Medical catheter mold and process parameter synchronous construction method based on multi-parameter fusion analysis

Abstract

The invention discloses a medical catheter mold and process parameter synchronous construction method based on multi-parameter fusion analysis. The method comprises the steps that a mapping model of the mold size and the target product size is established; establishing a related equation of production efficiency-traction speed-extrusion flow to obtain the extrusion flow; calculating the rotating speed of the screw, and substituting the rotating speed into the simplified screw transmission equation to obtain the size of the mold; calculating a melting stretching distance, establishing a numerical simulation model, and describing a melt flow behavior by using a melt viscosity model corresponding to a product material; initial process parameters are set, numerical simulation is conducted, if the size of a simulation product is not within the tolerance zone range, the gradient and the step length are calculated, simulation is conducted after the process parameters are corrected till the range requirement is met, and the die size and the process parameters at the moment are output. According to the invention, in the extrusion processing production process of the precise medical catheter, the time required by the design of the extrusion die is reduced, the design precision of the extrusion die is improved, and the debugging range of extrusion process parameters is narrowed.

Description

Technical Field

[0001] The present invention relates to the field of medical catheter extrusion processing, and in particular to a method for synchronously constructing a medical catheter mold and process parameters through multi-parameter fusion analysis. Background Art

[0002] Interventional therapies emerged in the 20th century and have rapidly developed in recent decades, driving the invention and advancement of interventional medical devices. Medical catheters, one of the most common interventional medical devices, function primarily to create precise pathways between the human body and the external environment. Due to their need for human intervention, medical catheter diameters are strictly limited to millimeters or even microns, with wall thicknesses in the submillimeter or micron range, and tolerances down to the micron level. This presents significant challenges for the extrusion process of precision medical catheters. The design, manufacture, and modification of extrusion dies, as well as the precise selection of extrusion process parameters, are crucial steps in the entire precision medical catheter extrusion process. Currently, the design, manufacture, and modification of precision medical catheter dies often rely excessively on engineers' personal experience or on reliance on manufacturers' past process examples. Extrusion process parameters are often determined through trial and error after mold fabrication, including on-machine testing, machine adjustments, and mold repairs. This traditional approach consumes significant time and financial resources, severely hindering both efficiency improvements and cost control in the production of precision medical catheters. Summary of the Invention

[0003] In response to the shortcomings of the existing technology, the present invention proposes a method for synchronously constructing medical catheter molds and process parameters through multi-parameter fusion analysis, which reduces the time required for extrusion mold design in the precision medical catheter extrusion processing and production process, improves the extrusion mold design accuracy, and narrows the debugging range of extrusion process parameters.

[0004] The specific technical solutions are as follows:

[0005] A method for synchronously constructing a medical catheter mold and process parameters through multi-parameter fusion analysis includes the following steps:

[0006] Step 1: Establish a mapping model between mold dimensions and target product dimensions to obtain the ratio of mold inner and outer diameters and length;

[0007] Step 2: Based on the principle of conservation of mass, establish a correlation equation between production efficiency, pulling speed, and extrusion flow rate. First, determine the pulling speed based on the target product length and production efficiency, and then determine the extrusion flow rate based on the target product cross-sectional area and pulling speed.

[0008] Step 3: Calculate the screw speed according to the empirical formula. Substitute the screw speed, extrusion flow rate and the ratio of the inner and outer diameters of the mold into the simplified screw transmission equation to solve for the inner and outer diameters of the mold.

[0009] Step 4: Obtaining a melt stretching distance according to the extrusion flow rate and the mold temperature set during the extrusion process;

[0010] Step 5: Based on the obtained mold size and melt stretching distance, a numerical simulation model is established. The melt viscosity model obtained by rheological testing of the material used to prepare the target product is used to describe the melt flow behavior and set the initial process parameters.

[0011] Step 6: Perform numerical simulation to obtain a simulation product;

[0012] Step 7: Determine whether at least one of the inner diameter or outer diameter of the simulated product is within the tolerance range of the target product size. If so, output the mold size and process parameters at this time; if not, execute step 8;

[0013] Step 8: Use the adaptive gradient descent method to correct the process parameters and repeat steps 6 and 7.

