No abstract

Functional-surface microstructures are widely used in industrial practice. During the fabrication of microstructures in micro-electrical discharge machining (micro-EDM), the thermal and physical characteristics of both workpieces and electrode materials at room temperature and high temperatures have an important in uence on surface quality and distribution of recast layer. In order to study the in uence of different electrode material characteristics on the surface integrity of microstructures machined using micro-EDM, red copper, brass, copper-tungsten and tungsten electrode were used to perform micro-EDM on both Ti-6Al-4V alloy and 304 stainless steel. In the experiment, electrode with groove arrays featuring high copying accuracy and surface quality was designed to carry out powder mixed electrical discharge machining (PMEDM) on Ti-6Al-4V alloy, and the machining results were evaluated based on four indicators: microstructure morphology, tool electrode wear (TEW), material removal rate (MRR), and recast layer thickness (RLT). Simultaneously, the surface morphology and recast layer thickness changes of 304 stainless steel workpieces machined using the above four types of electrodes, using both normal polarity and negative polarity micro-EDM were quantitatively analyzed. The results showed that copper-tungsten electrode is recommended to machine Ti-6Al-4V alloy because it has a smaller TEW (139 µm), the highest MRR (255.39 mm 3 /min), and a thinner recast layer thickness (3.35 µm). This was followed by copper electrode, which featured good machining performance and machinability. When machining 304 stainless steel with negative polarity, the TEW of copper electrode and tungsten electrode was the smallest, and the thickness of recast layer was able to be effectively reduced to about 3 µm.

No abstract

High-speed mechanical drilling based on the micro-bit is the mainstream process technology for machining micro-holes in the printed circuit board (PCB). However, the above process to obtain PCB micro-holes is prone to defects, such as hole burrs and nail heads in the hole. In this paper, the micro electrical discharge machining (micro-EDM) was used as an auxiliary means for machining PCB micro-holes to effectively eliminate the defects such as hole burrs and nail heads. However, during the process of micro-EDM, the micro-bit will be gradually worn, thus negatively affecting the machining quality of PCB micro-holes. To solve the above problems, in this paper, the temperature field model of micro-EDM-assisted machining of PCB micro-holes was established to predict the micro-bit wear by analyzing the temperature field with COMSOL Multiphysics software. This paper made an extensive study of the influences of spindle speed, machining voltage, and pulse width on temperature field and micro-bit wear. The simulation results show that with the increase in machining voltage and pulse width, the temperature of PCB micro-hole machining increases, resulting in an increase in micro-bit wear. The spindle rotation is beneficial to the updating of the machining medium and the discharge of heat generated from EDM. Therefore, with the increase in spindle speed, the temperature of PCB micro-hole machining and the micro-bit wear is reduced.

Functional-surface microstructures are widely used in industrial practice. During the fabrication of microstructures in micro-electrical discharge machining (micro-EDM), the thermal and physical characteristics of both workpieces and electrode materials at room temperature and high temperatures have an important influence on surface quality and distribution of recast layer. In order to study the influence of different electrode material characteristics on the surface integrity of microstructures machined using micro-EDM, red copper, brass, copper-tungsten and tungsten electrode were used to perform micro-EDM on both Ti-6Al-4V alloy and 304 stainless steel. In the experiment, electrode with groove arrays featuring high copying accuracy and surface quality was designed to carry out powder mixed electrical discharge machining (PMEDM) on Ti-6Al-4V alloy, and the machining results were evaluated based on four indicators: microstructure morphology, tool electrode wear (TEW), material removal rate (MRR), and recast layer thickness (RLT). Simultaneously, the surface morphology and recast layer thickness changes of 304 stainless steel workpieces machined using the above four types of electrodes, using both normal polarity and negative polarity micro-EDM were quantitatively analyzed. The results showed that copper-tungsten electrode is recommended to machine Ti-6Al-4V alloy because it has a smaller TEW (139 µm), the highest MRR (255.39 mm3/min), and a thinner recast layer thickness (3.35 µm). This was followed by copper electrode, which featured good machining performance and machinability. When machining 304 stainless steel with negative polarity, the TEW of copper electrode and tungsten electrode was the smallest, and the thickness of recast layer was able to be effectively reduced to about 3 µm.