A large tow dry fiber ultrasonic yarn spreading and infiltrating and 3D printing efficient integrated system

Abstract

A kind of large tow dry fiber ultrasonic drawing and infiltration and 3D printing high-efficiency integrated system, including the installation of integrated ultrasonic drawing and infiltration 3D printing system each function part on aluminium profile mounting frame and double X-axis 3D printing platform;Double X-axis 3D printing platform is XYZ three-coordinate motion and control system with two groups of parallel X-axis, two groups of X-axis can be controlled alone or can act in concert, with good repeatability positioning accuracy;Aluminium profile mounting frame is as the supporting installation frame of each function part, and is sleeved on double X-axis 3D printing platform;External control box L and external control box R are symmetrically arranged on the two sides of double X-axis 3D printing platform, and interact with the control system of double X-axis 3D printing platform itself, to realize the collaborative control to each function part;The present application utilizes ultrasonic vibration and cavitation effect of ultrasonic wave in liquid, and the twistless large tow of various fibers is continuously ultrasonic drawing, and normal temperature solid resin matrix is infiltrated into tow, and then 3D printing is carried out with it as wire material.

Description

Technical Field

[0001] This invention relates to the field of fiber-reinforced composite material 3D printing technology, specifically to a high-efficiency integrated system for ultrasonic spreading and impregnation of large-tow dry fibers and 3D printing. Background Technology

[0002] With the advent of various high-strength and high-toughness fiber materials, and the industrial mass production of untwisted large tow fibers of 6K, 12K, and 24K and above, the 3D printing technology of fiber-reinforced composite materials that can only use tows of less than 3K as raw materials can no longer meet the production needs of large composite component parts.

[0003] 3D printing equipment for fiber-reinforced composite materials using filaments with a density of less than 3K as raw materials mostly relies on commercially available FDM thermoplastic resin 3D printing equipment. The only modification is to the FDM print head of the 3D printer, adding an inlet for dry fibers at the filament feed position or nozzle. The fiber-reinforced composite material 3D printing is achieved by relying on the pushing and adhesion of the FDM resin filaments during the printing process. Therefore, the existing equipment has the following drawbacks: limited by the specifications of existing FDM thermoplastic resin filaments and FDM nozzles, it can only use filament bundles of 3K or less for printing; furthermore, due to the pushing action of the resin filaments, the fiber bundles in the printed part are concentrated on one side of the printing path, while other areas are pure resin matrix, resulting in extremely poor uniformity of fiber-resin distribution; simultaneously, the dry fibers only combine with the molten resin at the print head nozzle, causing the room-temperature solid resin to be unable to effectively wet the interior of the fiber bundle. Within the filament bundle variation range of 1K to 3K, as the number of monofilaments in the bundle increases, the wetting effect of the resin matrix in the composite material becomes even worse, and obvious resin voids will appear inside the composite material filament bundle. The randomness of such defects will pose an unpredictable safety hazard, seriously affecting the mechanical properties of the composite material components. Therefore, breaking the dependence on traditional FDM print heads and filaments and solving the wetting problem of large untwisted filament bundles of 6K or more in the 3D printing process is the key to developing 3D printing equipment for large-tow fiber-reinforced composite materials. Summary of the Invention

[0004] To overcome the shortcomings of the prior art, the purpose of this invention is to provide a highly efficient integrated system for ultrasonic spinning and impregnation of large-tow dry fibers and 3D printing. This system utilizes ultrasonic vibration and the cavitation effect of ultrasound in liquids to continuously spin untwisted large-tow fibers of various types (with a number of monofilaments greater than or equal to 6K) and impregnates the fiber bundle with a room-temperature solid resin matrix. This allows the fiber bundle to be used as a filament material for 3D printing, thereby significantly expanding the fiber bundle specifications and types applicable to fiber-reinforced composite material 3D printing processes and effectively improving the resin impregnation within the fiber bundle.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] A highly efficient integrated system for ultrasonic spreading, impregnation, and 3D printing of large-tow dry fibers includes various functional components of an integrated ultrasonic spreading and impregnation 3D printing system, a dual X-axis 3D printing platform, an aluminum profile mounting frame, an external control box L, and an external control box R. Each functional component of the integrated ultrasonic spreading and impregnation 3D printing system adopts a modular design, integrated and mounted on the aluminum profile mounting frame and the dual X-axis 3D printing platform in the form of detachable sliders. The dual X-axis 3D printing platform is an XYZ three-coordinate motion and control system with two sets of parallel X-axis axes. The two sets of X-axis can be controlled individually or move collaboratively, exhibiting good repeatability and positioning accuracy. The aluminum profile mounting frame serves as the supporting frame for each functional component, fitting onto the dual X-axis 3D printing platform. The external control boxes L and R are symmetrically arranged on both sides of the dual X-axis 3D printing platform, interacting with the platform's own control system to achieve coordinated control of the various functional components.

[0007] The integrated ultrasonic yarn spreading and impregnation 3D printing system comprises nine different functional units. These nine functional units are arranged sequentially from the outside to the inside and from top to bottom, according to the order in which the fiber bundle passes. They are: magnetic powder damping functional unit, tension detection functional unit, tension buffering functional unit, ultrasonic dry filament spreading functional unit, ultrasonic melting and impregnation functional unit, bundled filament feeding functional unit, composite material print head, shearing functional unit, and full-platform high-power cooling fan.

[0008] The magnetic powder damping functional unit includes a fiber bundle tray, a winding drive toothed disc, a magnetic powder damper, and a damper mounting bracket. The lower end of the damper mounting bracket is fixed on an aluminum profile mounting bracket, and the magnetic powder damper is fixed on the damper mounting bracket. A winding drive toothed disc is set on the back of the fiber bundle tray. Under external drive, the winding drive toothed disc causes the untwisted large filament bundle to be wound from the large roll of fiber yarn onto the fiber bundle tray.

[0009] The tension detection function includes a combined tension sensor and a sensor mounting bracket. The combined tension sensor is fixed on the sensor mounting bracket, and the lower end of the sensor mounting bracket is fixed on the aluminum profile mounting bracket. The structure of the upper part ensures that the center line of the three guide wheels on the combined tension sensor coincides with the expected fiber bundle path.

[0010] The tension buffering functional unit includes a buffer mounting bracket, a double-rod cylinder, a cylinder mounting plate, a fixed guide wheel support rod, a movable guide wheel support rod, a guide wheel shaft set screw, a PTFE guide wheel sleeve, a guide wheel bearing, a guide wheel shaft, a bore spring retainer, and a shaft spring retainer; the PTFE guide wheel sleeve, guide wheel bearing, guide wheel shaft, bore spring retainer, and shaft spring retainer together form a shaft-mounted guide wheel; the shaft-mounted guide wheel and the fixed or movable guide wheel support rod together form a buffer guide wheel assembly; the tension buffering functional unit... All parts are integrated and installed on the buffer section mounting bracket, which is fixed to the aluminum profile mounting bracket. In the tension buffer function section, a double-rod cylinder is used as passive overload protection for the wire bundle tension. The double-rod cylinder is fixed on the cylinder mounting plate. The cylinder mounting plate and the groove on the cylinder body of the double-rod cylinder cooperate to position the front and rear positions of the double-rod cylinder. The cylinder mounting plate is connected to the double-rod cylinder, and the remaining part is connected to the side plate in the center hole of the buffer section mounting bracket, realizing the integrated installation of the double-rod cylinder on the buffer section mounting bracket.

[0011] The tension buffering function section is equipped with three buffer guide wheel assemblies. Two of the buffer guide wheel assemblies are fixed on both sides of the double-rod cylinder along the fiber path direction, and one buffer guide wheel assembly is installed at the top of the piston rod of the double-rod cylinder to bear the tension on the fiber bundle path. The three buffer guide wheel assemblies are arranged in a triangular pattern along the fiber path direction. The fiber paths (i.e., internal common tangents) between the two fixed buffer guide wheel assemblies and the buffer guide wheel assembly at the top of the piston rod are parallel to each other, ensuring that the conversion relationship "the resultant force of the fiber bundle on the buffer guide wheel assembly at the top of the piston rod = the actual tension in the fiber bundle × 2" remains unchanged.

