Structure Optimization And Driving Waveform Design Of The Piezoelectric Inkjet Printing Unit

Piezoelectric inkjet printing technology is widely used in document printing and additivemanufacturing because of its high precision,high stability and high adaptability.The core technology of piezoelectric inkjet has not been mastered for a long time in our country.In this paper,a self-developed piezoelectric inkjet printing head is studied.The following is the main contents of this paper:(1)The basic working principles of piezoelectric inkjet printing units were introduced,including the structure of piezoelectric inkjet printing units,the vibration mechanism of piezoelectric actuators and the theory of pressure waves and the droplet formation pressure ripple formation.The manufacturing process of the piezoelectric inkjet printing head was briefly introduced.The above contents provided the theoretical basis for the simulation and experiment below.(2)The finite element simulation model of the piezoelectric actuator was established to study the effect of the each structure size on amplitude.After considering various factors to find the appropriate value range,the optimal structure sizes of the piezoelectric actuator was determined by the orthogonal testing method.The length of the Si O2 vibration plate is 700 ?m,the width of it is 130 ?m,the thickness is 1 ?m,the thickness of PZT is 1 ?m,the width ratio of PZT to Si O2 is 0.9 and the thickness of Parylene is 600 nm.(3)The piezoelectric ink-jet unit and the the two-phase flow finite element simulation model were established to optimize the driving waveform.In this paper,a new method to design the driving waveform of piezoelectric inkjet printhead was proposed.The laser Doppler vibration test and numerical simulation were combined to determine the parameters of the unipolar trapezoidal waveform.Firstly,the step response time of piezoelectric actuated vibration plate was obtained by self-analysis of the attenuated vibration waveform after a pulse excitation.The voltage rising time trise was set as 5 ?s and the voltage falling time tfall was set as 3 ?s.Secondly,a test waveform with long voltage dwelling time was designed to simulate the velocity wave caused by a single voltage rising or falling section at the nozzle.Finally,the voltage dwelling time tdwell was determined to be 16 ?s according to the superposition principle of the velocity wave.(4)The laser doppler vibration test was performed on piezoelectric actuators with different structural sizes,and the correctness of the simulation results is verified from theamplitude variation trend and the vibration mode.The piezoelectric inkjet unit is applied with different parameters of driving signal.After comparing the drops observation results such as the size of the meniscus,size and speed of the droplet,length of the liquid injection and the ink droplet formation process,the effectiveness of waveform design method was verified.