Dry Forming of Aluminium Sheet Metal: Influence of Different Types of Forming Tool Microstructures on the Coefficient of Friction

Abstract

In the sheet metal forming industry lubricants are applied in forming processes to expand the technological boundaries by reducing friction and wear. The friction between tool and sheet metal is crucial to the deep drawing process. Due to economic and ecological reasons the aim of the manufacturers is to reduce or even avoid the use of lubricants. Consequently, this approach enables both a shortening of the process chains and an essential saving of resources. The advantages of structured forming tools in lubricated processes concerning the reduction of the coefficient of friction by the appearance of lubricating micro pockets are well-known. However, without using any lubricant this effect does not work. In this case the contact area is reduced by structuring the forming tool which affects the tribological system.In this paper the influence of microstructures with different geometries and surface treatments (uncoated / a-C:H:Si-coating) on the coefficient of friction in dry metal forming of the alloy AA5182 is compared to the frictional behaviour of unstructured forming tools using lubricant as reference. Before coating, the forming tools are machined by milling to generate tribologically effective microstructures. With the use of a strip drawing plant the effects of different surface microstructures and materials on the coefficient of friction are investigated.