[0012] The ultrasonic dry yarn spreading function unit comprises two parts: an ultrasonic spreading rod assembly and a dry yarn spreading guide assembly. The dry yarn spreading guide assembly is fixed to the crossbeam of the aluminum profile mounting frame via a dry yarn spreading guide rod mounting bracket, and its spreading guiding function is achieved by the dry yarn spreading guide rod. The ultrasonic spreading rod assembly is correspondingly mounted on a small column at the top of the aluminum profile mounting frame. It slides and locks on the small column via a sliding groove on the ultrasonic spreading rod mounting bracket, thereby adjusting the relative distance between the ultrasonic spreading rod assembly and the dry yarn spreading guide assembly, and thus adjusting the wrap angle of the yarn bundle on the ultrasonic spreading rod. The size of this wrap angle will affect the ultrasonic dry yarn spreading effect.

[0013] The ultrasonic melt wetting function unit comprises four parts: ultrasonic yarn spreading rod assembly, yarn spreading and wetting guide assembly, liquid level monitoring and adjustment assembly, and resin scraper assembly. The ultrasonic yarn spreading rod assembly is completely identical to the ultrasonic yarn spreading rod assembly in the ultrasonic dry yarn spreading function unit, and it also has the function of adjusting the yarn spreading wrap angle. The two are interchangeable.

[0014] The yarn spreading and impregnation guide assembly in the ultrasonic melting and impregnation functional section is fixed on the crossbeam of the aluminum profile mounting frame through the yarn spreading and impregnation guide rod mounting bracket. Its yarn spreading and guiding function is realized by the yarn spreading and impregnation guide rod, and its impregnation function is realized by heating the melting resin pool. The heating and temperature monitoring of the melting resin pool are realized by the heating rod and thermistor embedded inside it. The relevant feedback control functions are integrated in the external control box (L and R).

[0015] The liquid level monitoring and adjustment component in the ultrasonic melting and wetting function is fixed to the crossbeam of the aluminum profile mounting bracket via a liquid level monitoring and adjustment mounting bracket. Its liquid level monitoring function is realized by a liquid level sensor, and its liquid level adjustment function is realized by a screw feeder. When the liquid level is lower than the sensing position of the liquid level sensor, the small DC geared motor in the screw feeder starts and drives the feeding screw to rotate. Under the push of the feeding screw, the room temperature solid resin powder (or small particles) in the hopper feeding cylinder falls into the heated and molten resin pool. When the room temperature solid resin melts and the liquid level in the heated and molten resin pool reaches the sensing position of the liquid level sensor, the small DC geared motor in the screw feeder stops running. This cycle repeats to maintain the resin liquid level in the heated and molten resin pool in a dynamic and stable state. The relevant feedback control functions are integrated into the external control box L and the external control box R.

[0016] The resin scraper assembly in the ultrasonic melting and impregnation function is installed at the edge of the heated melting resin pool. It is used to scrape off excess resin from the surface of the fiber bundle after ultrasonic impregnation and to allow the scraped resin to fall back into the heated melting resin pool. The function of the resin scraper assembly is achieved by the scraper heating roller and the resin scraper.

[0017] The scraper heating roller in the resin scraper assembly is fixed to the edge of the heated molten resin pool. Its heating and temperature monitoring are also achieved by heating rods and thermistors embedded inside. Correspondingly, the resin scraper can also maintain a certain temperature under the heat radiation of the scraper heating roller. The resin scraper is installed on a micro-motion slide. By adjusting the micro-motion slide, the distance between the scraper heating roller and the resin scraper can be precisely controlled.

[0018] The bundled yarn feeding function unit consists of two parts: a bundle guiding component and a bundled yarn feeding component. The bundle guiding component in the bundled yarn feeding function unit is realized by a PTFE bundle wheel with a shaft. The fiber bundle passing through the resin scraper assembly still maintains good fluidity of the resin matrix. Under the guidance of the V-groove of the PTFE bundle wheel with a shaft, the originally flattened fiber bundle gathers to the bottom of the V-groove under tension, realizing the initial bundle after the yarn is spread and wetted. Under the guidance of the PTFE bundle wheel with a shaft, it completes a 90° turn and enters the bundled yarn feeding component.

[0019] The bundled wire feeding assembly in the bundled wire feeding functional section is fixed on the crossbeam of the aluminum profile mounting frame through the bundled wire feeding mounting frame and the wire feeding heating block mounting frame. Its function is realized by three parts: the bundled heating block and the bundled nozzle, the wire feeding extruder and the wire feeding motor, and the wire feeding heating block and the wire feeding guide nozzle.

[0020] The function of the bundled heating block and bundled nozzle in the bundled filament feeding assembly is to heat, bundle, and shape the prepreg filament after it has been initially bundled and guided by the PTFE take-up wheel with a shaft, and to further control the resin content in the prepreg filament by controlling the orifice diameter of the bundled nozzle. The bundled heating block and bundled nozzle are mounted on a bundled heating block support with slots, and the bundled heating block and bundled nozzle are adjusted to their left and right positions along the slots. A filament cooling nozzle is also installed on one side of the bundled heating block support to blow cooling gas onto the bundled and shaped prepreg filament, so that the prepreg filament is cooled quickly after being heated. To prevent the bundled heating block from affecting the operating temperature of the filament feeding extruder and filament feeding motor below, a support heat insulation pad is introduced between the bundled heating block support and the bundled filament feeding mounting frame.

[0021] The filament feeding extruder and filament feeding motor in the bundled filament feeding assembly are mounted on the bundled filament feeding mounting frame via a filament feeding motor fixing plate. The filament feeding extruder and filament feeding motor are respectively mounted on the front and rear sides of the filament feeding motor fixing plate to achieve filament feeding and tension reduction of the pre-impregnated filament bundle. The filament feeding extruder has a traction effect on the fiber bundle upstream, and its traction force is the key power source for the fiber bundle to overcome the channel resistance. At the same time, its traction effect is also one of the reasons for ensuring a constant tension in the fiber bundle upstream. The filament feeding extruder has a pushing and feeding effect on the fiber bundle downstream, so that the tension in the downstream fiber bundle is almost zero. The filament feeding speed of the filament feeding extruder is provided by the rotation speed of the filament feeding motor and is consistent with the moving speed of the composite material printing head in the working state.

[0022] The bundled filament feeding mounting frame has slots, and the filament feeding motor fixing plate is adjusted back and forth along the slots to ensure that the pre-impregnated filaments coming out of the bundled nozzle can smoothly enter the filament feeding extruder.

[0023] The filament feeding heating block and filament feeding guide nozzle in the bundled filament feeding assembly are fixed to the crossbeam of the aluminum profile mounting frame via the filament feeding heating block mounting bracket. This is used to reheat the cooled prepreg filament bundle. Since the prepreg filament bundle will then enter the composite material print head, which is constantly moving during the printing process, the short section of prepreg filament bundle before the composite material print head will constantly swing left and right. If the resin matrix in the filament bundle remains solid at room temperature, its rigidity will be too high for the large prepreg filament bundle, causing the composite material print head to jam. Moreover, if the resin matrix of the prepreg filament bundle at room temperature breaks, it is very easy to cause the fiber itself to break, which will force the printing work to stop. At this time, the filament feeding heating block and filament feeding guide nozzle are arranged below the filament feeding extruder to reheat and guide the cooled filament. A filament feeding heating block heat insulation pad is introduced between the filament feeding heating block and the filament feeding heating block mounting bracket.

[0024] The function of the composite material printhead is realized by two parts: the printhead filament heating block and the printing heating block and the printhead nozzle. The printhead filament heating block is used to heat and soften the pre-impregnated composite material filaments again, so that the pre-impregnated filaments can enter the composite material printhead. The filaments entering the composite material printhead finally enter the printing heating block and the printing nozzle, and the composite material 3D printing is completed under the guidance and compaction ironing action of the printing nozzle.

[0025] The composite material printhead is integrated into two parts: the filament feed heating block and the printing heating block, and the printhead nozzle, through a printhead box-type mounting bracket. A heat insulation pad for the filament feed heating block is introduced below the filament feed heating block and then mounted on the filament feed heating block support plate. The filament feed heating block support plate serves as the top cover plate and is connected to the printhead box-type mounting bracket. Similarly, a heat insulation pad for the printing heating block is introduced above the printing heating block and then mounted below the printhead box-type mounting bracket. A box-type heat insulation plate is also introduced on the back plate of the printhead box-type mounting bracket and then connected to the X-axis slider of the dual X-axis 3D printing platform through a slider connector.

[0026] In the shearing function section, pneumatic shears are used to cut the printed filament bundles. Two pneumatic shears are fixed below the origins of the two X-axis via shear mounting brackets. When a composite material printhead finishes printing and returns to its X-axis zero point, the limit switch at the zero point will simultaneously trigger the corresponding pneumatic shears to cut the redundant prepreg filament bundles dragged by the composite material printhead. A small section of prepreg filament bundle will remain below the cut composite material printhead. This serves two purposes: firstly, to prevent the filament bundle from shrinking back into the printing heating block due to cooling; and secondly, to ensure better adhesion between the prepreg filament and the printing platform when printing begins again.

