When the twin-screw extruder works, the screw head part will produce very large pressure, usually around 14MPa, sometimes even more than 30MPa. This pressure is a strong axial thrust to the screw, and the thrust is the thrust bearing. The bearing capacity of the stop bearing is related to the diameter, and the larger the diameter, the stronger the bearing capacity. The central distance between the two screws of the parallel twin screw is limited, and it is obvious that a large size stop bearing can not be chosen. This is usually a small diameter bearing on use, the core problem of this approach is: load each thrust bearing to bear must be uniform, otherwise bearing large load destroyed early, the load to bear other bearings, will also be made into other overload bearing damage. The consequences of this continuous failure are very serious. Therefore, the transmission system structure of parallel twin screw extruder is generally complex. Compared with conical twin screw extruder, gearbox has high manufacturing cost and complex maintenance.