(2) Bulging method: one is to put rubber in the tube and compress it with a punch to make the tube bulge; Another method is hydraulic bulging, in which liquid is filled in the middle of the pipe, and the pipe is expanded into the required shape by liquid pressure. This method is mainly used to produce corrugated pipes.
(3) Rolling method: put the core into the tube, roll the periphery, and process the round edge.
④ Bending forming method: There are three common methods, one is drawing method, the other is stamping method, and the third is roller method, which has 3-4 rollers, two fixed rollers and one adjusting roller. By adjusting the distance between the fixed rollers, the finished pipe fittings are bent.
⑤ Punching method: use the conical core on the punch to enlarge the pipe end to the required size and shape.
⑥ Forging method: Stamping and stretching the end or part of the pipe with a forging press to reduce the outer diameter of the pipe fitting. Commonly used forging presses are rotary, connecting rod and roller.