Numerical simulation and optimization of extrusion runner of thermoplastic polyurethane limit spring based on response surface method

With thermoplastic polyurethane (TPU) limit spring extruder head as the research object, the relevant material parameters of the constitutive equation of raw TPU were obtained by the rheological property test. Numerical simulation of the flow process of TPU in the extrusion runner was carried out based on the software Polyflow, and in the meanwhile, a second-order regression model of standard deviation of velocity (Sd) at the exit of the forming section was established by response surface method, and the influence law of extrusion runner structure on the melt flow uniformity of TPU was explored. The results showed that after optimization the structure parameters of extrusion runner were as follows: the length of the forming section of 165 mm, the expansion angle of 25°, and the number of diverter shuttles of 6. After optimization the predicted value of Sd at the exit of the forming section of extrusion runner was 0.531 m/s and was only 0.188% different from the actual value of Sd(0.532 m/s), which indicated that the model was more accurate, and the model could be used for the prediction and optimization of the structure parameters of extrusion runner.