Method for producing secondary mold elements

A method for producing a secondary mold element on an elongate, circumferentially closed hollow section while maintaining a shape of the closed hollow section by means of internal high-pressure shaping, with the secondary mold element being shaped locally by an expansion of material of the hollow section using a high-pressure fluid therein, and being supported under control during the shaping process by a counter plunger that yields outward with increasing shaping, comprising:

• inserting the counter plunger in a recess of a mold for shaping the secondary mold element while maintaining the shape of the closed hollow section;
• inwardly upsetting the hollow section material at the location of the secondary mold element using the counter plunger, whereby the hollow shaped material in an area of the inward upsetting is pressed circumferentially and endwise by the high-pressure fluid at the plunger while maintaining the shape of the closed hollow section;
• and
• externally upsetting the hollow section material by retracting the plunger which constantly abuts the hollow section during the entire shaping process, in conjunction with the internal high pressure to form the secondary mold element while maintaining the shape of the closed hollow section.