[0027] The entire printing platform is cooled by a powerful cooling fan, which greatly improves the cooling speed of the prepreg yarn after printing and enhances the shaping ability of the prepreg yarn.

[0028] In the integrated ultrasonic yarn spreading and impregnation 3D printing system, the three nozzles in each functional unit—the bundle nozzle, the filament feeding guide nozzle, and the printing nozzle—have progressively smaller filament outlet diameters. The printing nozzle diameter is 0.5 mm smaller than that of the bundle nozzle, which to some extent compresses the resin in the pre-impregnated filament bundle. Simultaneously, under the action of their respective heating blocks—the bundle heating block, the filament feeding heating block, and the printing heating block—tiny resin molten pools are formed inside the nozzles, further promoting the impregnation of the resin matrix within the fiber bundle.

[0029] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0030] This invention utilizes ultrasonic vibration and the cavitation effect of ultrasound in liquids to continuously ultrasonically untwistrate large bundles of various fibers (with a single filament count of ≥6K) and impregnates the bundles with a room-temperature solid resin matrix, thereby enabling 3D printing using these bundles as filaments. This overcomes the limitation of existing fiber-reinforced composite material 3D printing equipment, which can only print bundles of 3K or less, significantly expanding the applicability of fiber-reinforced composite material 3D printing technology and effectively improving the resin wettability within the bundles.

[0031] The integrated ultrasonic yarn spreading and impregnation 3D printing system of this invention adopts a modular design for all nine functional parts, which greatly reduces the maintenance and replacement costs of each part. It is integrated and installed on the aluminum profile mounting frame and the dual X-axis 3D printing platform in the form of detachable sliders. This allows the relative positions between the functional parts to be adjusted according to actual needs. At the same time, it is convenient to set up multiple fiber bundle spreading and impregnation paths in parallel to expand and upgrade the integrated ultrasonic yarn spreading and impregnation 3D printing system with multiple print heads.

[0032] In this invention, the driving, detection, feedback, and temperature control functions of each functional unit are integrated into external control boxes L and R. These two control boxes are symmetrically arranged on both sides of the dual X-axis 3D printing platform, interacting with the platform's own control system to achieve coordinated control of each functional unit. This control method facilitates the use of the entire integrated ultrasonic yarn spreading and impregnation 3D printing system for large-tow hybrid fiber composite materials. Only commands need to be issued to the dual X-axis 3D printing platform's control system to achieve interactive control of the entire system.

[0033] In this invention, a winding drive toothed disc is provided on the back of the fiber bundle material tray in the magnetic powder damping functional section. The winding drive toothed disc can make the process of winding untwisted large filament bundles from large roll fiber yarn spindles to the fiber bundle material tray more convenient under external drive.

[0034] This invention uses a double-rod cylinder in the tension buffering function section as a passive overload protection for the wire bundle tension, which compensates for the lag in the action of the magnetic powder damper; at the same time, the double-rod cylinder itself has a good guiding effect, eliminating the need for an additional guide rail slider mechanism to guide its movement direction, which greatly simplifies the structural composition of the tension buffering function section.

[0035] In both the ultrasonic dry yarn spreading function and the ultrasonic melting and wetting function, this invention employs an ultrasonic yarn spreading rod assembly that can slide up and down and lock along a small column at the top of the aluminum profile mounting frame. By adjusting the position of the ultrasonic yarn spreading rod assembly, the distance between the ultrasonic yarn spreading rod and the dry yarn spreading guide rod (or the spreading and wetting guide rod) can be changed, thereby adjusting the wrap angle of the yarn bundle on the ultrasonic yarn spreading rod. By adjusting the size of this wrap angle, the optimal ultrasonic yarn spreading and wetting effect can be obtained.

[0036] This invention establishes a "two-stage, multi-stage" ultrasonic yarn spreading and impregnation technology route along the entire transport path of the untwisted large-tow fiber. "Two-stage" refers to two ultrasonic yarn spreading processes—one dry and one wet—utilizing ultrasonic vibration and the cavitation effect of ultrasound waves in liquids in the ultrasonic dry yarn spreading functional section and the ultrasonic melt impregnation functional section. "Multi-stage" refers to the yarn spreading and impregnation process in the ultrasonic melt impregnation functional section, and the formation of small resin molten pools inside the nozzles by the three nozzles (bundling nozzle, yarn feeding guide nozzle, and printing nozzle) and their corresponding heating blocks (bundling heating block, yarn feeding heating block, and printing heating block) in each functional section. This further promotes the impregnation of the resin matrix within the fiber bundle. The decreasing aperture of the three nozzles (bundling nozzle, yarn feeding guide nozzle, and printing nozzle) further compresses the resin in the pre-impregnated fiber bundle, further enhancing the wettability of the resin matrix within the fiber bundle.

[0037] This invention incorporates a liquid level monitoring and adjustment component in the ultrasonic melting and impregnation function to maintain a dynamically stable resin level in the heated melting resin tank. In actual operation, it was found that the amount of resin in the heated melting resin tank affects the amount of excess resin carried on the pre-impregnated yarn after ultrasonic spreading and impregnation. Therefore, by setting up the liquid level monitoring and adjustment component to control the liquid level in the heated melting resin tank, the stability of the impregnation effect can be better guaranteed.

[0038] The present invention includes a resin scraper assembly in the ultrasonic melt impregnation function section, which is used to scrape off excess resin from the surface of the fiber bundle after ultrasonic impregnation. The distance between the scraper heating roller and the resin scraper can be adjusted by a micro-motion slide to precisely control the uniformity of resin content in the pre-impregnated fiber bundle.

[0039] The resin scraper assembly in this invention is installed at the edge of the heated and molten resin pool, which allows the scraped resin to fall back into the heated and molten resin pool, effectively improving the utilization rate of the resin matrix material.

[0040] The bundle feeding function of this invention uses a PTFE bundle gathering wheel with a V-groove. Under the guidance of the V-groove, the originally flattened fiber bundle gathers towards the bottom of the V-groove under tension, thus achieving the initial gathering of the prepreg bundle in a simple way, and effectively solving the problem of twisting and curling of wide prepreg during the bundling process.

[0041] In this invention, the prepreg yarn bundle completes a 90° turn under the guidance of the PTFE take-up wheel and enters the bundle feeding assembly, thus gradually transitioning from the yarn spreading and impregnation stage to the 3D printing stage, thereby realizing integrated ultrasonic yarn spreading and impregnation 3D printing.

[0042] In this invention, a filament feeding extruder is used to reduce tension in the prepreg filament bundle. For the fiber bundle within the entire ultrasonic spreading and impregnation 3D printing system path, the filament feeding extruder is the watershed between the presence and absence of tension in the filament bundle. On one hand, the traction force of the filament feeding extruder provides a key power source for the upstream fiber bundle to overcome the channel resistance. On the other hand, the pushing and feeding action of the filament feeding extruder on the downstream fiber bundle reduces the tension in the downstream fiber bundle to almost zero, improving the adhesion of the prepreg filament bundle to the printing platform and greatly contributing to improved printing quality.

[0043] The shearing function in this invention employs a passive triggering method. The pneumatic shears are positioned below the origin of the X-axis. When the composite material printhead completes printing and returns to its X-axis zero point, the limit switch at the zero point triggers the pneumatic shears to cut the redundant prepreg filaments dragged by the composite material printhead. This passive triggering method greatly reduces the control difficulty of the shearing action.

[0044] This invention fully utilizes the viscosity-temperature characteristics of room-temperature solid resin matrix and combines them with the technical characteristics of fiber-reinforced composite material 3D printing process. It sets up six heating stages (heating of molten resin pool, scraper heating roller, bundle heating block, filament feeding heating block, print head filament feeding heating block, and printing heating block) and three cooling stages (filament cooling nozzle, full-platform powerful heat dissipation fan, and long-distance natural cooling between the filament feeding guide nozzle and the composite material print head). This effectively ensures the wettability of the resin matrix inside the large filament bundle, while ensuring that the pre-impregnated filament can be held and conveyed in the filament feeding extruder, can be bent at will during the printing process, and can quickly adhere and set after printing.

[0045] In this invention, all guide wheels in each functional part of the integrated ultrasonic yarn spreading and impregnation 3D printing system are made of polytetrafluoroethylene, which reduces fiber wear while preventing resin adhesion. Attached Figure Description

[0046] Figure 1 This is a schematic diagram of the overall composition of the present invention.

