In-situ foaming and extrusion integrated 3D printing device and printing method

Abstract

The application discloses an in-situ foaming and extruding integrated 3D printing device and a printing method, and belongs to the technical field of multifunctional additive manufacturing. The device comprises a foaming cavity, a rotating main shaft, folding blades, a push rod assembly, a rack plunger, an exhaust valve and a driving inter-finger coupling assembly. The foaming cavity can be used as a plunger cylinder, and a discharge port detachably connected with a plug or a printing needle is arranged at the lower end of the foaming cavity; the rotating main shaft is provided with the folding blades which can be switched between an unfolded position and a retracted position; the rack plunger is driven by a worm transmission mechanism to reciprocate along the axial direction; the exhaust valve is automatically closed when the cavity pressure rises through a magnetic self-closing mechanism to automatically close the exhaust passage; the push rod assembly is mechanically linked with the rack plunger, and the folding blades are automatically driven to be folded and unfolded along with the axial movement of the plunger; and the inter-finger coupling assembly is switched through the axial position. The problems that the foam ceramic ink in the prior art introduces cavities when being transferred and filled, destroys the stability of the foam structure, and causes poor printing continuity due to the loss of volatile components are solved.

Description

Technical Field

[0001] This invention belongs to the field of multifunctional foam ceramic additive manufacturing technology, specifically relating to an in-situ foaming and extrusion integrated 3D printing device and printing method. Background Technology

[0002] The statements in this section are merely background information related to the present invention and do not necessarily constitute prior art.

[0003] Lightweight, high-strength foam ceramics are important structural and functional materials, characterized by their lightweight nature and unique porous structure, offering broad application prospects in fields such as biomedicine, filtration and separation, and thermal insulation and energy absorption. Combined with 3D printing technology, they can be used to customize biomimetic materials, metamaterials, and other potentially revolutionary new materials. Traditional processes typically employ direct foaming to prepare particle-stabilized foam ceramic ink, which is then transferred to a printing barrel and extruded using a pneumatic plunger or screw to create ceramic components with complex shapes and hierarchical porous structures.

[0004] However, the process of transferring foam ink from the foaming device to the printing barrel is a critical step affecting printing stability and component quality. Because particle-stabilized foam inks typically have high apparent viscosity and poor flowability, achieving dense filling during manual loading is difficult, easily trapping air and forming localized voids. These voids cause pressure fluctuations inside the barrel during subsequent extrusion, leading to discontinuous extrusion of foam filaments, flow fluctuations, and even filament breakage, thus reducing dimensional accuracy and structural integrity. While vacuum degassing or centrifugal degassing can typically remove internal air bubbles from ordinary high-viscosity slurries, particle-stabilized foam ceramic inks are prone to instability phenomena such as foam drainage, bubble coalescence, and Ostwald curing under vacuum or centrifugal conditions, resulting in foam structure damage, deterioration of pore size distribution, and alterations in rheological properties. Summary of the Invention

[0005] To address the aforementioned problems, this invention provides an integrated in-situ foaming and extrusion 3D printing device and method, which solves the problems in the prior art where voids are introduced and foam structure stability is damaged during the transfer and filling of foam ceramic ink between the foaming device and the printing cylinder, as well as the loss of volatile components leading to poor printing continuity and low forming accuracy.

[0006] To achieve the above objectives, the present invention is implemented through the following technical solution: In a first aspect, the present invention provides an integrated in-situ foaming and extrusion 3D printing device, comprising a foaming cavity, a rack plunger, a rotating spindle, a worm gear, and a finger coupling assembly. The finger coupling assembly has two shifting positions, which are respectively engaged with the rotating spindle and the worm gear for transmission. The foaming cavity can serve as a plunger cylinder, and its lower end is provided with a discharge port. A rotating spindle is disposed within the foaming cavity, and a folding blade is mounted on the rotating spindle. The folding blade can switch between an unfolded position and a retracted position. A rack plunger is also disposed on the rotating spindle, and the rack plunger is coaxially engaged with the rotating spindle. The rack plunger is driven by a worm gear transmission mechanism to reciprocate along the axial direction. An exhaust valve is installed on the rack plunger. The exhaust valve is provided with an exhaust channel. The exhaust channel is in the open state when the pressure in the foaming chamber is lower than the set value, and switches to the closed state when the pressure in the foaming chamber rises to the set value. A push rod assembly is disposed within the rotating spindle. The push rod assembly is mechanically linked to the rack plunger. When the rack plunger moves axially, it drives the push rod assembly to switch the folding blade between an unfolded and retracted position. The finger coupling assembly is connected to the rotating spindle drive when it is engaged with the finger teeth of the rotating spindle coupling, and is connected to the worm drive when it is engaged with the finger teeth of the worm coupling.

