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用掺入粉末的工作液进行电火花加工由于工具电极和工件表面间形成大的静电电容,大面积电火花加工难以获得光洁表面。本文作者们曾用硅电极有效地解决了这一问题,并使加工表面耐腐蚀、耐磨损。然而用很硬很脆的硅作为工具电极材料有难于成形的缺点。本文介绍在工作液中掺入硅、铝、石墨等粉末后对电火花精加工所产生的效果。实验结果表明,即使所用的工具电极是紫铜电极,在石油类工作液中掺入上述粉末对于获得光洁表面非常有效。在同样的加工条件下,用铝粉或石墨粉能使加工表面比用硅粉时更为光洁。当在每升工作液中掺入2克铝粉而用紫铜工具电极加工 SKH—51高 相似文献
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石墨电极在彩电模具电火花加工中的应用 总被引:1,自引:1,他引:0
通过彩电前壳模具喇叭网孔镶件电火花加工,对紫铜电极和石墨电极加工结果进行分析比较,指出石墨材料在制作大电极,特别是在对电极损耗有严格要求的电火花加工时,石墨电极比紫铜电极有许多优点。指出专用石墨作电火花加工电极的优势正逐渐被大家认识,将成为企业首选的电火花加工电极材料。 相似文献
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以高温镍基合金Inconel718为加工材料,利用液氮蒸发气与空气混合形成低温冷却气体对电火花工具电极进行冷却,以降低电火花工具损耗。以冷却温度为变量进行电火花加工研究。利用粗糙度测量仪TR200和扫描电镜Quanta250对工件表面粗糙度和表面形貌进行分析。结果表明:当脉冲作用时间较短时(脉冲宽度90μs),在相同电参数下,低温冷却电火花加工可降低加工工件的表面粗糙度,在0℃时的表面粗糙度最低,比普通电火花加工的低3.7%~9.5%;随着冷却温度的降低,表面粗糙度会有所增加。电极损耗随着冷却温度的降低而降低,冷却温度在-60℃时的电极损耗比0℃的降低了40%以上。当电参数较小时,低温冷却电火花加工后的工件表面形成微裂纹且裂纹密度随冷却温度的降低而增加。在一定参数下,低温冷却工具电极对降低工件表面粗糙度和工具电极损耗效果显著,某些情况下可能会增加表面的微裂纹。 相似文献
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H. C. Tsai B. H. Yan F. Y. Huang 《International Journal of Machine Tools and Manufacture》2003,43(3):593
Electrode materials for electrical discharge machining (EDM) are usually graphite, copper and copper alloys because these materials have high melting temperature, and excellent electrical and thermal conductivity. The electrodes made by using powder metallurgy technology from special powders have been used to modify EDM surfaces in recent years, to improve wear and corrosion resistance. However, electrodes are normally fabricated at high temperatures and pressures, such that fabrication is expensive. This paper proposes a new method of blending the copper powders contained resin with chromium powders to form tool electrodes. Such electrodes are made at low pressure (20 MPa) and temperature (200 °C) in a hot mounting machine. The results showed that using such electrodes facilitated the formation of a modified surface layer on the work piece after EDM, with remarkable corrosion resistant properties. The optimal mixing ratio, appropriate pressure, and proper machining parameters (such as polarity, peak current, and pulse duration) were used to investigate the effect of the material removal rate (MRR), electrode wear rate (EWR), surface roughness, and thickness of the recast layer on the usability of these electrodes. According to the experimental results, a mixing ratio of Cu–0wt%Cr and a sinter pressure of 20 MPa obtained an excellent MRR. Moreover, this work also reveals that the composite electrodes obtained a higher MRR than Cu metal electrodes; the recast layer was thinner and fewer cracks were present on the machined surface. Furthermore, the Cr elements in the composite electrode migrated to the work piece, resulting in good corrosion resistance of the machined surface after EDM. 相似文献
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A. Muttamara Y. Fukuzawa N. Mohri T. Tani 《Journal of Materials Processing Technology》2009,209(5):2545-2552
Technologies for machining advanced insulating ceramics are demanded in many industrial fields. Recently, several insulating ceramics, such as Si3N4, SiC and ZrO2, have been successfully machined by electrical discharge machining (EDM). As unstable discharges occur during the machining of Al2O3 ceramics, inferior machining properties have been obtained. The formation mechanism of the electrical conductive layer on the EDMed surface is much different as compared to other ceramics. In addition to this, the electrically conductive layers are not formed sufficiently to adhere to the EDMed workpiece surface and keep a stable and continuous discharge generation on the ceramics. Graphite is widely used as electrode material in EDM. It is expected that carbon from graphite electrode implant and generate a conductive layer. Copper, graphite (Poco EDM-3) and copper-infiltrated-graphite (Poco EDM-C3) electrodes were used to compare the effects of generation of a conductive layer on alumina corresponding to EDM properties. The electrical discharge machining of 95% pure alumina shows that the EDM-C3 performs very well, giving significantly higher material removal rate (MRR) and lower electrode wear ratio than the EDM-3 and copper electrodes. The value of MRR was found to increase by 60% for EDM-3 with positive electrode polarity. As for EDM-C3, MRR was increased by 80% under the same condition. When the results were investigated with energy dispersive spectroscopy (EDS), no element of copper was observed on the conductive layer with both EDM-3 and EDM-C3. However, surface resistivity of a conductive layer created with EDM-C3 is less than with EDM-3. Surface roughness was improved to 25 μm with positive polarity of EDM-C3. 相似文献
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Apiwat Muttamara Yasushi Fukuzawa Naotake Mohri Takayuki Tani 《Journal of Materials Processing Technology》2003,140(1-3):243-247
Electrical discharge machining (EDM) is used as a precision machining method for the electrically conductive hard materials with a soft electrode material. But recently we succeeded to machine on insulating material by EDM. The technology is named as an assisting electrode method. The EDMed surface is covered with the electrical conductive layer during discharge. The layer holds the electrical conductivity during discharge. For micro-EDM, the wear of tool electrode becomes lager ratio than the normal machining. So the micro-machining is extremely difficult to get the precision sample.
