Numerical and experimental evaluation of chip evacuation and lubricant flow using optimized drill heads for ejector deep hole drilling

Abstract Ejector deep hole drilling offers great potential to utilize the typical advantages of deep hole drilling processes on conventional machining centers in a cost-effective and resource-efficient manner. However, maintaining reliable chip evacuation and stable process conditions often relies on high flow volumes of metalworking fluid, resulting in considerable energy consumption in industrial settings. Therefore, to analyze the highly sophisticated chip evacuation dynamics of the process, two flow-optimized drill heads and a reference drill head were evaluated with smoothed particle hydrodynamics simulation using experimentally obtained chip shapes. In addition, modified drill heads were additively manufactured and experimentally investigated to validate the numerical results and to determine the positive effect on the necessary fluid flow for a stable ejector drilling process. The modifications aim to improve chip evacuation by reducing vortex formation and optimizing flow conditions near the cutting zone. Therefore, the minimum volume flow required for a stable drilling process without chip clogging is reduced, leading to an energy-efficient sustainable ejector drilling process.