The screw sleeve wrapped around the outside of the screw can be made into a unitary structure, but usually equipped with a jacket for circulating heating of steam or superheated oil, or as circulating water cooling, the purpose of which is to accurately adjust the extruder. The temperature of each working section. Most screw sleeves are equipped with pressure sensors and temperature sensors and are fitted with temperature control screw sleeves.
The inner surface of the nut is usually formed into a groove shape, some are linear grooves, and some are spiral grooves. The spiral groove creates a downstream flow for boosting, while the linear groove blocks downstream. Thus, a linear groove results in a lower flow rate, but its mechanical shearing action is greater. The gap distance between the screw and its sleeve is usually kept to a minimum to reduce leakage flow.