A thin-walled tube extrusion system and a method for manufacturing a thin-walled tube

Abstract

The present application belongs to the technical field of medical instrument catheter extrusion, and relates to a thin-walled tube extrusion system and a method for preparing a thin-walled tube by using the system. The extrusion system mainly comprises a material preparation system, a feeding system, a plasticizing and molding system, a pressure closed loop system, a pre-molding system, a vacuum sizing system, a cooling molding system, an ultrasonic traction closed loop system and a cutting molding system. Through the system, after the extrusion material is treated by the material preparation system, it is fed to the plasticizing and molding system through the feeding system, and then is pre-molded by the pre-molding system, and then is sequentially passed through the vacuum sizing system and the cooling molding system, and then the size of the tube body is precisely controlled by the ultrasonic traction closed loop system, and finally the thin-walled tube is obtained after being treated by the cutting molding system. The thin-walled tube prepared by the method has a small tube body wall thickness and good consistency, and has high extrusion precision, which can reach ±0.015mm. The extruded tube body has good size stability. The size change of the tube body can be monitored in real time, deviation can be corrected in time, the product qualified rate can be improved, and the cost can be reduced.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of medical device catheter extrusion, and relates to a thin-walled tube extrusion system and a method for preparing a thin-walled tube by using the system. BACKGROUND

[0002] In recent years, interventional therapy technology is widely used in the treatment of cardiovascular and cerebrovascular diseases, urogenital system diseases and tumors, etc. This technology is widely welcomed due to its advantages of minimally invasive, wide indications, fast postoperative recovery, safety and effectiveness, and is an important development trend of future medicine. In the interventional therapy technology, vascular interventional therapy is the most demanding and highest barrier to entry subfield, and the related consumables used in this field occupy a core position in high-value consumables. One of the indispensable and higher value consumables is a vascular interventional catheter. From the cross-sectional structure of the vascular interventional catheter, the tube wall structure is usually a three-layer structure of an inner layer, an intermediate layer and an outer layer. The inner layer has the effect of reducing the friction between the balloon, stent and other interventional materials and the inner cavity of the catheter, and preventing thrombosis; the intermediate layer is a stainless steel wire or fiber wire braided structure to avoid the collapse of the inner cavity; and the outer layer determines the shape, hardness and friction with the inner wall of the blood vessel. Since interventional therapy devices are gradually becoming smaller, vascular interventional catheters are required to have a smaller outer diameter and a larger inner cavity, that is, to have the characteristics of a large cavity and a thin wall.

[0003] Both the inner layer tube and the outer layer tube of the vascular interventional catheter are thin-walled tubes, which are extruded from high molecular materials, with a wall thickness controlled below 0.09mm and an extrusion precision within ±0.02mm. Due to the high processing precision, the development time of thin-walled tubes is relatively short in China, and domestic clinical use has basically relied on imports for a long time. At present, there is still a big gap between domestic extrusion technology and foreign technology. The minimum wall thickness of the extruded tube body can be controlled at 0.1mm, and the extrusion precision can usually reach ±0.05mm. However, the extrusion process is prone to size instability and uneven wall thickness, which cannot meet the clinical use requirements.

[0004] In view of the above problems, in order to break the situation of foreign technology monopoly, it is necessary to develop a thin-walled tube extrusion system and a method for preparing a thin-walled tube, so as to realize the high precision of the geometric size of the extruded product and the high uniformity of the microstructure of the material. SUMMARY

[0005] Based on this, the purpose of the present application is to provide a thin-walled tube extrusion system and a method for preparing a thin-walled tube.

[0006] To achieve the above purpose, the technical scheme adopted by the present application is as follows:

[0007] The present application provides a kind of thin-walled pipe extrusion system, including preparation system, blanking system, plastic forming system, pressure closed loop system, preforming system, vacuum sizing system, cooling forming system, ultrasonic traction closed loop system and cutting forming system;After the material to be extruded is treated by preparation system, it is discharged to plastic forming system by blanking system, is preformed after passing through pressure closed loop system again, in turn through vacuum sizing system and cooling forming system, then the size of pipe body is precisely controlled by ultrasonic traction closed loop system, finally gets thin-walled pipe pipe body after being treated by cutting forming system.

[0008] The preforming system is used for the precooling shaping of the size of thin-walled pipe pipe body, mainly includes preforming device, the preforming device includes head die part, micro shaping part and connecting piece 6, both ends of the connecting piece 6 are integrally connected with the head die part and the micro shaping part through threads,

[0009] Further, the head die part in the preforming device includes front mouth die 7 and front mandrel 8;The front mouth die 7 is T-shaped structure, one end is convex cylinder, the middle part is tapered hollow runner with four circular threaded holes around;The tapered solid front mandrel 8 is installed in the front mouth die 7. The micro shaping part in the preforming device includes rear gland 1, front end circumference is equipped with 4 screws for adjusting wall thickness micro head 2, rear mandrel 5 installed in micro head 2 and having step clamping groove at front end, micro mouth die 4 installed in step clamping groove of rear mandrel 5 and equipped with front gland 3 outside;The front gland 3 is connected with the micro head 2 by screw;The rear gland 1 is installed at the rear end of the micro head 2, and the rear end of the rear mandrel 5 is fixed. The connecting piece 6 in the preforming device is a flow channel structure;The side close to the micro head 2 is provided with a convex threaded column connected with the micro head 2, and the side close to the head die part is connected with the front mouth die 7 through the screw passing through the circular threaded hole in the hollow flow channel.

[0010] The pressure closed loop system is used for the first precise control of the size of thin-walled pipe pipe body, mainly includes melt pump for conveying material, pressure sensor, pressure controller;The output pressure parameters of molten particles are input in the memory of pressure controller, when the molten particles in extruder barrel pass through melt pump, pressure sensor collects pressure input information in real time, and pressure controller automatically adjusts the screw speed of extruder according to its change.

[0011] Further, the melt pump in the pressure closed loop system comprises a pump shell, a driving gear, a driven gear, a sliding bearing, front and rear end plates and a shaft seal, and the melt is transported by the change of working volume caused by the mutual engagement of the driving gear and the driven gear. The pressure sensor detects the change of the melt pump feeding pressure value, converts the detected pressure signal into an electric signal and transmits it to the programmable logic controller, which issues a signal to the pressure controller through comparison and calculation. After receiving the signal sent by the programmable logic controller, the pressure controller adjusts the output frequency of the frequency converter and the rotating speed of the extrusion screw by dynamic adjustment, so as to keep the pressure value within the set range.

[0012] The ultrasonic traction closed loop system is used for secondary precision control of the size of the thin-walled pipe body, mainly comprising a laser diameter gauge, an ultrasonic thickness gauge and a traction controller. The laser diameter gauge is used for real-time measurement of the outer diameter of the pipe body, and the ultrasonic thickness gauge is used for measurement of the inner diameter and wall thickness value. The traction controller compares the collected outer diameter signal with the set value, and when there is a deviation, the traction controller converts the traction signal into an analog quantity and issues a deviation signal to the traction machine, which adjusts the traction speed by using the signal.

