## 3 Description, Implementation and Results of Experiments  
An input experiment to test the LTS application for parameter measurement was conducted for cylindrical surface turning. For the experiment, we selected steel C45 with a specimen of 40 mm diameter and 150 mm length, shown as Table 2.  
After verification of the selected LTS on TS-A, the experiments could be continued, as it was shown that this LTS is suitable for measuring the deviation of geometrical parameters of the machined surface. In the next step, the experiments were performed on TS-B according to Table 1, and the results of the experiments are reported in this section. The deviation of the diameter \(\Delta_{d}\) and the wear of the flank side of the cutting insert (\(VB_{B}\)) were measured after each experiment. Each value of the diameter deviation and the value of the wear of the flank side of the cutting insert is a value obtained from eight repetitions (with two cutting insert). The diameter deviation was measured directly in the working zone of the machine tool with LTS, i.e., after machining the surface of the workpiece without switching it off. The measurement system for the LTS is shown in Figure 2. The surface wear of the cutting insert was measured and analyzed using a Carl Zeiss Primotech D/A ESD microscope, as shown in Figure 8. \begin{table}
\begin{tabular}{c c} \hline
**Steel C45** & **\%** \\ \hline C & 0.48 \\ Mn & 0.70 \\ Si & 0.20 \\ Cr & max 0.25 \\ Ni & max 0.30 \\ P & 0.040 \\ S & 0.040 \\ \hline \end{tabular}
\end{table} 
Table 2: Chemical composition of steel C45 [41]. Figure 7: LTS with 3D-printed sensor holder. In all experiments, regular wear was observed on the flank side of cutting insert, so \(VB_{B}\) values were measured according to ISO 3685. This parameter was important for the analysis of the impact on the next studied parameter diameter deviation for steel C45. An example of a \(VB_{B}\) measurement is shown in Figure 9.  
The experiments were planned according to the Taguchi L16 orthogonal array for three input factors such as depth of cut (\(a_{p}\)), feed (\(f\)), and cutting speed (\(v_{c}\)) in four levels, as shown in Table 3. The Taguchi L16 orthogonal array represents 16 experiments, which were always turned with a new cutting edge on a 210 mm long experimental piece (3 cuts with a length of 70 mm). After turning, the machined area was measured with the LTS. The diameter deviation was measured for a defined start and reference point (with a diameter deviation value of 0 mm), which was defined in the specimen axis. Figure 8: Measurement and analysis of flank wear on the cutting insert by Carl Zeiss Primotech D/A ESD microscope. Figure 9: (**a**) Cutting insert wear, \(VB_{B}\)—flank wear 163.8 μm; (**b**) another view from face part of the damage on cutting insert. The experimental results of the wear of the flank side and the diameter deviation are listed in Table 4.  
The results of the experiments and the diagrams of the main effects are presented in Figure 10 (\(\Delta_{d}\) and \(VB_{B}\)), showing that the resulting parameter \(VB_{B}\) wear of flank gradually increases with increasing depth of cut, feed, and cutting speed. The greatest influence of the input factors was found in the order of cutting speed, depth of cut, and feed. The deviation of the diameter increases significantly when the depth of cut changes from level 1 to 2 of the depth of cut, but it is also reversed from level 2 to 3 of the depth of cut and increases gradually from level 3 to 4 of the depth of cut. The lowest value was displayed at a depth of cut of level 1. During the feed, lower values were measured from level 3 to 4. The lowest value of diameter deviation was measured at a feed of 0.4 mm. The influence of the cutting speed is significant to obtaining lower deviations of the average from level 1 to 2 of the cutting speed.