Enhancing Single Channel MQL through Bypass Controlled Design for Deep Hole Drilling with Small Diameter Tool

Abstract

Because of significant energy savings, enablement of higher machining speed as well as environmentally friendly features, Minimum Quantity Lubrication (MQL) has been efficiently used for many machining processes. However, in deep hole drilling with small tools (tool diameter D< 5 mm and length L>25 D) there is a bottleneck for the single-channel MQL system. The single-channel MQL, based on the Venturi principle, has difficulty generating the required oil quantity due to dropped air pressure difference during the deep hole drilling process. In this paper, a system concept based on a bypass design is proposed and investigated in static and dynamic laboratory tests. In the static test, the oil volume with and without bypass control was measured. Through the spray pattern test, the aerosol distribution and the reaction time are analyzed. A dynamic machining trial with a drill tool (D=4.5 mm, L= 40 D) was carried out with the proposed system. The tool wear was tracked and analyzed up to 100 meters in drilling distance. The result shows that the single-channel MQL with a bypass control is able to overcome this limitation and enables a uniform and continuous aerosol flow to tooltips.