[0013] Further, the laser diameter gauge in the ultrasonic traction closed loop system is used for real-time detection of the diameter and ovality of the thin-walled pipe. The specific control process is as follows: when the light beam emitted by the laser passes through the polyhedral scanning mirror and the scanning optical system, a continuous high-speed scanning light beam parallel to the optical axis is formed, which scans the thin-walled pipe placed in the measurement area at high speed and is received by the photoelectric receiver placed opposite the thin-walled pipe. When the light beam scans the thin-walled pipe, the light on the photoelectric receiver is blocked. By analyzing the signal output by the photoelectric receiver, the diameter data of the thin-walled pipe is obtained. The ultrasonic thickness gauge is used for measuring the wall thickness of the thin-walled pipe and calculating the inner diameter of the thin-walled pipe. The specific control process is as follows: the ultrasonic thickness gauge is installed in a water tank close to the laser diameter gauge and with stable water flow. The ultrasonic signal pulse is emitted from the sensor, contacts the surface of the thin-walled pipe through the water medium, a part is reflected back to the probe, and the other part is reflected back to the probe through the thickness of the thin-walled pipe. The thickness of the thin-walled pipe is calculated by measuring the time of ultrasonic wave propagation in the material. The traction controller is used for adjusting the traction speed. When the size information of the thin-walled pipe collected by the system deviates from the set value, the system converts the traction signal into an analog quantity and issues a deviation signal, which is used to adjust the traction speed to ensure the stability of the extrusion of the thin-walled pipe.

[0014] The vacuum sizing system comprises a vacuum sizing sleeve and a vacuum box, and is used for adjusting the outer diameter and roundness of the thin-walled pipe. The vacuum sizing sleeve mainly comprises a fixed disc and a vacuum sleeve. The fixed disc is a disc-shaped disc connected with the vacuum tank through threads. The vacuum sleeve is a cylinder with a cylindrical inner cavity in the middle.

[0015] The cooling and shaping system comprises a water pump, a refrigerating machine and a cooling water tank connected with the refrigerating machine; a certain amount of purified water is added into the water tank of the cooling water tank before the thin-walled pipe is extruded, the temperature of the cooling water is adjusted to 10-15 DEG C, the control precision is + / - 0.05 DEG C, the water is cooled by the cooling system of the refrigerating machine, the cooling water is sent into the cooling water tank by the water pump, the pipe embryo is pulled into the cooling water tank, the pipe embryo is immersed in the cooling water, the temperature of the pipe embryo is reduced and the pipe embryo is secondarily shaped.

[0016] The application further provides a method for preparing the thin-walled pipe, which is mainly realized by the thin-walled pipe extrusion system provided by the application and mainly comprises the following steps.

[0017] S1, material preparation: selecting appropriate materials according to the use of the thin-walled pipe; starting the material preparation system, and directly using the materials or pre-treating the materials by drying before use;

[0018] S2, material feeding: feeding the materials obtained in step S1 into a material feeding system, starting the material feeding system, adjusting the parameters of the material feeding system, making the materials uniformly enter the screw melting and stably feed, connecting the circulating cooling water at the feeding opening to reduce the temperature of the feeding opening and ensure smooth feeding;

[0019] S3, plasticizing: starting the plasticizing and forming system, selecting a precision extruder suitable for the size of the pipe body, selecting a screw suitable for the properties of the materials, setting the temperature of each zone of the cylinder and the temperature of the flange to be 140-230 DEG C, and setting the speed of the main machine to be 20-40 r / min, so that the materials are fully plasticized;

[0020] S4, pressure closed loop: starting the pressure closed loop system, setting the temperature of the melt pump to be 140-230 DEG C and the pressure parameter to be 30-55 Pa, so that the materials plasticized in step S3 are uniformly output;

[0021] S5, pre-shaping: starting the pre-shaping system, so that the materials melted in step S4 firstly pass through the die head die part, are extruded by the front die 7, and then pass through the micro-shaping part to be preliminarily shaped and are extruded by the micro die 4, so as to achieve the effect of pre-cooling and shaping;

[0022] S6, vacuum sizing: starting the vacuum sizing system, selecting a water-immersed vacuum sizing sleeve suitable for the size of the pipe body, arranging the vacuum sleeve along the axial direction of the pipe material, and arranging uniform vacuum holes with a diameter of 1.0-1.5 mm on the circumference; the vacuum sleeve is a cylinder, has a cylindrical inner cavity in the middle, and the length of the cylindrical inner cavity is 8-10 times the outer diameter of the pipe body; the pipe embryo passes through the vacuum sizing sleeve and enters the vacuum tank, the vacuum degree of the vacuum tank is adjusted to be 50-70 KPa, the distance between the vacuum sizing sleeve and the micro die 4 is adjusted to be 20-30 mm, and the outer diameter and roundness of the thin-walled pipe are adjusted;

[0023] S7, cooling and shaping: according to the size of the pipe body, a cooling water tank with a length of 4m-6m is selected, the cooling and shaping system is started, the system parameters are set, and the thin-walled pipe blank is subjected to secondary cooling and shaping;

[0024] S8, ultrasonic traction closed-loop control: the traction machine is opened, the traction speed is set according to the product size and the extrusion speed, and after the extrusion is stable, the ultrasonic traction closed-loop control system is opened;

[0025] S9, cutting and shaping: the cutting and shaping system is started, a ring-shaped cutting machine is used, and the product is cut to an appropriate length according to the use requirements to prepare the thin-walled pipe.

[0026] Further, the material in step S1 includes an elastic polymer material or a mixture of an elastic polymer material and a developing agent; the elastic polymer material includes any one of polyurethane, nylon, and polyvinyl chloride with a hardness in the range of 25-75 degrees of Shore; the developing agent includes any one of barium sulfate, bismuth oxychloride, and tungsten; the weight content of the developing agent in the mixture is 25%-50%. The material pretreatment process is: using a dehumidifying dryer equipped with a rotating wheel device to dry the material, setting the drying temperature to 80-110°C, the drying time to 4-6 hours, and monitoring the dew point to be lower than -40°C; the moisture content in the material after drying is below 0.02%.

[0027] Further, the feeding system in step S2 includes a forced feeding device, a rotating shaft support structure is provided in the hopper of the feeding device, a spiral blade is welded, and a frequency converter is built-in; the feeding speed is adjusted to 10-15Hz.

