Abstract
In tube electrode high-speed electrochemical discharge machining (TSECDM), mixed products are constantly produced in the narrow machining gap by simultaneous discharge erosion and electrochemical dissolution. For the high-efficiency removal of these products from the machining gap, a tool electrode with an optimized helical structure was utilized in TSECDM in this study. Firstly, the concentration distributions of the processed products in the machining gap using tube electrode tools with three typical helical structures were studied through the simulation of solid–liquid coupling; this showed that a trapezoidal helical structure benefited the reduced accumulation of products in grooves and the effective removal of products from the machining gap. Secondly, the main geometric parameters of the trapezoidal helical structure, including the helical groove depth, pitch, and tooth angle, were optimized by gap flow-field simulation to enhance the removal effect on processed products. Finally, it was verified that the trapezoidal helical electrode showed a definitive and significant advantage over the ordinary cylindrical electrode in effectively removing processed products from the machining gap by the comparison of flow-field simulations and actual machining experiments.
Highlights
To improve heat dissipation and working reliability, gas film-cooling holes are widely used in aero-engine turbine blades [1,2]
Tube-electrode high-speed electrochemical discharge machining (TSECDM), a hybrid manufacturing method of electrical discharge machining (EDM) and electrochemical machining (ECM) that exploits the advantages of these two technologies to achieve high machining efficiency [3], machining accuracy [4], and surface quality [5], is potentially applicable for the fabrication of film-cooling holes
Plaza et al investigated the effect of the geometric parameters of helical electrodes on micro-EDM drilling performance, experimentally showing the effective removal of the debris from the machining gap as the machining depth increased [15]
Summary
To improve heat dissipation and working reliability, gas film-cooling holes are widely used in aero-engine turbine blades [1,2]. Complex mixed machining by-products, including both molten metal particles and electrochemically dissolved materials, are continuously produced in the narrow machining gap [6,7] This greatly increases the risk of excessive product accumulation and the deterioration of the flow field environment, seriously reducing the processing quality of the holes [8,9]. Hung et al proposed a machining method of micro-EDM that matched the rotational helical tool electrode with the ultrasonic disturbance of the flow field, obtaining micro-hole structures with high surface quality and machining precision with the optimum processing parameters [13]. Nastasi and Koshy studied the effect of different tool electrode geometries on blind-hole machining by electrical discharge drilling Through comparative experiments, they concluded that the electrode with a radial slot had a better material removal rate than a cylindrical electrode [14]. Fang et al introduced a helical cylindrical electrode to wire electrochemical micromachining in order to facilitate electrolyte refreshment in the machining gap, achieving microstructure fabrication with good uniformity [17]
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