Study On Structure Optimization And Jet Performance Of Piezoelectric Inkjet Printing Head

Piezoelectric micro-jet technology has been widely used in many industrial fields due to its fast response and high accuracy,such as inkjet printing,additive manufacturing,LCD manufacturing,microfluidic chips,solar cells,and nanotechnology.Piezoelectric inkjet printing has the advantages of high precision,good printing quality,less energy consumption and environmental protection,and has become an significant developing direction of digital printing technology.Its working principle is to apply voltage pulse to the piezoelectric element in the piezoelectric printing head.Because the piezoelectric material has inverse piezoelectric effect,the piezoelectric element vibrates and generates pressure wave in the ink channel,resulting in the fluid ejecting from the nozzle under the action of pressure,and the liquid drops are formed by jet fracture.Piezoelectric ink-jet behavior includes multiple physical fields,such as solid,fluid and air.In the process of ink-jet it involves electromechanical coupling of piezoelectric element,acoustic structure coupling of chamber and fluid,and two-phase flow coupling of droplet flying in air.Therefore,it has great significance to study the driving characteristics of piezoelectric inkjet printing and the coupling characteristics of droplet injection.The main research contents of this paper include:(1)The characteristics of the piezoelectric ink-jet printing drive system in bending mode were studied,the finite element simulation model of the piezoelectric driver in the piezoelectric ink-jet printing head was established,and the influence law of the structural parameters of PZT piezoelectric film,SiO2 vibrating plate and Parylene protective layer on the driving characteristics of the piezoelectric driver was determined.The structural parameters of the actuator are optimized.(2)The dynamic characteristics of the fluid in the ink chamber are studied theoretically.Based on the derivation of the acoustic governing equation describing the pressure channel inside the ink cavity of piezoelectric inkjet printing head,a coupling model of acoustic structure based on the narrow channel theory was established to study the driving mechanism of acoustic pressure wave inside the cavity and the interaction between acoustic pressure wave and the ejected fluid.(3)The finite element simulation model of the piezoelectric inkjet printing head was established.The acoustic coupling characteristics of the piezoelectric actuator and the fluid in the cavity were analyzed when the printing head was working.The effects of structural parameters,fluid properties and resonant frequency on the acoustic pressure of the nozzle were studied(4)The influence of external excitation parameters and fluid parameters on injection characteristics is studied.A two-phase flow model of droplet injection from nozzle to air was established.The transient results of acoustic structure coupling analysis were used as the boundary conditions of pressure inlet for hydrodynamic analysis.The effects of piezoelectric pulse excitation parameters and fluid physical properties on droplet injection performance of inkjet system were obtained.