[0028] Further, the ultrasonic traction closed-loop control process in step S8 specifically includes the following steps:

[0029] S81, the traction machine is opened, the traction speed is set, and the traction ultrasonic closed-loop system is opened;

[0030] S82, setting product size and parameters: setting the standard value, upper and lower limits, linear speed, control upper and lower limits, control range, data acquisition information, and correction factor of the product size; wherein,

[0031] The standard value of the product size includes the standard value of the nominal diameter, the inner diameter, the wall thickness, and the ovality; the upper and lower limits include the upper limit value and the lower limit value required by the product;

[0032] The linear speed is a reference speed of a statistical program start and an automatic control start, and the minimum linear speed is a percentage of a standard linear speed; the control upper and lower limits are multiples of a traction speed set when a closed loop is started, and determine the upper limit and the lower limit of the traction speed; the control range setting determines the upper and lower limits of the pipe size of the closed loop adjustment, that is, the closed loop control is adjusted within the upper and lower limits of the pipe size, and the control range is set to 15% to 20%; the data acquisition information is acceleration, minimum average time and minimum failure time; the acceleration is the experienced time of a frequency converter or a servo controller from starting to full speed; the minimum average time is the time of each sampling; the minimum failure time is the time of waiting for two samplings; and the correction factor is the size deviation range of the closed loop adjustment, that is, the closed loop adjustment range, and the size deviation is converted into the traction speed through an analog quantity to intelligently control the adjustment of the traction speed.

[0033] S83, pipe body position checking: an ultrasonic thickness gauge is installed at a place where water flow is stable and close to the laser diameter gauge, four evenly distributed sensor sensing probes are arranged on the circumference, and the four probes are used to detect the pipe body wall thickness and the inner diameter; the pipe body passes through the ultrasonic thickness gauge and is centered, and at this time, the four probes on the display screen all have detection digital display;

[0034] S84, waveform checking: whether the four sensors have two peak waveforms is checked; the measurement, product and trigger item all have data display as normal;

[0035] S85, wall thickness correction: the actual wall thickness of the pipe body is measured, the electronic display data are compared, if there is deviation, the actual measured wall thickness value is input, and the wall thickness data are corrected;

[0036] S86, closed loop extrusion: real-time deviation correction adjustment of the traction speed, the laser detection probe measures the outer diameter of the pipe body in real time, the inner diameter and the wall thickness value measured by the ultrasonic detection probe are combined, the traction controller compares the signal of the outer diameter with the set value, when there is deviation, the traction controller converts the traction signal into an analog quantity, and sends a deviation signal to the traction machine, and the traction machine adjusts the traction speed by using the signal.

[0037] The application further provides a thin-walled pipe prepared by the thin-walled pipe preparation method, and the thin-walled pipe has the characteristics that the single-side wall thickness is 0.075 mm ± 0.015 mm; and the thin-walled pipe is any one of a guide catheter, a microcatheter and a biliary stent outer sleeve.

[0038] The application has the following beneficial effects:

[0039] 1. The present application provides a thin-walled pipe extrusion system, which adds a pre-cooling shaping device after an extrusion die, precisely controls the size of a vacuum sizing sleeve, cooling temperature, etc., cooperates with a pressure closed-loop system and an ultrasonic traction closed-loop system to ensure extrusion stability, improve extrusion precision, and solve the problems of unstable size, large wall thickness and poor consistency of thin-walled pipes in the extrusion process.

[0040] 2. The present application provides a thin-walled pipe extrusion system, wherein the pressure closed-loop system plays a role in stabilizing pressure and controlling flow, so as to minimize the tolerance of the extruded pipe body and make more pipe bodies from unit weight of material, thereby saving material consumption and reducing manufacturing cost.

[0041] 3. The present application provides a thin-walled pipe extrusion system, wherein the extrusion pre-shaping system plays a role in pre-cooling shaping, improving the roundness and precision of the pipe body.

[0042] 4. The present application provides a thin-walled pipe extrusion system, wherein the ultrasonic traction closed-loop system uses a laser diameter gauge and an ultrasonic thickness gauge to continuously and uninterruptedly detect the outer diameter, inner diameter, ovality and wall thickness of the thin-walled pipe in real time with high precision, thereby improving the accuracy and comprehensiveness of the detection results.

[0043] 5. The present application provides a thin-walled pipe extrusion system, wherein the feeding system prevents the bridging and caking of the material by stirring and extruding the material, so as to make the material enter the screw uniformly and ensure the stability of feeding.

[0044] 6. The present application provides a thin-walled pipe extrusion system, wherein the vacuum sizing system draws a pipe blank and a vacuum sizing sleeve into vacuum, and the pipe blank tightly adheres to the inner wall of the vacuum sizing sleeve under the action of negative pressure to achieve the effect of shaping, thereby ensuring the stability of the outer diameter and roundness of the pipe body.

[0045] 7. The present application provides a thin-walled pipe extrusion system, wherein the cooling forming system reduces the temperature of the pipe blank to achieve the effect of secondary shaping.

[0046] 8. The present application provides a method for preparing a thin-walled pipe, and the pipe prepared by the method has small and consistent wall thickness, high extrusion precision, and can reach ±0.015 mm. The extruded pipe body has good size stability.

[0047] 9. The present application provides a method for preparing a thin-walled pipe, which can monitor the size change of the pipe body in real time, correct deviation in time, improve the product qualification rate, and reduce cost. BRIEF DESCRIPTION OF DRAWINGS

[0048] In order to make the technical solutions of the present application clearer, the drawings needed to be used in the embodiments or prior art description will be briefly introduced as follows. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can also be obtained according to these drawings without creative labor for those skilled in the art.

[0049] Figure 1 is a schematic diagram of a thin-walled pipe extrusion system. Figure 1

[0050] Figure 2 is a structural diagram of a preforming device. Figure 2

[0051] Figure 3 is a structural diagram of a preforming device (viewed from the direction of the micro die 4). Figure 3

[0052] Figure 4 is a split structural diagram of a preforming device module. Figure 4

[0053] Figure 5 is a structural diagram of a front mandrel in a preforming device. Figure 5

[0054] Figure 6 is a structural diagram of a front die in a preforming device. Figure 6

[0055] Figure 7 is a structural diagram of a connecting piece in a preforming device. Figure 7

[0056] Figure 8 is a structural diagram of a rear gland in a preforming device. Figure 8

[0057] Figure 9 is a structural diagram of a micro head in a preforming device Figure 9

[0058] Figure 10 is a structural diagram of a front gland in a preforming device. Figure 10

[0059] Figure 11 is a structural diagram of a micro die in a preforming device. Figure 11

[0060] Figure 12 is a structural diagram of a rear mandrel in a preforming device. Figure 12

[0061] Figure 13 is a flow chart of an ultrasonic traction closed loop. Figure 13

[0062] Figure 14 is an online wall thickness monitoring chart of Example 1. Figure 14

[0063] Figure 15 is an online ovality monitoring chart of Example 1. Figure 15

[0064] Figure 16 is an online wall thickness monitoring chart of Example 2. Figure 16 ​​​​​​​​​​​​​​​​

[0065] Figure 2 shows an online wall thickness monitoring chart for Example 1. Figure 17 Figure 3 shows an online ovality monitoring chart for Example 2.

[0066] Figure 4 shows an online wall thickness monitoring chart for Example 3. Figure 18 Figure 5 shows an online ovality monitoring chart for Example 3.