In this paper to obtain a fine and precise ceramics sample, some trials were carried out considering the EDM conditions, tool electrodes material and assisting electrode materials. Insulating Si3N4 ceramics were used for workpiece. The machining properties were estimated by the removal rate and tool wear ratio. To confirm the change of micro-machining process, the discharge waveforms were observed. The micro-machining of the Ø0.05 mm hole could be machined with the commercial sinking electrical discharge machine. 相似文献
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The electrical discharge machining (EDM) process produces the recast layer with or without cracks on the surface that requires a remedial post-treatment in the manufacture of critical or highly stressed surfaces. One of the frequently used post-treatment processes is also the abrasive electrochemical grinding (AECG) and it has been widely used in the precision machining of difficult-to-cut materials due to an enhanced surface integrity and productivity. The aim of this study is to investigate improvability of surface integrity in terms of machining voltage, electrolyte flow rate and table feed rate parameters of AECG in EDMed Ti6Al4V alloy. Scanning electron microscopy (SEM), X-ray diffraction (XRD), energy dispersive spectrograph (EDS) and surface roughness measurement were performed to study the surface characteristics of the machined samples. Experimental results indicate that the AECG process effectively improves the surface roughness and eliminates the EDM damages completely by setting suitable grinding parameters. 相似文献
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Two types of permanent mould materials, spheroidal graphite (SG) cast iron and Al-Si alloy with various compositions, were selected to study the effect of heterogeneous second phase on material removal rate (MRR) by the electro-discharge machining (EDM) process. Fe-Si alloy and Al-1wt%Si alloy with a mainly single-phase structure were also prepared for comparison.Experimental results indicated that the amount and morphology of second phase particles significantly influence the material removal rate (MMR). This is closely related to ridge density and discharge density during the EDM process.The EDMed surface of the specimens had a continuously ridged appearance and the ridge density increases with higher amount of second phase. Worthy of notice is that the graphite particles are embedded in the troughs on the EDMed surface of SG cast iron, while the eutectic silicon particles are located on the ridge region in the case of Al-Si alloys. 相似文献
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The study investigated the feasibility of modifying the surface of Al–Zn–Mg alloy by a combined process of electric discharge machining (EDM) with ball burnish machining (BBM). A novel process that integrates EDM and BBM is also developed to conduct experiments on an electric discharge machine. Machining parameters of the combined process, including machining polarity, peak current, power supply voltage, and the protruding of ZrO2, are chosen to determine their effects on material removal rate, surface roughness and the improvement ratio of surface roughness. In addition, the extent to which the combined process affects surface modification is also evaluated by microhardness and corrosion resistance tests. Experimental results indicate that the combined process of EDM with BBM can effectively improve the surface roughness to obtain a fine-finishing and flat surface. The micropores and cracks caused from EDM are eliminated during the process as well. Furthermore, such a process can reinforce and increase the corrosion resistance of the machined surface after machining. 相似文献
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Some Considerations to Machining Characteristics of Insulating Ceramics-Towards Practical Use in Industry- 总被引:3,自引:0,他引:3
Machining of insulating ceramics can be realized in EDM by using the assisting electrode method. After a tool electrode cuts through the assisting electrode, a carbon layer covers the ceramics' surface during EDM. This carbon layer, formed from the decomposition of the hydrocarbon working oil, enhances the ceramics surface's conductivity. In this paper, machining phenomena of insulating ceramics are considered towards practical use in industry. Several kinds of insulating ceramics and assisting electrode materials are investigated under considerations of various machining characteristics; and high speed machining in W-EDM is carried out under conditions of lower tension than usual. 相似文献
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通过对电极的优化设计制造、工件定位的精度保证、工件的定位加工3个方面提高电火花加工的精度。详细讨论了如何降低和消除电极加工精度误差、电火花加工机的几何精度误差、工件电极的校正精度误差、定位精度误差等对电火花加工精度的影响,从而提高电火花加工精度。 相似文献
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采用辅助电极法,在设定加工条件下对绝缘性陶瓷材料Si3N4进行了电火花加工实验,分析了加工中生成导电膜的原因,研究了加工条件、加工深度与生成导电膜的厚度、电阻等特性的关系,指出了加工深度对生成导电膜的影响较大,且加工深度越深,生成导电膜厚度越厚、电阻越小。 相似文献