# Stochastic Evaluation of Cutting Tool Load and Surface Quality during Milling of HPL
## 3 High-Pressure Laminate HPL Milling Results
### Evaluation of Milling Surface Roughness Measurement  
The roughness parameters \(R_{a}\) and \(R_{z}\) of the milled workpiece were evaluated in the longitudinal and transverse directions at predefined measuring points, see Equations (1), (2) and Figure 5. The values obtained for the parameter \(R_{a}\) are recorded in Table 9 and for the parameter \(R_{z}\) in Table 10.  
\begin{table}
\begin{tabular}{c c c c c c c} \hline \hline \multicolumn{2}{c}{**Point of Measurement**} & \multicolumn{5}{c}{**Measurement Direction**} & \multicolumn{5}{c}{**R\_/\_/\_/**mm/**} \\ \hline  & Transverse & 1.897 & 4.748 & 3.637 & 3.427 & 1.173 \\ \hline
**1** & Longitudinal & 2.077 & 1.525 & 1.815 & 1.806 & 0.276 \\ \hline  & Transverse & 2.606 & 1.781 & 1.671 & 2.019 & 0.417 \\ \hline
**2** & Longitudinal & 2.398 & 1.926 & 3.620 & 2.648 & 0.874 \\ \hline
**3** & Transverse & 1.727 & 2.052 & 2.563 & 2.114 & 0.344 \\ \hline  & Longitudinal & 4.704 & 2.228 & 2.009 & 2.980 & 1.497 \\ \hline  & Transverse & 2.731 & 2.987 & 2.987 & 2.902 & 0.121 \\ \hline  & Longitudinal & 2.003 & 2.034 & 2.900 & 2.312 & 0.509 \\ \hline  & Transverse & 4.116 & 3.133 & 4.081 & 3.777 & 0.455 \\ \hline  & Longitudinal & 3.716 & 2.539 & 2.724 & 2.993 & 0.633 \\ \hline  & Transverse & 3.622 & 2.813 & 3.006 & 3.147 & 0.345 \\ \hline  & Longitudinal & 2.357 & 4.916 & 3.764 & 3.679 & 1.282 \\ \hline  & Transverse & 1.624 & 1.667 & 2.315 & 1.869 & 0.316 \\ \hline  & Longitudinal & 1.563 & 2.001 & 1.991 & 1.852 & 0.250 \\ \hline  & Transverse & 3.344 & 0.991 & 2.231 & 2.189 & 0.961 \\ \hline  & Longitudinal & 1.367 & 2.556 & 2.046 & 1.990 & 0.596 \\ \hline  & Transverse & 1.75 & 1.237 & 1.185 & 1.391 & 0.255 \\ \hline  & Longitudinal & 2.668 & 2.073 & 6.920 & 3.887 & 2.643 \\ \hline \hline \end{tabular}
\end{table}
Table 10: Results of \(R_{z}\) roughness measurement of milled surface of milled HPL material.  
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline \multicolumn{2}{c}{**Point of Measurement**} & \multicolumn{5}{c}{**R\_/\_/\_/**mm/**} \\ \hline  & Transverse & 0.333 & 1.012 & 0.465 & 0.603 & 0.294 \\ \cline{2-6}
**1** & Longitudinal & 0.425 & 0.294 & 0.410 & 0.376 & 0.059 \\ \hline  & Transverse & 0.501 & 0.452 & 0.335 & 0.429 & 0.070 \\ \hline  & Longitudinal & 0.509 & 0.452 & 1.064 & 0.675 & 0.276 \\ \hline  & Transverse & 0.467 & 0.452 & 0.732 & 0.550 & 0.129 \\ \hline  & Longitudinal & 1.450 & 0.536 & 0.368 & 0.785 & 0.475 \\ \hline  & Transverse & 1.338 & 1.385 & 1.376 & 1.366 & 0.020 \\ \hline  & Longitudinal & 0.607 & 0.594 & 0.734 & 0.645 & 0.063 \\ \hline  & Transverse & 1.263 & 1.238 & 1.366 & 1.289 & 0.055 \\ \hline  & Longitudinal & 0.793 & 0.604 & 0.793 & 0.7 In general, the surface roughness is higher in the up milling than in down milling. This is also true for HPL material, as can be seen from the results in the graphs in Figures 12 and 13. Up milling achieves a significantly higher profile parameter \(R_{z}\), compared with down milling in both transverse and longitudinal directions.  
The measured values of the roughness parameter \(R_{a}\) of the HPL surface ranged from 0.222 to 1.385 \(\upmu\)m in the transverse direction, and from 0.289 to 1.923 \(\upmu\)m in the longitudinal direction for down milling. For up milling, the range of parameter \(R_{a}\) was 0.991 to 4.748 \(\upmu\)m in the transverse direction, and 1.367 to 6.92 \(\upmu\)m in the longitudinal direction.  
Figure 12: Average values of the parameters \(R_{a}\), and \(R_{z}\) in the transverse direction.  
Figure 13: Average values of the parameters \(R_{a}\), and \(R_{z}\) in the longitudinal direction.  
The obtained results have not yet been published in the literature outside of our work, and can be used not only for numerical modelling but also for engineering design or optimisation of new machine tools; see e.g., Section 4.