Mechanism And Experimental Study Of A Piezoelectric Jet Printer For High Viscosity Molten Fluid

3D printing technology is considered to be an important technology,which promote the development of manufacturing industry in the third industrial revolution.Micro droplet jetting manufacture(MJM)is a new 3D printing technology developed in recent years.It is widely used in biomedical manufacturing,three-dimensional microstructure manufacturing,microelectronics industry,micro-spacecraft,special equipment production and other fields.At present,the jet printing apparatus is mainly developed for the injection of low viscosity molten liquid such as paraffin wax,low melting point metal and alloy material,resin,polymer,and the like.The existing high viscosity droplet ejection device is mainly used for jetting adhesive at room temperature in the electronic manufacturing process.Therefore,this paper combines the Ministry of Science and Technology Technology Innovation Fund Project(NO: 12C26212201364)and National Natural Science Foundation of China(NO: 51475198)research content.By analyzing the mechanism of molten liquid jetting,at the same time,the motion model of the lever magnification system is established and the equation of motion is deduced.A piezoelectric jet printing for high viscosity molten fluid is proposed creatively.A new printing device provided for the 3D printing field.The main contents of the thesis on the study are as follows:(1)Theoretical analysis of molten droplet ejection processThe mathematical model of the inertial force between the viscous force and surface tension of the molten liquid is deduced.This paper expatiates on the working process and the jetting mechanism of the stem impact droplet jet technology.The flow velocity of the liquid in the nozzle is deduced when the stem strikes the nozzle by the simplified model of the stem moving down and striking the nozzle.The relationship between the velocity of the droplet jet and the movement speed of the stem,the structural parameters of the stem and the nozzle is obtained.The volume of the droplet ejection is divided into two parts for the derivative analysis.The mathematical model of the single injection droplet volume is deduced.The flow field was simulated by Fluent during the process of the stem striking the nozzle.The pressure cloud and velocity cloud was obtained at different times.The flow field under the parameters such as stem stroke,stem speed,stem radius,nozzle diameter,nozzle length and nozzle angle are simulated,and the different variables on the pressure and speed is obtained.It provided guidance for the structural design and experimental analysis of the melt droplet ejection device.(2)Model analysis of micro displacement amplification systemThe structure and working principle of the molten droplet-on-demand jetting device was introduced.The force model of the lever magnification system set up.Ansys Workbench used analysis the strength of the lever.The motion model of the lever magnification system is established and the equation of motion is deduced.Matlab used to solve the motion equation of the lever amplification system.The maximum displacement of the stem and the corresponding up and down movement time discussed at different reset spring stiffness and preload.And the limit frequency is obtained.When the driving voltage is 130 V,the maximum displacement of the valve stem is 292.68?m,the downward movement time is 0.504 ms and the upward movement time is 0.542 ms.(3)Thermodynamics research of the molten droplet jet printing systemAnsys Workbench used to analyze the mechanism of the temperature rise of the piezoelectric stack.The heat is partly derived from the heat transferred from the heater.The other part comes from the heat generated by the piezoelectric stack working.The working mechanism of the thermal insulation device and the thermal heat sink was analyzed and discussed.The operating temperature of the piezoelectric stack at the limit frequency was analyzed by Ansys Workbench.Subsequently,the prototype was made and the thermal insulation performance of the heat insulation device and heat dissipation performance of the heat-dissipating device were respectively tested.The feasibility of the design was demonstrated.(4)Experiment analysis of melt droplet jet printingThe stem movement state test bench was set up.The movement curve of the stem was measured by laser measurement.The stem speed and stroke with different voltage,and the movement speed of the stem corresponding to different voltage rise time was obtained.The influencing factors on the droplet ejection were obtained by different droplet injection experiments,such as different driving voltage,stem speed,stem diameter,nozzle structure parameters and supply pressure.Finally,the jetting system printed a variety of models by the platform through the computer teaching software to set different trajectories.When used the stem diameter of 0.8mm,nozzle cone angle of 90 °,the voltage drop of 95 V,nozzle diameter of 50?m,voltage rise time of 50?s,voltage drop time of 400?s,the supply pressure of 0.05 MPa,low voltage hold time of 0.8ms,storage The liquid chamber and the nozzle temperature of 80°C and 120°C,the molten polyurethane liquid is ejected,and the diameter of the ejected liquid droplets is 275 ?m.A thin wall model is deposited by repeated jetting motion,and the thickness of the model is 0.3mm.In this paper,the jetting mechanism of high viscosity molten fluid is discussed by combining the theory of piezoelectricity,fluid mechanics,fluid dynamics,flow field simulation,mechanical dynamics and thermodynamics.A piezoelectric jetting device for high viscosity molten liquid is proposed.The research work provides a theoretical and technical basis for the molten fluid jet printing device design.