Fast pressure threshold estimation and pressure field reconstruction during extruding micro plastic catheters

The melt pressure at the die entrance is an important parameter for judgment of working conditions during a screw extrusion process for manufacturing micro plastic catheters. In this study, a general strategy for fast estimating the pressure threshold at the die entrance and reconstructing the pressure field in the die is proposed. Firstly, the pressure drop per length in a commonly used die was obtained by analyzing the monotonicity, concavity, and convexity of the equivalent melt viscosity and shape factor functions. Then the pressure thresholds were estimated, the pressure fields were reconstructed, and the screw speed thresholds were obtained. The calculation methods were verified in multiple examples, including annular single-lumen catheters, irregular-shaped single-lumen catheters, and irregular-shaped double-lumen catheters. The practical experiments showed that all the actual pressures were included in the calculated pressure thresholds, all the Pearson correlation coefficients between reconstructed pressure fields and simulated pressure fields were greater than 0.98, and the maximum errors between the actual screw speed and the screw speed thresholds were within 7.4%. The proposed strategy can help extruder operators judge the extruder working conditions and significantly reduce the wasted time and materials during the adjustment of extruders.