Surface roughness analysis for improving punching tools performance of 5754 aluminium alloy

Abstract

The use of lightweight materials in the automotive industry, as a key element in fuel economy, is a growing trend to meet the global emissions reduction agreement. Aluminium, in the form of stamped sheet, has the potential to be used extensively in vehicle as a high-specification structural and skin parts. However, compared to steel, aluminium is more difficult to stamp, thus the optimized techniques and manufacture strategies learned in steel stamping are not adequate given the complex processability of aluminium alloys. To achieve the quality standards, it is necessary to optimize aluminium stamping processes by developing specific techniques, geometries, and functional surfaces on tooling. In this work, the influence of tool geometry and surface roughness, as well as the use of lubricant during the punching process of 5754 aluminium sheets have been evaluated in a pilot plant under similar industrial conditions. Before the pilot plant test, different tool surface roughness qualities were evaluated at lab scale using a ball on disc test. Subsequently, performance of coated tools was evaluated through “coated ball” on “5754 aluminium disc” tests. The best combination between lubricant and coating was used to perform the aluminium punching process in the pilot plant, where two types of geometry and roughness of tool were analysed. Results were expressed in terms of aluminium adhesion on tool surface. Polished surface before coating deposition and geometry punches were the key factor to improve the process.