The size of the mandrel should be determined according to the wall thickness requirements of the pipe. The best mold is 3 ~ 8mm larger than the outer diameter of the pipe, and the water jacket also depends on the type of pipe produced. If it is a water supply pipe, it should be greater than 200 1 to 2MM, so don't worry about product shrinkage and insufficient product pressure. If it is communication, the power standard is 200. If you want to increase profits, you are not afraid of 198 or 199, which is within the tolerance range.