Mechanism and experimental study on additive printing of warp knitted vamp

Transfer process of aqueous polyurethane dispersion (PUD) has a significant influence on the additive printing for warp knitted vamp. Research on transfer mechanism contributes to a true understanding of additive printing that develops based on engineering experience. This paper presents an innovative numerical modeling approach to establish a computational fluid dynamics (CFD) model describing the additive printing process. And the distribution characteristics of the wedge flow field in additive printing are systematically analyzed. More importantly, the hydrodynamic pressure near the squeegee tip plays a crucial role in aqueous PUD transfer. And the variation in the pressure and velocity with the squeegee movement in the flow field at one particular point is obtained. Then Printing experiment platform is developed to study the variation in transfer amount of aqueous PUD with printing force, angle and velocity. The comparison of experimental and simulation results indicates that the transfer amount of aqueous PUD conforms to Darcy's law. Thus, CFD model is used as a bridge to link printing parameters to transfer amount, describing the phenomena well in additive printing, and further reveals the mechanism of aqueous PUD transfer.