Stretch-forming device and method for stretch forming a workpiece and stretch-formed part

Abstract

A stretch-forming device is provided for stretch forming a workpiece, which has a first bending device having a first bending stamp and a first bending shoe and a second bending device having a second bending stamp and a second bending shoe. In addition, the stretch-forming device has a first shaft and a second shaft, the first shaft mounted so it is rotatable around a first axis and providing a first support surface for the workpiece, and the second shaft mounted so it is rotatable around a second axis and providing a second support surface for the workpiece. The first bending stamp and the second bending stamp are components of a first part of the stretch-forming device, and the first bending shoe and the second bending shoe are components of a second part of the stretch-forming device. The first part and the second part are movable relative to one another. The second part has a first recess and a second recess, the first bending shoe and the first shaft situated on opposite sides of the first recess and the second bending shoe and the second shaft situated on opposite sides of the second recess.

1 . A stretch-forming device for a stretch forming of a workpiece, comprising:
 a first bending device adapted to bend a first end area of the workpiece, the first bending device comprising a first bending stamp and a first bending shoe;   a second bending device adapted to bend a second end area of the workpiece, the second bending device comprising a second bending stamp and a second bending shoe;   a first shaft mounted and rotatable around a first axis and adapted to provide a first support surface for the workpiece;   a second shaft mounted and rotatable around a second axis and adapted to provide a second support surface for the workpiece;   a first part comprising the first bending stamp and the second bending stamp; and   a second part formed of a first bending jaw and the second bending shoe, the second part movable relative to the first part and the second part comprising a first recess and a second recess,   wherein the first bending shoe and the first shaft are situated on opposite sides of the first recess and the second bending shoe and the second shaft are situated on opposite sides of the second recess.   
     
     
         2 . The stretch-forming device according to  claim 1 , wherein the first bending stamp and the second bending stamp are situated on opposite sides of the first part, and the first bending shoe and the second bending shoe are situated on opposite sides of the second part. 
     
     
         3 . The stretch-forming device according to  claim 1 , wherein a height of the first bending stamp varies over a length of the first bending stamp. 
     
     
         4 . The stretch-forming device according to  claim 1 , wherein a height of the second bending stamp varies over a length of the second bending stamp. 
     
     
         5 . The stretch-forming device according to  claim 1 , wherein an orientation of the first bending stamp is adapted to a geometry of the workpiece. 
     
     
         6 . The stretch-forming device according to  claim 1 , wherein an orientation of the second bending stamp is adapted to a geometry of the workpiece. 
     
     
         7 . The stretch-forming device according to  claim 1 , wherein a lateral distance between the first bending stamp and the first bending shoe is adapted such that a predetermined clamping force is settable for the workpiece. 
     
     
         8 . The stretch-forming device according to  claim 1 , wherein a lateral distance between the second bending stamp and the second bending shoe is adapted such that a predetermined clamping force is settable for the workpiece. 
     
     
         9 . The stretch-forming device according to  claim 1 , further comprising a deep-drawing device that comprises a forming stamp and a matrix. 
     
     
         10 . The stretch-forming device according to  claim 9 , wherein the forming stamp is a first component of the first part of the stretch-forming device and the matrix is a second component of the second part of the stretch-forming device. 
     
     
         11 . The stretch-forming device according to  claim 1 , wherein the first part is an upper part and the second part is a lower part. 
     
     
         12 . The stretch-forming device according to  claim 1 , wherein the first bending shoe comprises a first clamping device and the second bending shoe comprises a second clamping device, the first clamping device is situated adjacent to the first recess and the second clamping device is situated adjacent to the second recess. 
     
     
         13 . The stretch-forming device according to  claim 12 , wherein the first clamping device comprises a plate and a clamping insert. 
     
     
         14 . The stretch-forming device according to  claim 12 , wherein the second clamping device comprises a plate and a clamping insert. 
     
     
         15 . The stretch-forming device according to  claim 13 , wherein the plate comprises a polyurethane plastic. 
     
     
         16 . The stretch-forming device according to  claim 14 , wherein the plate comprises a rubber. 
     
     
         17 . The stretch-forming device according to  claim 13 , wherein the plate comprises a compressed-gas spring. 
     
     
         18 . The stretch-forming device according to  claim 1 , wherein the second part comprises a first brake shoe and a second brake shoe, the first brake shoe situated below the first shaft and adjacent to the first recess, and the second brake shoe situated below the second shaft and adjacent to the second recess. 
     
     
         19 . The stretch-forming device according to  claim 18 , wherein the first brake shoe and the second brake shoe comprise a polyurethane plastic. 
     
     
         20 . The stretch-forming device according to  claim 18 , wherein the first brake shoe and the second brake shoe comprise a rubber. 
     
     
         21 . The stretch-forming device according to  claim 18 , wherein the first brake shoe and the second brake shoe comprise a compressed-gas springs. 
     
     
         22 . A method for stretch forming a workpiece with a stretch-forming device, the stretch-forming device comprising:
 a first bending device adapted to bend a first end area of the workpiece, the first bending device comprising a first bending stamp and a first bending shoe;   a second bending device adapted to bend a second end area of the workpiece, the second bending device comprising a second bending stamp and a second bending shoe;   a first shaft mounted and rotatable around a first axis and adapted to provide a first support surface for the workpiece;   a second shaft mounted and rotatable around a second axis and adapted to provide a second support surface for the workpiece;   a first part comprising the first bending stamp and the second bending stamp; and   a second part formed of a first bending jaw and the second bending shoe, the second part movable relative to the first part and the second part comprising a first recess and a second recess,   wherein the first bending shoe and the first shaft are situated on opposite sides of the first recess and the second bending shoe and the second shaft are situated on opposite sides of the second recess, the method comprising:
 placing the workpiece at least on the first support surface, the second support surface, the first bending shoe and the second bending shoe; 
 moving the first part relative to the second part such that the first end area is clamped between the first bending stamp and the first bending shoe and the second end area is clamped between the second bending stamp and the second bending shoe; and 
 pre-stretching the workpiece. 
   
     
     
         23 . The method according to  claim 22 , wherein the pre-stretching the workpiece produces a stretch-formed part of an outer skin of a motor vehicle and the stretch-formed part has a pre-stretching VR in a range approximately 4%≦VR≦8%.