## 4 Conclusions  
The feed speed of the cutting head is one of the most important and technologically most easily adjustable technological parameters affecting the quality parameters Ra and Rz. Figures 9 and 10 show plotted dependencies of surface roughness \(Ra\), \(Rz\) versus depth of material at the given cutting head feed rates of separating the respective materials. The measured and evaluated surface area of 0.11-19.91 \(\upmu\)m gradually passed from smooth to rough surface zone (Figure 8). Therefore, the measurement results can be summarized as follows:  
* The plotted dependencies show that surface roughness varies linearly the deeper the AWJ cut. * All plotted dependencies show a growing trend of roughness values. * As the feed rate decreases, the smooth zone size (characterized by lower roughness values) increases. * It occurs primarily in the first cut zone of the machined surface. This can also be seen in the plotted dependencies where the smallest initial surface roughness is (Figures 9 and 10). * The values of the \(Ra\) and \(Rz\) parameters of the smooth zone are closest to each other, but even at these values, a difference in surface roughness is apparent, depending on the speed of the cutting head. * The \(Ra\) and \(Rz\) parameter values of the AL120, AL220 and SS050, SS120 samples show a linear increase. The AL370 and SS150 samples exhibit a rather exponential increase in the \(Ra\) and \(Rz\) parameter values and their value trend is jump-like. * Linearly increasing roughness is true for both the smooth and medium smooth zones (from 0.11 \(\upmu\)m to 8.91 \(\upmu\)m). An exponential increase in value occurs in the medium rough and rough (end) zone of the surface from 11.11 \(\upmu\)m to 19.91 \(\upmu\)m.
* It follows from the cuts and the measured values compared that the AWJ material separation technology shows equally manifesting increases. Occurrence of reliefs on the sectioned surfaces in both soft (AL) and hard metal materials (SS) was less frequent in the samples made of aluminum than in the samples made of stainless steel. * This means that a different cutting head speed must be used to achieve the same surface roughness in different materials. We can say that the roughness of the sample surfaces produced by the DRC Company did not exceed the declared roughness of any of the samples used. The task of the experiment was to compare and evaluate the surface of samples produced by the AWJ technology at the DRC Company and to evaluate the measurement methods. The company declares that the surface roughness of each sample produced is not greater than that shown in Table 2 for each of the samples. The values measured with the contact roughness meter Mitutoyo SJ 400 show its first obvious disadvantage compared to the LPM device. The contact roughness meter does not provide for a complete picture of the surface under evaluation or the roughness of its individual parts. This is because, in measuring the 800 \(\upmu\)m section of the surface (the section covered by the tip of the instrument over the measured surface), the result is a single average value of the roughness parameters \(Ra\) and \(Rz\). When measured with LPM, the measurement result is a set of values that describe the surface areas at each measurement step. The LPM also evaluates the largest depression and the largest protrusion of the surface under evaluation, i.e., it evaluates several parameters in the individual measurement steps. Another advantage is the creation of a 3D image of the examined surface where it is possible to better see the surface nature of the object being measured. [PERSON] suggested the concept of application of laser profilometry to evaluation of the nature of the surface of the workpiece separated by the advanced water jet technology; [PERSON] prepared testing samples; [PERSON] and [PERSON] designed and performed experimental measurements in the laboratory; [PERSON] and [PERSON] analyzed and evaluated measured data; [PERSON] contributed materials and analysis tools; [PERSON] wrote the paper.