# Adjustment of Wire Vibrations in Order to Improve Geometric Accuracy and Surface Roughness at WEDM
## 4 Results of Experiments
### Measurement of Wire Tool Electrode Vibrations during Electrical Discharge Machining  
As a part of the performed experimental measurements, on-line monitoring of the actual values of the vibration amplitude values of the wire tool electrode, during WEDM, on an Agiccut Classic 3S electroerosion device, was performed using a PDV 100 portable digital vibrometer laser measuring device. The measurement procedure is shown in Figure 10.  
Figure 10: Measurement of vibration amplitude of Ms wire tool electrode using a PDV 100 portable digital vibrometer on an Agiccut Classic 3S electroerosion machine (AGIE SA, Losone, CH, Switzerland). Figure 9: Geometric deviations of cylindrticity (\(z_{Cmax}\)) vs. surface roughness (\(Ra\)) of experimental samples of circular cross-sections after WEDM for various parameters of \(H_{w}\). Amplitude vibrations were recorded during WEDM of the individual experimental samples of circular cross-sections with diameters (\(\sigma_{Cy}\)) in the range of 5.0-120 mm and thicknesses of machined material measuring \(H_{w}\) = 10.0, 50.0, and 100.0 mm. Figure 11 shows the individual courses during the machining of EN 40 CrMnMoS8-6 tool steel by WEDM with a wire tool electrode of \(\sigma_{TE}\) = 0.25 mm. In the first case, from the recording of the vibrations of the wire tool electrode of \(\sigma_{TE}\) = 0.25 mm during the electrical discharge machining of the experimental samples with a circular cross-section of \(\sigma_{Cy}\) = 5.0 mm and a thickness of the machined material of \(Hw\) = 10.0 mm, made using EN 40 CrMnMoS8-6 tool steel, several higher harmonic amplitude peaks can be observed in the first phase of measurements. These were caused by the onset of the wire tool electrode to the working position. At a critical oscillation frequency of the wire tool electrode of around 3 kHz, an increase in the oscillation amplitude value to 15 \(\upmu\)m was recorded. After stabilization of the electroerosion process, the vibration frequency of the wire tool electrode ranged from 5 kHz to 25 kHz with an oscillation amplitude up to 10 \(\upmu\)m. In the second case, during electrical discharge machining of the experimental samples with a circular cross-section of \(\sigma_{Cy}\) = 80.0 mm and thickness of the machined material of \(Hw\) = 50.0 mm, several amplitude peaks, with values of around 60 \(\upmu\)m, can be observed again at a critical frequency of around 5 kHz. After stabilization of the electroerosion process, the amplitude vibration of the wire tool electrode increased to 15 \(\upmu\)m at a frequency of 10-40 kHz. In the latter case, in experimental samples of the circular cross-section with \(\sigma_{Cy}\) = 120.0 mm and a thickness of machined material of \(Hw\) = 100.0 mm, after wire tool electrode onset to the working position and stabilization of the electroerosion process, the amplitude vibration of the wire electrode increased to 20 \(\upmu\)m at a frequency of 10-40 kHz. Increased amplitude vibrations of the wire electrode with a value of 60 \(\upmu\)m was recorded at a critical frequency of around 3 to 6 kHz Based on an analysis of the recorded values of the amplitude vibrations of the wire tool electrode during electrical discharge machining, an increase in wire electrode amplitude vibrations was identified with an increasing value in the parameters of \(Hw\) and \(\sigma_{Cy}\). This finding fully corresponds to the fact that, with an increasing diameter of the cylindrical profile, and with an increase in the height of the eroded profile, the geometric inaccuracy of the eroded surface decreases. This also confirms our assumption that this increase is caused by the wire tool electrode vibrations. Therefore, it is necessary to focus further research on the possibility of eliminating these vibrations during the electroerosion process.