Sonja Kieren-Ehses, Tobias Mayer, Benjamin Kirsch, Jan C. Aurich

• Micro end mills are characterized by high abrasive wear. To counteract this high abrasive wear, metalworking fluids can be applied. There are various methods to supply these fluids. One of these methods is the minimum quantity lubrication (MQL). The objective of this research is to investigate the influence of the supply direction and air pressure of a MQL system on the process result when micro milling. Micro milling tests were carried out using micro end mills made of cemented carbide with an effective diameter of 50 \(\mu \text {m}\) . When machining commercially pure titanium, the supply direction was varied at four levels relative to the feed direction (0 \({}^{\circ }\) , 90 \({}^{\circ }\) , 180 \({}^{\circ }\) and 270 \({}^{\circ }\) ) and the air pressure at three levels (0.1 MPa, 0.2 MPa and 0.3 MPa). At each air pressure, the spindle speed was varied at three levels (30,000 rpm, 60,000 rpm, 120,000 rpm). Tool wear, surface quality, burr formation, and manufacturing accuracy were analyzed. In terms of the supply direction, the best results were obtained with a supply direction of 180 \({}^{\circ }\) (in feed direction) — the lowest roughness and the most uniform slot bottom structure were machined. Regarding the influence of the supply direction on tool wear and manufacturing accuracy, no significant differences could be found. With regard to the air pressure, no clear result could be achieved. The influence of the spindle speed on the process results was higher than the influence of the air pressure. However, it is possible to select a suitable air pressure depending on the spindle speed.