced once a month, and it is necessary to clean DC motor regularly. Sometimes even cooling air is needed to pass DC into the cleaner from outside the workshop.

2. The drawback of indirect drive screw extruder is: the existence of slip on the belt, a belt can cause a certain degree of energy loss, and additional mechanical devices have increased the possibility of failure. Noise is the biggest flaw of DC motor, due to brand brush, rotor pollution, motor temperature too high, inadequate exhaust and electrical shock. Therefore, it must be at high expense for screw extruder to use DC motor, such as higher maintenance cost.