Mechanism And Experiment Study On Electrical Spark-induced Ablation Milling By Gas-liquid Mixture Function Electrode

Traditional Electrical Discharge Machining (EDM) uses the heat generated by spark dischargebetween the tool electrode and workpiece to remove the workpiece material; the machining efficiencyis limited because of the factors such as pulse energy output or processing surface quality.Accordingly, this paper put forward spark-induced ablation processing method by gas-liquid mixturefunction electrode—inputs high pressure oxygen and working fluid into processing area by functionelectrode, and the surface material is activated by electrical spark and produced combustion reactionwith oxygen, which greatly improve the machining efficiency; During the machining, the workingfluid plays role of cooling, deionization and clearance, which is beneficial to the stability ofprocessing and good processing surface. According to the specific method, the thesis conducts themechanism and experiment research, the main content are as follows:(1) Construct relevant testing system. Design function electrode, sealed and clamped device offunction electrode, driving power supply, working fluid circulation system and oxygen supply system,and choose suitable pulse power supply.(2) Research ablation milling processing mechanism. Analyze processing mechanism frommachining efficiency, surface microstructure, discharge characteristics and thermal process. The results show that discharge breakdown mainly occurs in gas-liquid mixture; the electrons bombardmentand the combustion reaction between oxygen and workpiece play the major role in the micro process;thermal process is basically composed of heat released by combustion and spark discharge. The microprocess could be divided into four stages: dielectric breakdown to form discharge channel; melt andgasify workpiece material; spark and ablation remove metal material and deionization.(3) Research electrode loss. Conduct polarity contrast experiment and find ablation milling issuitable for positive polarity processing. Research the influence of electrical and non-electricalparameters to volume relative loss and compare with traditional EDM milling. Under same conditions,ablation milling electrode loss ratio is only1.1%, while traditional EDM milling is9%. From thecovering layer on electrode end face, analyze electrode relative length loss under different conditions,which provide sufficient basis to reduce electrode loss and realize electrode online compensation.(4) Experiment research on technological rules. Research influence of electrical andnon-electrical parameters to machining efficiency and surface roughness, results show that Ablationmilling machining efficiency can reach to96.3mm3/min and obtain the finished surface which the surface roughness Ra is8.1μm, while traditional EDM milling is15.8mm3/min and correspondingsurface roughness Ra is7.1μm.Then conduct cavity milling experiment aiming Cr12throughstratified milling way and obtain fine processing effect.