Effects of beam power and feed rate in the process of cutting fresh wood with a CO2 laser on water contact angle on the cut surface

The paper describes a study on the effects of beam power and feed rate in the process of cutting fresh wood with a CO₂ laser on water contact angle on the cut surface. The study involved several broadleaved tree species (oak, birch, alder, plum, and apple tree) and one coniferous species (pine). Samples were cut with a Trumpf TLC1005 laser equipped with a TruFlow 6000 CO₂ resonator at a wavelength of 10.6 μm at three power output settings (1 kW, 2 kW, and 3 kW) and one feed rate (0.4 m∙min^− 1). Contact angle was measured by pipetting a drop of distilled water on the wood surface and recording the process with a camera. Subsequently, images of the drop were analyzed over one minute at 10 s intervals to determine changes in contact angle for each of the cases examined. It was not possible to measure the contact angle on saw-cut samples as the water was immediately absorbed, while water drops placed on laser-cut samples remained on the surface for over 60 s, with the contact angle decreasing over time for the examined species from an average of 90° to 40°. The higher beam power settings (2 or 3 kW) were found to be preferable for the hardwood species (oak, birch, alder, and apple tree). In turn, in the case of the softwood species (pine), the laser power output did not matter, as both at the low (1 kW) and high (3 kW) settings the drop did not spread over the surface quickly. Finally, the optimum beam power for plum tree wood was found to be 1 kW.