Research On Key Technologies Of Composited Drive 3D Printing Jetting System With High Viscosity Micro Droplets

The industry 4.0 era puts higher demands on manufacturing technology.Among various manufacturing technologies that may be suitable for future national defense,energy,information technology and other needs,3D printing technology has attracted much attention and is considered to be the basic advanced manufacturing technology leading the next generation of intelligent manufacturing revolution.However,the existing 3D printing equipment is difficult to meet the high-precision,multi-material requirements which required for modern functions and smart material preparation.In order to further improve the printing precision,the 3D printing technology is combined with the inkjet printing technology to produce uniform micro droplets through the print head and realizing high-precision printing of complex three-dimensional structures.However,the viscosities of materials commonly used in 3D printing are relatively high,and the mature inkj et printing technology is difficult to directly use for material ejection and printing.Therefore,it is necessary to develop a new type of 3D printing head with high driving force and high precision.Optimizing the formation of droplets and optimizing the shape and surface properties of the nozzles are effective ways to improve the accuracy of 3D printing.By optimizing the driving control method,the forming process of material droplets can be more precisely controlled,the volume of material droplets can be reduced,and the printing accuracy can be improved.By optimizing the shape and surface properties of the nozzle,the diameter of the nozzle hole is reduced,and the flow coefficient and the flow velocity coefficient of the nozzle are improved,and the printing efficiency and printing precision are improved.For the optimization of the drive control method,a 3D printing head driven by pneumatic and piezoelectric combination is proposed to solve the problem of difficult forming and low forming accuracy of high viscosity materials in 3D printing.For the optimization and preparation process of micro nozzle,two kinds of processing techniques are proposed,which correspond to the high-efficiency processing and high-precision processing.The main research results are as follows:From the theoretical point of view,the fluid properties of many different materials in 3D printing are deeply analyzed.Combined with the theory of droplet formation and simulation model,the effects of different fluid properties on the volume of micro droplets are studied.The results show that fluid viscosity is the most important factor affecting the volume of droplets in fluid properties,which lays a theoretical foundation for the subsequent research.A composited drive control method based on piezoelectric drive and pneumatic drive is proposed to reduce the volume of droplets with high viscosity.By analyzing the formation process of droplets,the pressure of the liquid chamber is controlled by pneumatic driving,and the movement of the structure of the nozzle is controlled by piezoelectric driving,which accelerates the fracture process of the liquid column and reduced the volume of droplets.The structure of 3D printing head is designed and the simulation model is established,and the feasibility of producing high-viscosity micro droplets with composited drive is verified.An efficient fabrication process of micro nozzles based on femtosecond laser and plasma processing is proposed.Initial nozzle is machined on the surface of polyimide by femtosecond laser.Argon and oxygen were used as gas sources for plasma surface treatment.The hydrophilicity of the inner surface of the polyimide nozzle was maintained for a long time by increasing the surface roughness while introducing hydrophilic groups.A hybrid electrochemical techniques combined electrolysis and electroplating is proposed for the fabrication of micro nozzles.The shape and surface properties are precisely controlled in the process,which further improves the stability and consistency of the micro droplets formation.The effects of different nozzle shapes on the flow field are analyzed and the nozzle structure is optimized.The simulation model of the electroplating is established.By controlling the trajectory of the auxiliary anode during the electroplating process,a micro nozzle with an accurate and controllable shape is obtained.Combined with the high-speed camera observation system,a 3D printing experimental platform is built and the formation experiment of high-viscosity micro droplets is carried out.A pneumatic control system that can achieve rapid changes in negative-positive-negative air pressure is designed and optimized.By studying the droplet formation process under different control parameters,the droplet formation process and droplet volume with pneumatic driving and composited drive are compared and analyzed,and the beneficial effects of composited drive for high-viscosity micro droplet formation was verified.