[0014] Furthermore, in step 1, the expression of the mapping model is as follows:

[0015]

[0016] Where, is the outer diameter of the mold, is the inner diameter of the mold, is the outer diameter of the target product, is the inner diameter of the target product; b cf The bias coefficient obtained by solving the ratio of inner and outer diameters is set manually according to actual production; L d is the length of the mold, k d The weight coefficient for solving the mold length is set manually according to actual production.

[0017] Furthermore, in step 2, the correlation equation of production efficiency-pulling speed-extrusion flow rate is expressed as follows:

[0018] V t =P e L t

[0019]

[0020] Where V t is the traction speed, P e For production efficiency, L t is the target product length; Q is the extrusion flow rate, is the outer radius of the target product, is the inner radius of the target product.

[0021] Furthermore, in step three, the empirical formula is expressed as:

[0022] N=k N T m +b N

[0023] Where N is the screw speed, k N The weight coefficient for solving the screw speed is set manually according to actual production; T m is the melting point of the material used to prepare the target product, b N The bias coefficient for solving the screw speed is set manually according to actual production;

[0024] The simplified screw transmission equation is as follows:

[0025]

[0026]

[0027] Where Q is the extrusion flow rate, L is the total length of the screw, λ is the coordinate in the direction of the screw length, and h(λ) is the function of the depth of the screw groove changing with the direction of the screw axis. is a function of the change in the thread angle with the direction of the screw axis; K is a measure of the ease with which the mold allows the melt to pass under pressure difference drive, D s is the major diameter of the screw, k is the ratio of the inner and outer diameters of the mold, Indicates the inner radius of the mold, is the outer radius of the mold.

[0028] Furthermore, in step 6, the following continuity equation and momentum equation are satisfied during the numerical simulation process:

[0029]

[0030] In the formula, the center axis of the mold is the z-axis, the melt flow direction is the positive direction, and according to the right-hand rule, the two directions perpendicular to the z-axis are defined as the x-axis and the y-axis respectively, u x is the component of the velocity vector u in the x direction, u y is the component of velocity vector u in the y direction, u z is the component of the velocity vector u in the z direction; ρ is the melt density, represents the inertial force per unit volume of the flowing melt; g is the acceleration due to gravity, ρg represents the mass force per unit volume; T is the stress tensor, represents the divergence of the stress tensor per unit volume.

[0031] Furthermore, in step 6, the following conditions are met during the numerical simulation process:

[0032] Boundary condition at the mold inlet: ux =u y =0, The melt flow rate is the extrusion flow rate Q;

[0033] Mold wall boundary condition: u n =u s =0, where u n is the normal velocity of the mold wall, u s is the tangential velocity of the mold wall; the tangent direction of the mold wall is parallel to the axis of the mold;

[0034] Free surface conditions of the melt stretching section: The normal velocity of the free surface of the melt stretching section is 0, and f n =f s =0, where f n is the normal force on the free surface, f s is the tangential force of the free surface; the tangent direction of the free surface is parallel to the axis of the mold;

[0035] Boundary conditions at the outlet of the melt-stretching section: the tangential velocity at the outlet of the melt-stretching section is 0, the normal velocity is equal to the pulling velocity; the normal direction of the outlet of the melt-stretching section is parallel to the axis of the mold.

[0036] Furthermore, the process parameters include: screw speed, pulling speed, and melt stretching distance.

[0037] Furthermore, in step eight, the calculation expressions of the gradient and step size corresponding to the adaptive gradient descent method are as follows:

[0038]

[0039] S (j) =k S

[0040] Where G (j) is the gradient of the jth iteration, k G It is the correction coefficient for gradient solution, which is set manually according to actual production; represents the outer diameter of the simulated product obtained by the j-th iteration simulation, is the outer diameter of the target product; represents the inner diameter of the simulated product obtained by the j-th iteration simulation, is the target product inner diameter; S (j) is the step size, k S The step length is set manually based on actual production;

[0041] The expressions of the corrected process parameters are as follows:

[0042] P (j+1) =P (j) -G (j)S (j)

[0043] Where, P (j+1) is the process parameter value for the j+1th iteration, P (j) Take the values of the process parameters for the jth iteration.

