Method for the multi-axis shaping of a hollow workpiece and supporting core for use in the method

Abstract

A method is provided for the multi-axis shaping of a hollow workpiece, such as a polygonal hollow workpiece. The hollow space of the workpiece has introduced into it a supporting core, which has a central body with at least two differently oriented, inter-communicating cylinder bores and also has pistons, which are accommodated in the cylinder bores and can be subjected to the action of pressure fluid through a fluid connection of the central body. Prior to the radial shaping of the workpiece in a radial press, in a process in which at least two radial dimensions are to be decreased, the supporting core is expanded radially, with the pistons being extended out of the cylinder bores by the pistons being subjected to the action of pressure fluid.

What is claimed is: 
     
         1 . A method for multiaxial forming of a hollow workpiece (W), in particular a square tube ( 8 ), a hexagonal tube or another polygonal hollow workpiece (W), comprising:
 a) providing the hollow workpiece (W) to be formed;   b) inserting a support core ( 10 ) into the cavity (H) of the workpiece (W), wherein the support core ( 10 ) comprises a central body ( 11 ) with differently oriented cylinder bores ( 13 ) communicating with one another and with pistons ( 17 ) which are accommodated therein and can be pressurized by a pressurized fluid through a fluid connection ( 21 ) of the central body ( 11 ), the differently oriented cylinder bores ( 13 ) being offset from one another in the axial direction and cylinder bores of different orientation not being arranged in a common plane;   c) radial expanding of the support core ( 10 ) while extending the pistons ( 17 ) out of the cylinder bores ( 13 ) by pressurizing the pistons ( 17 ) with pressurized fluid;   d) inserting the workpiece (W) to be formed into a radial press;   e) radial forming of the workpiece (W) in the radial press with reduction of at least two radial dimensions;   f) opening the radial press;   g) removing the formed workpiece (W) from the radial press; and   h) removing the support core ( 10 ) from the cavity (H) of the workpiece (W).   
     
     
         2 . The method of  claim 1 , wherein in step e) the pistons ( 17 ) move into the cylinder bores ( 13 ) in a controlled manner. 
     
     
         3 . The method of  claim 2 , wherein in step e) the pressurized liquid is discharged in a controlled manner through the fluid connection ( 21 ) of the central body ( 11 ) while maintaining a counterpressure. 
     
     
         4 . The support core for use in the method of  claim 1  comprising a central body ( 11 ) with differently oriented, mutually communicating cylinder bores ( 13 ) and pistons ( 17 ) which are accommodated therein and can be pressurized by pressurized fluid through a fluid connection ( 21 ) of the central body ( 11 ), wherein the differently oriented cylinder bores ( 13 ) are offset from one another in the axial direction and cylinder bores of different orientation are not arranged in a common plane. 
     
     
         5 . The support core of  claim 4 , wherein the cylinder bores ( 13 ) are realized as through bores ( 14 ), in each of which two pistons ( 17 ) travelling in opposite directions are accommodated. 
     
     
         6 . The support core of  claim 4 , wherein the cylinder bores ( 13 ) communicate with each other via an axial channel ( 15 ). 
     
     
         7 . The support core of  claim 4 , wherein at least two pairs of cylinder bores ( 13 ) oriented parallel to one another are provided, offset axially relative to one another, i.e. in the axial direction of the support core ( 10 ). 
     
     
         8 . The support core of  claim 7 , wherein the pistons ( 17 ) traveling in the same direction are coupled to one another via pressure plates ( 18 ). 
     
     
         9 . The support core of  claim 8 , wherein the pressure plates ( 18 ) each have a flat workpiece support surface(S). 
     
     
         10 . The support core of  claim 8 , wherein the pressure plates ( 18 ) each have an uneven, in particular a one- or two-dimensionally domed or curved workpiece support surface(S).