Influence of different heating methods on springback of mild steel plate during dieless bending process

摘要

Dieless bending process is an effective and efficient flexible sheet metal forming method. It has been applied in many fields such as shipbuilding, chemical engineering and shell structure construction. For large and thick sheet metal, a new flexible sheet metal forming method of incremental bending based on minimum energy principle has been presented by our team. However, owing to the effect of the springback phenomenon and the bending limit of the metal plates during the dieless bending process, the metal forming quality is limited. So we present an induction-assisted heating method to reduce the influence of springback and the bending limit. In this paper, the influence of heating method and temperature on the springback of mild steel are investigated. Firstly, three kinds of heating methods are adopted to heat the flat plate during the dieless bending process. The first is to linearly heat the plate at stamping position to a specific temperature during the whole stamping process, the second is to linearly heat the plate at stamping position to a specific temperature after the plate is stamped to the designated position, and the third is to heat the whole plate to a specific temperature during the whole stamping process. The flat plate was heated to three different temperatures (20°C, 250°C and 500°C) for each case. Meanwhile, the forming force was detected and recorded by the force sensor mounted on the stamping tool of the dieless bending machine. Results showed that there is almost no springback when the stamping depth is 60 mm and the temperature is 500°C with the second heating method. It was also found that the forming force was reduced from 480N to 280N with temperature increasing form 20°C to 500°C and the second heating method can decrease the springback behaviour of the mild steel plate most effectively. This study provides useful reference for the further research on dieless incremental bending process with high efficiency and high precision.