Feasibility assessment of parallelized helical drilling

Abstract

With the average power of commercial ultrafast lasers reaching the kW-level, process parallelization is required to avoid detrimental quality issues, such as caused by heat accumulation. This is especially relevant in the case of helical drilling, as the processing strategy is only employed when precise geometry, high-quality surface finish, tight tolerances, and high reproducibility are a priority. We illustrate that parallelization by means of a multipass process is conceptually attractive for pulsed drilling processes, but also challenging due to limitations imposed by the properties of appropriate beam-steering devices. While paraxial beam propagation methods applied to the suggested setup predict no aberrations, deviations from the idealized solution are a concern. Our experimental proof-of-principle investigations show that parallelization by means of a deflector preceding the helical drilling optics is possible while ensuring nearly identical processing parameters for all parallelly processed boreholes.