Springback analysis and control in small radius air bending

A critical factor for quality small lot sheet metal production is the contr ol of flange angles. For small radius pressbrake bending operations, i.e., punch radius less than sheer thickness, control of angle requires extensive setup time, making small batch runs inefficient. This paper demonstrates t he use of relatively simple measurements of material 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 model-based approach with accurate on-line loaded angle measurement. An analytic bending model is developed which provides insights into the mat erial and geometric variables that affect springback. Estimates are made of the relative sensitivity of springback to changes in these variables. In a ddition, a set of variable ratios are determined which are linearly related to springback and thus serve as the input data for a lineal regression mod el of springback based on experimental results.