Mechanism And Experimental Study On Microstructure Of High Voltage Electrostatic Jet Printing

In view of the traditional additive manufacturing technology was difficult to prepare the microstructure with small size,controllable shape and even abrasive distribution,a new method of electrostatic jet printing microstructure was proposed in this paper.The electrostatic liquid is supplied to the nozzle by the precise injection pump,the liquid surface is refluxed under the action of high-voltage electrostatic field to form a micro jet,and the silicon carbide abrasive particles are rearranged under the restraint of the micro jet,so as to achieve the purpose of uniform distribution of silicon carbide abrasive particles and controllable microstructure of size and shape.In this paper,the process of conical jet in the coupled field was simulated and the experiments of droplet,line and microstructure of jet printing were carried out:(1)The basic principle of jet was analyzed and the process of conical jet was simulated.The factors that affect jet drop mode,cone jet mode and multi jet mode were summarized,and the V-Q diagram of stability boundary was drawn.By coupling the control equations of electric field and flow field,the control equations of jet flow were calculated.The three-dimensional simulation model of needle plate electrode was established by COMSOL software.The distribution of electric field intensity of plate without tip and with tip offset of 0.4 mm was compared.A two-dimensional coupled field simulation model of conical jet is established to study the influence of different jet printing process parameters on the shape,electric field strength,process characteristics and flow path of conical jet and the tip effect of conical jet.(2)A four-axis motion table for electrostatic jet printing experiment was designed and constructed,and the printing materials were selected.After analyzing and testing the electrostatic solution containing only light cured resin and tween,a stable electrostatic suspension was prepared by adding silicon carbide abrasive particles.The problems of jet deflection and air breakdown were solved.Compared with three image processing methods of wear particle distribution,Tesson polygon method,fractal theory box dimension method and grid counting method,the variation coefficient grid method was used to describe the uniformity of wear particle distribution.The influence of different process parameters on the effect of electrostatic liquid jet printing was characterized by the combination of confidence,uniformity of line width and deposition density of silicon carbide abrasive.(3)The different parameters that affect the jet printing effect were studied.Three factors and four levels orthogonal table were designed to carry out the electrostatic liquid pulse droplet spray test.Through visual analysis and variance analysis,it was found that the injection speed of peristaltic pump was the most important factor affecting the particle size.Based on the electrostatic liquid continuous line spray test,the experimental parameters were set as the needle plate distance of 3 mm,the moving speed of worktable of 20 mm/s,and the injection speed of injection pump of 2mm/h,when the needle plate voltage was 3.0 k V,thin lines with a width of 144 mm could be printed,line width decreased with the decrease of injection speed,which was consistent with the influence rule of different parameters in simulation on jet beam,and established the process parameter range for line layer by layer spraying out microstructure;in simulation,jet self corresponded to jet printing due to tip effect,and used electrostatic suspension with abrasive particles to spray out microstructure of ring,the research results showed that time had no obvious effect on the uniformity of abrasive distribution,abrasive particles tend to gather when the needle plate voltage was low,and the moving speed of the turntable was increased moderately,which had obvious effect on the uniformity of abrasive distribution and the improvement of the shape and size.So as to further grasp the law of spray printing,the spray printing of large aspect ratio micro structure abrasives,size shape controllable ring structure,micro channel soft mold and other micro structure cases were finally achieved.