In addition to the temperature, the screw speed also exerts a major influence on the quality of the extrudate.
Low screw speeds mean that the melt has to spend a long time in the extruder, with the result that it may become damaged by heat.

Excessive screw speeds also lead to thermal decomposition due to friction.

Fig. 1 specifies guide values for the screw speed as a function of the diameter.

Fig. 1: Screw speed range as a function of diameter