[0007] As a further implementation, the exhaust valve includes a lower valve housing, an upper valve housing, an exhaust plunger, a control spring, a lower magnet, and an upper magnet. The lower valve housing is threadedly connected to the rack plunger, with four springs evenly distributed on the plunger. The control spring is connected between the lower end of the lower valve housing and the exhaust plunger. The exhaust plunger has a damping hole, and the lower magnet and a rubber ring are fitted onto the exhaust plunger. The upper valve housing is connected above the lower valve housing and has an exhaust hole. The upper magnet is installed inside the upper valve housing. Under the elastic force of the control spring, the exhaust plunger remains in a downward position, keeping the exhaust passage in an open position. The upper magnet and the lower magnet are arranged opposite each other, and when the exhaust plunger moves upward to the position where the two magnets are attracted to each other, the exhaust passage remains in a closed position.

[0008] As a further implementation, the push rod assembly includes a push rod, a stop block, and a stop block spring; the stop block has a limiting groove that cooperates with the push rod, and the stop block spring provides an elastic force to extend the stop block outward; the arc-shaped end of the stop block, in the extended state, forms an arc-shaped surface contact with the inner wall of the rack plunger; the push rod is connected to the folding blade, and when the stop block is axially displaced under the drive of the inner wall of the rack plunger, the push rod drives the folding blade to switch between an unfolded position and a retracted position; the stop block has a dead point position, and after the stop block reaches the dead point position, it can be pressed into the interior of the rotating spindle.

[0009] As a further implementation, the inner wall of the rack plunger is provided with an upper sealing ring and a lower sealing ring; the installation height of the upper sealing ring is higher than the highest height of the end of the folding blade when it is in the retracted position; the installation height of the lower sealing ring is higher than the shoulder position of the rotating spindle when the rack plunger is at its highest position, so that the lower sealing ring is disengaged from the rotating spindle body.

[0010] As a further implementation, the rotating spindle is mounted on the fixed spindle via an angular contact ball bearing. The upper end of the rotating spindle is provided with coupling fingers. When the inter-finger coupling assembly engages with the coupling fingers at the upper end of the rotating spindle, it drives the rotating spindle to rotate. The upper end of the fixed spindle is connected to the worm gear via an angular contact ball bearing. The lower end of the worm gear is provided with coupling fingers. When the inter-finger coupling assembly engages with the coupling fingers at the lower end of the worm gear, it drives the worm gear to rotate.

[0011] As a further implementation, the fixed spindle is divided into upper and lower sections, which are detachably connected by a fixed coupling and set screws. The lower section of the fixed spindle, together with the rotating spindle and the parts in contact with the material, constitutes a detachable cleaning unit.

[0012] As a further implementation, a detachable closure is connected to the discharge port, the closure including a plug and a printing needle, the plug and the printing needle being interchangeably mounted on the discharge port.

[0013] Secondly, the present invention also provides a printing method for an integrated in-situ foaming and extrusion 3D printing device, comprising the following steps: Foaming steps: Raise the rack plunger to the highest position, the folding blades unfold during the raising process, the discharge port is closed, ceramic particles, surfactant and solution are added into the foaming cavity, the finger coupling assembly is switched to the first position and connected to the rotating spindle, the rotating spindle is driven to rotate, the material in the cavity is stirred and foamed until a stable foam ink is formed. Exhaust procedure: Switch the finger coupling assembly to the second position and connect it to the worm gear, drive the rack plunger to move downward, and discharge excess gas in the cavity through the exhaust valve. After the cavity pressure increases, the exhaust valve will automatically close. Printing steps: Replace the plug at the discharge port with a printing needle, drive the rack plunger to continue moving downwards, the stop block moves downwards with the rack plunger, pushes the push rod to retract the folding blade, and as the rack plunger continues to move downwards, the stop block is pushed into the main shaft; during the downward movement of the rack plunger, foam ink is stably extruded through the printing needle, and continuous printing is achieved by coordinating the movement speed of the rack plunger and the movement speed of the printing needle; Reset Steps: After printing is complete, replace the printing needle with a plug, drive the rack plunger to move upward, creating negative pressure in the cavity. The exhaust valve resets and opens under the negative pressure, and the folded blades unfold again as the rack plunger moves upward until the rack plunger returns to its highest position, and the device returns to the initial foaming state.

