Highly reproducible laser micro drilling of titanium-based HLFC sections

The reduction of fuel-consumption is an environmentally relevant priority of the aviation industry. One of the key technologies in this field is the hybrid laminar flow control (HLFC), which is based on perforated sections on the leading edge of aircrafts. Up to now the economic efficiency as well as the quality of several micro drilling processes, such as laser drilling, cannot meet the requirements of a high-speed and large-area generation of micro holes with highly reproducible diameter. In this paper, an approach for a highly reproducible laser micro drilling of 0.8 mm thick titanium is presented. The influences of drilling parameters on process stability and bore diameter are discussed. With a commercially viable system technology based on a short pulsed fiber laser and a galvano-scanner, a stable production of micro holes of 35 μm to 90 μm in diameter with a through-going bore density of about 95 % was realized at drilling rates up to 175 holes/s. In terms to improve the inner form and to enlarge the hole diameter, a chemical pickling was carried out. Depending on the required dimension, this results in bores of 50 μm to 130 μm in diameter with deviations less than 10 %.