Parameterization and Simulation of a Cooling Channel Cross-Section in Single-Lip Drilling

Deep drilling with single-lip drills (SDLs), especially in materials that are difficult to machine such as Inconel 718, results in very high thermomechanical stress due to the material properties. The process is mainly influenced by the tool geometry, cutting forces, chip removal, and the cooling lubricant. Due to the straight flutes of the tools, chip removal is only possible through the cooling lubricant. For this reason, there is a cooling channel inside the tool. By increasing the diameter of the cooling channel, a larger volume flow and higher pressure at the cutting edges can improve cooling and chip removal. Modern methods such as numerical simulation provide important valuable insights. In this study, the coolant distribution during drilling was numerically analyzed. The aim was to reduce thermomechanical loads, which has a positive effect on tool wear and friction load. For systematic optimization, a mathematical model was developed to describe the cross-sectional geometry of the SDL. Based on parameterized sub-geometries, transition conditions, and experimental average values for the feed force and torque, numerical modification was performed using an iterative simulation model that considered the material´s mechanical strength. The maximum possible enlargement of the cooling channel while maintaining the strength requirements was analyzed on a total of 30 models. The cross-sectional area achieved an increase of 45.5% compared to the initial geometry.