EUROPEAN CONGRESS AND EXHIBITION ON ADVANCED MATERIALS AND PROCESSES - EUROMAT 2021

Due to the advancing miniaturization and the trend towards downsizing of components, bores on complex surfaces with small diameters and high aspect ratios are increasingly required. Typical examples can be found in medical technology for the machining of complex contoured implants and in the aerospace industry to produce cooling holes in turbine blades. The conventional process chain to machine these bores consist of a milling process to produce a flat spot, mechanical pilot hole drilling and the subsequent single-lip deep hole drilling process. Motivated by the constantly growing demands for shorter process times and more efficient production, laser drilling can be used to machine pilot holes directly on complex surfaces. The laser drilling process is characterized by short process times and enables wear-free machining. By using a hybrid machine tool concept, the advantages of both processes are combined synergistically, so that the flexibility of the laser process to machine on complex surfaces, is matched with the high bore quality of single-lip deep hole drilling. Two different laser strategies are used in the investigations to produce pilot holes with a diameter of d = 0.5 mm using a single pulse and a diameter of d = 1.5 mm using a helical laser drilling process. In addition to the laser process parameters pulse power, pulse duration, focus distance and process gas, the influences of the workpiece geometry (flat, angled, curved) and the workpiece material are analyzed. Besides the stainless steel X2CrNiMo17-12-2, the steel 20MnCr5 is used in the untreated as well as in the case hardened condition. The investigations of the laser process are followed by single-lip deep hole drilling tests to demonstrate the potential of laser pilot holes to guide the single-lip tool at the beginning of the deep hole drilling process.