A multi-material seamless material switching adaptive extrusion system and method

Abstract

This invention belongs to the field of additive manufacturing and 3D printing technology, and specifically relates to a multi-material seamless switching adaptive extrusion system and method. It includes a multi-path material supply unit, a main extrusion channel, and a main extrusion nozzle, as well as a multi-path switching valve body, a bypass circulation channel, an in-situ rheological sensing module, an active temperature control sleeve, and a controller. The multi-path material supply unit stores multiple printing materials and outputs material via an external proportional air valve driven by air pressure. Its output end is connected one-to-one with each input end of the multi-path switching valve body. This invention can achieve seamless switching of heterogeneous materials within 50ms, with a clear interface and no obvious mixing. Through full-volume in-situ rheological sensing and dual-loop adaptive adjustment of air pressure and temperature, it effectively improves the consistency of printed linewidth and interlayer bond strength, while avoiding filler sedimentation and ensuring the stability of printed part performance.

Description

Technical Field

[0001] This invention belongs to the field of additive manufacturing and 3D printing technology, and in particular relates to a multi-material seamless material switching adaptive extrusion system and method. Background Technology

[0002] Direct-write 3D printing, an additive manufacturing technology based on extrusion principles, boasts advantages such as wide material adaptability, low equipment cost, and ease of operation. It can cover a broad range of material systems, from low-viscosity hydrogels to high-viscosity composite materials, and has irreplaceable application value in fields such as soft robot manufacturing, flexible electronic device fabrication, and multi-material tissue engineering scaffold construction. With the continuous growth in demand for integrated molding of heterogeneous materials in high-end manufacturing, multi-material direct-write 3D printing has become one of the core development directions in the additive manufacturing field.

[0003] However, existing multi-material direct-write 3D printing technologies still have key technical shortcomings: existing solutions typically use independent extrusion of multiple nozzles, Y-shaped confluence channels, or valve-controlled switching channels to achieve material switching. Before switching, non-printing materials are prone to being in a static or low-flow state, resulting in slow material switching response (200ms~2s) and wide interface transition areas. At the same time, existing solutions mostly rely on preset pressure or offline rheological parameters for extrusion control, making it difficult to compensate for rheological drift caused by factors such as temperature fluctuations and filler settling in real time, which in turn leads to defects such as uneven printing linewidth, fluctuations in interlayer bond strength, and uneven material composition.

[0004] To address these issues, we propose a multi-material seamless material switching adaptive extrusion system and method. Summary of the Invention

[0005] The purpose of this invention is to address the above-mentioned problems by providing a multi-material seamless material switching adaptive extrusion system and method.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: a multi-material seamless material switching adaptive extrusion system, including a multi-path material supply unit, an extrusion main channel and a main extrusion nozzle, and also including a multi-path switching valve body, a bypass circulation channel, an in-situ rheological sensing module, an active temperature control sleeve and a controller;

[0007] The multi-channel material supply unit is used to store various printing materials and outputs materials by air pressure through an external air pressure proportional valve. Its discharge end is connected to each input end of the multi-channel switching valve body.

[0008] The output end of the multi-channel switching valve body is connected to the main extrusion channel and is driven by a servo drive motor to switch the material path.

[0009] One end of the bypass circulation channel is connected to the bypass return ends of each of the multi-way switching valve bodies, and the other end is connected to the return end of the multi-way material supply unit, forming a closed loop for continuous internal circulation of non-printing materials.

[0010] The in-situ rheological sensing module is integrated into the main extrusion channel and is located between the discharge end of the multi-channel switching valve body and the main extrusion nozzle. It is used to collect pressure drop data of the printing material flowing through it in real time.

[0011] The active temperature control sleeve is installed on the multi-channel material supply unit and is used to regulate the temperature of the printing material stored inside it;

[0012] The controller is electrically connected to the servo drive motor, the in-situ rheological sensing module, the active temperature control sleeve, and the pressure proportional valve.

[0013] In the aforementioned multi-material seamless material changing adaptive extrusion system, the multi-path material supply unit includes at least two storage tanks and a material cylinder frame, wherein the storage tanks are fixed on the material cylinder frame;

[0014] The top of the storage tank is provided with a pneumatic interface connected to a pneumatic proportional valve, and the side wall of the storage tank is provided with a return interface connected to a bypass circulation channel. The storage tank is made of stainless steel and the inner wall is mirror polished.

[0015] The number of active temperature control sleeves is the same as the number of storage tanks, and the active temperature control sleeves are wrapped around the outer wall of the storage tanks one by one.

[0016] In the above-mentioned multi-material seamless material switching adaptive extrusion system, each input end of the multi-way switching valve body is provided with a feed port, the output end is provided with a discharge port, and each bypass return end is provided with a bypass return port.

[0017] The number of feed inlets and bypass return outlets is the same as the number of storage tanks. The feed inlets are connected to the discharge end of the corresponding storage tank through a conveying pipeline. The discharge outlets are connected to the main extrusion channel. The bypass return outlets are connected to the return end of the corresponding storage tank through a bypass circulation channel.

