## 1 Introduction
They defined a methodology according to which we can partially evaluate the efficiency and quality of radiation beam cutting by the proportion of the cutting joint width on the cut upper workpiece surface to the cutting joint width on the cut workpiece bottom (the so-called ratio). The focal point position and laser power are the principal factors affecting the ratio. In the case of the upper board's surface kerf, the focal point position has the main role, and in the case of the lower kerf, the laser power and cutting speed have the main effect on the lower kerf width. The roughness of the cut section decreases as the focal point position and laser power increase. The roughness increases as the cutting speed and air pressure increase. Smoother cut sections could be processed, but with an increase in the processing operating cost. [PERSON] et al. [48] investigated the effect of different focal point positions on the cut surface quality. They found that a smooth surface of the workpiece middle can be achieved with less charring with the focal point at or slightly above the middle. Most of these results are in harmony with previous published research in the case of wood and wood composites [49; 50; 51]. The focal point position was also investigated by [PERSON] et al. [40]. In their research, they achieved the best quality of particleboard laser cutting when the beam was focused on the surface of the composite material. In the case of wood, [PERSON] et al. investigated the significance of the focus position of the CO\({}_{2}\) laser optical system when hardwood cutting [52]. They concluded that the focal point should be at a location Z/2 below the surface to achieve a maximum average laser power density, where Z is the focal length (depth of focus). They verified these results by experimental observations. [PERSON] et al. [53] used a CO\({}_{2}\) laser to cut a wide range of Malaysian wood and plywood. The processing variables taken into account were the laser power, focal point position, nozzle size, assist gas pressure, types of assist gas, cutting speed, and delay time. The wood properties observed were the thickness, density, and moisture content of wood. The analyses considered the geometric and dimensional accuracy (straight sideline length, diameter of the circle, kerf width, and percent over cut), material removal rate, and severity of burning. A guideline for cutting a wide range of Malaysian wood has been outlined. The influence of the laser power, cutting speed, and shield gas on the cut quality in the case of hard and soft timber was confirmed by [PERSON] et al. [6]. [PERSON] [54] dealt with the moisture content and its influence on the process of pine wood cutting by a beam of radiation generated by a CO\({}_{2}\) laser in his work. He found that the cutting speed of wetter wood is slower compared to drier wood. The reason for this is that the moisture content in wood increases the thermal conductivity, which results in energy loss in the heating zone. [PERSON] and [PERSON] [41] showed that the CO\({}_{2}\) laser beam is almost completely absorbed by wood. This result has been confirmed by [PERSON] [42], who claimed that a CO\({}_{2}\) laser is most suitable for wood processing due to the wavelength used. The authors of the research [55; 56] proved that a cut section quality with less roughness results from an increasing beam power. The optimal conditions for laser cutting were determined by several authors using theoretical models. [PERSON] and [PERSON] [57] explored the possibilities of cutting wood and particleboards with various levels of laser power and different workpiece cutting speeds. They introduced a theoretical model that estimates the depth of the cut in terms of the material properties and cutting speed. The experimental cutting results were compared with theoretical predictions. Two correction parameters were introduced in the analysis to improve the theoretical model. Numerous other theoretical models for laser machining have been developed by other researchers, among them, [PERSON] et al.