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'Spring back compensation is used in metal forming to ensure that the final shape assumed by a piece of metal after being removed from a forming tool is the shape desired. Typically, when metal is being formed at room temperature, it will undergo both plastic and elastic deformation. After the metal workpiece is removed from the tool or deformation implement, the elastic deformation will be released and only the plastic deformation will remain; thus, the workpiece will "spring back" to a position between its original position and the position into which it was formed. Usually, spring back compensation is realized by over-bending the material by an amount corresponding to the magnitude of the spring back.

When bending metal, spring back compensation is done by pushing the workpiece further into the die. For other sheet metal forming operations like drawing, it entails deforming the sheet metal past the planned shape of the part so that when the part's elastic deformation is released, the plastic deformation in that part delivers the desired shape of the part. In the case of complex tools, spring back must be considered in the engineering and construction phases. Complex software simulations are often used, but frequently this is not enough to deliver the desired results. In such cases practical experiments are done, using trial-and-error and experience to correct the process. However, the results of the process are only stable if all influencing factors are the same.^[1] These include such things as yield strength, chemical composition, aging processes, and structure of the workpiece; tool wear; and temperature and deformation rate during the forming process.

Spring back assessment of final formed products is a difficult problem and is affected by the complexity of the formed shape. The NUMISHEET 93 conference benchmark problem involves the draw bending of a U-channel using three measured parameters. Parameter-less approaches have been proposed for more complex geometries but they need validation.^[2]

Practical example: electronic bending tools with spring-back compensation

Manufacturing of electrical assemblies produces components that are flat, using copper and aluminum. The mechanical properties of copper and aluminum are very different and require different programmable inputs in order to achieve the same dimensional characteristics.

Bending technology for flat material which measures each bend angle and provides spring back compensation is required. This gives the bend angle of flat materials true accuracy. This is attained by using bending prisms with electronic angular measurement technology. While bending two flat bolds supporting the material turn around. The bolds are directly connected to the angular sensors. A computer or rather the machine control then calculates the required final stroke. The spring back of every bend is compensated regardless of material type.

If the measuring accuracy is 0.1º, a high angle accuracy of +/- 0.2º is achieved instantly with the first workpiece without any rework. Because no adjustments are required, material waste amounts and setup times drop considerably. Even inconsistencies within a single piece of material are automatically adjusted.

References

^ Optimierung der Produkt- und Prozessentwicklung. ETH Zürich. 1999. p. 67. ISBN 978-3728126962.
^ Raghavan; et al. (September 2013). "Numerical assessment of springback for the deep drawing process by level set interpolation using shape manifolds". International Journal of Material Forming. 7 (4): 487–501. doi:10.1007/s12289-013-1145-8. S2CID 255585418.

M. Weck: Werkzeugmaschinen Maschinenarten und Anwendungsbereiche (VDI-BuchSpringer Vieweg Verlag, 6. Aufl. 2005 (2. August 2005), ISBN 3540225048
EHRT: Brochure Bending machines and tools., Rheinbreitbach, 2012.

[1] Optimierung der Produkt- und Prozessentwicklung. ETH Zürich. 1999. p. 67. ISBN 978-3728126962.

[2] Raghavan; et al. (September 2013). "Numerical assessment of springback for the deep drawing process by level set interpolation using shape manifolds". International Journal of Material Forming. 7 (4): 487–501. doi:10.1007/s12289-013-1145-8. S2CID 255585418.

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[2]