[0018] When there are two storage tanks, the multi-way switching valve body is a two-position five-way rotary slide valve, and its valve core is made of wear-resistant polytetrafluoroethylene material.

[0019] In the aforementioned multi-material seamless feeder adaptive extrusion system, the bypass circulation channel is made of polytetrafluoroethylene tubing with an inner diameter of 1.5 mm and a length of 80–120 mm.

[0020] In the aforementioned multi-material seamless feed-changing adaptive extrusion system, the in-situ rheological sensing module includes a fixed plate, a flow channel body, a micro-slit structure, and two microelectromechanical system pressure sensors.

[0021] The main body of the flow channel is fixedly installed on the fixed plate. The internal flow channel of the main body of the flow channel forms a section of the main extrusion channel. Its inlet is connected to the discharge port of the multi-way switching valve body, and its outlet is connected to the main extrusion nozzle.

[0022] The microslit structure is disposed in the internal flow channel of the main body of the flow channel. The two microelectromechanical system pressure sensors are respectively installed at the two ends of the microslit structure of the main body of the flow channel, and the sensing surface of the microelectromechanical system pressure sensor is flush with the inner wall of the main body of the flow channel.

[0023] The width of the microslit structure is 0.1–0.5 mm, the depth is 1–5 mm, and the length is 5–20 mm.

[0024] In the aforementioned multi-material seamless material exchange adaptive extrusion system, the microelectromechanical system pressure sensor has a measurement range of 300–1200 hPa, a resolution of 0.01 hPa, and a sampling rate of ≥200 Hz. The active temperature control sleeve uses a thermoelectric cooling semiconductor component, with a temperature control range of 15℃–80℃, a temperature control accuracy of ±0.5℃, and a response time of less than 2 seconds. Its inner wall is equipped with a PT1000 platinum resistance temperature sensor.

[0025] The controller is configured to calculate the dynamic viscosity of the material based on the pressure drop data, and adjust the extrusion pressure through the air pressure proportional valve and adjust the material temperature through the active temperature control sleeve according to the viscosity.

[0026] A multi-material seamless switching adaptive extrusion method, comprising the following steps:

[0027] S1, Dynamic Pressure Retention Bypass Circulation: During the printing process, the material in the non-printing state continuously circulates internally between the storage tank and the multi-way switching valve body through the bypass circulation channel. The circulation pressure is set to 60% to 80% of the printing pressure, and the circulation flow rate is controlled to be 0.5 to 2 mL / min.

[0028] S2, In-situ Rheological Sensing: When the printed material flows through the micro-slit structure of the in-situ rheological sensing module, two microelectromechanical system pressure sensors measure the pressure drop ΔP at both ends of the micro-slit structure in real time. The controller calculates the dynamic viscosity η of the fluid in real time according to the Hagen-Poiseuille law ΔP=12ηQL / (wh³), where Q is the extrusion flow rate, and L, w, and h are the length, width, and depth of the micro-slit, respectively.

[0029] S3, Dual-loop adaptive regulation of air pressure and temperature: The controller first continuously collects dynamic viscosity for 5 seconds during the stable extrusion stage of the material, calculates the average value as the dynamic viscosity reference value, and then adjusts based on the dynamic viscosity η calculated in real time, using the dynamic viscosity reference value as the basis. It constructs an air pressure regulation loop through an air pressure proportional valve and a temperature regulation loop through an active temperature control sleeve. The two regulation loops work together to correct the extrusion pressure and material temperature parameters. The air pressure regulation loop responds to and corrects high-frequency viscosity fluctuations with a frequency >1Hz, with a response time <10ms. The temperature regulation loop responds to and corrects low-frequency viscosity drift with a frequency <0.1Hz, with a temperature control accuracy of ±0.5℃.

[0030] S4, Seamless Material Switching: When the controller receives a material switching command, it controls the servo drive motor of the multi-channel switching valve body to drive the valve core to rotate, switching the flow direction of the material to be switched from the bypass circulation channel to the extrusion main channel, thus completing the material switching.

[0031] In the above-mentioned multi-material seamless switching adaptive extrusion method, the material switching in step S4 specifically includes the following sub-steps:

[0032] S41, Pre-compression stage: During the printing of the current material, the material to be switched continuously circulates in the bypass circulation channel. The controller determines the target printing pressure of the material to be switched at the target extrusion flow rate based on the preset rheological parameters of the material to be switched, the bypass circulation flow rate, and the pre-calibrated viscosity-pressure correspondence, and adjusts its circulation pressure to 90% to 100% of the target printing pressure.