[0067] Figure 19 Figure 6 shows a wall thickness monitoring chart for Comparative Example.

[0068] Figure 7 shows a four-probe result chart for tube body position inspection in the ultrasonic traction closed-loop system. Figure 20 Figure 8 shows a cross-sectional view of a thin-walled tube body.

[0069] Figure 9 shows a structure diagram of a vacuum sizing sleeve. Figure 21 Figure 10 shows a schematic diagram of the system. Figure 11 shows a schematic diagram of the system.

[0070] Figure 12 shows a cross-sectional view of a thin-walled tube body. Figure 22 Figure 13 shows a structure diagram of a vacuum sizing sleeve. Figure 14 shows a schematic diagram of the system.

[0071] Figure 15 shows a schematic diagram of the system. Figure 23 Figure 16 shows a structure diagram of a vacuum sizing sleeve. Figure 17 shows a schematic diagram of the system.

[0072] In the figure, 1 is a rear gland, 2 is a micro machine head, 3 is a front gland, 4 is a micro die, 5 is a rear core rod, 6 is a connecting piece, 7 is a front die, and 8 is a front core rod. DETAILED DESCRIPTION

[0073] The technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the accompanying drawings. The embodiments mentioned are implemented on the premise of the technical solutions of the present application, and a detailed implementation process is given, but it needs to be declared that the protection scope of the present application is not limited to the following embodiments.

[0074] The thin-walled tube extrusion system provided by the present application has the following main implementation manners:

[0075] As shown in the system schematic diagram, according to the purpose of the thin-walled tube, appropriate materials are selected, and after the extrusion materials are first processed by the material preparation system, they are discharged to the plasticizing and molding system through the discharging system, and then are preformed after passing through the pressure closed-loop system and the preforming system, and then pass through the vacuum sizing system and the cooling molding system in turn, and then the size of the tube body is precisely controlled through the ultrasonic traction closed-loop system, and finally the thin-walled tube body is obtained after being processed by the cutting molding system. Figure 1

[0076] The pressure closed loop system in the extrusion system is used for the first precise control of the thin-walled pipe body size, mainly including a melt pump for conveying the material, a pressure sensor and a pressure controller. The melt pump includes a pump shell, a driving gear, a driven gear, a sliding bearing, front and rear end plates and a shaft seal, and relies on the working volume change caused by the mutual engagement of the driving gear and the driven gear to convey the melt. The pressure sensor detects the change of the melt pump feeding pressure value, converts the detected pressure signal into an electric signal and transmits to a programmable logic controller. The programmable logic controller compares and calculates and sends a signal to the pressure controller. After receiving the signal sent by the programmable logic controller, the pressure controller adjusts the output frequency of the frequency converter and adjusts the extrusion screw speed to keep the pressure value in the set range.

[0077] In work, the output pressure parameters of the molten particles are input in the memory of the pressure controller. When the molten particles in the extruder barrel pass through the melt pump, the pressure sensor collects the pressure input information in real time, and the pressure controller automatically adjusts the screw speed of the extruder according to the change.

[0078] The pre-shaping system in the extrusion system is used for the pre-cooling shaping of the thin-walled pipe body size, mainly including a pre-shaping device, such as Figures 2-12 As shown in the figure, the pre-shaping device includes a head die part, a micro-shaping part and a connecting piece 6, the two ends of the connecting piece 6 are integrally connected with the head die part and the micro-shaping part through threads. The head die part includes a front port die 7 and a front core rod 8. The front port die 7 is a T-shaped structure, one end is a convex cylinder, the middle part is a tapered hollow runner with four circular threaded holes around; the tapered solid front core rod 8 is installed in the front port die 7. The micro-shaping part includes a rear gland 1, a micro head 2 with four screws on the circumference of the front end for adjusting the wall thickness, a rear core rod 5 installed in the micro head 2 and having a stepped clamping groove at the front end, and a micro port die 4 installed in the stepped clamping groove of the rear core rod 5 and externally provided with a front gland 3; the front gland 3 is connected with the micro head 2 through screws; the rear gland 1 is installed at the rear end of the micro head 2 to fix the rear end of the rear core rod 5. The middle part of the connecting piece 6 is a runner structure; the side close to the micro head 2 is provided with a convex threaded column connected with the micro head 2, and the side close to the head die part is connected with the front port die 7 through the screws passing through the circular threaded holes in the hollow runner.

[0079] In work, the dried material is added to the hopper, and the molten material is first passed through the head die part and extruded by the front port die, and then passed through the micro-shaping part for preliminary shaping and extruded by the micro port die to achieve the effect of pre-cooling shaping.

[0080] The vacuum sizing system in the extrusion system includes a vacuum sizing sleeve and a vacuum box, which is used for adjusting the outer diameter and roundness of the thin-walled pipe; as Figure 23As shown, the vacuum sizing sleeve mainly includes a fixed disc and a vacuum sleeve. The fixed disc is disc-shaped and is connected to the vacuum groove by threads. The vacuum sleeve is a cylinder with a cylindrical inner cavity in the middle.

[0081] During operation, a vacuum is drawn between the tube blank and the vacuum sizing sleeve. Under negative pressure, the tube blank fits tightly against the inner wall of the vacuum sizing sleeve to achieve the shaping effect, ensuring the stability of the outer diameter and roundness of the tube body.

[0082] The cooling and shaping system in the extrusion system includes a water pump, a chiller, and a connected cooling water tank. The cooling water tank, with a length of 4m to 6m, is selected based on the tube size. The cooling water tank is connected to a chiller that continuously circulates cooling water at constant temperature, pressure, and flow rate. Before extruding the thin-walled tube, a certain amount of purified water is added to the water tank of the cooling water tank to adjust the cooling water temperature to 10℃-15℃, with a control accuracy of ±0.05℃.

[0083] During operation, the water is cooled by the cooling system of the refrigeration unit, and then the cooling water is sent into the cooling water tank by the water pump. The tube blank is pulled into the cooling water tank, so that the tube blank is immersed in the cooling water, and the temperature of the tube blank is reduced for secondary shaping.

[0084] The ultrasonic traction closed-loop system in the extrusion system is used for secondary precision control of the dimensions of thin-walled tubes, and mainly includes a laser diameter gauge, an ultrasonic thickness gauge, and a traction controller. For example... Figure 13 The ultrasonic traction closed-loop process is shown. A laser diameter gauge is used to detect the diameter and ellipticity of the thin-walled tube in real time. When the laser beam passes through a multi-faceted scanning mirror and scanning optical system, it forms a continuous high-speed scanning beam parallel to the optical axis. This beam scans the thin-walled tube placed in the measurement area at high speed and is received by a photodetector placed opposite the tube. The light projected onto the photodetector is blocked as the beam scans the tube. By analyzing the signal output from the photodetector, the diameter data of the thin-walled tube is obtained. An ultrasonic thickness gauge is used to measure the wall thickness of the thin-walled tube and calculate its inner diameter. The ultrasonic thickness gauge is installed in a water tank with a stable water flow, close to the laser diameter gauge. An ultrasonic signal pulse is emitted from the sensor, passes through the water medium, and contacts the surface of the thin-walled tube. Part of the pulse is reflected back to the probe, and the other part is reflected back to the probe from the other side by the thickness of the thin-walled tube. By measuring the propagation time of the ultrasonic wave in the material, the thickness of the thin-walled tube is calculated. The traction controller is used to adjust the traction speed. When the size information of the thin-walled tube collected by the system deviates from the set value, the system will convert the traction signal into an analog quantity and issue a deviation signal. This signal is used to adjust the traction speed to ensure the stability of the thin-walled tube extrusion.

