# Adjustment of Wire Vibrations in Order to Improve Geometric Accuracy and Surface Roughness at WEDM
## 3 Materials and Methods  
Because the magnitude of the geometric deviations from circularity and cylindricity of a machined surface after WEDM depends on many factors, it was necessary to include these effects in the experiments. The results of their complex actions were obtained from the wire electrode vibrations, with varying frequencies and amplitudes. Table 1 shows the basic ranges of the main technological parameter settings. It also provides a preliminary analysis of the causes of wire tool electrode vibrations, which were obtained from available sources of information. From the analysis listed in Table 1, it is evident that an effective element in reducing the vibrations of the wire electrode during WEDM is an increase in the value of the technological parameter, \(t_{\mathit{off}}\). However, it should be emphasized that, with an increase in the value of the \(t_{\mathit{off}}\) parameter, there is also a significant loss of productivity in the electroerosion process. For the purpose of experimental measurements, samples with circular cross-sections with a material thickness of \(H_{w}\) = 10.0, 50.0, and 100.0 mm were made with a variable diameter in the range of \(\varpi_{Ci}\) = 5.0-120.0 mm. These dimensions were chosen in accordance with the valid standard STN ISO/TS 12781-1: 2008 Geometrical Product Specifications (GPS). All samples were made on an Agicut Classic 3S EDM (AGIE SA, Losone, Switzerland) (Figure 3), an autonomous CNC electroerosion device. Figure 2: Basic parameters of geometric deviations from (**a**) circularity and (**b**) cylindricity of machined surface after WEDM, prescribed by standard STN EN ISO 1101: 2019-06. \(A_{1}\)—is the position of the concentric circles with the center in \(C_{1}\), \(A_{2}\)—is the position of the concentric circles with the center in \(C_{2}\), \(\Delta r_{1}\), \(\Delta r_{2}\)—is the respective radial distances of the circles, \(T\)—is the tolerance zone, \(\Delta\)—is the cylindricity deviation, LSC—least squares mean circle, MCC—minimum circumscribed circle, MIC—maximum inscribed circle. The samples were made of tool steel, marked as EN 40 CrMnMoS8-6 (W.-Nr. 1.2312), from Bogner Edelstahl Czech Republic Ltd. This is an alloyed chromium-manganese-molybdenum steel with good hardenability and machinability, thanks to its high sulphur content, even in a hardened and tempered state. [PERSON] [28] states that, in practice, this material is used for the production of molds for plastics and light alloys with a low melting point, etc. It is suitable for chromium plating and nitriding up to a hardness of approx. 800 HV. For less demanding tools, it can be used in a refined state at 950 to 1100 N\(\cdot\)mm\({}^{-2}\) without further heat treatment. Table 2 shows the chemical composition and selected mechanical and physical properties of EN 40 CrMnMoS8-6 tool steel. \begin{table}
\begin{tabular}{c c c} \hline \hline
**Main Technological Parameters** & **Setting Range** &
\begin{tabular}{c} **Influence of Technological Parameter on** \\ **Wire Electrode Vibrations** \\ \end{tabular} \\ \hline Peak current & 1.0–15.0 & As the value of \(l\) increases, the vibrations of the wire electrode increase slightly. \\ \hline Pulse on-time duration & 11.0–19.0 & As the \(t_{on}\) value increases, the vibrations of the wire electrode increase significantly. \\ \hline Pulse off-time duration t\({}_{\text{off}}\) & 15.0–28.0 & As the \(t_{off}\) value increases, the vibrations of the wire electrode decrease substantially. \\ \hline Voltage of discharge & 65.0–90.0 & As the \(U\) value increases, the vibrations of the wire electrode increase slightly. \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Range of the main technological parameter settings in the production of experimental samples using WEDM technology, including an analysis of their expected effects on wire electrode vibrations. Figure 3: Production of experimental samples from tool steel on an Agiccut Classic 3S EDM electroerosion device.