Mechanism And Control On Extrusion Die Swell Deformation Of Profile Medical Multi-lumen Cavity Catheter

With the development of interventional medicine,polymer material interventional medical catheters continue to develop in the direction of precision.However,the coupling effect caused by the viscoelastic properties of the polymer material during the extrusion molding process and the fluctuations in the parameters of the manufacturing process will cause die swell of medical multi-lumen catheter to fluctuate,which seriously affect the dimensional accuracy of products.Therefore,it is still a technical challenge to prepare high-precision special-shaped medical multicavity catheter in engineering.The study of precision control of shaped medical multi lumen catheter is favored by scholars.Although the related research in our country is abundant,the mechanism of die swell of medical multi cavity catheter has not been fully understood,and its shape control is still in the unscientific state of trial and error.In this paper,the mechanism of the interaction between the radial deformation displacement of die swell,the radial secondary flow and the second normal stress difference is studied in the extrusion process of the multi cavity special-shaped medical catheter.The shape control mechanism of precision extrusion molding of special-shaped medical multi-lumen catheter was explored.The effects of volume flow and relaxation time on the precision extrusion of medical multi-lumen catheters were explored respectively.The main achievements are as follows:The effects of different process parameters and rheological parameters on the die swell of polymer medical multi cavity catheter were studied,1)The effects of different process parameters and rheological parameters on the die swell of polymer medical multi cavity catheter were studied,it was found that there was a positive correlation between die swell and secondary flow strength,however,there is a positive correlation between the secondary flow intensity and the second normal stress difference.Based on this universal change rule,it is proposed that the mechanism of die swell for extrusion of multi-cavity medical catheters is that the die swell and deformation of multi-cavity medical catheters are driven by the melt secondary flow along radially outward,the direct driving force of the secondary flow is the melt second normal stress difference in the extrusion process of multi-cavity medical catheters;2)It is found that the radial displacement of medical multicavity catheter in extrusion process is distributed unevenly along the loop line,which make medical multicavity catheter produce manufacturing error of ellipticity,the maximum ellipticity manufacturing error is as high as 6.2%,however,the secondary flow intensity is not evenly distributed along the loop line in the extrusion process of medical multicavity catheter,which will cause the manufacturing error of ovality of medical multicavity catheter products.Based on that the die swell and ellipticity manufacturing errors of medical multi-lumen catheter extrusion are driven by radial secondary flow,and it is found that the plunger flow of gas-assisted extrusion can make the shear deformation rate tends to zero,which can eliminate the radial secondary flow of medical multi cavity catheter by adjusting the second normal stress difference to zero.In this paper,it is proposed to precisely control the die swell and ovality manufacturing error by gas assisted extrusion of medical multicavity catheter,which can achieve precision molding of medical multicavity catheter...