Performance analysis of drills with structured surfaces when drilling CFRP/AA7075 stack under MQL condition

Abstract

When drilling multi-stack materials, the dissimilar material response, severe tool wear, and long hot metal chips pose serious challenges in achieving the requisite hole quality. There is difficulty in effectively lubricating the cutting zone as the drill penetrates deep into the drilled hole. Structuring the surfaces of cutting tools is an approach to improve their tribological performance. Micro-textures are created on the drill flute and margin surfaces using laser micro-machining to improve the micro-pool lubrication effect and reduce the friction during machining CFRP/aluminum alloy stacks. The performance of four different textured drills - dimple on flute, groove on flute, perpendicular and parallel grooves on margin – is compared with that of the non-textured drill. The thrust force, hole quality (roughness, roundness and delamination), tool wear (BUE and cutting edge rounding), and chip morphology are analyzed. Among the four textured drills, the dimple textured drill results in the best performance due to the improved micro-pool lubrication effect of micro-dimples in the flute region, thereby producing short metal chips and best hole quality. It also retains the texture depth for a longer duration as compared to the other textured drills.