[0085] In operation, the outer diameter of the pipe body is measured in real time by a laser diameter gauge, and the inner diameter and wall thickness are measured by an ultrasonic thickness gauge; the traction controller compares the collected outer diameter signal with the set value, and when there is a deviation, the traction controller converts the traction signal into an analog signal and sends a deviation signal to the traction machine, which adjusts the traction speed according to the signal.

[0086] The embodiment of the preparation of the thin-walled pipe by the thin-walled pipe extrusion system in the application is as follows:

[0087] Example 1 (the wall thickness of the extruded pipe body is 0.075 mm ± 0.015 mm, and a 25# extruder is used):

[0088] S1, preparation: prepare high-temperature-resistant elastic material nylon with a Shore hardness of 63 degrees, and use a dehumidifying dryer to dry the material, the drying temperature is 95 DEG C, the drying time is 4 hours, and the moisture content of the material is ensured to be 0.01%.

[0089] S2, blanking: start the blanking system, set the blanking speed to 10 Hz, make the material uniformly enter the screw melting and stabilize the blanking process, connect the circulating cooling water at the blanking port to reduce the temperature of the blanking port and ensure smooth blanking.

[0090] S3, plasticizing: start the plasticizing and forming system, select a 25# single-screw precision extruder, use a nylon pellet special screw with a length-diameter ratio of 28:1 and an equidistant gradual change structure, set the barrel zone 1 temperature to 185 DEG C, the zone 2 temperature to 190 DEG C, the zone 3 temperature to 190 DEG C, the flange temperature to 195 DEG C, the head temperature to 190 DEG C, and the mold temperature to 185 DEG C. Set the main machine speed to 35 r / min.

[0091] S4, pressure closed loop: start the pressure closed loop system, set the melt pump temperature to 190 DEG C, and the pressure value to 35 Pa.

[0092] S5, preforming: install the front die and the front mandrel and correct the positions to make the front mandrel centered in the front die. Install the connecting piece to connect the head. Install the rear mandrel and the rear die, fix the front gland and the rear gland. Add the dried material into the barrel, and extrude the molten material through the rear die by screw pressure. According to the wall thickness uniformity of the extruded product, adjust the wall thickness screw to ensure the uniformity of the wall thickness.

[0093] S6, vacuum sizing: select an inner diameter of 2.4 mm, a sizing length of 22 mm, a vacuum hole diameter of 1.0 mm, a vacuum degree of 65 KPa, and adjust the distance between the vacuum sizing sleeve and the rear die to 25 mm, so that the pipe embryo passes through the vacuum sizing sleeve and enters the vacuum box.

[0094] S7, cooling and shaping: use a 4m cooling water tank to pull the pipe embryo into the cooling water tank, set the cooling water temperature to 10 DEG C, and control the precision to be ± 0.05 DEG C.

[0095] S8, ultrasonic traction closed-loop control: open the traction machine, set the traction speed to 18 r / min-22 r / min. After the extruder runs stably, open the ultrasonic traction closed-loop system, set the product nominal diameter (standard value 2.200 mm, upper limit value 2.215 mm, lower limit value 2.185 mm), inner diameter (standard value 2.050 mm, upper limit value 2.065 mm, lower limit value 2.035 mm), wall thickness (standard value 0.075 mm, upper limit value 0.090 mm, lower limit value 0.060 mm), ovality (standard value 0.010 mm, upper limit value 0.015 mm, lower limit value 0.005 mm), minimum linear speed 10%, control upper limit 1.1, control lower limit 0.9, control range (20%), acceleration 1.0 SCES, minimum average time 0.5 SCES, minimum failure time 0.1 SCES, correction factor 15%. Check the tube position, normal waveform, input the measured wall thickness value, and correct the wall thickness. Use the ultrasonic thickness gauge and laser diameter gauge to monitor the tube inner diameter, outer diameter, wall thickness, and ovality information in real time. When there is a deviation between the measured value and the expected set value, the system will issue a deviation signal to adjust the traction speed to ensure the stability of the tube extrusion.

[0096] S9, cutting and forming: according to the product use requirements, cut to the appropriate length to obtain a thin-walled tube, the extrusion process is stable, the thin-walled tube wall thickness is uniform and thin, randomly select 30 tubes, test 10 points on each tube, the single-sided wall thickness result is 0.070 mm-0.080 mm, which meets the expected technical requirements.

[0097] Example 2 (extruded tube wall thickness is 0.075 mm ± 0.015 mm, using a 25# extruder):

[0098] Compared with Example 1, the difference is in the following steps:

[0099] S1, material preparation: prepare high-temperature-resistant elastic material TPU with a Shore hardness of 55 degrees, use a desiccant dryer to dry the material, drying temperature 100°C, drying time 3 hours, ensure that the moisture content of the material is 0.01%.

[0100] S3, plasticization: start the plasticization molding system, select a 25# single-screw precision extruder, use a thermoplastic polyurethane pellet special screw with a length-diameter ratio of 28:1 and an equidistant gradual change structure, set the barrel zone 1 temperature to 190°C, zone 2 temperature to 195°C, zone 3 temperature to 195°C, set the flange temperature to 195°C, the head temperature to 195°C, and the mold temperature to 190°C. Set the main machine speed to 30 r / min.

[0101] S4, pressure closed loop: start the pressure closed loop system, set the melt pump temperature to 195℃, and the pressure value to 45 Pa.

[0102] S8, ultrasonic traction closed loop control: turn on the traction machine and set the traction speed to 15-19 r / min. After the extruder runs stably, turn on the ultrasonic traction closed loop system and set the product nominal diameter (standard value 2.200 mm, upper limit value 2.215 mm, lower limit value 2.185 mm), inner diameter (standard value 2.050 mm, upper limit value 2.065 mm, lower limit value 2.035 mm), wall thickness (standard value 0.075 mm, upper limit value 0.090 mm, lower limit value 0.060 mm), ovality (standard value 0.010 mm, upper limit value 0.015 mm, lower limit value 0.005 mm), minimum linear speed 10%, control upper limit 1.1, control lower limit 0.9, control range (20%), acceleration 1.0 SCES, minimum average time 0.5 SCES, minimum failure time 0.1 SCES, correction factor 15%. Check the pipe body position and wave form, input the measured wall thickness value, and correct the wall thickness. Use the ultrasonic thickness gauge and laser diameter gauge to monitor the inner diameter, outer diameter, wall thickness, and ovality information of the pipe body in real time. When there is a deviation between the measured value and the expected set value, the system will issue a deviation signal to adjust the traction speed to ensure the stability of the pipe extrusion.

