Physics-Informed Simulated-Annealing Path-Planning for Mitigating Thermal Accumulation During Nanosecond Laser Drilling of PMMA Micro-Hole Arrays

The high-precision laser micromachining of thermally sensitive PMMA polymers is severely limited by thermal accumulation, which deteriorates the surface quality of micro-hole arrays. Current laser drilling path optimization strategies predominantly prioritize geometric efficiency by minimizing travel distance, whereas quantitative thermal-constrained path optimization for PMMA micro-hole drilling remains underexplored. This work proposes a constrained simulated-annealing (SAA) path-planning strategy that embeds physical thermal constraints (critical thermal radius R and spacing threshold M) into the classic meta-heuristic algorithm, effectively suppressing transient thermal superposition between adjacent micro-holes while maintaining acceptable machining efficiency. Compared with the conventional sequential scanning mode (SSM), the SAA strategy reduces the molten deposit width around micro-holes by 22.3% under identical machining conditions (3 W laser power, 60 mm/s scanning speed, and a single scanning pass). A inherent trade-off is also observed: the thermally isolated jump path increases the total travel distance, resulting in approximately 1.3-fold longer machining time. Benefiting from the suppressed thermal accumulation, the SAA path effectively eliminates thermal-induced micro-hole coalescence at a compact hole spacing of 50 μm, yielding well-defined micro-hole contours and enabling the reliable fabrication of high-quality E-shaped structural color patterns with tunable optical responses under natural light.