[0014] As a further implementation, in the foaming step, the rotation speed driving the rotating spindle is increased in stages: first, a ceramic particle suspension is formed at a first rotation speed, then a surfactant is added and the speed is increased to a second and a third rotation speed, which are maintained for a predetermined time. After adjusting the pH value of the system according to the foaming state, the speed is increased to a fourth rotation speed for full foaming until the volume of the foam ink no longer increases.

[0015] As a further implementation, in the venting step, after the rack plunger moves down to contact the foam ink, excess gas is slowly discharged through the damping orifice of the venting valve; when the foam ink blocks the damping orifice of the venting plunger, the cavity pressure continues to rise, and the venting plunger moves up until the upper magnet and the lower magnet are attracted to each other, keeping the venting channel closed; in the reset step, the upward movement of the rack plunger creates a negative pressure in the cavity, and the upper magnet and the lower magnet disconnect under the action of the negative pressure, the venting plunger resets under the action of the gas control spring, and the venting channel reopens.

[0016] Compared with the prior art, the advantages and positive effects of this invention are: This invention integrates the foaming, storage, and extrusion processes into a single sealed cavity, avoiding air introduction and mechanical disturbance during the transfer and filling of foam ink. This effectively reduces aging phenomena such as foam drainage, bubble merging, and Ostwald curing, maintaining the uniformity of cell size, porosity, and particle network structure. Through the mechanical linkage between the rack and pinion plunger and the push rod assembly, the folded blades automatically retract as the plunger moves down and automatically unfold as the plunger moves up, eliminating the need for a separate drive mechanism. The interdigital coupling assembly enables the shared drive for both foaming and stirring and plunger extrusion functions, simplifying the mechanical structure of the device and providing an equipment foundation for the continuous and automated development of foam ceramic additive manufacturing.

[0017] This invention shortens the time interval between foaming and printing due to closed-loop in-situ foaming, reduces the loss of volatile components such as ethanol, ammonia, and acid-base regulators, helps maintain the stability of slurry composition, pH value, and rheological properties, and improves extrusion pressure stability and printing continuity.

[0018] This invention utilizes a magnetic self-closing exhaust valve structure, which can actively expel excess gas from the cavity before extrusion and automatically close and seal after the cavity pressure increases, without requiring external control signals. The structure is simple and reliable. Attached Figure Description

[0019] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0020] Figure 1 This is a schematic diagram of the overall structure of the in-situ foaming and extrusion integrated 3D printing device of the present invention; Figure 2 This is a structural diagram of the push rod assembly of the device of the present invention; Figure 3 For the present invention Figure 1 Enlarged view of a portion of point A in the middle; Figure 4 This is a diagram of the plug structure of the device of the present invention; Figure 5 This is a schematic diagram of the apparatus of the present invention during the foaming stage; Figure 6 This is a schematic diagram of the device of the present invention during the exhaust stage; Figure 7 This is a schematic diagram of the device of the present invention during the printing stage; Figure 8 This is a schematic diagram of the device of the present invention during the reset phase; Figure 9 This is a partial enlarged view of the sealing ring of the present invention; Figure 10 This is a structural diagram of the finger coupling assembly of the device of the present invention; Figure 11 This is a top view of the finger coupling assembly of the device of the present invention.

[0021] In the diagram: 1. Needle; 2. Foaming chamber; 3. Folded blade; 4. Push rod assembly; 401. Stop block; 402. Stop block spring; 403. Push rod; 5. Rotating spindle; 6. Exhaust valve; 601. Exhaust plunger; 602. Air control spring; 603. Rubber ring; 604. Lower magnet; 605. Lower valve housing; 606. Upper magnet; 607. Upper valve housing; 7. Angular contact ball bearing; 8. Second-stage fixed spindle; 9. Sealing ring; 10. Rack plunger; 11. Finger coupling assembly; 1101. Finger coupling; 1102. Pulley driven rod; 1103. Pulley tension spring; 1104. Pulley; 1105. Fixed back plate; 12. Fixed coupling; 13. Set screw; 14. First-stage fixed spindle; 15. Worm gear; 16. Plug. Detailed Implementation

