Influence of different metal working fluids when micro machining cp-titanium with 50 µm diameter micro end mills

Abstract

The increasing demand for micro structures and micro parts requires precise and efficient machining processes. One suitable process for the production of these structures is micro milling. Via micro milling it is possible to manufacture products with high geometric diversity and structures in a large spectrum of different materials. However, a limiting factor of the micro milling process is the high abrasive wear at the cutting edges of the micro end mills. This can be explained by size-effects, especially the high cutting edge radius to chip thickness-ratio (rß/h-ratio). High rß/h-ratios result in a high amount of ploughing as the cutting edge cannot be considered as sharp. This in turn leads to a further increase of wear of the cutting edge and ultimately in increased temperatures in the contact area, favoring the formation of built-up edges. Both, the wear of the cutting edges and the built-up edge formation have negative effects on the process results and reduce the capability as well as the efficiency of the whole process. A further reduction of the cutting edge radius is not possible because of the grain size of the cemented carbide used. One way to reduce friction and heat generation in machining processes is the use of metal working fluids. In micro milling, the wetting behavior of these fluids plays a more decisive role as in conventional machining due to the size of the structures and the surface tension of the fluid. In this paper, different fluids (isopropanol, sodium dodecylsulfate and cutting oil) with high wetting capability will be applied at minimum quantity lubrication and the results are compared to dry machining of cp-titanium. With this research, the quality of micro milled surfaces can be optimized regarding e.g. surface roughness or burr formation enabling the production of parts with an even higher functionality.