Papers by Keyword: Electric Discharge Machining (EDM)

Abstract: A new method of electric discharge machining (EDM) is proposed for slicing a large silicon carbide (SiC) ingot in order to realize low kerf loss and fast cut. This principle is based on the rotating ingot, and it is called the rotating slicing method (RSM). It would be defecate the cutting chip effectively and one-point discharge. In this paper, we reported results of examinations of the RSM experimentally. Unstable discharge was not observed. Discharge damages on the wire surface were fewer than those of the conventional method. Net cutting speed was almost the same as the present method for the 2-inches ingot. The rotation axis of the ingot should be perpendicular to the feed direction of the wire, and it is important to fix the performance of the EDM such as the kerf loss. Roughness of the cutting surface was 3.4 µm of R_a

Abstract: The gas presented in the discharge gap which was generated by the decomposition and vaporization of the dielectric due to the extremely high temperature in the EDM process plays an important role in the aspect of EDM performance. In this paper, the relative gas volume in the discharge gap is investigated when water-in-oil (W/O) emulsion was used as dielectric. Parameters, such as peak current, pulse duration, water content of the W/O emulsion were researched. Experimental results show that the relative gas volume in the discharge gap was significantly affected by discharge energy. Besides the discharge energy, water content of W/O emulsion is another significant factor that affects the gas volume in the discharge gap.

Abstract: A new method based on electric discharge machining (EDM) was developed for cutting a silicon carbide (SiC) ingot. The EDM method is a very useful technique to cut hard materials like SiC. By cutting with the EDM method, kerf loss and roughness of sample are generally smaller than those obtained by cutting with a diamond saw. Moreover, the warpage is smaller than that by the diamond saw cutting, and the cutting speed can be 10 times faster than that of the diamond saw at the present time. We used wires of 50 mm and 100 mm diameters in the experiments, and the experimental results of the cutting speed and the kerf losses are presented. The kerf loss of the 50 mm wire is less than 100 mm, and the cutting speed is about 0.8 mm/min for the thickness of a 6 mm SiC ingot. If we can maintain the cutting speed, the slicing time of a 2 inches diameter ingot would be about seven hours.

Abstract: This paper investigates the effect of electric discharge machining (EDM) process parameters and powder mixed in dielectric on surface properties of three die steel work materials; namely High Carbon High Chromium (HCHCr), EN 31 and Hot Die Steel (HDS). The mechanism of material deposition from the suspended powder and/or tool electrode is reported. Current emerged as the most significant factor affecting the microhardness along with powder mixed in the dielectric and electrode material. Amongst the two electrode materials, copper-tungsten along with tungsten powder had the best microhardness. Selected samples were analyzed for X-ray Diffraction (XRD) followed by microstructure analysis using a Scanning Electron Microscope (SEM). The results showed significant material transfer from the electrode as well as powder either in free form or in compound form. It was concluded that surface modification of die steels can be done by incorporating simple modifications in the EDM set-up resulting in higher microhardness and superior wear resistance of the machined surface.

Abstract: — Parametric optimization of electric discharge machining (EDM) is a challenging task. Many researchers have employed different multi-objective optimization techniques for the same. This work employs multi-response signal-to-noise (MRSN) technique to find the optimum factor/level combination of input parameters. Experiments have been conducted on die-sinking EDM by taking heat treated D2 steel as work piece and copper as tool electrode. Experiments have been designed as per Taguchi’s L36 orthogonal array. Two cases v.i.z. high cutting efficiency and high surface finish have been taken. Analysis of variance (ANOVA) is employed to indicate the level of significance of machining parameters in both the cases. Finally, results have been verified experimentally and a significant improvement in material removal rate and surface roughness is observed.

