Heat accumulation during pulsed laser materials processing

TLDR

Laser materials processing with ultra‑short pulses yields precise, high‑quality results with minimal thermal damage, but increasing average power and repetition rates cause significant heat accumulation. The study aims to analytically investigate multi‑pulse laser processing to uncover the mechanisms of heat accumulation and its impact on processing quality. The authors develop a comprehensive analytical model of multi‑pulse processing that elucidates the fundamental mechanisms of heat accumulation. The model explains experimental results for drilling microholes in CrNi‑steel and cutting CFRP, and yields an estimate of the maximum average power permissible at a given repetition rate.

Abstract

Laser materials processing with ultra-short pulses allows very precise and high quality results with a minimum extent of the thermally affected zone. However, with increasing average laser power and repetition rates the so-called heat accumulation effect becomes a considerable issue. The following discussion presents a comprehensive analytical treatment of multi-pulse processing and reveals the basic mechanisms of heat accumulation and its consequence for the resulting processing quality. The theoretical findings can explain the experimental results achieved when drilling microholes in CrNi-steel and for cutting of CFRP. As a consequence of the presented considerations, an estimate for the maximum applicable average power for ultra-shorts pulsed laser materials processing for a given pulse repetition rate is derived.