[0033] S42, Instantaneous Pulse: 50ms before the switching command is officially issued, the controller outputs a short-term control command to the proportional valve of the material path to be switched, causing its output pressure to rise briefly to form a high-pressure pulse. The pressure amplitude of the high-pressure pulse is 110% to 120% of the target printing pressure determined in step S41, and its duration is 20 to 30ms. At the same time, the controller outputs a control command to the proportional valve of the current printing material path, causing its bypass circuit pressure to drop briefly to form a negative pressure pulse. The pressure amplitude of the negative pressure pulse is 5% to 10% of the current material printing pressure, and its duration is 20 to 30ms.

[0034] S43, Physical Channel Change: The servo drive motor drives the rotary slide valve core of the multi-way switching valve body to rotate, switching the flow direction of the material to be switched from the bypass to the main extrusion channel. The mechanical action time is 20-30ms.

[0035] S44, Seamless Transition and Adaptive Adjustment: After the switch is completed, the in-situ rheological sensing module monitors the viscosity of the new material entering the main extrusion channel in real time. The air pressure regulating ring and temperature regulating ring start compensation adjustment to make the extrusion flow rate reach a stable state within 100ms with a deviation of no more than ±5% from the target extrusion flow rate.

[0036] In the above-mentioned multi-material seamless material exchange adaptive extrusion method, in step S3, when the sudden change in the current dynamic viscosity relative to the dynamic viscosity reference value exceeds ±15%, the air pressure regulating ring immediately adjusts the output pressure of the air pressure proportional valve for compensation. When the current dynamic viscosity is detected to deviate from the dynamic viscosity reference value for more than 30 seconds by more than ±10%, the temperature regulating ring activates the active temperature control sleeve to regulate the temperature.

[0037] Compared with existing technologies, the advantages of a multi-material seamless material-changing adaptive extrusion system and method are as follows:

[0038] 1. By setting up a dynamic pressure retention bypass circulation loop, non-printing materials can be kept in a continuous internal circulation state between the valve body and the storage tank. This reduces the delay in starting pressure establishment caused by the static material in traditional solutions and shortens the material switching time from 200ms to 2s to less than 50ms. This helps to reduce the mixing area at the junction of different materials and makes the boundaries of multi-material interfaces clearer and more regular.

[0039] 2. By setting up an in-situ rheological sensing module and a dual-loop adaptive adjustment system for air pressure and temperature, the printing material can flow through the in-situ rheological sensing module in its entirety, enabling full-flow online viscosity detection. At the same time, the air pressure adjustment loop compensates for high-frequency viscosity fluctuations, and the temperature adjustment loop corrects low-frequency viscosity drift, effectively reducing the adverse effects of temperature fluctuations, filler agglomeration, and other factors on the uniformity of printed linewidth and the stability of interlayer bond strength.

[0040] 3. By setting up a closed bypass internal circulation loop, the non-printing material is in a shear flow state, which can reduce the filler sedimentation and component stratification caused by static placement of the composite printing material containing filler, improve the consistency of the extruded material composition, and reduce the fluctuation range of properties such as conductivity and mechanical strength of the printed parts. Attached Figure Description

[0041] Fig. 1 This is a schematic diagram of the structure of a multi-material seamless material switching adaptive extrusion system provided by the present invention;

[0042] Fig. 2 This is a schematic diagram of the multi-channel switching valve body structure of a multi-material seamless material changing adaptive extrusion system provided by the present invention;

[0043] Fig. 3 This is a schematic diagram of the in-situ rheological sensing module structure of a multi-material seamless material changing adaptive extrusion system provided by the present invention.

[0044] In the diagram: 1. Storage tank, 2. Multi-channel switching valve body, 3. Servo drive motor, 4. Inlet, 5. Outlet, 6. Bypass return port, 7. Fixing plate, 8. Micro-slit structure, 9. Microelectromechanical system pressure sensor, 10. Active temperature control sleeve, 11. Material cylinder frame. Detailed Implementation

[0045] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0046] like Figs. 1-3 As shown, a multi-material seamless material switching adaptive extrusion system includes a multi-path material supply unit, an extrusion main channel and a main extrusion nozzle, as well as a multi-path switching valve body 2, a bypass circulation channel, an in-situ rheological sensing module, an active temperature control sleeve 10 and a controller.

[0047] The multi-channel material supply unit is used to store various printing materials. It outputs materials by air pressure through an external air pressure proportional valve. Its discharge end is connected to each input end of the multi-channel switching valve body 2. The multi-channel material supply unit includes at least two storage tanks 1 and a material cylinder rack 11. The storage tank 1 is fixed on the material cylinder rack 11. The top of the storage tank 1 is provided with an air pressure interface connected to the air pressure proportional valve, and the side wall of the storage tank 1 is provided with a return interface connected to the bypass circulation channel. The storage tank 1 is made of stainless steel and the inner wall is mirror polished. By setting the stainless steel storage tank 1 with a mirror polished inner wall, the stainless steel material has excellent mechanical strength and chemical corrosion resistance, which can be adapted to printing materials with different chemical properties. The mirror polished inner wall can reduce material adhesion and residue, reduce the risk of material forming and solidifying on the tank wall, and facilitate the cleaning and maintenance of the storage tank 1, effectively reducing the risk of cross-contamination between different batches and different types of materials.

