The invention relates to a method for shaping a hollow body from a tubular blank inserted into a shaping tool that can be opened and closed, by internal high pressure introduced into the interior of the blank. The cross section of the blank, prior to the internal high-pressure shaping, can be changed and pre-shaped from a round or rectangular shape, depending on the workpiece. In order to be able to produce workpieces with a circumference that varies considerably over the length without overstretching the material, according to the invention, for pre-shaping the blank, a dent that differs in depth over its length is formed in the blank. During the internal high-pressure shaping of the pre-shaped blank to form a hollow body, a U-shaped fold is formed from the dent that projects into the interior of the hollow body, with the walls of the fold abutting one another directly and merging at the periphery with the circumferential wall of the hollow body. The two walls of the fold are permanently connected to one another and the two walls of the fold are preferably permanently welded together in the vicinity of the circumference of the hollow body.

Method and apparatus for manufacturing a hollow body from a tubular blank by internal high-pressure shaping

Ein Verfahren und eine Vorrichtung zur Herstellung von Teilen mit Hilfe der Innen-Hochdruck-Umformtechnik, bei denen mehrere formende Arbeitsstufen in mindestens einem Formwerkzeug durchlaufen werden, bei denen von gewalzten, gezogenen oder geschweisten Rohren mit beliebig geformten Rohrquerschnitten ausgegangen wird, sollen dahingehend verbessert werden, das geomatrisch komplizierte Teile hergestellt werden konnen, ohne das die alles entscheidende Bruchdehnung uberschritten wird und das trotz dieser Moglichkeit mit tragbaren Innendrucken gearbeitet werden kann. DOLLAR A Dazu wird vorgesehen, das durch mindestens eine vorverformte Arbeitsstufe das jeweilige Rohr derart geformt wird, das an jeder Querschnittsstelle des vorgeformten Rohres die bei der Vorverformung erzielten Umfangsmase in der Endverformungsstufe beibehalten werden, und die Vorrichtung von mindestens einer IHU-Form (2) und einem Stempel-Matrize-Werkzeug (4) gebildet ist.

Verfahren und Vorrichtung zur Herstellung von Teilen mit Hilfe der Innen-Hochdruck-Umformtechnik

A blank is pre-formed, and a bulge of varying depth is formed in it. During internal high pressure forming of this, the bulge is formed into a U-shaped fold (6). The fold projects into the hollow body (4) formed from the blank, with a circumference, which varies considerably over its length. The walls (7) of the fold engage on each other and merge into the outside wall (8) of the hollow body at the periphery. The fold walls are welded together.

Method of manufacturing a hollow body from a tube by internal high-pressure forming

In the hydroforming tubular blanks (W), which is economical in machinery and highly-productive, the main press frame has a piston-cylinder closure system (5) acting on a moulding tool with two or more die halves (2, 3), in which high internal pressure will be applied to the tubular blank. Outside the closure system, during die closure, the swaging profile (G) of the die halves preforms the blank. Simultaneously, internal pressure P1 is introduced into the blank. During the remainder of the hydroforming process, the workpiece remains in the mould. Also claimed is the apparatus used for the above process.

Arndt Birkert

Papers

Hydroforming process obviating long-stroke, expensive machinery