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The recast layer on the inside surface of tool electrode. a, b Tap water, h 8 mm, Vf 15 μm/s; c, d NaCl solution, h 8 mm, Vf 15 μm/s
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The discharge craters and recast material are the characteristics of the surface machined by using EDM, which deteriorate the surface quality and other properties such as fatigue strength of the workpiece. In this study, a new combined machining method which utilizes a thin foil as tool electrode and combines EDM and ECM into a single process for s...
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When SiC is melt-bonded with Ni electrode, a regrowth layer containing C is formed due to the dissolution of C into the molten NiSi, deteriorating its electrical properties. We found that the regrowth layer can be suppressed by giving the surface of the SiC substrate a wavy shape. A wavy-shape substrate with appropriate periodic length and amplitud...
Citations
... There was a non-processing time stage that separated from the workpiece, which was inefficient and could not be improved further. Wu [11] carried out electrolysis and EDM composite machining on the workpiece with a thin foil electrode and obtained a good surface quality. However, with the same machining parameters, a thin foil electrode with a thickness of 0.1 mm was employed, and the combined machining incision width reached 1.85 mm, while the EDM incision width was 0.4 mm. ...
The narrow groove structure is employed in a number of industries, including the prefabrication of narrow grooves before the workpiece is cracked. It is critical to do research on how to achieve efficient and cost-effective narrow groove processing. A novel technique of foil electrode EDM machining for narrow grooves was developed, and the flow field models of the discharge gap under the different injection methods were first simulated. The experimental study of pulse voltage, pulse frequency, duty cycle, and feed speed was carried out. The single-factor experiment showed that when the pulse voltage was 100 V, the pulse frequency was 25 kHz, the duty cycle was 40%, and the feed speed was 8 µm/s. After optimizing the parameters, a narrow groove with good geometrical dimensions and quality was obtained with an average width of 214.30 µm, an average depth of 642.33 µm, and a depth ratio (groove depth/(groove depth + wear depth)) of 0.708. An insulation treatment experiment was carried out for the discharge phenomenon on the side of the foil electrode that occurred during the experiment. The experiment indicated that the insulation treatment avoided the discharge on the side of the electrode to a certain extent and improved the quality of the groove.
... Electrical discharge machining (EDM) is a commonly technology for processing titanium alloy [1,2], which completes material removal through the electric spark discharge. In the process of EDM, the recast layers are easily generated on the workpiece surface [3][4][5]. In the process of the interaction between the electric spark discharge and the workpiece, the partially molten workpiece was not expelled in time [6]. ...
Titanium alloy has been widely applied in industrial fields because of its excellent material properties. Electrical discharge machining (EDM) is commonly technology for processing titanium alloy. When titanium alloy was processed by EDM, a recast layer was inevitably be produced on its surface, which can adversely affect the surface quality and working life. Focus on the above problem, this paper proposed to add B4C powders into the spark oil and cooperate with the tool electrode sloshing for powder mixed electrical discharge machining (PMEDM) of titanium alloy, which can reduce the thickness of the recast layer and thereby improve the quality of the machined surface. Firstly, B4C powders were mixed in the spark oil and the PMEDM of the titanium alloy was carried out. In this step, the thickness of recast layer was preliminarily reduced and the quality of machined surface was improved. Secondly, when the PMEDM of the titanium alloy was nearly completed, the tool electrode sloshed along the machine tool spindle within the EDM gap. Combining PMEDM with the tool electrode sloshing, the recast layer on the machined surface was further eliminated and the quality of machined surface was further improved. By adding 3000 mesh B4C powders into the spark oil, the paper carried out the PMEDM of titanium alloy combining with the tool electrode sloshing. Under the action of appropriate process parameters, the micro-groove structure with surface roughness Ra of 0.205 μm was obtained in the titanium alloy and the recast layer on the machined surface was almost invisible.