[0048] The output end of the multi-way switching valve body 2 is connected to the main extrusion channel and is driven by the servo drive motor 3 to switch the material path. Each input end of the multi-way switching valve body 2 is equipped with a feed port 4, and the output end is equipped with a discharge port 5. Each bypass return end is equipped with a bypass return port 6. The number of feed ports 4 and bypass return ports 6 is the same as the number of storage tanks 1. The feed port 4 is connected to the discharge end of the corresponding storage tank 1 through a conveying pipeline. The discharge port 5 is connected to the main extrusion channel. The bypass return port 6 is connected to the return end of the corresponding storage tank 1 through a bypass circulation channel. When there are two storage tanks 1, the multi-way switching... The valve body 2 is a two-position five-way rotary spool valve. Its valve core is made of wear-resistant polytetrafluoroethylene (PTFE). By setting up a multi-way switching valve body 2 driven by a servo drive motor 3, the rotation of the valve core and the switching sequence can be controlled to meet the speed and positioning requirements of material channel switching, providing a basis for rapid material switching. The use of wear-resistant PTFE valve core can ensure the sealing effect between the valve body and the valve core, reduce the frictional resistance of the valve core rotation, and reduce material residue due to the chemical inertness of PTFE, which helps to extend the service life of the valve body and reduce the risk of cross-contamination between different materials.

[0049] One end of the bypass circulation channel is connected to the bypass return ends of each of the multi-way switching valve body 2, and the other end is connected to the return end of the multi-way material supply unit, forming a closed loop for continuous internal circulation of non-printing materials. The bypass circulation channel is connected one-to-one with the bypass return port 6 of the multi-way switching valve body 2 and the return interface on the side wall of each storage tank 1. The bypass circulation channel uses polytetrafluoroethylene (PTFE) tubing with an inner diameter of 1.5 mm and a length of 80-120 mm. By using PTFE tubing of the above dimensions to construct the bypass circulation channel and form a closed internal circulation loop, the non-printing material can be kept in a shear flow state, suppressing fluid thickening due to static stagnation and eliminating the delay in start-up pressure establishment caused by material static stagnation. This pipeline size can control the circulation flow rate and the shear rate inside the pipe within a reasonable range. While suppressing filler sedimentation through continuous shearing, it also takes into account pipeline pressure drop loss. At the same time, PTFE tubing has the characteristics of chemical corrosion resistance and low material adhesion, and can be used with various printing materials such as water-based, oil-based and filler-based materials.

[0050] The in-situ rheological sensing module is integrated into the main extrusion channel, located between the discharge end of the multi-way switching valve body 2 and the main extrusion nozzle. It is used to collect real-time pressure drop data of the printing material flowing through it. The in-situ rheological sensing module includes a fixed plate 7, a flow channel body, a micro-slit structure 8, and two microelectromechanical system (MEMS) pressure sensors 9. The flow channel body is fixedly mounted on the fixed plate 7. The internal flow channels of the flow channel body form a section of the main extrusion channel. Its inlet connects to the discharge port 5 of the multi-way switching valve body 2, and its outlet connects to the main extrusion nozzle. The micro-slit structure 8 is located within the flow channel body. Inside the internal flow channel, two microelectromechanical system (MEMS) pressure sensors 9 are respectively installed at both ends of the microslit structure 8 corresponding to the main body of the flow channel. The sensing surfaces of the MEMS pressure sensors 9 are flush with the inner wall of the main body of the flow channel. The two MEMS pressure sensors 9 are respectively located at the upstream and downstream ends of the microslit structure 8. The flush installation of the sensing surfaces with the inner wall of the flow channel avoids disturbance to the local flow field caused by protrusions or depressions of the sensing surfaces, ensuring the accuracy of pressure acquisition. By detecting the pressure before and after the slit, pressure difference data is obtained, providing parameter basis for dynamic viscosity calculation.

[0051] The microslit structure 8 has a width of 0.1–0.5 mm, a depth of 1–5 mm, and a length of 5–20 mm. By setting the microslit structure 8 with the above dimensions, the geometric parameters optimized based on the Hagen-Poiseuille law can generate a measurable pressure drop, which is convenient for measurement by the microelectromechanical system pressure sensor 9. It can also reduce the risk of flow channel blockage of high-viscosity materials. At the same time, it can match the shear rate of the fluid when passing through the slit with the shear rate when the nozzle is extruded, so that the detected viscosity data can reflect the actual extrusion state of the material.

[0052] The measurement range of the MEMS pressure sensor 9 is 300–1200 hPa, the resolution is 0.01 hPa, and the sampling rate is ≥200 Hz. By setting the above measurement range, resolution, and sampling rate, the MEMS pressure sensor 9 can cover most of the working pressure range of direct-write printing. The high resolution helps to capture minute viscosity changes, and the high sampling rate enables real-time capture of instantaneous viscosity fluctuations, providing data support for millisecond-level compensation of the pressure regulating ring.

