Press Straightening of Round Bars Based on a Local Deflection Control Strategy

Conventional operator-guided press straightening of round bars relies on operator experience and repeated trial pressing. This study proposes a local deflection control strategy that combines measurement, rotational alignment, model-based reverse bending, and remeasurement after unloading. A circular-arc approximation relates local deflection to full-length straightness. A conditional deflection superposition relationship is derived for initially curved bars under three-point bending and used with a finite difference model to predict pressing displacement. Finite element simulations assess the superposition relationship and the load–displacement response. In the investigated superposition cases, seven of eight relative errors are below 4%, with a maximum of 5.81%. The calculated load–displacement curves agree with the finite element results for both materials. Experiments on GCr15 and 60Si2Mn bars with a diameter of 20 mm and a length of 1.5 m demonstrate full-length straightness below 1‰ for the reported cases. These results demonstrate the feasibility of the prediction-and-feedback strategy for the tested single-peak bars.