[0047] Figure 2 This is a schematic diagram of the composition of the various functional parts of the present invention.

[0048] Figure 3 This is a cross-sectional view of the fiber bundle path in each functional part of the present invention.

[0049] Figure 4 This is a schematic diagram of the magnetic powder damping functional unit of the present invention.

[0050] Figure 5 This is a schematic diagram of the tension detection function unit of the present invention.

[0051] Figure 6 This is a schematic diagram of the tension buffer function of the present invention.

[0052] Figure 7 This is a schematic diagram of the ultrasonic dry yarn spreading function of the present invention.

[0053] Figure 8 This is a schematic diagram of the ultrasonic melting and wetting functional part of the present invention.

[0054] Figure 9 This is a schematic diagram of the components of the bundled wire feeding function of the present invention.

[0055] Figure 10 This is a schematic diagram of the print head and cutting function of the present invention. Detailed Implementation

[0056] The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0057] See Figure 1 , Figure 2 , Figure 3 A highly efficient integrated system for ultrasonic spinning, impregnation, and 3D printing of large-tow dry fibers is disclosed. This system comprises functional units of an integrated ultrasonic spinning, impregnation, and 3D printing system, a dual X-axis 3D printing platform, an aluminum profile mounting frame, an external control box L, and an external control box R. The functional units of the integrated ultrasonic spinning, impregnation, and 3D printing system are the core components of this invention, mounted on the aluminum profile mounting frame and the dual X-axis 3D printing platform. The dual X-axis 3D printing platform is an XYZ three-coordinate motion and control system with two sets of parallel X-axis axes. The two sets of X-axis axes can be controlled individually or collaboratively, exhibiting excellent repeatability. The aluminum profile mounting frame serves as the main support frame for each functional unit, fitting onto the dual X-axis 3D printing platform. The external control boxes L and R are symmetrically arranged on both sides of the dual X-axis 3D printing platform, interacting with the platform's own control system to achieve coordinated control of the various functional units.

[0058] See Figure 2 , Figure 3 The integrated ultrasonic yarn spreading and impregnation 3D printing system comprises nine different functional units, arranged sequentially from the outside to the inside and from top to bottom according to the fiber bundle path: magnetic powder damping unit 1, tension detection unit 2, tension buffering unit 3, ultrasonic dry filament spreading unit 4, ultrasonic melting and impregnation unit 5, bundled filament feeding unit 6, composite material print head 7, shearing unit 8, and a full-platform high-power cooling fan 9. Each functional unit adopts a modular design and is integrated and installed on the aluminum profile mounting frame and dual X-axis 3D printing platform in the form of detachable sliders (depending on the actual situation, the functional units can be added or removed in groups to meet the 3D printing needs of different levels of fiber-reinforced composite materials).

[0059] See Figures 2 to 10 Each functional unit 1 to 9 is integrated on an aluminum profile mounting bracket or a dual X-axis 3D printing platform via its own parts named "xx mounting bracket (104, 202, 301, 404, 406, 503, 504, 603, 610, 617, 704, 802)". These parts named "xx mounting bracket (104, 202, 301, 404, 406, 503, 504, 603, 610, 617, 704, 802)" are equipped with slide grooves (or side plates) and fastening connection holes that are adapted to the shape and size of the aluminum profile cross section or the size of the slider of the dual X-axis 3D printing platform, so as to realize the modular loading, unloading and replacement of each functional unit 1 to 9.

[0060] See Figure 3 , Figure 4 The magnetic powder damping functional unit 1 includes a fiber bundle tray 101, a winding drive gear 102, a magnetic powder damper 103, and a damper mounting bracket 104. The lower end of the damper mounting bracket 104 is provided with a groove and fastening connection holes adapted to the shape and size of the aluminum profile cross-section, used to fix the magnetic powder damping functional unit 1 to the crossbeam of the aluminum profile mounting bracket. The upper part of its structure ensures that the centerline of the fiber bundle tray 101 coincides with the expected fiber bundle path. The magnetic powder damper 103 provides tension damping for the fiber bundle, and the magnetic powder damper 103 is connected by bolts... The assembly is fixed on the damper mounting bracket 104. The fiber bundle tray 101 is used to supply untwisted large filament bundles for the entire integrated ultrasonic yarn spreading and impregnation 3D printing system. The center of the fiber bundle tray 101 has a through hole with a keyway that can be tightly matched with the output shaft of the magnetic powder damper 103 to transmit the torque output by the magnetic powder damper 103. A winding drive toothed disc 102 is provided on the back of the fiber bundle tray 101. The winding drive toothed disc 102 can make the process of winding the untwisted large filament bundle from the large roll of fiber yarn into the fiber bundle tray 101 more convenient under external drive.

[0061] See Figure 3 , Figure 5 The tension detection function unit 2 includes a combined tension sensor 201 and a sensor mounting bracket 202. The combined tension sensor 201 is used to monitor and provide feedback on the tension on the fiber bundle path in real time. The combined tension sensor 201 is fixed to the sensor mounting bracket 202 by bolts. The lower end of the sensor mounting bracket 202 is provided with a sliding groove and fastening connection holes that are adapted to the shape and size of the aluminum profile cross section. It is used to fix the tension detection function unit 2 to the crossbeam of the aluminum profile mounting bracket. The structure of its upper part ensures that the center line of the three guide wheels on the combined tension sensor 201 coincides with the expected fiber bundle path.

[0062] See Figure 6 The tension buffering function unit 3 is used to compensate for the lag in the action of the magnetic powder damper 103. The tension buffering function unit 3 includes a buffer mounting bracket 301, a double-rod cylinder 302, a cylinder mounting plate 303, a fixed guide wheel support rod 304, a moving guide wheel support rod 305, a guide wheel shaft set screw 306, a PTFE guide wheel sleeve 307, a guide wheel bearing 308, a guide wheel shaft 309, a hole spring retainer 310, and a shaft spring retainer 311. The PTFE guide wheel sleeve 307, guide wheel bearing 308, guide wheel shaft 309, hole spring retainer 310, and shaft spring retainer 311 constitute a... Figure 6 The guide wheel with shaft; the guide wheel with shaft, together with the fixed guide wheel support rod 304 or the movable guide wheel support rod 305, forms a Figure 6 The buffer guide wheel assembly in the middle;

[0063] See Figure 6 All parts of the tension buffer function unit 3 are integrated and installed on the buffer unit mounting bracket 301. The front and rear sides of the buffer unit mounting bracket 301 are provided with side plates and fastening connection holes that are adapted to the shape and size of the aluminum profile cross section, for fixing the tension buffer function unit 3 to the crossbeam of the aluminum profile mounting bracket. A series of threaded holes or through holes are provided on the upper surface of the buffer unit mounting bracket 301 and on the side plates in the center hole, for realizing the integrated installation of other parts in the tension buffer function unit 3.

[0064] See Figure 3 , Figure 6In the tension buffering function section 3, a double-rod cylinder 302 is used as a passive overload protection for the fiber bundle tension. The double-rod cylinder 302 is fixed to the cylinder mounting plate 303 by bolts. There is a row of protruding rectangular bosses at the center line of the cylinder mounting plate 303. These bosses can cooperate with the grooves on the cylinder body of the double-rod cylinder 302 to position the front and rear positions of the double-rod cylinder 302, so as to ensure that the center line of several buffer guide wheel assemblies coincides with the expected fiber bundle path. The cylinder mounting plate 303 is provided with a series of threaded holes or through holes, some of which are used to connect to the double-rod cylinder 302 by bolts, and the remaining parts are connected to the side plate in the center hole of the buffer section mounting frame 301 by bolts, thereby realizing the integrated installation of the double-rod cylinder 302 on the buffer section mounting frame 301.

[0065] See Figure 3 , Figure 6 In the tension buffering function section 3, a double-rod cylinder 302 is used as a passive overload protection for the fiber bundle tension. Therefore, the pressure of compressed air introduced into the double-rod cylinder 302 should correspond to the fiber bundle tension to be controlled. When the tension in the fiber bundle is greater than the set tension, the resultant force of the fiber bundle on the top of the piston rod of the double-rod cylinder 302 is greater than the gas pressure inside the cylinder. The force difference on both sides causes the piston rod of the double-rod cylinder 302 to contract, making the originally taut fiber bundle loose, thus releasing the overload tension in the fiber bundle. When the tension in the fiber bundle is less than the set tension after being released, the gas pressure inside the cylinder will again be greater than the resultant force of the fiber bundle on the top of the piston rod of the double-rod cylinder 302. The force difference on both sides will again cause the piston rod of the cylinder to extend, making the originally insufficiently tensioned fiber bundle tight. This passive adjustment process provides the magnetic powder damper 103 in the magnetic powder damping function section 1 with magnetic reaction time, maintaining the dynamic stability of the tension on the fiber bundle path.

