Visualization and Analysis of Tool-Fluid Interactions in Through-Tool MQL Drilling

Abstract

The motive of the research is to understand and identify the principles behind the fluid flow and its interaction with the cutting geometry in through-tool Minimum Quantity Lubrication (MQL) drilling. In MQL, pressurized air (typically 4 – 8 Bar) and a very low quantity of lubricant (typically 5 – 300 ml/h) is used to provide cooling and lubrication to the cutting zone. The bulk of the lubricant is converted into mist using the pressurized air and then delivered to the cutting zone. The higher surface area of the lubricant droplets improves the heat transfer capacity and the penetration depth of the droplets over bulk lubricant. It is well known that the tool wear is not homogenous along the cutting edge of the drill and therefore, while using little quantities of lubricant to provide lubrication, like in MQL, targeted delivery of the lubricant is of core importance. Therefore, in this study experimental as well as numerical attempts are made to visualize and measure the lubricant distribution in the through-tool channels and consequently on the cutting edge of the drill. The effect of drill geometry and cutting zone morphology on the lubricant flow distribution is investigated. The results show that the rotation of the drill and the channel geometry affect the velocity profile of the primary phase and the lubricant distribution. The exit location of the through-tool channels should be kept as close to the cutting edge as possible since the lubricant struggles penetrating to the cutting edge.