Abstract: In this paper, surface residual stress in the cold working tool steel (Cr12MoV) by EDM was investigated by X-350 X-ray residual stress analyzer and method of DJP-2 electrolytic polishing instrument to remove layer by layer in the different EDM conditions. The results show that the distribution of surface residual stress generated not only by the peak discharge current and pulse width, but also by pulse interval. The same depth from the surface, residual stress of material after hardening is larger than the residual stress after annealing, With the different combination of tool electrode and work-piece material, the form of the discharge between two electrodes and the proportion of energy put between two electrodes are different, surface residual stress are also different. Different processing liquid for processing, the depth of residual stress generated is much the same, but closer to the surface, the worse the cooling capacity (quench degrees) and surface physical properties of processing fluids, the greater the residual stress. EDM, the generation and control of the surface residual stress depends on the choice such as processing power criteria, work-piece material, electrode materials and processing liquid. Surface residual stress after processing can be used to eliminate high-temperature heat treatment.

Abstract: This work screens electrode materials used in EDM and proposes some potential electrodes for future industrial applications. Traditional graphite, W, and Mo EDM electrodes have low TWR due to their high melting points; while, Zn, brass, and Cu often experience too much tool wear. As to some newly developed alloy and composite materials, their machining performances depend on not only their melting points but also their microstructures. Cu-W alloy has high wear resistance but it is susceptible to shape loss due to its internal porosity. By contrast, Cu-graphite, Cu-ZrB₂ and Cu-TiB₂ composites show good capabilities of removing material with little wear loss and therefore could be promising for future usages.

Abstract: A new concavo-convex electrode has been designed and employed and it was reported that electrical discharge machining (EDM) of particulate reinforced metal matrix composites with this kind of new electrode can accelerate the debris discharge during machining so that it has a higher material removal rate (MRR) compared to the case where a normal electrode was employed. Since there are many factors that can affect the MRR in the EDM process with the concavo-convex electrode, in order to determine which is the most important factor and to optimize the machining parameters, the relative importance of the various cutting parameters on material removal rate was established using an orthogonal experimental analysis in this study. The results of the analysis suggest that to achieve a high MRR for particulate reinforced aluminum 6061 with 10-vol% Al2O3 (10ALO) or 20vol% Al2O3 (20ALO) using a concavo-convex electrode, the duty cycle is the most influential factor among current, pulse duration and duty cycle.

Abstract: The aim of this work is to investigate the possibility of improvement of surface roughness in the wire-EDMed sample by usinig ultrasonic wave and abrasive particle suspension. For this study, two-type ultrasonic polishing methods were used. Removal of the white layers on surface of EDMed sample depended largely on the movement of the suspended particles : the white layers are removed by the impact of free moving particles due to ultrasonic wave, so-called micro chipping mechanism. Even though the surface roughness was improved very slowly, 3-dimensional fine polishing was achieved in wire-EDMed micro PIM molds. These results indicated that micro polishing by ultrasonic wave using suspension is applicable to improvement of surface roughness of micro parts with 3-dimensional complex shape.

Abstract: The Samples of Polycrystalline Diamond (PCD) Cutting Tool Were Machined by Adjusting the Main Parameters of Electrical Discharge Machining (EDM). after the Machining, the Phases Were Analyzed by X-Ray Diffraction Analyzer and the Surface Layer Microstructure Were Observed by Scanning Electronic Microscope. the Fundamental Component of Machined PCD Cutting Tool Affected Layer Was Obtained and the Reason of Bring Affected Layer Was Analyzed. the Relationship Curves between Pulse Width, Working Electric Current and Depth Affected Layer, Surface Roughness Were Summarized. the Relationship between PCD Cutting Tools that Was Machined by EDM and Cutting Tool Flank Width, Workpiece Surface Roughness Were Analyed.The Results Showed that to Adjust Electical Discharge Machining Parameter, such as Pulse Width and Machining Electric Currents, Can Reduce the Depth of Affect Layer and Extend the Service Life of PCD Cutting Tool.These Researches Provide Valuable Test Reference for Drawing up Electrical Discharge Machining Technics of PCD Cutting Tool and Cutting Tool’s Life.