The sizing process in the PE pipe production line is a crucial step in the manufacturing of PE pipes. Its function is to cool and solidify the molten pipe billet that exits the die head, thereby obtaining precise geometric dimensions and a smooth surface.

The sizing methods mainly include the inner diameter sizing method and the outer diameter sizing method. Since international and domestic standards mostly base the specifications on the outer diameter of the pipe, production lines generally adopt the outer diameter sizing process.

The outer diameter sizing process can be divided into pressure sizing and vacuum sizing. Compared with pressure sizing, vacuum outer diameter sizing has become the mainstream technology, featuring simple and rapid pipe feeding, less waste, good cooling effect on the inner wall, precise control of size tolerance, small pipe deformation, low internal stress, no risk of screw plug wear, and independent temperature control of the die head and sizing device.

The molds (die heads) mostly adopt basket-type die heads or spiral分流 type extrusion composite die heads， which have the characteristics of convenient adjustment and uniform output. The aim is to achieve low-temperature high plasticization extrusion. The sizing sleeve is the key sizing component， usually in the form of a tube， made of brass， copper-boron alloy or aluminum， and cooled by water ring or slotting process to ensure the accuracy of pipe material formation.