[0103] S9, cutting and forming: cut to the appropriate length according to the product use requirements to obtain a thin-walled pipe. The extrusion process is stable, the thin-walled pipe wall thickness is uniform and thin, and 30 pipes are randomly selected for inspection, with 10 points randomly selected for each pipe. The single-sided wall thickness test results are 0.068-0.079 mm, which meets the expected technical requirements.

[0104] Example 3 (extruded pipe wall thickness 0.075 mm ± 0.015 mm, using a 25# extruder):

[0105] The difference between this example and Example 1 is in the following steps:

[0106] S1, preparation: prepare high-temperature-resistant elastic material polyvinyl chloride with a Shore hardness of 40 degrees, which does not need to be dried.

[0107] S3, plasticization: start the plasticization forming system, select a 25# single screw precision extruder, use a polyvinyl chloride pellet special screw with a length-diameter ratio of 28:1 and an equidistant gradual change structure, set the barrel zone 1 temperature to 160℃, zone 2 temperature to 170℃, zone 3 temperature to 180℃, set the flange temperature to 175℃, the head temperature to 165℃, and the mold temperature to 170℃. Set the main machine speed to 30 r / min.

[0108] S4, pressure closed loop: start the pressure closed loop system, set the melt pump temperature to 180°C, and the pressure value to 55 Pa.

[0109] S8, ultrasonic traction closed loop control: turn on the traction machine and set the traction speed to 18-22 r / min. After the extruder runs stably, turn on the ultrasonic traction closed loop system and set the product nominal diameter (standard value 2.200 mm, upper limit value 2.215 mm, lower limit value 2.185 mm), inner diameter (standard value 2.050 mm, upper limit value 2.065 mm, lower limit value 2.035 mm), wall thickness (standard value 0.075 mm, upper limit value 0.090 mm, lower limit value 0.060 mm), ovality (standard value 0.010 mm, upper limit value 0.015 mm, lower limit value 0.005 mm), minimum linear speed 10%, control upper limit 1.1, control lower limit 0.9, control range (20%), acceleration 1.0 SCES, minimum average time 0.5 SCES, minimum failure time 0.1 SCES, correction factor 15%. Check the tube position and wave form, input the measured wall thickness value, and correct the wall thickness. Use the ultrasonic thickness gauge and laser diameter gauge to monitor the tube inner diameter, outer diameter, wall thickness, and ovality information in real time. When there is a deviation between the measured value and the expected set value, the system will issue a deviation signal to adjust the traction speed to ensure the stability of the tube extrusion.

[0110] S9, cutting and forming: cut to the appropriate length according to the product use requirements to obtain a thin-walled tube. The extrusion process is stable, the thin-walled tube wall thickness is uniform and thin, and 30 tubes are randomly selected for inspection, with 10 points randomly selected for each tube. The single-sided wall thickness test results are 0.072-0.081 mm, which meets the expected technical requirements.

[0111] Example 4 (extruding a developing tube with a wall thickness of 0.075 mm ± 0.015 mm using a 25# extruder):

[0112] The differences between this example and Example 1 are as follows:

[0113] S1, preparation: prepare a high-temperature-resistant elastic material nylon with a Shore hardness of 63 degrees and containing 25% barium sulfate developer. Use a desiccant dryer to dry the material, with a drying temperature of 95°C and a drying time of 4 hours to ensure that the moisture content of the material is 0.01%.

[0114] Example 5 (extruding a developing tube with a wall thickness of 0.075 mm ± 0.015 mm using a 25# extruder):

[0115] The differences between this example and Example 1 are as follows:

[0116] S1, material preparation: prepare a high-temperature-resistant elastic material nylon with a Shore hardness of 35 degrees and containing 40% bismuth oxychloride developer, use a desiccant dryer to dry the material, drying temperature 95°C, drying time 4 hours, ensure that the moisture content of the material is 0.01%.

[0117] S3, plasticization: start the plasticization molding system, select a 25# single screw precision extruder, use a nylon pellet special screw with a length-diameter ratio of 28:1 and an equidistant gradual change structure, set the barrel zone 1 temperature to 170°C, zone 2 temperature to 175°C, zone 3 temperature to 180°C, set the flange temperature to 175°C, the head temperature to 170°C, and the mold temperature to 170°C. Set the main machine speed to 30r / min.

[0118] S4, pressure closed loop: start the pressure closed loop system, set the melt pump temperature to 175°C and the pressure value to 30Pa.

[0119] Example 6 (extrusion developing tube wall thickness 0.075mmm±0.015mm, using 25# extruder):

[0120] The difference between this example and example 2 is as follows:

[0121] S1, material preparation: prepare a high-temperature-resistant elastic material TPU with a Shore hardness of 55 degrees and containing 30% barium sulfate developer. Use a desiccant dryer to dry the material, drying temperature 100°C, drying time 3 hours, ensure that the moisture content of the material is 0.01%.

[0122] Example 7 (extrusion developing tube wall thickness 0.075mmm±0.015mm, using 25# extruder):

[0123] The difference between this example and example 2 is as follows:

[0124] S1, material preparation: prepare a high-temperature-resistant elastic material TPU with a Shore hardness of 30 degrees and containing 50% tungsten developer, use a desiccant dryer to dry the material, drying temperature 100°C, drying time 3 hours, ensure that the moisture content of the material is 0.01%.

[0125] S3, plasticization: start the plasticization molding system, select a 25# single screw precision extruder, use a thermoplastic polyurethane pellet special screw with a length-diameter ratio of 28:1 and an equidistant gradual change structure, set the barrel zone 1 temperature to 180°C, zone 2 temperature to 190°C, zone 3 temperature to 195°C, set the flange temperature to 190°C, the head temperature to 190°C, and the mold temperature to 180°C. Set the main machine speed to 25r / min.

[0126] S4, pressure closed loop: start the pressure closed loop system, set the melt pump temperature to 190°C, and the pressure value to 40 Pa.

[0127] Comparative Example (extrusion pipe wall thickness of 0.075 mm ± 0.015 mm, using a 25# extruder):

[0128] S1, preparation: prepare high-temperature-resistant elastic material nylon with a Shore hardness of 63 degrees, use a desiccant dryer to dry the material, the drying temperature is 95°C, and the drying time is 4 hours.

[0129] S2, blanking: start the forced blanking device, and set the blanking speed to 10 Hz.

