The role of screws in plastics machinery

The screw is a key component of the plastic machine, and its effect is to transport, melt, tamp, mix and apply pressure to the plastic. All this is carried out according to the rotation of the screw in the barrel, it is not difficult to see that the effect of the screw in the plastic machinery and equipment is crucial.

When the screw rotates, the plastic will cause friction and mutual fitness movement for the inner cavity of the barrel, the bottom edge of the screw groove, the pushing surface of the screw edge and the middle of the plastic and the plastic. The push forward of the plastic is the result of this type of fitness movement, and the heat caused by friction is also digested and absorbed to raise the temperature of the plastic and melt the plastic. The construction of the screw will immediately jeopardize this level of efficacy.

At the same time, the rotation of the screw causes the cutting effect of the melt film in the middle of the solid bed and the inner cavity of the cylinder, and then the solid melt between the melt film and the solid bed. Along with the spiral change of the solid bed, the volume of the solid bed gradually decreases, while the volume of the solution pool gradually expands.

If the rate of thinning of the solid bed is less than the rate of thinning of the deep layer of the spiral groove, the solid bed is likely to partially or completely block the spiral groove, causing melting to undulation. Or because of partial pressure because the melting rate of various plastics, the viscosity of the solution, the melting temperature range, the relative sensitivity of the viscosity to the temperature and shear rate, the corrosion of the high-temperature dissolved vapor, the friction resistance between the plastic particles is very different, In general, the general universal screw in the practical sense will occur when the production and processing of some plastics with very obvious solution characteristics, a certain section of cutting heat is too high, which can generally be removed according to the reduction of the screw speed ratio, but this will inevitably harm the productivity.