Springback compensation
The springback compensation is the compensation of the springback that must be taken into account when bending a workpiece with dimensional accuracy .
methodic procedure
During the plastic-elastic deformation of a workpiece, springback occurs at the end of a bending process. In order to obtain precisely dimensioned bent parts, the elastic springback must be compensated. This is usually done by bending the material over the angle of springback. For the bending process this means in practical implementation for simple tools that the bending punch moves deeper into the bending prism.
In the case of complex tools, springback must already be taken into account in the design phase. Complex software simulations are carried out for this purpose. However, this is often not enough to deliver the desired results in practice. If this is the case, tests are carried out and the tools are improved with the help of a target / actual comparison. However, the results (workpieces) are only always of the same type if all determining influencing factors remain the same. (ETH Zurich, p. 67)
Above all, this includes:
- Chemical composition
- Structure of the material (e.g. rolling direction during production)
- Tool wear
- Material temperature
- Aging processes of the raw material (e.g. significant for aluminum and copper)
- Forming speed
This list of factors can be continued.
Practical example: Electronic bending tools with springback compensation
In the electrical industry (high voltage technology, switch cabinet construction), flat materials made of copper and aluminum are processed in particular. The properties of these materials vary significantly from batch to batch. Dieter Ehrt developed the bending process with springback compensation for flat materials as early as the 1960s, which made it possible to achieve high bending accuracy for flat materials.
In bending prisms with electronic angle measurement, two flattened bolts twist during bending. Rotation of the bolts is recorded immediately by rotary encoders. The computer then calculates the required post-bending from the measured values. This compensates for the springback regardless of the properties of the material.
If the measuring accuracy of the rotary encoder is 0.1 °, a high angle accuracy of +/- 0.2 ° is achieved with the first workpiece without reworking. The scrap that is often common when setting up machines is eliminated. Fluctuations in the quality of the material during production no longer affect the accuracy.
See also
Literature and references
- M. Weck: Machine tools, machine types and areas of application. 6th edition Springer Vieweg Verlag, 2005, ISBN 3-540-22504-8 .
- ETH Zurich: Optimization of product and process development. vdf Hochschulvlg, 1999, ISBN 3-7281-2696-9 .
- EHRT Maschinenbau: Bending machines and bending tools brochure. , Rheinbreitbach, 2012.