Electrically-Assisted Incremental Forming of Invar 36 Sheet

The Invar 36 alloy is widely used in aerospace and precision instruments for its extremely low coefficient of thermal expansion below Curie temperature (230 ℃). The conventional method of manufacturing Invar moulds is hot-pressing forming, which requires two dies and causes high cost, slow efficiency, and challenges in forming intricate surfaces. To resolve these issues, an electrically-assisted incremental forming (ESIF) process is used for Invar 36 sheet metal forming. In this process, the forming step size, temperature, and tool diameter are the key factors affecting the final forming quality. Through an orthogonal array, the influence of these parameters on the thickness and contour deviation of ESIF was studied in this study using a finite element (FE) simulation model. The study reveals that the minimum thickness and RMSE of contour deviation are primarily influenced by the tool diameter and temperature, respectively. The optimum process parameters to form the part were determined to be: a step size of 1.0 mm, a forming temperature of 600 ℃, and a tool diameter of 12 mm.