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+{{Short description|Machining technique}}
-Due to the plastic-elastic characteristic of a metal, it is typical that any deformation of sheet metal at room temperature will have both elastic and plastic deformation. After the metal work piece is removed from the tool or deformation implement, the elastic deformation will be released and only the plastic deformation will remain. When a metal forming tool is planned and designed to deform a work piece, the shape imparted by the tool will be a combination of elastic and plastic deformation. The release of the elastic deformation is the spring back often observed at the end of a metal forming process.
-The spring back has to be compensated to achieve an accurate result.
+''''Spring back compensation''' is used in [[metal forming]] to ensure that the final shape assumed by a piece of metal after being removed from a forming tool is the shape desired. Typically, when metal is being formed at room temperature, it will undergo both [[plastic deformation|plastic]] and [[elastic deformation]]. After the metal workpiece is removed from the tool or deformation implement, the elastic deformation will be released and only the plastic deformation will remain; thus, the workpiece will "spring back" to a position between its original position and the position into which it was formed. Usually, spring back compensation is realized by over-bending the material by an amount corresponding to the magnitude of the spring back.
-Usually that is realized by overbending the material correspondent to the magnitude of the spring back.
-That means for the practical side of the bending process, the bending former enters deeper into the bending prism.
-For other sheet metal forming operations like drawing it entails deforming the sheet metal past the planned net shape of the part, so that when springback is released from the part, the plastic deformation in that part delivers the desired shape of the part. In the case of complex tools the spring back has to be already considered in the engineering and construction phases. Therefore complex software simulations are used.
+When bending metal, spring back compensation is done by pushing the workpiece further into the die. For other [[sheet metal]] forming operations like [[Drawing (manufacturing)|drawing]], it entails deforming the sheet metal past the planned shape of the part so that when the part's elastic deformation is released, the plastic deformation in that part delivers the desired shape of the part. In the case of complex tools, spring back must be considered in the engineering and construction phases. Complex software simulations are often used, but frequently this is not enough to deliver the desired results. In such cases practical experiments are done, using trial-and-error and experience to correct the process. However, the results of the process are only stable if all influencing factors are the same.<ref>{{Cite book|title = Optimierung der Produkt- und Prozessentwicklung|publisher = ETH Zürich|year = 1999|isbn = 978-3728126962|pages = 67}}</ref> These include such things as yield strength, chemical composition, aging processes, and structure of the workpiece; tool wear; and temperature and deformation rate during the forming process.
-Frequently this is not enough to deliver the desired results. In such cases practical experiments are done, using the trial-and-error plus experience method to correct the tool. However, the results (workpieces) are only stable, if all influencing factors are the same.<ref>{{Cite book|title = Optimierung der Produkt- und Prozessentwicklung|publisher = ETH Zürich|year = 1999|isbn = 978-3728126962|location = |pages = 67}}</ref>
+Spring back assessment of final formed products is a difficult problem and is affected by the complexity of the formed shape. The NUMISHEET 93 conference benchmark problem involves the draw bending of a U-channel using three measured parameters. Parameter-less approaches have been proposed for more complex geometries but they need validation.<ref>{{cite journal |last=Raghavan |date=September 2013 |title=Numerical assessment of springback for the deep drawing process by level set interpolation using shape manifolds |journal=International Journal of Material Forming |doi=10.1007/s12289-013-1145-8|volume=7 |issue=4 |pages=487–501|s2cid=255585418 |display-authors=etal}}</ref>
-This mainly includes:
-* Yield strength of the sheet
-* Chemical composition of the sheet
-* Structure of the material (e.g. direction of grain during production process)
-* Wear of tools
-* Material temperature
-* Aging processes of the raw material (significant for aluminium and copper)
-* Deformation rate
-The list of factors may be continued. Springback assessment of final formed products is a difficult problem and is affected by the complexity of the formed shape. The NUMISHEET 93 conference benchmark problem involves the draw bending of a U-channel using three measured parameters. Parameterless approaches have been proposed for more complex geometries but need validation.<ref>{{cite journal |last=Raghavan |date=September 2013 |title=Numerical assessment of springback for the deep drawing process by level set interpolation using shape manifolds |journal=International Journal of Material Forming |doi=10.1007/s12289-013-1145-8|volume=7 |issue=4 |pages=487–501|display-authors=etal}}</ref>
 ==Practical example: electronic bending tools with spring-back compensation==
-{{Multiple issues|section=yes|
-{{advert|section|date=November 2017}}
 {{unreferenced section|date=November 2017}}
-}}
 [[File:Bending tool for Standard bending EHRT.jpg|thumb|Electronic bending tool with integrated angle measurement and spring-back compensation]]
+Manufacturing of electrical assemblies produces components that are flat, using copper and aluminum. The mechanical properties of copper and aluminum are very different and require different programmable inputs in order to achieve the same dimensional characteristics.
-The electrical industry mostly uses flat materials of copper and aluminium producing equipment for the electrical industry, especially switchgear and busbar production. The properties between two different charges of those materials vary strongly, having a critical influence on the dimensions.
-In the 60s, Dieter Ehrt invented the bending technology for flat material which measures each bend angle and provides spring back compensation. This gives the bend angle of flat materials true accuracy. This is attained by using bending prisms with electronic angular measurement technology.  The principle is easy, but smart: While bending two flat bolds supporting the material turn around. The bolds are directly connected to the angular sensors.  A computer or rather the machine control then calculates the required final stroke. The spring back of every bend is compensated regardless of material type.
+Bending technology for flat material which measures each bend angle and provides spring back compensation is required. This gives the bend angle of flat materials true accuracy. This is attained by using bending prisms with electronic angular measurement technology. While bending two flat bolds supporting the material turn around. The bolds are directly connected to the angular sensors. A computer or rather the machine control then calculates the required final stroke. The spring back of every bend is compensated regardless of material type.
-If the measuring accuracy is 0.1º, a high angle accuracy of +/- 0.2º is achieved instantly with the first work piece without any rework. Because no adjustments are required, material waste amounts and setup times drop considerably. Even inconsistencies within a single piece of material are automatically adjusted.
+If the measuring accuracy is 0.1º, a high angle accuracy of +/- 0.2º is achieved instantly with the first workpiece without any rework. Because no adjustments are required, material waste amounts and setup times drop considerably. Even inconsistencies within a single piece of material are automatically adjusted.
 ==See also==
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 {{Reflist}}
 * M. Weck: ''Werkzeugmaschinen Maschinenarten und Anwendungsbereiche (VDI-Buch''Springer Vieweg Verlag, 6. Aufl. 2005 (2. August 2005), {{ISBN|3540225048}}
-* ETH Zürich: ''Optimierung der Produkt- und Prozessentwicklung.'' vdf Hochschulvlg, 1999, {{ISBN|3728126969}}.
 * EHRT: ''Brochure Bending machines and tools.'', Rheinbreitbach, 2012.