Laser engraving of copper and copper-based materials

Abstract

This thesis investigates the optimization of laser parameters for deep and fast engraving of commercially pure copper. Three fiber pulsed lasers were utilized, first being a 20-watt nanosecond laser, second being a 300-watt nanosecond laser that is based on the MOPA technology, and last being a 4.85-watt femtosecond laser that operates in the green light wavelength of 515 nanometres. Given copper’s high reflectivity in the near-infrared spectrum (~94 %) and moderate reflectivity in the green light spectrum (~42 %), the study explores the influence of parameters such as pulse duration, pulse repetition rate, and scan speed on engraving depth. Unlike most prior studies that focused on the micrometre or nanometre scale engraving, this research targets the millimetre scale engraving without having a concern for the surface quality.

The experimental results reveal that power output is the dominant factor in achieving fast and deep engraving depth, but optimization of other parameters such as pulse duration and pulse repetition rates can double the engraving efficiency. Parameter such as scan speed also plays a part and optimizing this can affect the result of the engraving. Despite the theoretical compatibility of green wavelength lasers on copper, the femtosecond laser was not optimal for fast, deep engraving due to its low power output. However, it produced the best surface quality and minimal thermal effects, making it ideal when precision and minimal heat-affected zones are important. In contrast, the higher power nanosecond lasers transferred significantly more heat to the workpieces, requiring cooling time post-engraving. These findings highlight the importance of balancing power, pulse characteristics, and process parameters to match application specific goals in copper laser engraving.