Design and Flow Field Dynamics of a Novel Spiral Die Head for Film Blowing

Extrusion molding die heads play a critical role in film production, with their structure directly influencing product quality, production efficiency, and die life cycle. This study focused on optimizing the film blowing process by designing a new spiral die head and analyzing the flow field dynamics. The model was constructed via a three-dimensional Boolean operation following fluid mechanics principles to establish a mathematical model based on the die head’s structure and material properties. By varying parameters such as the inlet flow rate, buffer groove length, shaping section length, and non-Newtonian index, the velocity and pressure fields were analyzed using the finite element method. The results show that increasing the inlet velocity and non-Newtonian index significantly impacted the velocity uniformity, inlet and outlet pressure, and pressure drop. A higher inlet velocity led to increased fluctuations in outlet velocity and a higher inlet pressure, while a higher non-Newtonian index resulted in a more uniform outlet velocity and a reduced fluctuation, though with a higher inlet pressure and flow channel pressure drop. The lengthening of the buffer groove and shaping section had minimal effect on the outlet velocity uniformity but increased the inlet and outlet pressures and pressure drop at each stage. This study concluded that a uniform velocity distribution, lower pressure, and reduced energy consumption are crucial for high-quality film production. The optimal parameter values were found to be an inlet flow rate of 0.03 m/s, buffer groove length of 40 mm, shaping section length of 20 mm, and non-Newtonian index of 0.36. These findings provide a theoretical foundation for optimizing die head design and improving thin film quality in practical applications.