Abstract
To further explore the machining characteristics of very high-frequency micro-electrical discharge machining (VHF micro-EDM), the range of radio frequency (RF) power amplifier was expanded to 110 MHz, and the power of the RF power amplifier was also greatly increased up to 91 W. The principle of the VHF pulse generator was discussed in detail, and an electro-thermal model suitable for VHF micro-EDM was established to determine the diameter of the plasma channel and the energy distribution ratio. Experimental studies for VHF micro-EDM were also carried out, and the effects of power and frequency on machining characteristics were then analyzed and discussed. The results show that at the same frequency, the higher the power is, the higher the material removal rate (MRR) and the larger the number of discharge craters. At the same power, both the MRR and the size of discharge craters first increase and then decrease with increasing frequency and peak at 65 MHz. For a copper workpiece, when the frequency is 110 MHz and the total power of the power amplifier is 8.0 W, 5.6% of the energy is used for the material removal of the workpiece and the finest processing surface is obtained with the surface roughness Ra = 12 nm. The average diameter of the discharge craters is as small as 0.268 μm, and the diameter of the plasma channel is only 0.350 μm. In addition, the effects of different workpiece materials and dielectric fluids are also analyzed in this paper.
Highlights
The manufacturing requirements of micro-scale parts and microstructures have become increasingly extensive with the development of modern science and technology [1]
To study the erosion characteristics of VHF micro-EDM, it is very important to accurately obtain the single discharge energy, the fraction of the energy distributed to the workpiece and the diameter of the plasma channel generated by the discharge
For the experiments that were to determine the material removal rate (MRR) and tool electrode wear ratio (TWR), the processing time was relatively long to ensure the accuracy of the measurement results
Summary
The manufacturing requirements of micro-scale parts and microstructures have become increasingly extensive with the development of modern science and technology [1]. A recurring topic in micro-EDM is to obtain higher surface quality by reducing the single discharge energy. The single discharge energy generated by the micro-EDM power supply directly affects the size of the single erosion crater and affects the surface quality. For an RC-type power supply, a lower single discharge energy and finer machined surface are often obtained by reducing the voltage or the equivalent capacitance of the gap [20,21,22]. Compared with the traditional power supply, its pulse frequency is up to 90 MHz, its single discharge energy is lower, and nano-level erosion craters can be obtained. To further explore the machining characteristics and technical rules of VHF micro-EDM by using this new power supply and to master the scale range of the plasma channel in VHF microEDM and the distribution of energy, the VHF pulse generator is upgraded in this paper. VHF micro-EDM experiments are carried out, and the results are discussed in detail
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