Analysis of Material Deformation and Wrinkling Failure in Conventional Metal Spinning Process

Abstract

Sheet metal spinning is one of the metal forming processes, where a flat metal blank is rotated at a high speed and formed into an axisymmetric part by a roller which gradually forces the blank onto a mandrel, bearing the final shape of the spun part. Over the last few decades, sheet metal spinning has developed significantly and spun products have been widely used in various industries. Although the spinning process has already been known for centuries, the process design still highly relies on experienced spinners using trial-and-error. Challenges remain to achieve high product dimensional accuracy and prevent material failures. This PhD project aims to gain insight into the material deformation and wrinkling failure mechanics in the conventional spinning process by employing experimental and numerical methods. In this study, a tool compensation technique has been proposed and used to develop CNC multiple roller path (passes). 3-D elastic-plastic Finite Element (FE) models have been developed to analyse the material deformation and wrinkling failure of the spinning process. By combining these two techniques in the process design, the time and materials wasted by using the trial-and-error could be decreased significantly. In addition, it may provide a practical approach of standardised operation for the spinning industry and thus improve the product quality, process repeatability and production efficiency. Furthermore, effects of process parameters, e.g. roller path profiles, feed rate and spindle speed, on the variations of tool forces, stresses, strains, wall thickness and wrinkling failures have also been investigated. Using a concave roller path produces high tool forces, stresses and reduction of wall thickness. Conversely, low tool forces, stresses and wall thinning have been obtained in the FE model which uses the convex roller path. High feed ratios help to maintain original blank thickness but also lead to material failures and rough surface finish. Thus it is necessary to find a “trade off” feed ratio for a spinning process design.