[0053] Active temperature control sleeves 10 are installed on the multi-channel material supply unit to regulate the temperature of the printing material stored inside. The number of active temperature control sleeves 10 is the same as the number of storage tanks 1, and they are wrapped around the outer wall of the storage tanks 1 one by one. They are used to regulate the temperature of the printing material inside the storage tanks 1. The active temperature control sleeves 10 adopt thermoelectric cooling semiconductor components, with a temperature control range of 15℃~80℃, a temperature control accuracy of ±0.5℃, and a response time of less than 2s. The inner wall is equipped with a PT1000 platinum resistance temperature sensor. The active temperature control sleeves 10, which adopt thermoelectric cooling semiconductor components, can achieve bidirectional temperature control from 15℃ to 80℃. The temperature control accuracy of ±0.5℃ can correct the viscosity drift caused by temperature. The response speed of less than 2s can follow the changes in ambient temperature. Together with the PT1000 platinum resistance temperature sensor on the inner wall, closed-loop temperature control is achieved, thereby improving the stability of the temperature regulation loop in compensating for material viscosity drift.

[0054] The controller is electrically connected to the servo drive motor 3, the in-situ rheological sensing module, the active temperature control sleeve 10, and the air pressure proportional valve. The controller is configured to calculate the dynamic viscosity of the material based on the pressure drop data, and adjust the extrusion pressure through the air pressure proportional valve and the material temperature through the active temperature control sleeve 10 according to the viscosity. By setting the controller electrically connected to each functional component, it can calculate the dynamic viscosity of the material based on the real-time pressure drop data, and coordinate the air pressure proportional valve and the active temperature control sleeve 10 to adjust the extrusion parameters. It can perform frequency segment compensation for high-frequency fluctuations and low-frequency drifts of the material viscosity, effectively ensuring the stability of the extrusion flow and the consistency of printing quality.

[0055] This embodiment also provides a multi-material seamless material switching adaptive extrusion method, which is implemented based on the above-mentioned multi-material seamless material switching adaptive extrusion system and includes the following steps:

[0056] S1, Dynamic Pressure Retention Bypass Circulation: During the printing process, the material in the non-printing state continuously circulates internally between the storage tank 1 and the multi-way switching valve body 2 through the bypass circulation channel. The circulation pressure is set to 60% to 80% of the printing pressure, and the circulation flow rate is controlled to be 0.5 to 2 mL / min.

[0057] S2, In-situ rheological sensing: When the printed material flows through the micro-slit structure 8 of the in-situ rheological sensing module, two microelectromechanical system pressure sensors 9 measure the pressure drop ΔP at both ends of the micro-slit structure 8 in real time. The controller calculates the dynamic viscosity η of the fluid in real time according to the Hagen-Poiseuille law ΔP=12ηQL / (wh³), where Q is the extrusion flow rate, and L, w, and h are the length, width, and depth of the micro-slit, respectively.

[0058] S3, Dual-Loop Adaptive Regulation of Air Pressure and Temperature: The controller first continuously collects dynamic viscosity for 5 seconds during the stable extrusion stage of the material, calculates the average value as the dynamic viscosity reference value, and then adjusts it based on the real-time calculated dynamic viscosity η, using the dynamic viscosity reference value as the basis. It constructs an air pressure regulation loop through the air pressure proportional valve and a temperature regulation loop through the active temperature control sleeve 10. The two regulation loops work together to correct the extrusion pressure and material temperature parameters. The air pressure regulation loop responds to and corrects high-frequency viscosity fluctuations with a frequency >1Hz and a response time <10ms. The temperature regulation loop responds to and corrects low-frequency viscosity drift with a frequency <0.1Hz and a temperature control accuracy of ±0.5℃. When the sudden change in the current dynamic viscosity relative to the dynamic viscosity reference value exceeds ±15%, the air pressure regulation loop immediately adjusts the output pressure of the air pressure proportional valve for compensation. When the current dynamic viscosity continuously deviates from the dynamic viscosity reference value for more than 30 seconds by more than ±10%, the temperature regulation loop activates the active temperature control sleeve 10 to regulate the temperature.

[0059] S4, Seamless Material Switching: When the controller receives a material switching command, it controls the servo drive motor 3 of the multi-channel switching valve body 2 to drive the valve core to rotate, switching the flow direction of the material to be switched from the bypass circulation channel to the extrusion main channel, thus completing the material switching.

[0060] Material switching specifically includes the following sub-steps:

[0061] S41, Pre-compression stage: During the printing of the current material, the material to be switched continuously circulates in the bypass circulation channel. The controller determines the target printing pressure of the material to be switched at the target extrusion flow rate based on the preset rheological parameters of the material to be switched, the bypass circulation flow rate, and the pre-calibrated viscosity-pressure correspondence, and adjusts its circulation pressure to 90% to 100% of the target printing pressure.

