In order to study the sputtering phenomenon caused by droplet impact on the hydrophobic surface in inkjet printing,droplet impact experiment and finite element simulation were carried out in this study.By adjusting the droplet velocity,two kinds of impact results,deposition and sputtering were occurred,and the impact process was analyzed by finite element method.It was found that there was a local competitive relationship among inertial force,viscous force and surface tension in the front part of droplet spreading.According to this,the form of dimensionless coefficient K was obtained by dimensional analysis,and the critical value K=107.5 from deposition to sputtering was obtained by data fitting.The results showed that the increase of density,diameter and velocity will lead to the increase of inertia force and promote sputtering.The increase of surface tension will promote droplet retraction and inhibit sputtering.The increase of viscosity will increase the viscosity dissipation,thus weakening the inertia force and inhibiting sputtering.By using this law,the maximum safe speed of quantitative printing can be deduced and the printing efficiency can be improved while the printing quality is guaranteed.
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