Process for the production of tubular structural parts fabricated from PGM materials and having circumferential undulating bulges

A process for the production of tubular structural parts fabricated from POM materials and having circumferential undulating bulges, said process comprising:

• a) forming a tube piece having a smooth wall, two tube ends and an external diameter with a cylindrical forming die, said forming die comprising two axial ends, and a plurality of formers with radial undulating recesses, axial contact surfaces and an internal diameter, said formers being movably arranged in spaced apart relationship, and said forming die having at each end a press tool,
• b) inserting the smooth-walled tube piece into the cylindrical forming die with an internal diameter that corresponds substantially to the external diameter of the tube piece,
• c) sealing the tube ends with said press tool, and filling a space that is thus formed inside the tube piece completely with a hydraulic fluid, and
• d) producing a hydraulic internal pressure by exerting an axial compression by each press tool driving the formers of the forming die together in such a way that under simultaneous shortening of the tube piece bulges are formed in the wall of the tube piece that correspond to the recesses of the driven together formers of the forming die.