[0062] S42, Instantaneous Pulse: 50ms before the switching command is officially issued, the controller outputs a short-term control command to the pneumatic proportional valve of the material path to be switched, causing its output pressure to rise briefly to form a high-pressure pulse. The pressure amplitude of the high-pressure pulse is 110% to 120% of the target printing pressure determined in step S41, and its duration is 20 to 30ms. At the same time, the controller outputs a control command to the pneumatic proportional valve corresponding to the current printing material path, causing its bypass circuit pressure to drop briefly to form a negative pressure pulse. The pressure amplitude of the negative pressure pulse is 5% to 10% of the current material printing pressure, and its duration is 20 to 30ms.

[0063] S43, Physical channel change: Servo drive motor 3 drives the rotary slide valve core of the multi-way switching valve body 2 to rotate, switching the flow direction of the material to be switched from the bypass to the main extrusion channel. The mechanical action time is 20-30ms.

[0064] S44, Seamless Transition and Adaptive Adjustment: After the switch is completed, the in-situ rheological sensing module monitors the viscosity of the new material entering the main extrusion channel in real time. The air pressure regulating ring and temperature regulating ring start compensation adjustment to make the extrusion flow rate reach a stable state within 100ms with a deviation of no more than ±5% from the target extrusion flow rate.

[0065] The operating principle of the present invention is now described as follows:

[0066] During the printing process, the multi-way switching valve body 2 always maintains one material channel that flows from the feed port 4 to the discharge port 5, and then into the main extrusion nozzle through the main extrusion channel to complete continuous extrusion. The remaining non-printing material flows out through the bypass return port 6 of the multi-way switching valve body 2 and returns to the return interface of the corresponding storage tank 1 through the bypass circulation channel. A closed and continuous internal circulation loop is formed between the storage tank 1 and the multi-way switching valve body 2. The controller maintains the circulation pressure of the non-printing branch at 60% to 80% of the printing pressure through each independent air pressure proportional valve, and controls the circulation flow rate at 0.5 to 2 mL / min, so that the non-printing material is continuously in a shear flow state, maintaining shear thinning characteristics, and at the same time driving the solid filler to be evenly dispersed. This can effectively avoid filler sedimentation and component stratification caused by static placement of the printing material. The active temperature control sleeve 10 wrapped around the outer wall of the storage tank 1 can perform closed-loop temperature control of the material inside the tank, effectively suppressing ambient temperature fluctuations and ensuring the stability of the material's rheological properties.

[0067] After the material in the printing state flows out of the discharge port 5 of the multi-way switching valve body 2, it enters the in-situ rheological sensing module connected in series on the main extrusion channel. The fluid flows through the micro-slit structure 8 inside the flow channel body. The micro-electromechanical system pressure sensor 9, which is installed flush at both ends of the micro-slit structure 8, collects the pressure drop data generated by the fluid passing through the slit in real time. Based on the Hagen-Poiseuille law, the controller calculates the dynamic viscosity of the current fluid within 5ms by combining the pre-stored micro-slit geometric parameters and the extrusion flow rate set by the system, thus realizing online rheological parameter detection of the entire flow rate.

[0068] The controller uses real-time viscosity data as a basis and performs frequency-segmented coordinated control through a pressure regulating loop and a temperature regulating loop. The pressure regulating loop is used to handle high-frequency viscosity fluctuations with a frequency higher than 1Hz. When the sudden change in the current dynamic viscosity relative to the viscosity reference value exceeds ±15%, the output pressure of the corresponding air pressure proportional valve is adjusted within 10ms to correct the extrusion flow rate through pressure compensation. The temperature regulating loop is used to handle low-frequency viscosity drift with a frequency lower than 0.1Hz. When the current dynamic viscosity is detected to deviate from the reference value for more than 30s continuously by more than ±10%, the active temperature control sleeve 10 of the corresponding storage tank 1 is activated. The material temperature is adjusted through a thermoelectric cooling semiconductor component. The rheological characteristics are corrected by utilizing the correlation between temperature and viscosity. The two regulation outputs are superimposed and work together to maintain the stability of the extrusion flow rate. The viscosity reference value is determined by the controller by taking the average value after continuously collecting the dynamic viscosity for 5s during the material stable extrusion stage.