[0130] S3, plasticization: start the plasticization molding system, select a 25# single-screw precision extruder, use a nylon pellet special screw with a length-diameter ratio of 28:1 and an equidistant gradual change structure, set the barrel zone 1 temperature to 185°C, zone 2 temperature to 190°C, and zone 3 temperature to 190°C, set the flange temperature to 195°C, the head temperature to 190°C, and the mold temperature to 185°C. Set the main machine speed to 35 r / min.

[0131] S5, extrusion: install a die and a mandrel suitable for the size of the pipe body and correct the position of the die and the mandrel. Add the dried material to the barrel, and extrude the molten material through the die by screw pressure.

[0132] S6, vacuum sizing: select an inner diameter of 2.4 mm, a sizing length of 22 mm, a vacuum hole diameter of 1.5 mm, a vacuum degree of 65 KPa, and adjust the distance between the vacuum sizing sleeve and the rear die to 25 mm, so that the pipe embryo passes through the vacuum sizing sleeve and enters the vacuum box.

[0133] S7, cooling and shaping: pull the pipe body into a cooling water tank, and the cooling water temperature is 10°C.

[0134] S8, traction machine traction: turn on the traction machine and set the traction speed to 18-22 r / min.

[0135] S9, cutting and shaping: cut to the appropriate length according to the product use requirements to obtain a thin-walled pipe. The thin-walled pipe has the phenomena of wall thickness deviation and size instability. Randomly select 30 pipes, and test 10 points on each pipe. The single-sided wall thickness is 0.085-0.114 mm, which does not meet the expected technical requirements.

[0136] Comparative results: all examples use pre-shaping devices and ultrasonic traction closed loop systems for extrusion, as shown in the four-probe result diagram of the pipe body position in the ultrasonic traction closed loop system. In addition, the online wall thickness monitoring and online ovality monitoring during the extrusion process of Examples 1-3 are shown in Figure 21 Figures 14-19 ​The wall thickness of the pipe body is 0.070mm-0.080mm, 0.068mm-0.079mm, 0.072mm-0.081mm, 0.068mm-0.081mm, 0.074mm-0.083mm, 0.072mm-0.080mm, and 0.070mm-0.082mm, and the standard deviation is 0.00295, 0.00344, 0.00292, 0.00363, 0.00247, 0.00229, and 0.00380, respectively. The pipe body is thin and has good consistency, the extrusion process is stable, meets the expected technical requirements, and the cross section of the pipe body of the thin-walled pipe is shown in Figure 22 The wall thickness of the pipe body is 0.070mm-0.080mm, 0.068mm-0.079mm, 0.072mm-0.081mm, 0.068mm-0.081mm, 0.074mm-0.083mm, 0.072mm-0.080mm, and 0.070mm-0.082mm, and the standard deviation is 0.00295, 0.00344, 0.00292, 0.00363, 0.00247, 0.00229, and 0.00380, respectively. The pipe body is thin and has good consistency, the extrusion process is stable, meets the expected technical requirements, and the cross section of the pipe body of the thin-walled pipe is shown in Figure 20 The wall thickness of the pipe body is 0.070mm-0.080mm, 0.068mm-0.079mm, 0.072mm-0.081mm, 0.068mm-0.081mm, 0.074mm-0.083mm, 0.072mm-0.080mm, and 0.070mm-0.082mm, and the standard deviation is 0.00295, 0.00344, 0.00292, 0.00363, 0.00247, 0.00229, and 0.00380, respectively. The pipe body is thin and has good consistency, the extrusion process is stable, meets the expected technical requirements, and the cross section of the pipe body of the thin-walled pipe is shown in

[0137] The wall thickness of the pipe body is 0.070mm-0.080mm, 0.068mm-0.079mm, 0.072mm-0.081mm, 0.068mm-0.081mm, 0.074mm-0.083mm, 0.072mm-0.080mm, and 0.070mm-0.082mm, and the standard deviation is 0.00295, 0.00344, 0.00292, 0.00363, 0.00247, 0.00229, and 0.00380, respectively. The pipe body is thin and has good consistency, the extrusion process is stable, meets the expected technical requirements, and the cross section of the pipe body of the thin-walled pipe is shown in

[0138] Case Maximum wall thickness / mm Minimum wall thickness / mm Average wall thickness / mm Standard deviation Example 1 0.080 0.070 0.075 0.00295 Example 2 0.079 0.068 0.074 0.00344 Example 3 0.081 0.072 0.076 0.00292 Example 4 0.081 0.068 0.075 0.00363 Example 5 0.083 0.074 0.078 0.00247 Example 6 0.08 0.072 0.077 0.00229 Example 7 0.082 0.07 0.077 0.00380 Comparative Example 0.114 0.085 0.100 0.00869

[0139] The above description of disclosed embodiments enables one skilled in the art to make or use the present application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein can be applied to other embodiments without departing from the spirit or scope of the application. Thus, the present application is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A thin-walled tube extrusion system, comprising a material preparation system, a feeding system, a plasticizing and molding system, a vacuum sizing system, a cooling and molding system, and a cutting and molding system, characterized in that, It also includes a pressure closed-loop system, a pre-designed system, and an ultrasonic traction closed-loop system, among which, The pressure closed-loop system is used for the initial precision control of the thin-walled tube body size. It mainly includes a melt pump for conveying materials, a pressure sensor, and a pressure controller. The output pressure parameters of the molten granules are input into the memory of the pressure controller. When the molten granules in the extruder barrel pass through the melt pump, the pressure sensor collects the pressure input information in real time, and the pressure controller automatically adjusts the screw speed of the extruder according to its changes. The pre-forming system is used for pre-cooling and shaping of thin-walled tubes. It mainly includes a pre-forming device, which includes a die head mold part, a micro-shaping part, and a connector (6). The die head mold part includes a front die (7) and a front mandrel (8). The micro-shaping part has four screws on the front circumference for adjusting the wall thickness of the micro die head (2). The connector (6) has a flow channel structure in the middle. The two ends of the connector (6) are connected to the die head mold part and the micro-shaping part by threads to form a whole. The ultrasonic traction closed-loop system is used for secondary precision control of the dimensions of thin-walled tubes, and mainly includes a laser diameter gauge, an ultrasonic thickness gauge, and a traction controller.

2. The thin-walled tube extrusion system according to claim 1, characterized in that, The front mold (7) of the machine head mold part in the pre-formed device has a T-shaped structure, with one end being a protruding cylinder and the middle part being a conical hollow flow channel with four circular threaded holes around it; the conical solid front mandrel (8) is installed inside the front mold (7).

3. The thin-walled tube extrusion system according to claim 1, characterized in that, The micro-shaping part of the pre-shaping device includes a rear pressure cover (1), a micro head (2) with four screws on the front circumference for adjusting the wall thickness, a rear mandrel (5) installed in the micro head (2) and having a stepped groove at the front end, and a micro die (4) installed in the stepped groove of the rear mandrel (5) and having a front pressure cover (3) on the outside; the front pressure cover (3) is connected to the micro head (2) by screws; the rear pressure cover (1) is installed at the rear end of the micro head (2) to fix the rear end of the rear mandrel (5).

