main reasons that the twin-screw extruder affects the uniformity of the extrudate

What are the main reasons that the twin-screw extruder experiment affects the uniformity of the extrudate? How does it affect it? How to control it?

(1) Temperature. Temperature has a significant impact on the extrusion of plastics and the performance of the parison: it can reduce the melt viscosity, improve the melt flowability, reduce the power consumption of the extruder; it can appropriately increase the screw speed without affecting the mixing Effect; help to improve the strength and brightness of the final product; help to improve the transparency of the final product. However, if the melt temperature is too high, the extruded parison is prone to sag and cause uneven longitudinal wall thickness of the parison. Therefore, this principle should be followed to set the heating temperature of the extruder, namely Under the premise that a smooth and uniform parison can be extruded without overloading the transmission system, in order to ensure a higher melt strength of the parison, a lower heating temperature should be used as much as possible.

(2) Melt pressure. The melt entering the machine head should be evenly pressed. Properly increasing the pressure of the melt in the extruder can make the materials uniformly mixed and stabilize the performance of the parison and the final product. In order to control the melt extrusion pressure, a melt pressure measuring instrument can be installed in the discharge section of the extruder

(3) Melt conveying speed. The larger the melt conveying speed, the larger the extruder's output. Increasing the transfer speed of the melt can improve the self-weight sagging of the parison and increase the wall thickness of the parison