The depth of the screw groove has an effect on the pressure, extrusion volume and temperature of the material. The extrusion volume of a deep-groove screw is highly sensitive to pressure changes. For example, when the resistance of a deep-groove screw is small, the extrusion volume increases with the increase of the groove depth; but when the resistance of the mold increases, the pressure drop changes slightly. It will cause the extrusion volume to decrease rapidly; on the contrary, when the die resistance of the shallow screw screw changes, the fluctuation of the extrusion volume is small. On the other hand, the pressure of the melt in the die can cause the change of the material temperature. Because the deep groove screw is sensitive to pressure, the material temperature is prone to large fluctuations, which will affect the quality of the extrudate. When the pressure changes, the shallow groove screw has a small effect on the material temperature.
The length of the homogenization section also has an impact on the extrusion volume. When it is longer, it will be less affected by the die resistance. Even if the lead die resistance changes and the pressure in the die fluctuates, the extrusion volume changes less.
The resistance of the die to the flow of materials is related to the cross-sectional size and length of the die and bush, which also affects the extrusion volume. The resistance encountered when the material flows is roughly inversely proportional to the cross-sectional area or length of the bush. The larger the cross-section or the shorter the straight part of the bush, the lower the resistance of the die. At this time, small fluctuations in the pressure in the die will cause a large change in the extrusion volume and affect the quality of the product.
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