# Adjustment of Wire Vibrations in Order to Improve Geometric Accuracy and Surface Roughness at WEDM
## 4 Results of Experiments
### Cylindricity Deviations vs. Roughness of Eroded Surface after Electrical Discharge Machining  
In terms of the evaluation complexity of the geometric precision of an eroded circular profile area, the maximum deviations in the cylindricity, \(z_{Cmax}\), were also identified. A Roundtest RA-120 measuring device was also used for the identification and evaluation of these deviations. The measurements were performed in the whole profile of experimentally  
Figure 6: Measurement of machined surface roughness parameters after WEDM with the Mitutoyo Surftest SJ 400 (Mitutoyo, Kawasaki, Japan) contact profilometer. Figure 7: Geometric deviations of roundness (\(y_{Cmax}\)) vs. surface roughness (\(Ra\)) of experimental samples of circular cross-sections after WEDM for various parameters of \(\upomega_{Ci}\) and \(H_{w}\). prepared samples, with the profile heights \(H_{w}\) = 10.0, 50.0, and 100.0 mm and diameters of \(\omega_{\text{Cy}}\) = 5.0, 20.0, 40.0, 80.0 and 120.0 mm. The graphical dependences in Figure 8 document the course of the deviations of the cylindricity (\(z_{Cmax}\)) vs. roughness of the machined surface (\(Ra\)) of the experimental samples after WEDM at the individual parameters of \(\omega_{Ci}\) and \(H_{w}\). From the diagrams in Figure 8, it can be observed that the values of geometric deviations from cylindricity (\(z_{Cmax}\)) of the machined surface after WEDM with an Ms wire electrode, \(\omega_{TE}\) = 0.25 mm, differed significantly depending on the diameter of the circular profile. The lowest value of \(z_{Cmax}\) = 45.6 \(\upmu\)m was recorded for a circular profile of \(\omega_{Cy}\) = 5.0 mm, which had a material thickness of \(H_{w}\) = 10.0 mm. On the contrary, the highest value of \(z_{Cmax}\) = 162.6 \(\upmu\)m was obtained for a circular profile of \(\omega_{Cy}\) = 120.0 mm, which had a material of thickness of \(H_{w}\) = 100.0 mm. Based on the results of the experimental measurements, it can be stated that, with an increasing diameter of the circular profile (\(\omega_{Cy}\)), there is a significant increase in the maximum geometric deviation of the cylindricity (\(z_{Cmax}\)) of the machined surface after WEDM. This increase is at a material thickness \(H_{w}\) = 10.0 mm at the level of \(z_{Cmax}\) = 32.9 \(\upmu\)m. At a material thickness of \(H_{w}\) = 100.0 mm, this increase is at the level of \(z_{Cmax}\) = 66.8 \(\upmu\)m.  
From the point of view of the complexity of the assessment of the results of experimental measurements, the graphical dependences are shown in Figure 9 were constructed. These graphical dependences document the course of the deviations of cylindricity \(z_{Cmax}\) vs. the roughness of machined area \(Ra\) of the experimental samples after WEDM at the individual parameters of \(\omega_{Ci}\) and \(H_{w}\). From the diagram in Figure 9, it can be observed that the values of the maximum geometric deviations of cylindricity (\(z_{Cmax}\)) of the machined circular cross-sectional area after WEDM also differ significantly, depending on the thickness change in the machined material (\(H_{w}\)). Based on the obtained results of experimental measurements, it can be stated that, with increasing thickness of the machined material (\(H_{w}\)), there is a significant increase in the maximum geometric deviation of the cylindricity (\(z_{Cmax}\)) of the machined surface during WEDM. This increase is smallest in a circular cross-section with a dimension \(\omega_{Cy}\) = 5.0 mm. In this cross-section, the geometric deviations from cylindricity increased by \(z_{Cmax}\) = 50.3 \(\upmu\)m. On the contrary, the largest increase in the geometric deviation of cylindricity is in the circular cross section with a dimension of \(\omega_{Cy}\) = 120.0 mm. In this cross-section, the geometric deviations from cylindricity increased by \(z_{Cmax}\) = 84.1 \(\upmu\)m.  
Figure 8: Geometric deviations of cylindricity (\(z_{Cmax}\)) vs. surface roughness (\(Ra\)) of experimental samples of circular cross-section after WEDM for different parameters of \(\omega_{Cy}\).