Three-zone screw

The three-zone screw is an important component of the plasticising unit of injection moulding machines and single-screw extruders. This unit, consisting of a heated barrel and a screw, melts and homogenises the moulding compound before it is formed in injection moulds or extrusion dies.

The three-zone screw, also known as a universal screw, consists of three zones: the feed zone, in which the granules are drawn in; the compression zone, where pressure is built up and air is forced out of the moulding compound; and the homogenising and metering zone, where an even distribution of temperature and additives takes place. Each zone is controlled independently of the others.