[0022] It should be noted that the following detailed description is illustrative and intended to provide further explanation of the invention. Unless otherwise specified, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0023] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of exemplary embodiments according to the invention. As used herein, unless otherwise expressly indicated by the invention, the singular form is intended to include the plural form as well. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0024] Example 1 This embodiment provides an integrated in-situ foaming and extrusion 3D printing device, such as... Figures 1-4 As shown, this device mainly consists of a foaming chamber 2, a rotating spindle 5, a folding blade 3, a push rod assembly 4, a rack and pinion plunger 10, an exhaust valve 6, a fixed spindle, a worm gear, and an active finger coupling assembly 11.

[0025] The foaming chamber 2 is a closed cylindrical chamber with a discharge port at its lower end. A plug 16 or a printing needle 1 can be detachably connected to the discharge port.

[0026] The rotating spindle 5 is coaxially mounted inside the foaming chamber 2, with folded blades 3 installed at its lower part. The rotating spindle 5 is supported and mounted on the second fixed spindle 8 by angular contact ball bearings 7. The fixed spindle is divided into two sections: a first fixed spindle 14 and a second fixed spindle 8, which are detachably connected by a fixed coupling 12 and set screws 13. This segmented, detachable design allows the second fixed spindle 8, along with the rotating spindle 5 and related material-contacting components, to be removed entirely by loosening the set screws 13, eliminating the need to disassemble the entire machine. This reduces the difficulty and cost of cleaning operations and avoids the risk of contamination of non-contact components by the cleaning fluid. The upper end of the first fixed spindle 14 is connected to a worm gear 15 via angular contact ball bearings 7, and the lower end of the worm gear 15 has coupling fingers; the upper end of the rotating spindle 5 also has coupling fingers.

[0027] The finger coupling assembly 11 has two shifting positions, respectively engaging with the rotating spindle and the worm gear. Under the action of the push rod 1101 and the push rod driven rod 1102, the finger coupling 1101 can switch axially between two positions: when engaged with the coupling fingers of the rotating spindle 5, it is connected to the upper coupling fingers of the rotating spindle 5, driving the rotating spindle 5 to rotate; when engaged with the coupling fingers of the worm gear 15, it is connected to the lower coupling fingers of the worm gear 15, driving the worm gear 15 to rotate, thereby driving the rack plunger 10 to move axially. A sealing ring 9 is provided between the rotating spindle 5 and the rack plunger 10. The sealing ring 9 is located on the top inner side of the rack plunger 10. Figure 9 By switching the axial position of the finger coupling assembly 11, a single servo motor can realize both foaming and stirring and plunger extrusion functions, eliminating the need for two independent drive systems, simplifying the mechanical structure of the device, and ensuring a rapid switching response between foaming and extrusion operations.

[0028] like Figures 10-11As shown, the fingertip coupling assembly 11 includes a fingertip coupling 1101, a lever driven rod 1102, a lever spring 1103, a lever 1104, and a fixed back plate 1105. The fingertip coupling 1101 is slidably mounted on the fixed back plate 1105 and rotatably connected to one end of the lever driven rod 1102. The other end of the lever driven rod 1102 is hinged to one end of the lever 1104 via a hinge shaft, which is fixedly mounted on the fixed back plate 1105. The lever driven rod 1102 and the lever 1104 are connected... 4. Spring fixing pins are provided in the middle of each part. Two spring fixing pins are equipped with lever springs 1103. The lever springs 1103 are in a tensioned state. When the lever 1104 is turned, the lever spring 1103 drives the lever driven rod 1105 to rotate under the action of tension, thereby driving the fingertip coupling 1101 to slide on the fixed back plate 1105, so as to achieve engagement with the rotating spindle 5 or the worm gear 15. The fingertip coupling 1101 is rotated by a servo motor, thereby driving the rotating spindle 5 and the rack and pinion plunger 10 to rotate.

[0029] The rack plunger 10 is sleeved around the rotating spindle 5 and the fixed spindle, coaxially engaging with the rotating spindle 5. Its outer circumferential rack meshes with the worm gear 15, and is driven by the worm gear 15 transmission mechanism to reciprocate axially. The inner wall of the rack plunger 10 is provided with an upper sealing ring 9 and a lower sealing ring 9. The installation height of the upper sealing ring 9 is higher than the highest height of the end of the folded blade 3 when it is in the retracted position, ensuring that when the rack plunger 10 moves downward during extrusion, the upper sealing ring 9 is always located above the blade retraction area, effectively preventing foam ink from leaking upward from the blade installation area and ensuring the sealing and pressure stability of the cavity during extrusion.