[0044] The beneficial effects of the present invention are:

[0045] The present invention estimates the die size and extrusion process parameters based on the target product size, production efficiency, screw speed, and simplified screw transmission equations in combination with empirical formulas, then obtains simulation values through numerical simulation and corrects the process parameters using an adaptive gradient descent method. The present invention coordinates empirical formulas, theoretical formulas, numerical simulations, and an adaptive gradient descent method to synchronously construct process parameters such as product, die, screw, temperature, screw speed, pulling speed, and melt stretching distance. This reduces the uncertainty of die size based on empirical design, reduces the time required for precision medical catheter extrusion die design, improves the accuracy of precision medical catheter extrusion die design, narrows the debugging range of extrusion process parameters, and saves time and cost for die design and on-machine debugging. The method proposed in the present invention can be used for the design of extrusion dies for various types of single-layer, single-lumen precision medical catheters. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Figure 1 It is a flow chart of a method for synchronously constructing a medical catheter mold and process parameters through multi-parameter fusion analysis in an embodiment of the present invention.

[0047] Figure 2 Schematic diagram of target product dimensions of a polyetheretherketone medical catheter in an embodiment of the present invention.

[0048] Figure 3 Schematic diagram of the screw dimensions to be used for extrusion of polyetheretherketone medical catheters in an embodiment of the present invention.

[0049] Figure 4 3 is the apparent viscosity curve of polyetheretherketone at 345° C. fitted by the Cross model in the embodiment of the present invention.

[0050] Figure 5 It is a schematic diagram of a numerical simulation model established according to data obtained in the calculation stage in an embodiment of the present invention.

[0051] Figure 6 This is a schematic diagram of the final product and its inner and outer diameter dimensions obtained by numerically simulating a polyetheretherketone medical catheter under given mold and process parameters in an embodiment of the present invention. DETAILED DESCRIPTION

[0052] The present invention will be described in detail below based on the accompanying drawings and preferred embodiments. The purpose and effects of the present invention will become more apparent. The present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only for explaining the present invention and are not intended to limit the present invention.

[0053] A method for synchronously constructing medical catheter molds and process parameters based on multi-parameter fusion analysis is proposed. The method is divided into a calculation stage of deriving mold size parameters from target product size parameters, and a numerical simulation correction stage.

[0054] like Figure 1 As shown in the figure, the calculation stage of deriving the mold size parameters from the target product size parameters is specifically implemented through the following steps:

[0055] S1: Establish a mapping model between the die-core geometry parameters and the target product dimensions, and obtain the ratio of the outer diameter to the inner diameter of the mold based on the known parameters. The specific mapping model is as follows:

[0056]

[0057] Where, is the outer diameter of the mold, that is, the die diameter, is the inner diameter of the mold, that is, the core rod diameter, is the outer diameter of the target product, is the inner diameter of the target product; b cf The bias coefficient for solving the mold geometric parameters is set manually according to actual production; L d is the length of the mandrel (or the length of the die, the lengths of the mandrel and the die are the same by default), k d The weight coefficient for solving the core rod length is set manually according to actual production.

[0058] In this embodiment, a single-layer single-lumen medical catheter made of polyetheretherketone is selected as the target product. The drawings of the target product are as follows: Figure 2 As shown, the outer diameter of the medical catheter can be seen inner diameter Single length L t =300mm. Take the bias coefficient b obtained by the mold geometric parameters cf =0.1 (recommended value), then the ratio of the outer diameter to the inner diameter of the mold is obtained according to the mapping model is 1.64; the weight coefficient k for solving the core rod length d =33.5 (recommended value), then the core rod length L can be calculated d It is 55mm.

[0059] S2: Based on the principle of conservation of mass, the correlation equation between production efficiency, traction speed, and extrusion flow rate is established. First, the traction speed is obtained based on the target product length and production efficiency, and then the extrusion flow rate is obtained based on the cross-sectional area of the target product and the traction speed. The specific correlation equation is as follows:

[0060] V t =P e L t

[0061]

[0062] Where V t is the traction speed, P e For production efficiency, L t is the length of each medical catheter product, that is, the target product length; Q is the extrusion flow rate, is the outer radius of the product, is the inner radius of the product.

