Screw rod is an important part of injection molding machine. Its role is to transport, compress, melt, stir and press plastics. All this is done by rotating the screw inside the barrel. When the screw is rotating, the plastics will cause friction and mutual movement between the inner wall of the cylinder, the bottom surface of the screw groove, the driving surface of the screw edge and the plastics and plastics. Advancing plastics is the result of this combination of motion, and heat from friction is absorbed to raise the temperature of plastics and melt them. The design structure of the screw rod will directly affect the degree of these effects.