[0066] See Figure 3 , Figure 6 Three buffer guide wheel assemblies are provided in the tension buffer function section 3. Two of the buffer guide wheel assemblies are fixed on both sides of the double-rod cylinder 302 along the fiber path direction, and one buffer guide wheel assembly is installed at the top of the piston rod of the double-rod cylinder 302 to bear the tension on the fiber bundle path. In order to avoid the change in the conversion relationship between the resultant force of the fiber bundle on the buffer guide wheel assembly installed at the top of the piston rod and the actual tension in the fiber bundle during the extension and retraction of the piston rod, the three buffer guide wheel assemblies are arranged in a triangular pattern along the fiber path direction. The fiber paths (i.e., the internal common tangents) between the two fixed buffer guide wheel assemblies and the buffer guide wheel assembly at the top of the piston rod are parallel to each other. This ensures that the conversion relationship of "the resultant force of the fiber bundle on the buffer guide wheel assembly at the top of the piston rod = the actual tension in the fiber bundle × 2" remains unchanged.

[0067] See Figure 3 , Figure 6In the tension buffer function unit 3, the buffer guide wheel assembly fixed on both sides of the double-rod cylinder 302 consists of a shaft-mounted guide wheel and a fixed guide wheel support rod 304; the shaft-mounted guide wheel consists of a PTFE guide wheel sleeve 307, a guide wheel bearing 308, a guide wheel shaft 309, a bore spring retaining ring 310, and a shaft spring retaining ring 311; the PTFE guide wheel sleeve 307 is mounted on the outer ring of the guide wheel bearing 308 through the bore spring retaining ring 310, and the guide wheel bearing 308 is mounted on the outer ring of the guide wheel bearing 308 through the shaft spring retaining ring 311. The guide wheel is mounted on the guide wheel shaft 309; the entire guide wheel with shaft is mounted on the lateral slot of the fixed guide wheel support rod 304 and fastened by the guide wheel shaft set screw 306; the two buffer guide wheel assemblies are mounted on the upper surface of the buffer part mounting bracket 301 through the fixed guide wheel support rod 304, respectively located on both sides of the double rod cylinder 302, and the lateral slots of the fixed guide wheel support rod 304 are arranged face to face to prevent the guide wheel with shaft from coming out of the fixed guide wheel support rod 304 under the continuous action of the fiber bundle tension.

[0068] See Figure 3 , Figure 6 In the tension buffering function unit 3, the buffer guide wheel assembly installed at the top of the piston rod of the double-rod cylinder 302 consists of a shaft guide wheel and a moving guide wheel support rod 305, which is used to bear the tension on the fiber bundle path. The shaft guide wheel is installed on the longitudinal slot of the moving guide wheel support rod 305 through the guide wheel shaft set screw 306, and is installed at the top of the piston rod of the double-rod cylinder 302 through the moving guide wheel support rod 305. Since the fiber bundle tension borne by this buffer guide wheel assembly is vertically downward, the slot position of the moving guide wheel support rod 305 is different from that of the fixed guide wheel support rod 304. It is set as a longitudinal slot with the opening facing upward to ensure the stability of the force.

[0069] See Figure 3 , Figure 7 The ultrasonic dry yarn spreading function unit 4 includes two parts: an ultrasonic spreading rod assembly and a dry yarn spreading guide assembly. The ultrasonic spreading rod assembly includes an ultrasonic spreading rod 401, an ultrasonic vibrator 402, a vibrator fixing plate 403, and an ultrasonic spreading rod mounting bracket 404. The dry yarn spreading guide assembly includes a dry yarn spreading guide rod 405 and a dry yarn spreading guide rod mounting bracket 406.

[0070] See Figure 3 , Figure 7 The yarn spreading guiding function of the dry yarn spreading guide assembly is realized by the dry yarn spreading guide rod 405, which is fixed to the dry yarn spreading guide rod mounting bracket 406 by bolts. The dry yarn spreading guide rod mounting bracket 406 is provided with side plates and fastening connection holes that are adapted to the shape and size of the aluminum profile cross section at the front and rear, for fixing the dry yarn spreading guide assembly to the crossbeam of the aluminum profile mounting bracket.

[0071] See Figure 3, Figure 7 The ultrasonic yarn spreading function of the ultrasonic yarn spreading rod assembly is realized by the ultrasonic yarn spreading rod 401 and the ultrasonic transducer 402. The ultrasonic transducer 402 generates the required ultrasonic vibration under the drive of the external control box (L and R). The ultrasonic yarn spreading rod 401 concentrates this vibration on the fiber bundle to achieve ultrasonic yarn spreading. The ultrasonic yarn spreading rod 401 is fastened to the large end face of the ultrasonic transducer 402 by the stud structure at its top. The two also need to be fixed into a whole with a special adhesive. The small end face of the ultrasonic transducer 402 is fixed into a whole with the transducer fixing plate 403 by a special adhesive. The lower surface of the transducer fixing plate 403 is provided with a circular stepped structure for positioning the ultrasonic transducer 402. The upper end of the transducer fixing plate 403 is provided with a series of through holes and is fixed to the ultrasonic yarn spreading rod mounting bracket 404 by bolts.

[0072] See Figure 3 , Figure 7 The ultrasonic yarn spreading rod assembly should be installed on the small column at the top of the aluminum profile mounting bracket corresponding to the dry yarn spreading guide assembly. It slides and locks on the small column through the sliding groove on the ultrasonic yarn spreading rod mounting bracket 404 to adjust the relative distance between the ultrasonic yarn spreading rod assembly and the dry yarn spreading guide assembly, thereby adjusting the wrap angle of the yarn bundle on the ultrasonic yarn spreading rod 401. The size of this wrap angle will affect the effect of ultrasonic dry yarn spreading.

[0073] See Figure 3 , Figure 7 , Figure 8 The ultrasonic melting and impregnation functional unit 5 comprises four parts: an ultrasonic yarn spreading rod assembly, a yarn spreading and impregnation guide assembly, a liquid level monitoring and adjustment assembly, and a resin scraper assembly. The yarn spreading and impregnation guide assembly includes a heated melting resin tank 501, a yarn spreading and impregnation guide rod 502, and a yarn spreading and impregnation guide rod mounting bracket 503. The liquid level monitoring and adjustment assembly includes a liquid level monitoring and adjustment mounting bracket 504, a liquid level sensor 505, a hopper-mounted feeding cylinder 506, a feeding screw 507, a feeding cylinder fixing plate 508, and a small DC geared motor 509 (the hopper-mounted feeding cylinder 506, the feeding screw 507, the feeding cylinder fixing plate 508, and the small DC geared motor 509 together form a screw feeder). The resin scraper assembly includes a scraper heating roller 510, a resin scraper 511, a micro-motion slide table 512, and a slide table fixing plate 513.

[0074] See Figure 3 , Figure 7 , Figure 8The ultrasonic yarn spreading rod assembly in the ultrasonic melt impregnation function unit 5 is completely identical to the ultrasonic yarn spreading rod assembly in the ultrasonic dry yarn spreading function unit 4. It is also composed of an ultrasonic yarn spreading rod 401, an ultrasonic vibrator 402, a vibrator fixing plate 403, and an ultrasonic yarn spreading rod mounting bracket 404. The installation method and working principle are also exactly the same, and it also has the function of adjusting the yarn spreading wrap angle. The two are interchangeable. The difference is that in the ultrasonic melt impregnation function unit 5, the yarn spreading and impregnation guide assembly is matched with the ultrasonic yarn spreading rod assembly.

[0075] See Figure 3 , Figure 8 The yarn spreading and impregnation guiding component is guided by the yarn spreading and impregnation guiding rod 502, which is fixed to the yarn spreading and impregnation guiding rod mounting bracket 503 by bolts. The yarn spreading and impregnation guiding rod mounting bracket 503 has side plates and fastening connection holes that are adapted to the shape and size of the aluminum profile cross section at the front and rear, which are used to fix the yarn spreading and impregnation guiding component to the crossbeam of the aluminum profile mounting bracket.