[0063] In this embodiment, the production efficiency P is required to be e At least 2900 pieces / h are needed. The pulling speed V can be calculated based on the correlation equation of production efficiency and pulling speed. t The extrusion flow rate Q is 416 mm according to the correlation equation of traction speed and extrusion flow rate. 3 / s.

[0064] S3: Calculate the screw speed based on the empirical formula and substitute it together with the ratio of the mold's outer diameter to its inner diameter obtained in S1 into the simplified screw drive equation to solve for the mold's geometric parameters. The specific empirical formula and screw drive equation are as follows:

[0065] N=k N T m +b N

[0066]

[0067] Where N is the screw speed, k N The weight coefficient for solving the screw speed is set manually according to actual production; T m is the melting point of the material used to prepare the target product, b N is the bias coefficient for solving the screw speed, which is set manually according to actual production; L represents the total length of the screw, λ represents the coordinate in the length direction of the screw (i.e., the axial direction), and h(λ) is the function of the change of the thread groove depth along the screw axis direction. is a function of the change in thread angle with the direction of the screw axis; K is a measure of the ease with which the mold allows the melt to pass through under pressure difference drive, D sis the major diameter of the screw, k is the ratio of the inner and outer diameters of the mold, Indicates the inner radius of the mold, is the outer radius of the mold.

[0068] In this embodiment, the weight coefficient k is obtained by taking the screw speed as the solution. N =-0.057 (recommended value), bias coefficient b for screw speed solution N =33 (recommended value), it is known that the material for preparing the target product is polyetheretherketone, and its melting point is T m =345℃, then the screw speed N can be calculated to be 13.3 rpm. Figure 3 As shown in the figure, the screw size parameters are: screw major diameter D s =30mm, lead 30mm, then the thread angle is about 17.6°; the length of the first section is 360mm, the depth of the first section thread groove is 4.5mm; the length of the second section is 240mm, the depth of the second section thread groove changes linearly with the bottom diameter, from 4.5mm to 1.35mm; the length of the third section is 240mm, the depth of the third section thread groove is 1.35mm. Substituting the screw size parameters and screw speed into the simplified screw transmission equation, the geometric parameters of the mold are obtained. 7.00mm, It is 4.27mm.

[0069] S4: The melt stretching distance is obtained by solving the empirical formula. The specific expression is as follows:

[0070] L w =k q Q+k t T d +b L

[0071] Where, L w is the melting stretching distance, that is, the distance between the water tank and the die, k q With k t are weight coefficients for solving the melting stretching distance, which are set manually according to actual production. d The die temperature set for the extrusion process, b L The bias coefficient for solving the melt stretching distance is set manually according to actual production.

[0072] Let the weight coefficient k for solving the melting stretching distance be q =-0.06 (recommended value), k t =0.3 (recommended value), bias coefficient b L =-9 (recommended value), the mold temperature T set during the extrusion process d=345℃, and substituting the extrusion flow Q calculated by S3, the melt stretching distance L can be calculated. w It is 70mm.

[0073] S5: Conduct rheological tests on the materials used to prepare the target product and establish a melt viscosity model.

[0074] In this embodiment, the material used to prepare the target product is polyetheretherketone, which is subjected to rheological testing, and the apparent viscosity curve of polyetheretherketone at 345°C as a function of shear rate is obtained by fitting with the Cross model, as shown in FIG. Figure 4 As shown in , the melt viscosity model is obtained.

[0075] like Figure 1 As shown in FIG, the numerical simulation correction stage is specifically implemented through the following steps:

[0076] N1: Based on the mold geometry and melt-stretch distance calculated during the calculation phase, a numerical simulation model is established. The melt flow behavior is described using the melt viscosity model obtained during the calculation phase. The numerical simulation model includes the mold flow zone and the free flow zone, with the free flow zone being the melt-stretch section.

