Abstract:Recent new technology developments were presented in the field of industrial bending operations, including flexible stretch forming and 3D rotary stretch forming. Attempts were made to give an overview of different mechanisms that influence dimensional accuracy, including local cross-sectional deformations such as suck-in and volume conservation effects, along with global deformations such as springback. An analytical model was developed to determine the particular influence of different material, geometry and process parameters on dimensional variability of bent components. The results were discussed in terms of overall process capability (C_p) and associated process windows. The results show that different governing mechanisms prevail in various bending operations, meaning that attention has to be placed on controlling those process parameters that really are important to part quality in each specific case. Several strategies may be defined for reducing variability. One alternative may be to design more robust process and tool technology that reduce the effect of upstream parameters on dimensional variability of the formed part. The results show that optimal tool design and technology may in specific cases improve the dimensional accuracy of a formed part. Based on the findings discussed herein, it is concluded that advances in industrial bending operations require focus on improving the understanding of mechanical mechanisms, including models and parameter development, new technology developments, including process, tool, measurement and control capabilities, and process discipline at the shop floor, combined with a basic philosophy of controlling process parameters rather than part attributes.

Key words: bending technology; tools; dimensional accuracy; distortions; springback; formability