Research On Diameter Consistency And Correlative Devices Of Microjet Hole Array Fabracted By Micro-EDM

Structural parts with micro jet hole array are important parts of nozzle ofindustrial inkjet printer, fuel spray nozzle, spinneret and other components.Diameter consistency of micro jet hole array determines injection quality. Forexample, industrial inkjet printer nozzle of which micro jet hole array directlyaffects speed and size of the ink droplet and uniform distribution of ink droplet onmoving paper or cloth, thus impacting print quality. As the core component ofprinter, micro nozzle is mainly monopolized by foreign manufacturers. The mainreason is that it is difficult to ensure diameter consistency of micro jet hole array inprinter nozzle, especially our country has not yet realized industrialized processingmicro jet hole array in field of micro electrical discharge machining (micro-EDM).Thus, domestic printer manufacturers only rely on imports of nozzle, which severelylimits the level of domestic printers.To resolve the technical problem that diameter consistency of micro jet holearray, processing support platform in micro-EDM machining system for micro jethole array, CCD vision measurement system, vacuum chuck for clamping workpiece,rotating spindle, macro/micro complex drive control system, control supplyconditions of dielectric fluid and electrode wear and its compensation technologywere studied in this dissertation.Improvement of vibration resistance and stability of machining system canminimize influence of external vibration disturbances on diameter consistency ofmicro jet hole array. Micro-EDM machining system for micro jet hole array wasdeveloped based on analysis of characteristics of micro jet hole array machined bymicro-EDM. The system has granite gantry structure which has good vibrationresistance and stability. The system has the function of electrode fabrication onlinecombining block electrical discharge grinding (BEDG) and wire electrical dischargegrinding (WEDG) and the function of CCD vision online measurement for diameterof electrode and micro jet hole array. All these provided a good processing platformfor improving diameter consistency of micro jet hole array machined bymicro-EDM.In order to combine large travel, low precision and low response of screw-nutpair macro drive system and little travel, high precision and rapid response ofpiezoelectric ceramic micro drive system, macro/micro complex feed system basedon programmable multi-axes controller (PMAC) was developed. Thus, micro-EDMmachining system realized high precision positioning of large travel and rapidresponse. Piezoelectric ceramic micro drive system realized micro compensation of electrode wear and rapid response of micro servo feed, which improved stability ofdischarge status in automatic processing of micro jet hole array. It provided areliable hardware support for improving diameter consistency of micro jet hole arrayprocessed by micro-EDM.Experiments were conducted to study influence of characteristics of deionizedwater and kerosene as dielectric fluid on theprocessing of micro jet hole array. Itfound that machining in deionized water had large machining gap, good flushingerosion effect, stable discharge status, large processing speed and other advantages,which were helpful to improve diameter consistency of micro jet hole array. Tofurther improve diameter consistency of micro jet hole array, flow field simulationon machining gap was analyzed under deionized water conditions. It analyzedeffects of flushing velocity, flushing angle and electrode rotation speed ondistribution and size of flow velocity in machining gap. Furthermore, it was verifiedthat adjusting flushing angle, enhancing flushing velocity and electrode rotationspeed were helpful to improve flow velocity in machining gap, flushing erosioneffect and stability of machining state, which improved diameter consistency ofmicro jet hole array machined by micro-EDM.To reduce influence of electrode wear on diameter consistency of micro jet holearray, electrode wear characteristics were studied in the process of single electrodemachining micro jet hole array. Electrode relative wear could be reduced byselecting appropriate processing conditions and optimizing processing parameters.Electrode wear model of machining micro jet hole array by micro-EDM wasestablished and electrode wear compensation method was put forward, whichreduced the effect of electrode wear excessive compensation or under compensationon diameter of hole. All these improved diameter consistency of micro jet holearray.Experiments about pulse power parameters were conducted to control theinfluence of machining gap fluctuation of micro-EDM on diameter consistency ofmicro jet hole array. Experiments about machining gap, processing efficiency andmachining quality of micro jet hole array were carried out to optimize pulse powerparameters. Based on above, experiments were conducted to process small batch ofmicro jet hole array.160groups of micro jet hole array samples had beensuccessfully processed and each group had256hole array with diameter less than50)im and diameter deviation less than2)im. Furthermore, exploratory experimentswere carried out to machine smaller size hole array and it achieved the processing ofmicro jet hole array with diameter of30)im and20)im. All above verified thefeasibility of micro jet hole array machined by micro-EDM in this dissertation.In brief, micro-EDM equipment for processing micro jet hole array andmachining process methods were studied systematically in this dissertation, which solved the technical problem of fabrication of key structure in micro jet parts ofindustrial inkjet printer and its diameter consistency of holes. This laid thefoundation to independently develop printer nozzle and to promote the developmentof inkjet printing technology.