[0076] See Figure 3 , Figure 8 The wetting function of the yarn spreading and wetting guide assembly is achieved by the heated molten resin pool 501. The surface of the heated molten resin pool 501 is coated with polytetrafluoroethylene to prevent the resin from solidifying and aging on its surface during long-term heating, thereby affecting its thermal conductivity. The heated molten resin pool 501 is connected to the yarn spreading and wetting guide rod 502 and the yarn spreading and wetting guide rod mounting bracket 503 by bolts. The heating and temperature monitoring of the heated molten resin pool are achieved by heating rods and thermistors embedded inside it. The relevant feedback control functions are integrated into the external control box (L and R).

[0077] See Figure 3 , Figure 8The liquid level monitoring and adjustment component in the ultrasonic melting and wetting functional unit 5 is fixed to the crossbeam of the aluminum profile mounting bracket via the liquid level monitoring and adjustment mounting bracket 504. Its liquid level monitoring function is achieved by the liquid level sensor 505, and its liquid level adjustment function is achieved by the screw feeder. The screw feeder is fixed to the liquid level monitoring and adjustment mounting bracket 504 via the feeding cylinder fixing plate 508. The feeding cylinder 506 with a hopper is fitted around the feeding screw 507 and installed on the front of the feeding cylinder fixing plate 508. The feeding screw 507 is connected to a small DC geared motor 509 via a blind hole with a keyway on its central shaft. The small DC geared motor 509 is installed on the back of the feeding cylinder fixing plate 508. When the liquid level... When the liquid level is below the sensing position of the liquid level sensor 505, the small DC geared motor 509 in the screw feeder starts and drives the feeding screw 507 to rotate. Under the push of the feeding screw 507, the room temperature solid resin powder (or small particles) in the hopper feeding cylinder 506 falls into the heated molten resin pool 501. When the room temperature solid resin melts and the liquid level in the heated molten resin pool 501 reaches the sensing position of the liquid level sensor 505, the small DC geared motor 509 in the screw feeder stops running. This cycle repeats to maintain the resin liquid level in the heated molten resin pool 501 in a dynamic and stable state. The relevant feedback control functions are integrated into the external control box (L and R).

[0078] See Figure 3 , Figure 8 The resin scraper assembly in the ultrasonic melting and impregnation functional unit 5 is located downstream of the fiber bundle path and is installed at the edge of the heated melting resin pool 501 via the slide table fixing plate 513. It is used to scrape off excess resin from the surface of the fiber bundle after ultrasonic impregnation and to allow the scraped resin to fall back into the heated melting resin pool 501. The main function of the resin scraper assembly is realized by the scraper heating roller 510 and the resin scraper 511.

[0079] See Figure 3 , Figure 8 The heating and temperature monitoring of the scraper heating roller 510 in the resin scraper assembly are also achieved by a heating rod and a thermistor embedded inside it. The purpose is to ensure the fluidity of the solid resin at room temperature and avoid tearing damage to the fibers during the scraping of excess resin. Correspondingly, the resin scraper 511 can also maintain a certain temperature under the heat radiation of the scraper heating roller 510. The resin scraper 511 is mounted on the micro-motion slide 512, which is mounted on the slide fixing plate 513. By adjusting the micro-motion slide 512, the distance between the scraper heating roller 510 and the resin scraper 511 can be precisely controlled to ensure that excess resin on the surface of the ultrasonically impregnated fiber bundle is scraped off while minimizing channel resistance.

[0080] See Figure 3 , Figure 9The bundled yarn feeding function unit 6 includes two parts: a bundled guide assembly and a bundled yarn feeding assembly. The bundled guide assembly includes a PTFE bundled wheel with a shaft 601, a bundled wheel fixing plate 602, a bundled guide mounting bracket 603, and a shaft end bolt fastener 604. The bundled yarn feeding assembly includes a bundled heating block 605, a bundled heating block bracket 606, a bracket heat insulation pad 607, a bundled nozzle 608, a yarn cooling nozzle 609, a bundled yarn feeding mounting bracket 610, a yarn feeding motor fixing plate 611, a yarn feeding motor 612, a yarn feeding extruder 613, a yarn feeding heating block 614, a yarn feeding heating block heat insulation pad 615, a yarn feeding guide nozzle 616, and a yarn feeding heating block mounting bracket 617.

[0081] See Figure 3 , Figure 9 The function of the bundle feeding functional unit 6 is mainly realized by the PTFE bundle gathering wheel 601 with shaft. The fiber bundle after passing through the resin scraper assembly still maintains good fluidity of the resin matrix. Under the guidance of the V-groove of the PTFE bundle gathering wheel 601 with shaft, the originally flattened fiber bundle gathers to the bottom of the V-groove under the action of tension, realizing the initial bundle after the yarn is spread and wetted. Under the guidance of the PTFE bundle gathering wheel 601 with shaft, it completes a 90° turn and enters the bundle feeding assembly. The PTFE bundle gathering wheel 601 with shaft end bolt fasteners 604 is installed on two bundle wheel fixing plates 602. The bundle wheel fixing plates 602 are installed on the bundle guiding mounting frame 603 with bolts. The lower end of the bundle guiding mounting frame 603 is provided with a wing plate and fastening connection holes that are adapted to the shape and size of the aluminum profile cross section, which are used to fix the bundle guiding assembly on the crossbeam of the aluminum profile mounting frame.

[0082] See Figure 3 , Figure 9 The bundled wire feeding assembly in the bundled wire feeding functional unit 6 is fixed on the crossbeam of the aluminum profile mounting frame through the bundled wire feeding mounting frame 610 and the wire feeding heating block mounting frame 617. Its function is mainly realized by three parts: the bundled heating block 605 and the bundled nozzle 608, the wire feeding extruder 613 and the wire feeding motor 612, and the wire feeding heating block 614 and the wire feeding guide nozzle 616.

[0083] See Figure 3 , Figure 9The function of the bundled heating block 605 and the bundled nozzle 608 in the bundled yarn feeding assembly is to heat, bundle, and shape the prepreg yarn after it has been initially bundled and guided by the PTFE take-up wheel 601, and to further control the resin content in the prepreg yarn through the orifice diameter of the bundled nozzle 608. The bundled heating block 605 and the bundled nozzle 608 are mounted on the bundled heating block support 606, which has a slot. The bundled heating block 605 and the bundled nozzle 608 can be adjusted left and right along the slot to ensure that the prepreg yarn exiting the bundled nozzle 608 can be smoothly fed. The prepreg yarn is fed smoothly into the extruder 613. A yarn cooling nozzle 609 is also installed on one side of the bundled heating block support 606 to blow cooling gas onto the prepreg yarn after bundled shaping, so that the heated prepreg yarn is cooled quickly. The room temperature solid resin in the prepreg yarn quickly recovers its rigidity and hardness under the action of the cooling gas, so as to facilitate yarn feeding and extrusion. In order to prevent the bundled heating block 605 from affecting the working temperature of the lower extruder 613 and the yarn feeding motor 612, a support heat insulation pad 607 is introduced between the bundled heating block support 606 and the bundled yarn feeding mounting frame 610.

[0084] See Figure 3 , Figure 9 In the bundled fiber feeding assembly, the fiber feeding extruder 613 and the fiber feeding motor 612 are mounted on the bundled fiber feeding mounting bracket 610 via a fiber feeding motor fixing plate 611. The fiber feeding extruder 613 and the fiber feeding motor 612 are respectively mounted on the front and rear sides of the fiber feeding motor fixing plate 611 to achieve fiber feeding and tension reduction of the pre-impregnated fiber bundle. For the fiber bundle in the entire ultrasonic yarn spreading and impregnation 3D printing system path channel, the fiber feeding extruder 613 is the watershed for the presence or absence of tension in the fiber bundle. The fiber feeding extruder 613 has a traction effect on the upstream fiber bundle, and its traction force is the key power source for the fiber bundle to overcome the channel resistance. Its traction effect is also one of the reasons for ensuring a constant tension in the upstream fiber bundle; the fiber feeding extruder 613 has a pushing and feeding effect on the downstream fiber bundle, so the tension in the downstream fiber bundle is almost zero. The feeding speed of the fiber feeding extruder 613 is provided by the rotation speed of the fiber feeding motor 612 and is consistent with the moving speed of the composite material print head 7 in the working state. This can ensure continuous fiber feeding while avoiding filament redundancy. In addition, the tension in the downstream fiber bundle of the fiber feeding extruder 613 is almost zero, which can improve the adhesion of the prepreg fiber bundle on the printing platform and help improve the printing quality.

[0085] See Figure 3 , Figure 9 The bundled filament feeding mounting bracket 610 has a slot, and the filament feeding motor fixing plate 611 can be adjusted in front and back along the slot to ensure that the prepreg filaments coming out of the bundled nozzle 608 can smoothly enter the filament feeding extruder 613.

