| In the past 60 years, electrical discharge machining (EDM) workingmedium has become the research focus all over the world. EDM in gas (DryEDM) proposed by Kunieda in 1997 is a milestone of development of EDM,which made people understand that not only the liquid medium can be usedin EDM. Dry EDM is environmental-friendly due to the using of harmlessgas such as air and nitrogen. Dry EDM has much lower TWR and muchbetter manufacturing flexibility compared with the traditional EDM.However, its poor machining stability and low material removal rate (MRR)set obstacle in its way to industry application.A new machining method named submersed gas-jetting EDM isproposed by Professor Zhao Wansheng etc. In this new method, toolelectrode is thin walled pipe from which the high-pressure gas is blown. Inthe process, workpiece is submersed in the water-based machining liquid, andthe high-pressure gas is used as its dielectric medium while water-basedmachining liquid plays a significant role which doesn't participate indischarge directly.After years of research, submersed gas-jetting EDM has made greatprogress. Compared with the dry EDM, submersed gas-jetting EDM can gethigher MRR, better surface quality. However, both of the MRR and theprocessing stability of submersed gas-jetting EDM are unideal.Methods to improve the machining stability and efficiency of submersedgas-jetting EDM were studied in this dissertation. A fluid circulating systemand a high-speed rotating equipment was designed and used in theexperiments. The effects of high-speed platform and ultrasonic vibrationdevice on submersed gas-jetting EDM were also experimentally studied. Thedischarge phenomenon of submersed gas jetting EDM with the aid of high-speed platform and ultrasonic vibration device is observed and analyzedrespectively. To evaluate the machining stability, a software system based onLABVIEW was developed to detect the situation of electric discharge. Theshort rate of submersed gas-jetting EDM is tested using the above mentionedsoftware。With the assisting of the high-speed platform, the effects of machiningparameters, such as pulse duration, pulse interval, peak current, gas pressure,platform speed and gas type were studied. The experimental result indicatedthat high-speed platform aided submersed gas-jetting EDM under propermachining parameters can obtain a high MRR of 35.2mm 3 /min, whileultrasonic vibration aided submersed gas-jetting EDM can get better surfacequality. |
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