## 3 Evaluation of the Measured Values
### Evaluation of Values Measured by Contactless Method  
This part of the paper describes the sample surface data measurement by the LPM system. Two graphic dependencies were created from the measured data for the _Ra_ and _Rz_ quality parameters, depending on the material of the measured area at given feed rates. The measured surfaces are examined at ten depths on three samples of stainless steel and three samples of aluminum. Parameters for setting the LPM input values for surface measurement are shown in Table 6. This behavior was in agreement with data observed by [PERSON] et al. [28] and [PERSON] et al. [29]. The material samples surface roughness values measured were processed, resulting in two graphical dependencies _Ra_ and _Rz_, for both materials examined. The results also confirm the conclusions of [PERSON] et al. [30] and [PERSON] et al. [31]:The graphical dependence for the \(Rz\) parameter (Figure 10) shows the surface roughness in measured material depths at given feed rates v = 120, 220, 370 for aluminum and 50, 120 and 150 for stainless steel. This behavior was in agreement with data observed by [PERSON] [34], [PERSON] et al. [35] and [PERSON] et al. [36]. In all samples, the curves of the \(Ra\) and \(Rz\) values have a rising tendency, depending on the increase in measured depth of the cut h.  
Figure 11 illustrates 3D models of scanned samples made of aluminum, which was created by juxtaposing a series of profiles measured by LPM. 3D models show the surface area of the experimental samples captured with the laser profilometer. The images show a clear effect of cutting speed on the surface quality. The comparison of 3D models made (Figure 11, Figure 12) shows a clear difference in the surface quality of aluminum and stainless-steel samples. In samples made of aluminum (AL120, AL220, AL370), a smoother cut is evident. Smoother passing of the water jet did not leave as deep depressions on the surface of these samples as it did on the samples made of stainless steel. It follows from the comparison of graphical dependencies of the \(Ra\) and \(Rz\) parameters (Figure 9, Figure 10) that the roughness values are less jump-like, which reflects lesser strength and greater toughness of the evaluated material. This behavior was in agreement with data observed by [PERSON] et al. [37] and [PERSON] et al. [38]. Figure 10: The graphical dependence of \(Rz\) on the measurement depth for AL120, AL220, AL370 and SS050, SS120, SS150. Figure 9: The graphical dependence of \(Ra\) on the measurement depth for AL120, AL220, AL370 and SS050, SS120, SS150. Figure 12 illustrates 3D models of the scanned stainless steel samples, created by juxtaposing a series of profiles measured by LPM. The effect of cutting speed on the quality of the stainless steel surface is shown here. In the experimental samples (SS050, SS120, SS150), greater difficulty of the water passing through the material is visible, with the water jet leaving more depressions on the sample surfaces. It follows from the comparison of graphical dependencies of the \(Ra\) and \(Rz\) parameters (Figure 9, Figure 10) that the roughness values are more jump-like, which reflects greater strength and lesser toughness of the material evaluated. Surface roughness in these experimental samples is greater in the smooth, medium and rough surface zones. In all samples, the curves of the \(Ra\) and \(Rz\) values have a rising tendency, depending on the increase in measured depth of the cut. This behavior is in agreement with data observed by [PERSON] et al. [39] and [PERSON] et al. [40] and [PERSON] et al. [41]. The Gain 1 mode measured the character of the surface in 180 step increments of 0.11 \(\upmu\)m. The entire surface area of the sample was measured at ten measured sites when measured with LPM and four measured sites when measured with Mitutoyo SJ400. For comparison and verification of the measured values, samples made of aluminum and stainless steel were measured by the Mitutoyo SJ400  
Figure 11: 3D model of the scanned EN5083 samples.