A critical factor for quality small lot sheet metal production is the control of flange angles. For small radius pressbrake bending operations, i.e., punch radius less than sheet thickness, control of angle requires extensive setup time, making small batch runs inefficient. This paper demonstrates the use of relatively simple measurements of material properties to provide the information necessary to estimate and control springback with accuracy approaching 1/4 degree. The control method combines the generality of a modelbased approach with accurate on-line loaded angle measurement. An analytic bending model is developed which provides insights into the material and geometric variables that affect springback. Estimates are made of the relative sensitivity of springback to changes in these variables. In addition, a set of variable ratios are determined which are linearly related to springback and thus serve as the input data for a linear regression model of springback based on experimental results.

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