[0077] In this embodiment, the numerical simulation model established is as follows Figure 5 As shown, the core rod length L d 55mm, melting stretching distance L w The outer diameter of the mold is 70mm 7.00mm inner diameter It is 4.27mm.

[0078] N2: Set the initial process parameters and perform numerical simulation based on the numerical simulation model and melt viscosity model established in step N1. The continuity equation and momentum equation of the numerical simulation are as follows:

[0079]

[0080] In the formula, the center axis of the mold is the z-axis, the melt flow direction is the positive direction, and according to the right-hand rule, the two directions perpendicular to the z-axis are defined as the x-axis and the y-axis respectively, u x is the component of the velocity vector u in the x direction, u y is the component of velocity vector u in the y direction, u z is the component of the velocity vector u in the z direction; ρ is the melt density, represents the inertial force per unit volume of the flowing melt; g is the acceleration due to gravity, ρg represents the mass force per unit volume; T is the stress tensor, represents the divergence of the stress tensor per unit volume.

[0081] The following boundary conditions should be met during the numerical simulation process:

[0082] ① Boundary condition of mold entrance, which is a dynamic boundary condition, satisfying u x =u y =0, The melt flow rate is equal to the extrusion flow rate Q calculated in the calculation stage.

[0083] ②Mold wall boundary condition, which is a no-slip wall boundary condition that satisfies u n =u s =0, where u n is the normal velocity of the mold wall, u s is the tangential velocity of the mold wall; and the normal direction of the mold wall is parallel to the radial direction of the mold, and the tangential direction is parallel to the axis of the mold.

[0084] ③ Free surface condition of the melt stretching section, which is a dynamic boundary condition, and satisfies the normal velocity of the free surface of the melt stretching section to be 0, and f n =f s =0, where f n is the normal force on the free surface, f s is the tangential force of the free surface, the normal direction of the free surface is parallel to the radial direction of the mold, and the tangential direction is parallel to the axis of the mold.

[0085] ④ Boundary conditions at the outlet of the melt stretching section. This condition is a dynamic boundary condition. The tangential velocity at the outlet of the melt stretching section is 0, the normal velocity is equal to the pulling velocity, and the initial normal velocity is equal to the pulling velocity V obtained in the calculation stage. t ; The tangential direction of the melt stretching section outlet is parallel to the radial direction of the mold, and the normal direction is parallel to the axis of the mold.

[0086] In this embodiment, the meshing of the numerical simulation model is carried out using a hexahedral mesh structure with 26544 mesh units. Figure 4 The Cross viscosity curve is shown in Figure 2, and the continuity equation, momentum equation and boundary condition constraints are used for numerical simulation to obtain the following: Figure 6 Simulated product shown.

[0087] N3: Determine whether at least one of the inner diameter or outer diameter of the simulated product obtained by numerical simulation falls within the tolerance range of the target product size. If so, output the mold size and process parameters at this time; if not, execute step N4.

[0088] N4: Calculate the gradient and step size to modify the process parameters and begin the next iteration, repeating steps N2 and N3 and re-simulating. The process parameters include screw speed, pull-off speed, and melt-draw distance. During the iterative process of modifying process parameters, only one of them is modified.

[0089] The calculation expressions of gradient and step size are as follows:

[0090]

[0091] S (j) =k S

[0092] Where G (j) is the gradient of the jth iteration, k G It is the correction coefficient for gradient solution, which is set manually according to actual production. represents the outer diameter of the simulated product obtained by the j-th iteration simulation, represents the inner diameter of the simulated product obtained by the jth iteration simulation; S (j) is the step size, k S The step length is set manually based on actual production.

[0093] The modified expressions of process parameters are as follows:

[0094] P (j+1) =P (j) -G (j) S (j)

[0095] Where, P (j+1) The process parameter value for the next iteration (i.e., j+1th iteration), P (j) Take the values of the process parameters for the current (i.e., j-th) iteration.

