Screw is an important part of injection molding machine. Its function is to transport, melt, compact, mix and press plastics. All of these are completed by the screw rotating in the barrel, which shows that the screw plays an important role in plastic machinery.

When the screw rotates, the plastic will produce friction and mutual movement to the inner wall of the barrel, the bottom surface of the screw groove, the advancing surface of the screw edge, and between the plastic and the plastic. The forward movement of the plastic is the result of this combination of motion, and the heat generated by friction is also absorbed to raise the temperature of the plastic and melt it. The structure of screw will directly affect the degree of these effects.

At the same time, the rotation of the screw makes the molten film between the solid bed and the inner wall of the barrel shear, thus melting the solid at the interface between the molten film and the solid bed. As the spiral shape of the solid bed moves forward, the volume of the solid bed decreases and the volume of the molten pool increases.

If the thickness of the solid bed decreases at a rate lower than that at which the groove depth becomes shallower, the solid bed may partially or completely block the screw groove, causing plasticization to fluctuate, or due to local pressure, due to the melting rate of various plastics, melt viscosity, melting temperature range, the sensitivity of viscosity to temperature and shear rate, the corrosiveness of high temperature decomposition gas, and the friction system between plastic particles Generally speaking, the shear heat of a certain section of common screw is too high when processing some plastics with outstanding melt characteristics. This phenomenon can be eliminated by reducing the screw speed, but this will inevitably affect the production efficiency.