[0086] See Figure 3 , Figure 9 The filament feeding heating block 614 and filament feeding guide nozzle 616 in the bundled filament feeding assembly are fixed to the crossbeam of the aluminum profile mounting frame via the filament feeding heating block mounting bracket 617, for reheating the cooled prepreg filament bundle. Since the prepreg filament bundle will then enter the composite material print head 7, which is constantly moving during the printing process, the short section of prepreg filament bundle before the composite material print head 7 will constantly swing left and right. If the resin matrix in the filament bundle remains solid at room temperature, its rigidity is too high for the large prepreg filament bundle, which will cause the composite material print head 7 to jam. Moreover, if the resin matrix of the prepreg filament bundle at room temperature breaks, it is very easy to cause the fiber itself to break, which will force the printing work to stop. At this time, arranging the filament feeding heating block 614 and filament feeding guide nozzle 616 below the filament feeding extruder 613 to reheat and guide the cooled filament will effectively solve the above problems. In addition, in order to reduce the impact of the temperature of the wire feeding heating block 614 on the operating temperature of the wire feeding extruder 613 and the wire feeding motor 612, a wire feeding heating block heat insulation pad 615 is introduced between the wire feeding heating block 614 and the wire feeding heating block mounting frame 617.

[0087] See Figure 3 , Figure 10 The composite material printhead 7 includes a printhead filament heating block 701, a filament heating block heat insulation pad 702, a filament heating block support plate 703, a printhead box-type mounting bracket 704, a box-type heat insulation sheet 705, a slider connector 706, a print heating block heat insulation pad 707, a print heating block 708, and a print nozzle 709.

[0088] See Figure 3 , Figure 10 The function of the composite material printhead 7 is mainly realized by two parts: the printhead filament heating block 701, the printing heating block 708, and the printhead nozzle 709. The printhead filament heating block 701 is used to reheat and soften the prepreg filament of the composite material (the distance from the filament feeding guide nozzle 616 to the composite material printhead 7 is relatively long, and the prepreg filament of the solid resin matrix at room temperature has cooled down) so that the prepreg filament can enter the composite material printhead 7. The filament entering the composite material printhead 7 finally enters the printing heating block 708 and the printing nozzle 709, and the composite material 3D printing is completed under the guidance and compaction ironing action of the printing nozzle 709.

[0089] The composite material printhead 7 is integrated with the filament heating block 701, the printing heating block 708, and the printhead nozzle 709 via a printhead box-type mounting bracket 704. To prevent the filament heating block 701 and the printing heating block 708 from affecting the X-axis slider, a filament heating block heat insulation pad 702 is introduced below the filament heating block 701 and then mounted on the filament heating block support plate 703. The filament heating block support plate 703 serves as the upper cover plate and is connected to the printhead box-type mounting bracket 704. Similarly, a printing heating block heat insulation pad 707 is introduced above the printing heating block 708 and then mounted below the printhead box-type mounting bracket 704. A box-type heat insulation plate 705 is also introduced on the back plate of the printhead box-type mounting bracket 704 and then connected to the X-axis slider of the dual X-axis 3D printing platform via a slider connector 706.

[0090] See Figure 3 , Figure 10 In the cutting function unit 8, pneumatic scissors 801 are used to cut the printed filament bundle. Two pneumatic scissors 801 are fixed below the origin of the two X-axis via scissor mounting brackets 802. When a composite material printhead 7 finishes printing and returns to its X-axis zero point, the limit switch at the zero point will simultaneously trigger the corresponding pneumatic scissors 801 to cut the redundant prepreg filament bundle dragged by the composite material printhead 7. After the cutting, a small section of prepreg filament bundle will remain below the composite material printhead 7. This is done to prevent the filament bundle from shrinking back into the printing heating block 708 due to cooling (if this happens, the filament bundle will have to be re-threaded to continue printing). On the other hand, leaving a small section of prepreg filament bundle will make it easier for the prepreg filament to adhere to the printing platform when the next printing starts, thus preventing the filament bundle from detaching and slipping during the initial printing stage.

[0091] See Figure 2 , Figure 3 The entire printing platform is cooled by a powerful cooling fan 9, which greatly improves the cooling speed of the prepreg yarn after printing, enhances the shaping ability of the prepreg yarn, and strengthens the adhesion between the yarn and the printing platform.

[0092] See Figure 2 , Figure 3 , Figure 9 , Figure 10In the integrated ultrasonic yarn spreading and impregnation 3D printing system, the filament outlet diameters of the three nozzles (bundling nozzle 608, filament feeding guide nozzle 616, and printing nozzle 709) in each functional unit decrease sequentially. The diameter of the printing nozzle 709 is 0.5 mm smaller than that of the bundled nozzle 608, which will compress the resin in the pre-impregnated filament bundle to a certain extent. At the same time, under the action of their respective heating blocks (bundling heating block 605, filament feeding heating block 614, and printing heating block 708), a tiny resin molten pool will be formed inside the nozzle to further promote the impregnation of the resin matrix inside the fiber bundle.

Claims

1. A highly efficient integrated system for ultrasonic spreading, impregnation, and 3D printing of large-tow dry fibers, characterized in that: The system comprises an integrated ultrasonic yarn spreading and impregnation 3D printing system, its functional components, a dual X-axis 3D printing platform, an aluminum profile mounting frame, and external control boxes L and R. Each functional component of the integrated ultrasonic yarn spreading and impregnation 3D printing system adopts a modular design, integrated and mounted on the aluminum profile mounting frame and the dual X-axis 3D printing platform using detachable sliders. The dual X-axis 3D printing platform is an XYZ three-coordinate motion and control system with two sets of parallel X-axis axes. The two sets of X-axis axes can be controlled individually or move collaboratively, exhibiting excellent repeatability. The aluminum profile mounting frame serves as the supporting frame for each functional component, fitting snugly onto the dual X-axis 3D printing platform. The external control boxes L and R are symmetrically arranged on both sides of the dual X-axis 3D printing platform, interacting with the platform's own control system to achieve coordinated control of the various functional components. By utilizing ultrasonic vibration and the cavitation effect of ultrasound in liquids, various untwisted large filament bundles of fibers are continuously ultrasonically untwisted. The number of monofilaments in the untwisted large filament bundles is greater than or equal to 6K. A room temperature solid resin matrix is ​​impregnated into the interior of the filament bundle, and then used as filament material for 3D printing. This expands the fiber bundle specifications and types applicable to the 3D printing process of fiber-reinforced composite materials and improves the resin wettability within the filament bundle. The integrated ultrasonic yarn spreading and impregnation 3D printing system comprises nine different functional parts, which are arranged sequentially from the outside to the inside and from top to bottom according to the fiber bundle path. These nine functional parts are: magnetic powder damping functional part, tension detection functional part, tension buffering functional part, ultrasonic dry yarn spreading functional part, ultrasonic melting and impregnation functional part, bundled yarn feeding functional part, composite material print head, shearing functional part, and full-platform high-power cooling fan. The ultrasonic melt wetting function unit comprises four parts: ultrasonic yarn spreading rod assembly, yarn spreading and wetting guide assembly, liquid level monitoring and adjustment assembly, and resin scraper assembly; the ultrasonic yarn spreading rod assembly is completely identical to the ultrasonic yarn spreading rod assembly in the ultrasonic dry yarn spreading function unit. The yarn spreading and impregnation guide assembly is fixed on the crossbeam of the aluminum profile mounting frame via the yarn spreading and impregnation guide rod mounting bracket. Its yarn spreading and guiding function is realized by the yarn spreading and impregnation guide rod, and its impregnation function is realized by heating the molten resin pool. The heating and temperature monitoring of the molten resin pool are realized by the heating rod and thermistor embedded inside it. The relevant feedback control functions are integrated into the external control box L and the external control box R. The liquid level monitoring and adjustment component is fixed to the crossbeam of the aluminum profile mounting bracket via a liquid level monitoring and adjustment mounting frame. Its liquid level monitoring function is realized by a liquid level sensor, and its liquid level adjustment function is realized by a screw feeder. When the liquid level is lower than the sensing position of the liquid level sensor, the small DC geared motor in the screw feeder starts and drives the feeding screw to rotate, and the room temperature solid resin powder or small particles in the hopper feeding cylinder fall into the heated molten resin pool. When the room temperature solid resin melts and the liquid level in the heated molten resin pool reaches the sensing position of the liquid level sensor, the small DC geared motor in the screw feeder stops running. This cycle repeats to maintain the resin liquid level in the heated molten resin pool in a dynamic and stable state. The relevant feedback control functions are integrated into the external control box L and the external control box R. The resin scraper assembly is installed at the edge of the heated and molten resin pool to scrape off excess resin from the surface of the fiber bundles after ultrasonic impregnation, and to allow the scraped resin to fall back into the heated and molten resin pool. The function of the resin scraper assembly is achieved by the scraper heating roller and the resin scraper. Heating and temperature monitoring in the resin scraper assembly are also achieved by the heating rod and thermistor embedded inside. The resin scraper is installed on a micro-motion slide, and the distance between the scraper heating roller and the resin scraper is precisely controlled by adjusting the micro-motion slide.

