Effect of Die Geometry on Flow Distribution

A standard die geometry was chosen with a diameter of 250 mm with 10 grooves, a helix angle of 20°, and an axial length of 250 mm. Further, the initial channel depth was 19 mm and the taper angle of the annular channel 2°. The total flow rate was taken as 82 cmys. The consistency index of the polymer melt is 0.145 Pa-s  

The development of the leakage flow along the length of the die is shown in Fig. 9.27. 

Flow rate in the helical channel versus reduced length 

In the midsection of the channel the spiral flow drops quickly and reaches almost zero value at about 2/3 the channel length this is where the leakage flow reaches its final distribution. 

The pressure gradient reduces at first, reaches a minimum at about the center region, and then increases to a relatively low value. It is clear that the pressure gra- 

---