Influence of tool surface on tribological conditions in conventional and dry sheet metal forming

The realization of lubricant free forming processes is motivated by an increasing demand for resource efficiency and higher environmental standards. Further potentials are the reduction of production steps and time. The dry conditions lead to an intensive interaction between tool and workpiece. Increasing friction and wear are the consequences. One approach to face these challenges is the implementation of tailored tool surfaces. Within this study the behavior of different tool surfaces under dry and lubricated conditions is investigated. In this regards, a flat strip drawing test was conducted to determine the friction coefficients depending on the tool surface properties resulting from various machining processes. Furthermore, a surface characterization before and after the experiments was performed to gain knowledge about the wear mechanisms. The tests series with dry strips lead to a higher friction level. Furthermore, the results show that the friction can be reduced when the grinding marks are orientated transversal to the drawing direction. A further friction reduction is achieved when applying polished tools.