Pulse Current Wire Electrochemical Machining Of Thick Structures

It is an important task in the field of mechanical processing and manufacturing that the large thickness ruled surface components of difficult-to-cut materials represented by the turbine-disk mortise structures of aeroengine,required to have high machining accuracy and strict surface quality.In this paper,pulsed current wire electrochemical machining(WECM)is studied for thick workpiece.It is proposed to use large aspect ratio micro-spiral wire electrodes with high-speed rotating to drive the electrolyte to produce axial motion and expel electrolysis products out of gap.At the same time,the processing speed can be further improved on the premise of ensuring the processing accuracy by optimizing the pulse frequency and assistant flushing fluid.The following work has been accomplished:(1)The circuit model of pulse current WECM was established,and the effects of workpiece thickness on the electrical signal and the width of the slit was analyzed.A gap flow field model of WECM was established.The effects of workpiece thickness,tool electrode cross section shape and axial assistant flushing fluid on the gap flow field characteristics were simulated.It was verified in principle that the large aspect ratio micro-spiral wire electrode with high-speed rotating and assistant flushing were used to drive the electrolyte to produce axial movement,promote the axial discharge of electrolysis products and improve the processing speed.(2)The preparation of large aspect ratio micro-spiral wire electrodes by multi-wire tool WECM was proposed.The effects of typical process parameters on the width and profile of spiral grooves were studied.Under the optimum parameters,11 wire electrodes were fabricated simultaneously to produce spiral electrodes with clear outline,uniform groove width,a pitch of 1 mm and an effective length of 20 mm.As a tool,a tree trunk structure of 10 mm thickness was fabricated stably with high consistency of slit size,verificated the feasibility of using spiral electrodes for electrolytic wire cutting.(3)The experiments on pulse current WECM with cylindrical wire electrode for thick workpiece were carried out,and the influence of typical process parameters on WECM was studied.The effects of thickness and pulse frequency on the electrical signals and processing speed of WECM circuit were analyzed and experimentally studied.The results show that,when the pulse frequency is 100 kHz and the workpiece below 15 mm thickness,the current can be fully charged to a stable state in the pulse width time,when the pulse frequency is more than 15 mm,the charging of the processing circuit is incomplete,and the current increases continuously in the pulse width time.When the pulse frequency is more than 20 kHz,the maximum feedrate decreases with the increase of the pulse frequency,and when the pulse frequency is less than 20 kHz,there is no significant difference in the maximum feedrate.Finally,a 20 mm thick mortise structure with roughness of Ra 0.494 ?m was fabricated at feedrate of 4 ?m/s.(4)The experimental of large aspect ratio micro-spiral wire electrode pulse current WECM for thick workpiece was carried out.At pulse frequency is 100 kHz,the maximum feedrate of the cylindrical wire electrode is 2 ?m/s,while the maximum feedrate of the spiral wire electrode can reach 3 ?m/s.The assistant flushing and lower frequency pulse current(20kHz)to improve the processing efficiency.At the inlet flow rate was 300 L/h of flushing device,the maximum feedrate of both the cylindrical wire electrode and the spiral wire electrode could reach 6.5 um/s,but the slit width of the spiral electrode was more narrow.