Papers by Keyword: Electro Discharge Machining (EDM)

Abstract: The EDM can machined some superhard conducting material that cannot be handled by the traditional method, such as carbide alloy, tool steel and engineering materials etc., however, it is also accompanied with slow material removal rate(MRR) and poor surface quality (surface roughness). For some fine machining having rigorous criterion on size and surface roughness, the EDM cannot meet the demand. Some researches indicate that the MRR of small hole by electrical discharge machining combined with ultrasonic vibration (UEDM) can increase in certain range, but the surface quality is still poor. Although there are lots of the researches on the UEDM, some debates on machining mechanism and applied scope existed, and technology of UEDM needs the further study. After small hole machined by the UEDM, it is polished by ultrasonic vibrating. Two steps are includes in this technology. In the first place, on a high velocity electro discharge small hole machine with high-pressure dielectric liquid and hollow electrode, a transducer and horn are attached between the spindle and the electrode. The ultrasonic vibration of the tool electrode is implemented by connecting the horn and the tool electrode together with a chucking appliance. The second, after the small hole is complete, with the same machine tool and tool electrode the process of polishing the inwall of the small hole is carried out by accompanying the ultrasonic vibration, revolution and feed of the tool electrode with the abrasive material. In the experiments, the reference point for UEDM is found and the new theory is proposed to explain the increase of the MRR and the decrease of the surface roughness value .The polish with the ultrasonic vibration can improve further the surface roughness. The ultrasonic vibrating polish after the hole by UEDM is an economical and effective technology, which realizes machining of two procedures in one machine tool. So the process for changing machine tool and tool is not needed any more and the efficiency is further improved.

Abstract: Although research on various diamond polishing techniques has been carried for years, some issues still need to be examined in order to facilitate application on large areas in a cost-efficient manner. A compositive technique for machining efficiently thick diamond films prepared by DC plasma arc jet is reported in the present paper. A two-stage polishing was applied on thick polycrystalline diamond films, by employing first electro-discharge machining (EDM) for rough polishing and subsequently mechanical polishing for finishing operations. Experimental results obtained clearly indicate the applicability of the proposed two-stage technique for fabricating transparent diamond films that can be used for the production of X-ray windows. Appropriate etching with EDM is an effective pretreatment method for enhancing the efficiency of rough polishing process in mechanical polishing of thick diamond film. The machined surfaces of diamond films are studied by Scanning Electron Microscope (SEM) and Raman Scattering Spectroscopy (Raman).

Abstract: Sintered NdFeB permanent magnet is widely used because of its excellent magnet property. But there is few report of machinbility of it. This paper presents an experimental investigation of the machining characteristics of sintered NdFeB permanent magnet using a combination process of electro-discharge machining (EDM) with ultrasonic machining (USM). The EDM / USM machining mechanisms are integrated to improve the machining efficiency. During the experiments, concentration of abrasive in the dielectric fluid is changed to explore its effect on the material removal rate (MRR). MRR of EDM /USM, conventional EDM and tool vibration aided EDM are compared, REWR and machined surface characteristics are also compared between them. From the experimental results, it is concluded that the combination EDM/USM process can increase the MRR and decrease the thickness of the recast layer. In the combination process, an appropriate abrasive concentration can improve its machining efficiency.

Abstract: Sintered NdFeB permanent magnet is widely used in many applications because of its excellent magnet property. However the report of EDM research on NdFeB magnet is not available. This paper presents a detailed investigation of the material removal mechanisms of sintered NdFeB magnet through analysis of the machining debris and the surface SEM quality. It is included three types of machining mechanisms: melting and evaporating, thermal cracking, spalling or whole grain removal.

Abstract: Polycrystalline diamond (PCD) exhibits a thermal conductivity similar to that of the electrically conductive chemical vapor deposition diamond (EC-CVD diamond) found to function as zero-wear electrodes at short pulse duration. In this study, PCD was used as electrodes applied to EDM on tungsten carbide. Two kinds of PCD (CTB-010 and CTH-025) with a flat surface were used. The wear of the PCD electrodes was about 1.5% for very short pulse duration such as te=1μs, but it was zero wear at te=30μs, though the wear of a Cu-W electrode was 10% even on the machine recommended conditions for the low wear. EDM experiment using a V-shaped PCD electrode with an included angle of 45° was also carried out and the performance was compared with the case using a V-shaped Cu-W electrode. Under the conditions of a no load voltage of 60V, a set peak current of 2A, and a medium pulse duration of te=15μs, there was no wear on PCD electrodes when observed under the SEM, whereas a 50μm-deep wear on the Cu-W electrodes even under the machine recommended condition for the low wear was observed.

Abstract: This paper proposes a new PCD (polycrystalline diamond) wheel with porous skeleton structure realized by removing the cobalt binder from PCD by EDM (electrodischarge machining), and investigates the grinding characteristics of the wheel. The pores are made successfully on PCD by adopting appropriate EDM conditions. The efficiency of making the pores is found to be higher, when the size of the diamond grains in the PCD material is small, and jumping motion to the copper electrode is not given during the EDM. A porous PCD grinding wheel made by this method using a rotating circular PCD (grain size of 10'm) disc of 20mm diameter has a good skeleton structure with sufficient projections on the wheel surface. A satisfactory grinding characteristics with a surface finish of Ra=0.02'm in grinding on a tungsten carbide work is achieved.

Abstract: This study concerns the formulation of a multi-parameter surface texture model in EDMachining of AISI D2 tool steel. The model is developed in terms of pulse current and pulse-on time which are the dominant machining conditions, via factorial design of experiments. By applying analysis of variance and statistical multi-regression analysis to the experimental data close correlation is proved between certain surface finish parameters and the machining conditions, with pulse current exerting the strongest influence. By applying this model the appropriate conditions for successful finish can be selected, as well as functional surface characteristics can be quantified.

Abstract: The use of Electrical Discharge Machining (EDM) for the manufacturing of moulds and dies is generally accomplished by using different cutting regimens, from roughing to finishing, until the specified surface finish and dimensional tolerances are met. Multistage planetary EDM can be used to simplify the production process. Benefits such as the reduction of machining time, the need for less electrodes, electrode wear minimization and the improvement of the final surface finish of the component can be obtained. Design of multistage planetary EDM strategies requires a sound knowledge of the optimum radius for each orbit that assures surface roughness and dimensional accuracy together with a minimum machining time. Therefore, it is necessary to know the “exact” value of the gap at each stage. In this paper the influence of different process variables on the design of multistage planetary EDM strategies is analyzed.

Abstract: A kind of new complex tools coating technology by EDM (Electrical Discharge Machining) is studied in this paper. Firstly the principle of this technology is discussed. In order to meet the coating requirement of the high-speed steel twist drill, milling cutter or other complex tools, a set of coating device is designed and fabricated secondly, and the tools with different dimension are coated successfully by this device. Finally the performance evaluation of coated twist drills is carried out through the drilling test.

Abstract: In this paper we present a multifunctional combined CNC machine that integrates the technology of USM, EDM and grinding. For non-conductive hard and brittle materials, the machine tool could perform ultrasonic machining and grinding machining combined ultrasonic vibration; for conductive hard and brittle materials, electrical discharge with or without ultrasonic vibration could be implemented. Conductive engineering ceramics have been used for elementary experiments, the results show that it is more efficient and more stable for processing this kind of materials by using the multifunctional combined CNC machine. On the basis of brief introduction about the structure of the machine tool, this paper emphasizes the form of control system, the gap state inspection that can be used to ensure the stability in processing and the principle for servo control.