Flattening of bent metal sheets as a remanufacturing operation

The reshaping of end-of-life or scrap sheet metal panels is a potential remanufacturing process, which enables significant environmental benefits over the traditional metal recycling routes. This paper experimentally investigates cold and warm press flattening of waste sheet metal for enabling remanufacturing. Samples of stainless steel, aluminium alloy, and low carbon steel were bent to various internal angles using v-die air bending operations. Then, flattening tests were conducted with a hydraulic press, with tools capable of heating up to 300 °C. The process parameters included dwell force, dwell time, and tool temperature. The target final angle after load release is set at 180°, but the flattening process typically induces springforward, and the final angle is generally larger than 180°. Springforward can be mitigated by using warm flattening conditions with all the tested materials. It can also be reduced if superposing a steel mesh between the top flattening die and the sheet. The paper demonstrates and explains the mechanical effects of the flattening process.