With excellent characteristics such as strong wear resistance, high hardness and good insulation, insulating hard and brittle materials such as optical glass and engineering ceramics are widely applied in modern industry. However, it is very difficult to machine these advanced insulating hard and brittle materials with traditional machining methods such as cutting or grinding, by which the dimensional accuracy or processing efficiency is very low. Electrochemical discharge machining (ECDM) process is an emerging non-traditional machining process that relies on spark discharge and chemical etching to etch materials and has great potential for machining various insulating hard and brittle materials. This paper introduces the gas film formation process and material etching mechanism during ECDM and summarizes the current research status in terms of electrical parameters, electrode structure, electrode motion, auxiliary liquid supply, and electrolytes that affect the processing performance of ECDM. Multi-energy field combined processing techniques have also attracted the interest of researchers. Various hybrid machining processes are introduced. Finally, the currently researches are summarized and some improvement measures that can improve the processing performance of ECDM are discussed for future research.
Semiconductor materials including Silicon (Si), Germanium (Ge), Gallium Arsenide (GaAs), and Silicon Carbide (SiC) are difficult to machine due to their high brittleness and low plasticity. Conventional machining methods such as dicing and blade cutting used to cause quality problems such as cracks, poor edges, and blue film damage. Electrical discharge machining (EDM) is an unconventional method in which the primary mechanisms of material removal encompass melting, vaporization, erosion, and crumbling. The utilization of thermal energy generated by controlled electrical pulses to extract material from workpieces has proven to be a highly effective approach in the machining of semiconductor materials. This paper reviewed the state-of-the-art technologies applied in machining semiconductors. The advantages and disadvantages of each method were summarized. The most recent research outcomes were introduced. Thermal physical removal model, material migration, dielectric fluid, and contact potential were discussed. The causes leading to multi-channel discharge phenomenon and the insight into the application of the new machining theories were presented. The latest technologies and future development trend were also discussed.
In order to improve the machining efficiency and the surface quality of EDM/ECM, adding a small amount of sodium nitrate into deionized water as the working medium, a novel simultaneous machining approach of EDM and ECM (SEDCM) was developed. In this work, a comparative study was conducted on the SEDCM performance of TC4 alloy using different electrode materials viz. brass, copper and copper-tungsten alloy. In addition, the effects of process parameters, such as peak current, pulse on time and gap voltage on material removal rate (MRR), tool wear rate (TWR), surface roughness (Ra), and surface micromorphology were investigated. The results show that brass electrode provides the smallest MRR, the highest TWR and the worst surface quality. The copper electrode has the smallest average diameter of a single discharge craters and the best surface finish. The MRR and TWR of copper-tungsten electrode are similar to those of copper electrode. As peak current increases, TWR increases and Ra deteriorates for all the electrodes, as well MRR increases and then decreases for copper and copper-tungsten electrodes. Increase in pulse on time and gap voltage, MRR and TWR increases and then decreases gradually. At higher pulse on time and gap voltage, Ra becomes greater for three type electrodes.
Thermal processes such as wire electro discharge machining (wire EDM) have an intrinsic heat affected zone (HAZ) and recast layer due to their thermal removal mechanisms. This layer is adverse to the fatigue life characteristics of the manufactured parts, and has to be removed by finishing operations. Wire electrochemical machining (wire ECM) is proposed as a finishing operation, as it can dissolve conductive materials without damaging the machined surface, and is similar in mechanical operation as wire EDM. An important drawback of electrochemical machining is the low accuracy when removing large amounts of materials in one pass, which is addressed by only machining a shallow depth by ECM after roughing by EDM (i.e., finishing allowance of 15 – 70 µm, the HAZ thickness). This paper presents an experimental study of electrochemical finishing 316L stainless steel wire EDM'ed parts. To improve the machining efficiency and the accuracy of the finished parts by eliminating reclamping, the process is implemented on a wire EDM machine. The wire electrode used in EDM roughing is also used in ECM finishing and is retraced along the contour of the part with an offset to increase or decrease the interelectrode gap. The experiments presented in this paper aim to gain insight in the relationship between the process parameters of wire ECM and the resulting machined surface, with respect to the machining depth, material removal rate (MRR), and surface roughness. A number of process optimization strategies are investigated, considering parameters such as the feed rate and the number of passes. Experimental results show that wire based electrochemical machining is a viable process to finish wire EDM parts, achieving removal depths greater than 20 µm with a surface roughness below 1 µm Ra.
