异形医用双腔导管挤出离模膨胀变形机理与调控

Extrusion Die Swell Deformation Mechanism and Control of Medical Heteromorphosis Double‑Cavitiy Catheter

如何准确预测和精密调控异形医用双腔导管的离模膨胀变形是实现其精密成型的关键技术。通过传统和气辅精密成型的对比分析,研究表明离模膨胀变形是由熔体的第二法向应力差驱动的径向二次流动所诱发,传统挤出成型会产生较大的第二法向应力差,第二法向应力差驱动诱发的径向二次流动是离模膨胀变形的直接驱动力,从而导致传统挤出成型的异形医用双腔导管不仅产生离模膨胀,而且还产生椭圆度误差,其最大离模膨胀比和椭圆度误差分别为1.86和6.3%。异形医用双腔导管的气辅精密挤出成型基本可以消除熔体的第二法向应力差,必然消除了挤出成型过程的径向二次流动,从而实现了异形医用双腔导管的精密控形。

The accurate prediction and precise control are two key technologies for the extrusion die swell deformation of medical heteromorphosis double-cavity catheter to realize the precision forming.A comparative analysis was performed for the traditional and gas-assisted precision extrusion forming.The results indicated that the extrusion die swell deformation was induced by the secondary flow driven by the second normal stress difference of the viscoelastic melt.On the other hand,a large second normal stress difference was generated during the traditional extrusion forming,and the secondary radial flow induced by the second normal stress difference was the direct driving force of the deformation caused by extrusion die swell.This led to the extrusion die swell and ellipticity error of the medical heteromorphosis double-cavity catheter obtained by traditional extrusion forming,and its maximum die swell ratio and ellipticity error were 1.86 and 6.3%,respectively.The second normal stress difference of the viscoelastic melt could be basically eliminated by the gas assisted precision extrusion forming of the medical heteromorphosis double-cavity catheter,which eliminated the secondary flow in the extrusion process.Therefore,the high-precision shape control could be realized for the medical heteromorphosis double-cavity catheter.