4. The thin-walled tube extrusion system according to claim 1, characterized in that, The pre-designed device has a protruding threaded post on the side of the connector (6) near the micro head (2) that is connected to the micro head (2), and the side near the head mold part is connected to the front mold (7) by a screw passing through the circular threaded hole on the hollow flow channel.

5. A thin-walled tube extrusion system according to claim 1, characterized in that, The vacuum sizing system includes a vacuum sizing sleeve and a vacuum chamber, used for adjusting the outer diameter and roundness of thin-walled tubes; the vacuum sizing sleeve mainly includes a fixed plate and a vacuum sleeve, the fixed plate is disc-shaped and connected to the vacuum groove by threads; the vacuum sleeve is a cylinder with a cylindrical inner cavity in the middle.

6. The thin-walled tube extrusion system according to claim 1, characterized in that, The cooling and shaping system includes a water pump, a refrigeration unit, and a cooling water tank connected to them. Before the thin-walled tube is extruded, a certain amount of purified water is added to the water tank of the cooling water tank, and the cooling water temperature is adjusted to 10℃-15℃ with a control accuracy of ±0.05℃. The water is cooled by the cooling system of the refrigeration unit, and then the water pump sends the cooling water into the cooling water tank. The tube blank is drawn into the cooling water tank, so that the tube blank is immersed in the cooling water, and the temperature of the tube blank is reduced for secondary shaping.

7. A method for preparing thin-walled tubes using the thin-walled tube extrusion system according to any one of claims 1-6, characterized in that, The main steps include: S1, Material preparation: Select appropriate materials according to the application of the thin-walled tube; start the material preparation system, and use the materials directly or after drying and pretreatment for later use; S2, feeding: Add the material obtained in step S1 into the feeding system, start the feeding system, adjust the feeding system parameters to make the material enter the screw melt evenly and stabilize the feeding process, connect the circulating cooling water at the feeding port to reduce the temperature of the feeding port and ensure smooth feeding; S3, Plasticizing: Start the plasticizing and molding system, select a precision extruder suitable for the tube size, select a suitable screw according to the material properties, set the temperature of each zone of the barrel and the flange temperature to 140℃-230℃, and set the main machine speed to 20r / min-40r / min to fully plasticize the material. S4, Pressure Closed Loop: Start the pressure closed loop system, set the melt pump temperature to 140℃-230℃ and the pressure parameters to 30Pa-55Pa, so that the material plasticized by S3 is output evenly. S5, Pre-forming: Start the pre-forming system so that the material melted in step S4 first passes through the die head mold part and is extruded from the front die (7), and then passes through the micro-forming part for preliminary shaping and is extruded from the micro die (4) to achieve the effect of pre-cooling and shaping; S6, Vacuum sizing: Start the vacuum sizing system, select a water-immersed vacuum sizing sleeve suitable for the tube size, the vacuum sleeve is set along the tube axis, and the circumference is provided with uniform vacuum holes with a diameter of 1.0mm-1.5mm; the vacuum sleeve is a cylinder with a cylindrical inner cavity in the middle, the size of the cylindrical inner cavity is 0.05-0.08mm larger than the outer diameter of the tube, and the length is 8-10 times the outer diameter of the tube; the tube blank enters the vacuum box through the vacuum sizing sleeve, the vacuum degree of the vacuum box is adjusted to 50KPa-70KPa, and the distance between the vacuum sizing sleeve and the micro die (4) is adjusted to 20mm-30mm; the outer diameter and roundness of the thin-walled tube are adjusted; S7, Cooling and Shaping: Select a cooling water tank with a length of 4m-6m according to the tube size, start the cooling and shaping system, set the system parameters, and perform secondary cooling and shaping on the thin-walled tube blank; S8, Ultrasonic traction closed-loop control: Turn on the traction machine, set the traction speed according to the product size and extrusion speed, and turn on the ultrasonic traction closed-loop control system after the extrusion is stable. S9, Cutting and Forming: Start the cutting and forming system, use a ring cutter to cut to an appropriate length according to the product requirements, and prepare a thin-walled tube.

8. The method for preparing a thin-walled tube according to claim 7, characterized in that, The material in step S1 includes an elastic polymer material or a mixture of an elastic polymer material and a developer; the elastic polymer material includes any one of polyurethane, nylon, and polyvinyl chloride with a hardness in the range of Shore 25 to 75 degrees; the developer includes any one of barium sulfate, bismuth oxychloride, and tungsten; the developer content in the mixture is 25%-50% by weight.

9. The method for preparing a thin-walled tube according to claim 7, characterized in that, The material pretreatment process described in step S1 is as follows: the material is dried using a dehumidifying dryer equipped with a rotary device, the drying temperature is set to 80℃-110℃, the drying time is 4-6 hours, and the dew point is monitored to be below -40℃; the moisture content in the dried material is below 0.02%.

10. The method for preparing a thin-walled tube according to claim 7, characterized in that, The feeding system described in step S2 includes a forced feeding device. The hopper of the feeding device is equipped with a rotating shaft support structure, welded with spiral blades, and has a built-in frequency converter; the feeding speed is adjusted to 10Hz-15Hz.

11. The method for preparing a thin-walled tube according to any one of claims 8-10, characterized in that, Step S8, the ultrasonic traction closed-loop control process, specifically includes the following steps: S81, turn on the traction machine, set the traction speed, and turn on the traction ultrasonic closed-loop system; S82, Set product dimensions and parameters: Set product dimension standard values, upper and lower limits, linear speed, control upper and lower limits, control range, data acquisition information, and correction factor; S83, Pipe position inspection: Install an ultrasonic thickness gauge in a place where the water flow is relatively stable and close to the laser diameter gauge in the water tank. It has 4 evenly distributed sensor probes around its circumference, which are used to detect the pipe wall thickness and inner diameter. Pass the pipe through the ultrasonic thickness gauge and center it. At this time, the detection numbers of all 4 probes will be displayed on the screen. S84, Waveform Check: Check if all 4 sensors have 2 peak waveforms; if the measurement, product, and trigger items all display data, it is considered normal. S85, Correct wall thickness: Measure the actual wall thickness of the tube, compare it with the data displayed on the electronic display, and if there is a deviation, input the actual measured wall thickness value to correct the wall thickness data; S86, Closed-loop extrusion: Real-time correction and adjustment of traction speed. The laser detection probe measures the outer diameter of the tube in real time. Combined with the inner diameter and wall thickness measured by the ultrasonic detection probe, the traction controller compares the acquired outer diameter signal with the set value. When there is a deviation, the traction controller converts the traction signal into an analog quantity and sends a deviation signal to the traction machine. The traction machine uses this signal to adjust the traction speed.

12. A thin-walled tube prepared using the method for preparing thin-walled tubes according to claim 11, characterized in that: The wall thickness on one side is 0.075mm ± 0.015mm; including any one of the following: guiding catheter, microcatheter, or biliary stent sheath.

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