[0096] In this embodiment, the tolerance range of the target product size is The process parameters of the first numerical simulation are screw speed N = 13.3r / min, traction speed V t =14.5mm / min, mold temperature T d =345℃, the obtained simulation product is as follows Figure 6 As shown, the simulation size 1.86mm, Since the inner and outer diameters of the simulated product are not within the tolerance range, process parameter correction is required, and the pulling speed is used as the corrected process parameter, that is, P (1) =14.5m / min. According to the magnitude of the traction speed, the correction coefficient k is taken from the gradient solution. G=10 (the correction coefficient is used to represent the current order of magnitude of the corrected process parameter, and the absolute value of the correction coefficient in the next iteration is attenuated to three-quarters of the absolute value of the current iteration correction coefficient. The positive and negative values need to be adjusted according to the corrected process parameter), step size k S =2π (recommended value), then the process parameter P of the second numerical simulation is calculated (2) =13.9m / min, and this traction speed is substituted into the numerical simulation model for re-simulation to obtain the simulation results of the second numerical simulation: 1.96mm, The inner diameter and outer diameter of the product obtained by numerical simulation are both within the tolerance range of the target product size, and the iteration ends. The final mold size parameters and process parameters are output as follows: mold outer diameter inner diameter Mandrel length L d =55mm, melting stretching distance L w =70mm, screw speed N=13.3r / min, traction speed V t =13.9m / min, die temperature T d =345℃.

[0097] Based on the established production efficiency and actual size requirements of the target product, the method of the present invention uses a mechanism analysis method to accurately estimate mold dimensions and process parameters. It then uses numerical simulation to iteratively correct the process parameters, precisely correlating the mold dimensions and process parameters and optimizing them together. The application of this method can significantly reduce the time required to design precision medical catheter extrusion dies, significantly narrow the debugging range of extrusion process parameters, and reduce the uncertainty of die dimensions based on empirical design. This, in turn, comprehensively saves time and cost in mold design and commissioning, while improving design accuracy.

[0098] Those skilled in the art will understand that the foregoing descriptions are merely preferred embodiments of the invention and are not intended to limit the invention. Although the invention has been described in detail with reference to the foregoing examples, those skilled in the art will still be able to modify the technical solutions described in the foregoing examples or substitute equivalents for some of the technical features therein. Any modifications, equivalent substitutions, etc. made within the spirit and principles of the invention shall be included within the scope of protection of the invention.

Claims

1. A method for synchronously constructing a medical catheter mold and process parameters based on multi-parameter fusion analysis, characterized in that: The following steps are involved: Step 1: Establish a mapping model between mold dimensions and target product dimensions to obtain the ratio of mold inner and outer diameters and length; Step 2: Based on the principle of conservation of mass, establish a correlation equation between production efficiency, pulling speed, and extrusion flow rate. First, determine the pulling speed based on the target product length and production efficiency, and then determine the extrusion flow rate based on the target product cross-sectional area and pulling speed. Step 3: Calculate the screw speed according to the empirical formula. Substitute the screw speed, extrusion flow rate and the ratio of the inner and outer diameters of the mold into the simplified screw transmission equation to solve for the inner and outer diameters of the mold. Step 4: Obtaining a melt stretching distance according to the extrusion flow rate and the mold temperature set during the extrusion process; Step 5: Based on the obtained mold size and melt stretching distance, a numerical simulation model is established. The melt viscosity model obtained by rheological testing of the material used to prepare the target product is used to describe the melt flow behavior and set the initial process parameters. Step 6: Perform numerical simulation to obtain a simulation product; Step 7: Determine whether at least one of the inner diameter or outer diameter of the simulated product is within the tolerance range of the target product size. If so, output the mold size and process parameters at this time; if not, execute step 8; Step 8: Use the adaptive gradient descent method to correct the process parameters and repeat steps 6 and 7.

2. The method for synchronously constructing a medical catheter mold and process parameters by multi-parameter fusion analysis according to claim 1 is characterized in that: In step 1, the expression of the mapping model is as follows: Where, is the outer diameter of the mold, is the inner diameter of the mold, is the outer diameter of the target product, is the inner diameter of the target product; b cf The bias coefficient obtained by solving the ratio of inner and outer diameters is set manually according to actual production; L d is the length of the mold, k d The weight coefficient for solving the mold length is set manually according to actual production.

