Spiral dies are divided into three categories, namely: Flat Spiral Die (FSD), Cylindrical Spiral Mandrel Die (SMD), and Conical Spiral Mandrel Die (CSD). These dies are used to produce films via blown film extrusion and multilayer films via co-extrusion. The goal is to improve the flow distribution and to decrease the pressure drop which will result in uniform film thickness and reduced energy dissipation. A viscous power-law fluid model shows that low-pressure drop and proper flow distribution can be achieved in a CSD simultaneously. As the number of grooves and the initial channel depth increases, the flow distribution becomes more uniform and the pressure drop decreases. Also, there is an optimum initial clearance and clearance increment angle. The model results show that the pseudo-plastic fluid has more appropriate performance than the Newtonian and dilatant fluids in improving the flow distribution and reducing the pressure drop.

螺旋模分为三类：扁平螺旋模（FSD），圆柱形螺旋芯模（SMD）和锥形螺旋芯模（CSD）。这些模具用于通过吹膜挤出生产膜，并通过共挤出生产多层膜。目的是改善流量分布并减少压降，这将导致均匀的薄膜厚度并减少能量耗散。粘性幂律流体模型表明，在CSD中可以同时实现低压降和适当的流量分配。随着凹槽数量和初始通道深度的增加，流分布变得更加均匀，并且压降减小。另外，还有一个最佳的初始间隙和间隙增量角。