Theoretical and simulation research on the double shim method for optimizing the exit uniformity of slot die
摘要
Studying the flow characteristics inside the slot die and optimizing its exit uniformity is essential to ensure the quality of coating products. This study proposes a double shim optimization method for improving the exit uniformity of a T-shaped dual-cavity slot die. In this paper, based on the existing theoretical model, the dividing shape curve equation of the double shim optimization method is derived, and the viscous shape factor is introduced in the equation, which can be applied to a multitude of internal cavity cross-section shapes. The pressure and velocity distribution characteristics inside the single shim and optimized double shim slot dies are compared via simulation, and the results prove the feasibility of the double shim optimization method. The results demonstrate that the double shim optimization significantly enhances the die’s exit uniformity. However, this method increases the die’s inlet pressure while improving exit uniformity. Within the acceptable range of the exit uniformity index, the inlet pressure can be reduced by combining the double shim optimization with a reduction in the slot die length, Ls2, thereby achieving the goal of improving exit uniformity without increasing inlet pressure. The optimization method proposed in this study can improve the exit uniformity by adjusting only two shims, effectively reducing the cost of remachining the slot die.