The screw is equidistant and unequal-depth variant, the length-diameter ratio l/d is 20~25 and the compression ratio is 314. The main parameters of the head are basically the same as the hard PVC. The expansion angle α of the shunt is greater than 60 °. Head compression ratio 10~20. The length of the core die and the straight part of the die is 10 times times of the wall thickness.
Die mouth, core mold size than the pipe diameter, outside diameter amplification 10%~30% advisable (by traction to achieve the required size).