2. The system according to claim 1, characterized in that: The magnetic powder damping functional unit includes a fiber bundle tray, a winding drive toothed disc, a magnetic powder damper, and a damper mounting bracket. The lower end of the damper mounting bracket is fixed on an aluminum profile mounting bracket, and the magnetic powder damper is fixed on the damper mounting bracket. A winding drive toothed disc is set on the back of the fiber bundle tray. Under external drive, the winding drive toothed disc causes the untwisted large filament bundle to be wound from the large roll of fiber yarn onto the fiber bundle tray.

3. The system according to claim 1, characterized in that: The tension detection function includes a combined tension sensor and a sensor mounting bracket. The combined tension sensor is fixed on the sensor mounting bracket, and the lower end of the sensor mounting bracket is fixed on the aluminum profile mounting bracket. The structure of the upper part ensures that the center line of the three guide wheels on the combined tension sensor coincides with the expected fiber bundle path.

4. The system according to claim 1, characterized in that: The tension buffering functional unit includes a buffer mounting bracket, a double-rod cylinder, a cylinder mounting plate, a fixed guide wheel support rod, a movable guide wheel support rod, a guide wheel shaft set screw, a PTFE guide wheel sleeve, a guide wheel bearing, a guide wheel shaft, a hole spring retainer, and a shaft spring retainer. The PTFE guide wheel sleeve, guide wheel bearing, guide wheel shaft, hole spring retainer, and shaft spring retainer form a shaft-mounted guide wheel. The shaft-mounted guide wheel, together with the fixed or movable guide wheel support rod, forms the buffer guide wheel assembly. All parts of the tension buffering functional unit are integrated and mounted on the buffer mounting bracket, which is fixed to an aluminum profile mounting bracket. A double-rod cylinder is used for passive overload protection of the wire bundle tension. The double-rod cylinder is fixed to the cylinder mounting plate, and the cylinder mounting plate engages with the groove on the cylinder body to position the double-rod cylinder. The cylinder mounting plate is connected to the double-rod cylinder, and the remaining part is connected to the side plate inside the center hole of the buffer mounting bracket, thus achieving integrated mounting of the double-rod cylinder on the buffer mounting bracket. The tension buffering function section is equipped with three buffer guide wheel assemblies. Two of the buffer guide wheel assemblies are fixed on both sides of the double-rod cylinder along the fiber path direction, and one buffer guide wheel assembly is installed at the top of the piston rod of the double-rod cylinder to bear the tension on the fiber bundle path. The three buffer guide wheel assemblies are arranged in a triangular pattern along the fiber path direction. The fiber paths (i.e., the internal common tangents) between the two fixed buffer guide wheel assemblies and the buffer guide wheel assembly at the top of the piston rod are parallel to each other, ensuring that the conversion relationship "the resultant force of the fiber bundle on the buffer guide wheel assembly at the top of the piston rod = the actual tension in the fiber bundle × 2" remains unchanged.

5. The system according to claim 1, characterized in that: The ultrasonic dry yarn spreading function unit comprises two parts: an ultrasonic spreading rod assembly and a dry yarn spreading guide assembly. The dry yarn spreading guide assembly is fixed to the crossbeam of the aluminum profile mounting frame via a dry yarn spreading guide rod mounting bracket, and its spreading guiding function is achieved by the dry yarn spreading guide rod. The ultrasonic spreading rod assembly is mounted on a small column at the top of the aluminum profile mounting frame. It slides and locks on the small column via a sliding groove on the ultrasonic spreading rod mounting bracket, thereby adjusting the relative distance between the ultrasonic spreading rod assembly and the dry yarn spreading guide assembly, and thus adjusting the wrap angle of the yarn bundle on the ultrasonic spreading rod. The size of this wrap angle will affect the ultrasonic dry yarn spreading effect.

6. The system according to claim 1, characterized in that: The bundled yarn feeding function unit consists of two parts: a bundle guiding assembly and a bundled yarn feeding assembly. The function of the bundle guiding assembly is realized by a shafted PTFE bundle wheel. Under the guidance of the V-groove of the shafted PTFE bundle wheel, the originally flattened fiber bundle gathers to the bottom of the V-groove under tension, realizing the initial bundle after the yarn is spread and wetted. Under the guidance of the shafted PTFE bundle wheel, it completes a 90° turn and enters the bundled yarn feeding assembly. The bundled wire feeding assembly is fixed on the crossbeam of the aluminum profile mounting frame through the bundled wire feeding mounting frame and the wire feeding heating block mounting frame. Its function is realized by three parts: the bundled heating block and the bundled nozzle, the wire feeding extruder and the wire feeding motor, and the wire feeding heating block and the wire feeding guide nozzle. The function of the bundle heating block and the bundle nozzle in the bundle feeding assembly is to heat and bundle the prepreg bundle after it has been initially bundled and guided by the PTFE take-up wheel with shaft, and to further control the resin content in the prepreg bundle by the orifice diameter of the bundle nozzle. The filament feeding extruder and filament feeding motor in the bundled filament feeding assembly are mounted on the bundled filament feeding mounting frame via a filament feeding motor fixing plate. The filament feeding extruder and filament feeding motor are respectively mounted on the front and rear sides of the filament feeding motor fixing plate to achieve filament feeding and tension reduction of the pre-impregnated filament bundle. The filament feeding extruder has a traction effect on the fiber bundle upstream, and its traction force is the key power source for the fiber bundle to overcome the channel resistance. At the same time, its traction effect is also one of the reasons for ensuring a constant tension in the fiber bundle upstream. The filament feeding extruder has a pushing and feeding effect on the fiber bundle downstream, so the tension in the fiber bundle downstream is almost zero. The filament feeding speed of the filament feeding extruder is provided by the rotational speed of the filament feeding motor and is consistent with the moving speed of the composite material printing head in the working state. The wire feeding heating block and the wire feeding guide nozzle in the bundled wire feeding assembly are fixed on the crossbeam of the aluminum profile mounting frame through the wire feeding heating block mounting bracket, and are used to reheat the cooled prepreg bundle.

7. The system according to claim 1, characterized in that: The composite material printhead integrates the filament feeding heating block and the printing heating block with the printhead nozzle via a printhead box-type mounting bracket. In the shearing function section, pneumatic shears cut the printed filament bundle. Two pneumatic shears are fixed below the origins of the two X-axis via shear mounting brackets. When a composite material printhead completes printing and returns to its X-axis zero point, the limit switch at the zero point simultaneously triggers the corresponding pneumatic shears to cut the redundant pre-impregnated filament bundle dragged by the composite material printhead. A small section of pre-impregnated filament bundle remains below the cut composite material printhead. This serves two purposes: firstly, to prevent the filament bundle from retracting into the printing heating block due to cooling; and secondly, to facilitate better adhesion between the pre-impregnated filament and the printing platform at the start of the next print.

8. The system according to claim 6, characterized in that: The function of the composite material printhead is realized by two parts: the printhead filament heating block and the printhead heating block and the printhead nozzle. The printhead filament heating block is used to heat and soften the pre-impregnated composite material filament again so that the pre-impregnated filament can enter the composite material printhead. The filament that enters the composite material printhead finally enters the print heating block and the printhead nozzle, and the composite material 3D printing is completed under the guidance and compaction ironing action of the printhead nozzle. In the integrated ultrasonic yarn spreading and impregnation 3D printing system, the three nozzles in each functional unit—the bundle nozzle, the filament feeding guide nozzle, and the printing nozzle—have progressively smaller filament outlet diameters. The printing nozzle diameter is 0.5 mm smaller than that of the bundle nozzle, which compresses the resin in the pre-impregnated filament bundle. Simultaneously, under the action of their respective heating blocks—the bundle heating block, the filament feeding heating block, and the printing heating block—tiny resin pools are formed inside the nozzles to further promote the impregnation of the resin matrix within the fiber bundle.

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