[0069] Upon receiving the material switching command, the controller first performs pre-pressure preparation: based on the real-time rheological data, circulation flow rate, and pre-calibrated viscosity-pressure relationship of the material to be switched in the bypass, it calculates the target printing pressure corresponding to the target extrusion flow rate. The circulation pressure of the branch to be switched is then increased to 90%–100% of the target printing pressure. 50ms before the switching action, the controller outputs a high-pressure pulse to the proportional valve of the branch to be switched, with an amplitude of 110%–120% of the target printing pressure and a duration of 20–30ms. Simultaneously, a negative pressure pulse is applied to the bypass circuit of the current printing branch, with an amplitude of 5%–10% of the current printing pressure. The flow path is switched within 20-30ms, with the help of instantaneous pressure difference to quickly change the direction of the fluid. Then, the servo drive motor 3 drives the rotary slide valve in the multi-way switching valve body 2 to rotate, and the flow path is switched within 20-30ms. The passage of the material to be switched is switched from the bypass return port 6 to the discharge port 5. The material then fills the in-situ rheological sensing module and is extruded from the nozzle. After the switch is completed, the microelectromechanical system pressure sensors 9 at both ends of the micro slit structure 8 monitor the viscosity data of the new material in real time. The air pressure-temperature dual-loop regulation system is activated synchronously to compensate, so that the extrusion flow rate is stabilized within 100ms to a state where the deviation from the target value does not exceed ±5%, thus completing the rapid and seamless switching of the material.

[0070] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A multi-material seamless material-changing adaptive extrusion system, comprising a multi-path material supply unit, a main extrusion channel, and a main extrusion nozzle, characterized in that, It also includes a multi-way switching valve body (2), a bypass circulation channel, an in-situ rheological sensing module, an active temperature control sleeve (10), and a controller; The multi-channel material supply unit is used to store various printing materials and outputs materials by air pressure through an external air pressure proportional valve. Its discharge end is connected to each input end of the multi-channel switching valve body (2). The output end of the multi-channel switching valve body (2) is connected to the main extrusion channel and is driven by the servo drive motor (3) to switch the material path; One end of the bypass circulation channel is connected to each bypass return end of the multi-way switching valve body (2), and the other end is connected to the return end of the multi-way material supply unit, forming a closed loop for continuous internal circulation of non-printing materials. The in-situ rheological sensing module is integrated into the main extrusion channel and is located between the discharge end of the multi-way switching valve body (2) and the main extrusion nozzle. It is used to collect pressure drop data of the printing material in real time. The active temperature control sleeve (10) is installed on the multi-channel material supply unit and is used to regulate the temperature of the printing material stored inside it; The controller is electrically connected to the servo drive motor (3), the in-situ rheological sensing module, the active temperature control sleeve (10), and the pressure proportional valve.

2. The multi-material seamless feed-changing adaptive extrusion system according to claim 1, characterized in that, The multi-channel material supply unit includes at least two storage tanks (1) and a material cylinder rack (11), wherein the storage tanks (1) are fixed on the material cylinder rack (11); The storage tank (1) is provided with a pneumatic interface connected to a pneumatic proportional valve at the top, and a return interface connected to a bypass circulation channel is provided on the side wall of the storage tank (1). The storage tank (1) is made of stainless steel and the inner wall is mirror polished. The number of active temperature control sleeves (10) is the same as the number of storage tanks (1), and the active temperature control sleeves (10) are wrapped around the outer wall of the storage tanks (1) one by one.

3. The multi-material seamless feed-changing adaptive extrusion system according to claim 2, characterized in that, Each input end of the multi-way switching valve body (2) is provided with a feed inlet (4), the output end is provided with a discharge outlet (5), and each bypass return end is provided with a bypass return outlet (6). The number of feed inlets (4) and bypass return ports (6) are the same as the number of storage tanks (1). The feed inlets (4) are connected to the discharge end of the corresponding storage tank (1) through a conveying pipeline. The discharge port (5) is connected to the main extrusion channel. The bypass return ports (6) are connected to the return end of the corresponding storage tank (1) through a bypass circulation channel. When there are two storage tanks (1), the multi-way switching valve body (2) is a two-position five-way rotary slide valve, and its valve core is made of wear-resistant polytetrafluoroethylene material.

4. The multi-material seamless feed-changing adaptive extrusion system according to claim 3, characterized in that, The bypass circulation channel uses polytetrafluoroethylene (PTFE) tubing with an inner diameter of 1.5 mm and a length of 80–120 mm.

5. The multi-material seamless feed-changing adaptive extrusion system according to claim 4, characterized in that, The in-situ rheological sensing module includes a fixed plate (7), a flow channel body, a micro slit structure (8), and two microelectromechanical system pressure sensors (9). The main body of the flow channel is fixedly installed on the fixed plate (7). The internal flow channel of the main body of the flow channel forms a section of the main extrusion channel. Its inlet is connected to the outlet (5) of the multi-way switching valve body (2), and its outlet is connected to the main extrusion nozzle. The micro-slit structure (8) is set in the internal flow channel of the main body of the flow channel. The two microelectromechanical system pressure sensors (9) are respectively installed at the positions of the two ends of the micro-slit structure (8) of the main body of the flow channel, and the sensing surface of the microelectromechanical system pressure sensor (9) is flush with the inner wall of the main body of the flow channel. The microslit structure (8) has a width of 0.1 to 0.5 mm, a depth of 1 to 5 mm, and a length of 5 to 20 mm.

