Numerical simulation of micro droplet formation combined with pneumatic and piezoelectric drive

3D printing has been widely used for rapid prototyping and rapid manufacturing. Achieving higher resolution is one of the main directions in the development of 3D printing technology. Inkjet printing has achieved micron level resolution with micro droplets produced by piezoelectric drive, and inkjet printing is considered to be a key technology in the field of 3D printing. The materials used in inkjet printing and 3D printing have different properties. The fluids or slurries used in 3D printing have higher viscosity than the ink. With the increase of the viscosity of materials, the diameter of droplets is increased and the resolution is decreased. In order to improve the printing performance of materials with high viscosity, a hybrid drive method based on piezoelectric drive and pneumatic drive is proposed. When fluid column with high viscosity is formed by pneumatic drive, the piezoelectric drive is combined to control the movement of monolithic structure. The breakage of the fluid column is accelerated by the vibration of print head and a smaller droplet is formed. The structure of print head with hybrid drive is designed, and a numerical analysis model is established to investigate the feasibility of micro droplets formation for fluids with different viscosity. The simulation results show that droplets with diameter smaller than the nozzle can be formed by the hybrid drive. With the increase of the viscosity, the advantages of hybrid drive are more significant than the single drive mode. The minimum diameter of the droplet is 47 μm when the viscosity is 1000 mPa·s, which is 55% of the single drive mode and 94% of the diameter of nozzle. The simulation results verified the feasibility of micro droplets formation for fluids with high viscosity by hybrid drive.