Identification of geometric errors of circular profiles at WEDM caused by the wire tool electrode vibrations and their reduction with support of acoustic emission method

Abstract

High geometric precision of the machined surface after Wire Electrical Discharge Machining (WEDM) is in present one of the key quality parameters placed on machine parts manufactured for a wide range of industries. Despite the fact that WEDM belongs to the most precise finishing technologies, the deviations from the required geometric shape occur in the production of parts with rotary surfaces. These geometric deviations subsequently manifest in practice not only in the assembly of individual parts of the final product, but also in the operation. Another not the less important criterion considered at WEDM is the productivity of the WEDM process itself. WEDM productivity, in turn, is associated with the low overall productivity due to the need to apply multiple finishing cuts to achieve the desired quality of the machined surface in terms of geometric accuracy. Based on the already performed research, it is clear that the deviations of the geometric accuracy of the machined surface after WEDM are mainly caused by the vibrations of the wire tool electrode. Therefore, by eliminating these vibrations, it would be possible to achieve a substantial increase of the quality of the eroded surface, and thus reduce the number of finishing cuts. Ideally, the required quality level of the machined surface would be achieved right at the first cut. This would significantly increase productivity, enabling the WEDM technology to compete with other technologies in terms of productivity. In order to eliminate these undesirable vibrations of the wire tool electrode and to increase the quality of the machined surface after WEDM in terms of its geometric accuracy, the technical solution was proposed that applies the method of acoustic emission or laser beam vibration sensing in order to dynamically adjust the current values of technological parameters by the control system of the electroerosion machine. This way the given solution will increase the production accuracy of the circular holes, save the production time, increase the productivity, and ultimately bring the overall increase of the WEDM process economic efficiency.