Analysis and optimization of the piercing process in laser beam cutting by means of high-speed X-ray imaging

Abstract

An in-process analysis of the piercing process at the beginning of a laser cut using high-speed X-ray imaging is presented for the first time. Sheets of stainless steel with thicknesses ranging from 10 mm to 30 mm were pierced by laser pulses at a wavelength of 1 μm with a peak power of 6 kW. With a constant pulse length and a constant peak power, a reduction of the piercing duration was achieved by increasing the pulse repetition rate, as long as the latter does not exceed a specific limit at which the sheet cannot be pierced successfully anymore. When the pulse repetition rate exceeds the thickness-specific limit, the growth of the piercing depths stagnates before the sheet is pierced through completely. Melt from the side walls starts to re-fill the bottom of the piercing hole and the diameter of the hole increases in the lower part. The time between the pulses is too short for the melt to move out of the hole. An optimization strategy is presented that results in a reduction of the piercing duration by 50%. • An in-process analysis of the piercing process at the beginning of a laser cut using high-speed X-ray imaging is presented. • An increase of the pulse repetition rate at constant pulse length and laser peak power leads to a reduction of the piercing duration. • When the pulse repetition rate exceeds the thickness-specific limit, the growth of the piercing depths stagnates. • An optimization strategy is presented that results in a reduction of the piercing duration by 50%.