Temporal and spatial heat input regulation strategy for high-throughput micro-drilling based on multi-beam ultrafast laser

High-throughput laser drilling is crucial for the processing of large-area micro-hole arrays, but the local heat accumulation effect in the processing significantly limits the fabrication quality, especially for multi-beam laser micro-drilling. Although cooling methods such as water or airflow is applied to enhance heat dissipation, the heat input regulation is a convenient and effective way to improve the processing quality. In this work, a novel temporal and spatial heat input regulation strategy is proposed for multi-beam laser micro-drilling to effectively suppress the local heat accumulation during the processing. The strategy consists of a scanning path planning model and an optimization method of key drilling parameters. The scanning path planning model is established based on the temperature field of the workpiece, which is dynamically calculated using a transient finite-difference method (FDM). In addition, an optimization method is proposed to match the drilling parameters with the designated scanning path. Via this heat input regulation strategy, a more homogeneous temperature distribution can be obtained in the multi-beam laser drilling of micro-hole arrays. The maximum temperature and duration of overheating that causes material oxidation are decreased by 10%, and 50%, respectively. With the realization of high-quality (recast-free) and high-throughput (2430 micro-holes in 210 s, or 12 micro-holes/s), the proposed strategy shows a promising prospect in the multi-beam drilling of micro-hole arrays and other laser processing with possible heat accumulation, such as large-area surface texture and precise engraving of micro-nano structures.