1. Punching method: extend the pipe end to the required size and shape, and use a tapered core on the punch.
2. Bulging method: one is to put the rubber into the pipe and extrude the upper part of the pipe with a punch, and the other is hydraulic expansion.
3. Forging method: pull out one end or part of the pipe with a die forging machine to reduce the outer diameter of the pipe.