Abstract

In conventional metal spinning, a tool follows a path composed of multiple forward and backward passes to form a spinning circular blank and produce axisymmetric components. The process is limited by two key workpiece failure types: wrinkling and excessive thinning leading to cracking. No precise rules have been established yet for toolpath design to avoid workpiece failure for a variety of shapes and materials. Therefore, toolpath generation today is still performed by trial and error. Although the effect of many toolpath parameters on the likelihood of failure has been investigated, very little evidence has been collected on the comparison between forward and backward toolpasses. Therefore, this study experimentally compares their effect on tool forces, thickness profile and workpiece shape. Aluminium cones with a 45° wall are used as starting shapes; one forward and one backward linear passes are performed for two values of toolpass distance increment Δz. The results show that a backward pass leads to higher thinning than a forward pass, but may also favour a lower wrinkling amplitude at the workpiece edge. Both quantities correlate to how far the workpiece flange folds back during the pass. Increasing Δz has a bigger impact on the backward pass conditions than on the forward pass