Design Of Piezoelectric Driven Dispenser And Study On Droplet Performance

Fluid dispensing technology is one of the key technologies in the modern electronics manufacturing industry,which enables the packaging and fixing of components by precisely distributing the fluid material to the specified location for coating.In recent years,piezoelectric injection technology has gradually become the mainstream of the market.Compared with traditional contact injection technology,piezoelectric injection technology has the advantages of high injection efficiency and good droplet consistency,and has become the mainstream research direction of the dispensing industry.In this paper,a new piezoelectric injection dispensing valve is designed to meet the growing needs of the domestic dispensing industry and to achieve high-frequency micro-injection of adhesive droplets by analysing the working principle and structural characteristics of existing injection valves.The main work of this thesis is as follows:(1)Theoretical analysis of the current main amplification methods,a semi-circular head double firing pin amplification mechanism is proposed,and the high frequency response characteristics and output performance of the amplification mechanism are verified through theoretical analysis and finite element simulation,and a prototype drive part is machined and tested for the actual output performance of the amplification mechanism,and a displacement of 309.3μm is obtained at a drive voltage of 120 V,which basically satisfies the piezoelectric injection valve’s This basically meets the demand for drive displacement of the piezoelectric injection valve.(2)The working principle of the piezoelectric injection valve and the basic dispensing requirements are analysed,a firing pin-nozzle hydrodynamic model is established,the superior performance of the spherical firing pin-tapered nozzle is analysed and the taper angle of the tapered nozzle is designed,the influence of parameters such as firing pin diameter,nozzle aperture,firing pin stroke and glue viscosity on the pressure and flow rate in the nozzle cavity is analysed using Fluent simulation,and the relationship between the spraying effect and the spraying speed is analysed.The general rule of spray dispensing was obtained.(3)The overall design and assembly of the prototype piezoelectric injection valve is completed on the premise of confirming the interference of the movement of the components and the sealing of the glue,and the complete experimental system of the injection valve is built on this basis with the displacement detection system,the signal control system and the glue supply and quality inspection system.(4)By analysing the fluid parameters of different dispensing materials,a glycerin/alcohol mixture was finally selected as the experimental material and the spraying performance of the prototype spraying valve was tested.The experiments and analyses on the morphology and diameter of the sprayed droplets by the supply pressure,signal duty cycle and signal frequency were completed,and the maximum spraying frequency of 400 Hz,the minimum droplet diameter of about 0.36 mm and the deviation of droplet consistency of about ±2.07% were achieved by using the glycerol/alcohol mixture with a mixing ratio of 1:1 in the tests.