Determining Curvature of Air Bent Parts by Digital Image Processing

  • M. L. Garcia-Romeu
  • J. A. Mayugo
  • J. Ciurana
Sheet metal forming: P. Picart


The dimensional accuracy of formed components is an important issue for stamping applications. The flexibility of the air bending process involve that for different bent angles, different final bent radius are obtained. For air bending parts, springback analysis and final angle measurement have usually been considered whereas final bent radius or curvature determination is pushed into the background. Even though this parameter is a non constant geometrical feature when punch bending radius is very small and there are few mechanical methods for measuring these non constant curvatures. This paper describes the measurement procedure of final bent radius through analysis and manipulation of scanned images of bent parts. The method fits different polynomial functions on bent profiles. Once the best adjustment is chosen, a zone curvature in an air bent part is defined and the radius on punch-sheet contact is quantified. For air bending conditions of small punch radius, this technique has given good results in order to determine the main geometrical features of an air bent part: final bent angle, final bent radius and curvature zone.


Curvature Air bending Image processing 


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  1. [1]
    Kurtaran, H. A novel approach for the prediction of bend allowance in air bending and comparison with other methods. Int. J. Adv. Manuf. Tech., 37; 486–495, 2008CrossRefGoogle Scholar
  2. [2]
    de Vin, L.J. Expecting the unexpected, a must for accurate brakeforming. J. Mat. Proc. Tech., 117; 244–248, 2001CrossRefGoogle Scholar
  3. [3]
    de Vin, L.J. Curvature prediction in air bending of metal sheet. J. Mater. Proc. Tech., 100; 257–261, 2000CrossRefGoogle Scholar
  4. [4]
    Fei, D. and Hodgson, P. Experimental and numerical studies of springback in air v-bending process for cold rolled TRIP steels. Nucl. Eng. Des., 236;1847–1851, 2006CrossRefGoogle Scholar
  5. [5]
    Mori,K. et al., Springback behaviour in bending of ultra-high-strength steel sheets using CNC servo press. Int. J. Mach. Tools Manuf., 47; 321–325, 2007CrossRefGoogle Scholar
  6. [6]
    Tekiner, Z. An experimental study on the examination of springback of sheet metals with several thicknesses and properties in bending dies. J. Mater. Proc. Tech., 145; 109–117, 2004CrossRefGoogle Scholar
  7. [7]
    Mkaddem, A. and Saidane, D. Experimental approach and RSM procedure on the examination of springback in wiping-die bending processes. J. Mater. Process. Technol., 189;325–333, 2007CrossRefGoogle Scholar
  8. [8]
    Chen, P. and Koç, M. Simulation of springback variation in forming of advanced high strength steels. J. Mater. Proc. Tech., 190; 189–198, 2007CrossRefGoogle Scholar
  9. [9]
    Carden, W.D. et al. Measurement of springback. Int. J. Mech. Sci., 44; 79–101, 2002zbMATHCrossRefGoogle Scholar
  10. [10]
    Kwok, S.K. and Lee, W.B. The development of a machine vision system for adaptive bending of sheet metals J. Mater. Proc. Tech., 48; 43–49, 1995CrossRefGoogle Scholar
  11. [11]
    Elkins K.L. and Sturges, R.H. Design of a sensor for on-line measurement of loaded bend angle for pressbrake control. Robot. Comput. Integ. Manuf., 17; 329–340, 2001CrossRefGoogle Scholar
  12. [12]
    Ferreira, J.A. Sun, P. and Grácio, J.J. Close loop control of a hydraulic press for springback analysis. J. Mater. Proc. Tech., 177; 377–381, 2006CrossRefGoogle Scholar
  13. [13]
    Hsu, Q. Comparison of different analysis models to measure plastic strains on sheet metal forming parts by digital image processing. Int. J. Mach. Tools Manuf., 43; 515–521, 2003CrossRefGoogle Scholar
  14. [14]
    Anokye-Siribor, K. and Singh, U.P. A new analytical model for pressbrake forming using in-process identification of material characteristics. J. Mater. Proc. Tech., 99; 103–112, 2000CrossRefGoogle Scholar

Copyright information

© Springer-Verlag France 2010

Authors and Affiliations

  • M. L. Garcia-Romeu
    • 1
  • J. A. Mayugo
    • 1
  • J. Ciurana
    • 1
  1. 1.Department of Mechanical Engineering and Industrial ConstructionUniversity of GironaGironaSpain

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