3. The method for synchronously constructing a medical catheter mold and process parameters by multi-parameter fusion analysis according to claim 1 is characterized in that: In the step 2, the correlation equation of production efficiency-pulling speed-extrusion flow rate is as follows: V t =P e L t Where V t is the traction speed, P e For production efficiency, L t is the target product length; Q is the extrusion flow rate, is the outer radius of the target product, is the inner radius of the target product.

4. The method for synchronously constructing a medical catheter mold and process parameters by multi-parameter fusion analysis according to claim 1 is characterized in that: In step 3, the empirical formula is: N=k N T m +b N Where N is the screw speed, k N The weight coefficient for solving the screw speed is set manually according to actual production; T m is the melting point of the material used to prepare the target product, b N The bias coefficient for solving the screw speed is set manually according to actual production; The simplified screw transmission equation is as follows: Where Q is the extrusion flow rate, L is the total length of the screw, λ is the coordinate in the length direction of the screw, and h(λ) is the function of the depth of the screw groove changing with the direction of the screw axis. is a function of the change in the thread angle with the direction of the screw axis; K is a measure of the ease with which the mold allows the melt to pass under pressure difference drive, D s is the major diameter of the screw, k is the ratio of the inner and outer diameters of the mold, Indicates the inner radius of the mold, is the outer radius of the mold.

5. The method for synchronously constructing a medical catheter mold and process parameters by multi-parameter fusion analysis according to claim 1 is characterized in that: In step 6, the following continuity equation and momentum equation are satisfied during the numerical simulation process: In the formula, the center axis of the mold is the z-axis, the melt flow direction is the positive direction, and according to the right-hand rule, the two directions perpendicular to the z-axis are defined as the x-axis and the y-axis respectively, u x is the component of the velocity vector u in the x direction, u y is the component of velocity vector u in the y direction, u z is the component of the velocity vector u in the z direction; ρ is the melt density, It represents the inertial force per unit volume of the flowing melt; g is the acceleration due to gravity, and ρg represents the mass force per unit volume; T is the stress tensor, represents the divergence of the stress tensor per unit volume.

6. The method for synchronously constructing a medical catheter mold and process parameters by multi-parameter fusion analysis according to claim 5, characterized in that: In step 6, the following conditions are met during the numerical simulation process: Boundary condition at the mold inlet: u x =u y =0, The melt flow rate is the extrusion flow rate Q; Mold wall boundary condition: u n =u s =0, where u n is the normal velocity of the mold wall, u s is the tangential velocity of the mold wall; the tangent direction of the mold wall is parallel to the axis of the mold; Free surface conditions of the melt stretching section: The normal velocity of the free surface of the melt stretching section is 0, and f n =f s =0, where f n is the normal force on the free surface, f s is the tangential force of the free surface; the tangent direction of the free surface is parallel to the axis of the mold; Boundary conditions at the outlet of the melt-stretching section: the tangential velocity at the outlet of the melt-stretching section is 0, the normal velocity is equal to the pulling velocity; the normal direction of the outlet of the melt-stretching section is parallel to the axis of the mold.

7. The method for synchronously constructing a medical catheter mold and process parameters by multi-parameter fusion analysis according to claim 1, characterized in that: The process parameters include: screw speed, pulling speed, and melt stretching distance.

8. The method for synchronously constructing a medical catheter mold and process parameters by multi-parameter fusion analysis according to claim 1, characterized in that: In step 8, the calculation expressions of the gradient and step size corresponding to the adaptive gradient descent method are as follows: S (j) =k S Where G (j) is the gradient of the jth iteration, k G It is the correction coefficient for gradient solution, which is set manually according to actual production; represents the outer diameter of the simulated product obtained by the j-th iteration simulation, is the outer diameter of the target product; represents the inner diameter of the simulated product obtained by the j-th iteration simulation, is the target product inner diameter; S (j) is the step size, k S The step length is set manually based on actual production; The expressions of the corrected process parameters are as follows: P (j+1) =P (j) -G (j) S (j) Where, P (j+1) is the process parameter value for the j+1th iteration, P (j) Take the values of the process parameters for the jth iteration.

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