Chip formation simulation and analysis of the mechanical loads during micro single-lip deep hole drilling of Inconel 718 with varying cooling lubricant pressure

The micro single-lip deep hole drilling process is subjected to many difficulties. Especially the machining of difficult-to-cut materials like the nickel-based alloy Inconel 718 results in high thermal and mechanical loads. Irregularities in the drilling process, which lead to early tool failures must be avoided. A major challenge for micro single-lip deep hole drilling is to generate favorable chips and guarantee good chip removal. Since the chip flute of single-lip deep hole drilling tools is straight, the only mechanism to transport the chips and remove them from the bore hole is the coolant flow. In this paper the mechanical loads and the resulting chip formation for various cooling lubricant pressures are analyzed using tools with a diameter of d = 2 mm. In the experiments feed force, drilling torque, tool wear, bore hole quality as well as diameter and roundness deviations were evaluated. Individual chips are digitized and prepared as CAD models for the future consideration of the chip removal in flow simulations of the cooling lubricant. Additional FEM computational analyses of the three-dimensional chip formation with a geometric representation of the chip shape were carried out. This way not only provides valuable validated information about the process and the chip formation but also creates a basis for further investigations, which will allow an innovative simulation of the coolant flow and considers the chip formation and the chip shape.