6. The multi-material seamless feed-changing adaptive extrusion system according to claim 5, characterized in that, The measurement range of the microelectromechanical system pressure sensor (9) is 300-1200 hPa, the resolution is 0.01 hPa, the sampling rate is ≥200 Hz, the active temperature control sleeve (10) adopts thermoelectric cooling semiconductor components, the temperature control range is 15℃-80℃, the temperature control accuracy is ±0.5℃, the response time is less than 2s, and its inner wall is equipped with a PT1000 platinum resistance temperature sensor; The controller is configured to calculate the dynamic viscosity of the material based on the pressure drop data, and adjust the extrusion pressure through the air pressure proportional valve and adjust the material temperature through the active temperature control sleeve (10) according to the viscosity.

7. A multi-material seamless material-changing adaptive extrusion method, which employs the multi-material seamless material-changing adaptive extrusion system as described in claim 6, characterized in that, The method includes the following steps: S1, Dynamic pressure residence bypass circulation: During the printing process, the material in the non-printing state continuously circulates between the storage tank (1) and the multi-way switching valve body (2) through the bypass circulation channel. The circulation pressure is set to 60% to 80% of the printing pressure, and the circulation flow rate is controlled to be 0.5 to 2 mL / min. S2, In-situ rheological sensing: When the printed material flows through the micro-slit structure (8) of the in-situ rheological sensing module, two microelectromechanical system pressure sensors (9) measure the pressure drop ΔP at both ends of the micro-slit structure (8) in real time. The controller calculates the dynamic viscosity η of the fluid in real time according to the Hagen-Poiseuille law ΔP=12ηQL / (wh³), where Q is the extrusion flow rate, and L, w, and h are the length, width, and depth of the micro-slit, respectively. S3, air pressure-temperature dual-loop adaptive adjustment: The controller first continuously collects dynamic viscosity for 5s during the material stable extrusion stage, calculates the average value as the dynamic viscosity reference value, and then adjusts based on the dynamic viscosity η calculated in real time, using the dynamic viscosity reference value as the basis. The controller constructs an air pressure adjustment loop through the air pressure proportional valve and a temperature adjustment loop through the active temperature control sleeve (10). The two adjustment loops work together to correct the extrusion pressure and material temperature parameters. The air pressure adjustment loop responds to and corrects high-frequency viscosity fluctuations with a frequency > 1Hz and a response time < 10ms. The temperature adjustment loop responds to and corrects low-frequency viscosity drift with a frequency < 0.1Hz and the temperature control accuracy is ±0.5℃. S4, Seamless material switching: When the controller receives the material switching command, it controls the servo drive motor (3) of the multi-way switching valve body (2) to drive the valve core to rotate, and switches the flow direction of the material to be switched from the bypass circulation channel to the extrusion main channel, thus completing the material switching.

8. The multi-material seamless material switching adaptive extrusion method according to claim 7, characterized in that, The material switching in step S4 specifically includes the following sub-steps: S41, Pre-compression stage: During the printing of the current material, the material to be switched continuously circulates in the bypass circulation channel. The controller determines the target printing pressure of the material to be switched at the target extrusion flow rate based on the preset rheological parameters of the material to be switched, the bypass circulation flow rate, and the pre-calibrated viscosity-pressure correspondence, and adjusts its circulation pressure to 90% to 100% of the target printing pressure. S42, Instantaneous Pulse: 50ms before the switching command is officially issued, the controller outputs a short-term control command to the proportional valve of the material path to be switched, causing its output pressure to rise briefly to form a high-pressure pulse. The pressure amplitude of the high-pressure pulse is 110% to 120% of the target printing pressure determined in step S41, and its duration is 20 to 30ms. At the same time, the controller outputs a control command to the proportional valve of the current printing material path, causing its bypass circuit pressure to drop briefly to form a negative pressure pulse. The pressure amplitude of the negative pressure pulse is 5% to 10% of the current material printing pressure, and its duration is 20 to 30ms. S43, Physical channel change: The servo drive motor (3) drives the rotating slide valve core of the multi-way switching valve body (2) to rotate, switching the flow direction of the material to be switched from the bypass to the main extrusion channel. The mechanical action time is 20-30ms. S44, Seamless Transition and Adaptive Adjustment: After the switch is completed, the in-situ rheological sensing module monitors the viscosity of the new material entering the main extrusion channel in real time. The air pressure regulating ring and temperature regulating ring start compensation adjustment to make the extrusion flow rate reach a stable state within 100ms with a deviation of no more than ±5% from the target extrusion flow rate.

9. The multi-material seamless material switching adaptive extrusion method according to claim 7, characterized in that, In step S3, when the sudden change in the current dynamic viscosity relative to the dynamic viscosity reference value exceeds ±15%, the pressure regulating ring immediately adjusts the output pressure of the pressure proportional valve to compensate. When the current dynamic viscosity is detected to deviate from the dynamic viscosity reference value for more than 30 seconds by more than ±10%, the temperature regulating ring activates the active temperature control sleeve (10) to regulate the temperature.

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