[0030] The installation height of the lower sealing ring 9 is higher than the shoulder of the rotating spindle 5 when the rack plunger 10 is at its highest position, so that the lower sealing ring 9 is disengaged from the shaft of the rotating spindle 5; this ensures that when the rack plunger 10 is raised to its highest position during the foaming stage, the lower sealing ring 9 does not generate additional frictional resistance to the rotating spindle 5, allowing the rotating spindle 5 to rotate freely at high speed, while avoiding abnormal wear of the sealing ring under high-speed rotation conditions.

[0031] An exhaust valve 6 is mounted on the rack plunger 10. The exhaust valve 6 includes a lower valve housing 605, an upper valve housing 607, an exhaust plunger 601, a control spring 602, a lower magnet 604, an upper magnet 606, and a rubber ring 603. The lower valve housing 605 is threaded onto the rack plunger 10. The control spring 602 is connected between the lower end of the lower valve housing 605 and the exhaust plunger 601. The exhaust plunger 601 has a damping hole in its center, and the lower magnet 604 and the rubber ring 603 are fitted onto the exhaust plunger 601. The upper valve housing 607 is fixed above the lower valve housing 605, has an exhaust hole at the top, and contains the upper magnet 606, which is positioned opposite to the lower magnet 604.

[0032] When the cavity pressure is lower than the set value, the exhaust plunger 601 remains in a downward position under the elastic force of the control spring 602, and the exhaust channel is in the open position. When the cavity pressure rises to the set value, the exhaust plunger 601 moves upward against the elastic force of the control spring 602 until the lower magnet 604 and the upper magnet 606 are attracted together. The rubber ring 603 closes the exhaust port, and the exhaust channel switches to the closed state and remains so. The exhaust valve 6 does not require an external control signal and can automatically open and close solely by changes in cavity pressure and magnetic attraction. After the magnet is attracted, it can keep the exhaust valve 6 closed under cavity pressure, preventing foam ink from leaking from the exhaust channel under extrusion pressure.

[0033] The rotating spindle 5 houses a push rod assembly 4. The push rod assembly 4 includes a push rod 403, a stop block 401, and a stop block spring 402. The stop block 401 has a limiting groove that mates with the push rod 403. The stop block spring 402 provides the elastic force that extends the stop block 401 outwards. In the extended state, the arc-shaped end of the stop block 401 forms an arc-shaped surface contact with the inner wall of the rack plunger 10. The push rod 403 is connected to the folding blade 3. When the rack plunger 10 moves downwards, its inner wall drives the stop block 401 to move axially downwards, causing the push rod 403 to switch the folding blade 3 from the unfolded position to the retracted position. When the stop block 401 reaches its dead center position, the rack plunger 10 continues to move downwards, and the stop block 401 is pressed into the rotating spindle 5, completely retracting the folding blade 3. When the rack plunger 10 moves upwards, the stop block 401 moves upwards accordingly, and the folding blade 3 unfolds again to the foaming working position.

[0034] The retraction and extension of the folding blade 3 are driven entirely by the axial movement of the rack and pinion plunger 10, eliminating the need for a separate blade drive mechanism and achieving automatic coordination between the blade retraction and extension and the plunger extrusion action. The dead point design of the stop block 401 ensures that the folding blade 3 is completely pressed into the rotating spindle 5 during the extrusion stage, without occupying the cavity space or interfering with the downward stroke of the rack and pinion plunger 10, thus ensuring continuous and stable extrusion of the foam ink.

[0035] Example 2 This embodiment provides a printing method for an in-situ foaming and extrusion integrated 3D printing device. This embodiment takes zirconia ceramic foam ink as an example. The raw materials used include zirconia ceramic particles, 5 wt% sodium dodecyl sulfate solution, ultrapure water, hydrochloric acid and potassium hydroxide.

[0036] The printing method includes a foaming stage, an venting stage, a printing stage, and a printing end reset stage, such as... Figures 5-9 As shown.

[0037] Foaming Stage: First, raise the rack plunger 10 to its highest position. At this point, the lower sealing ring 9 is higher than the shoulder of the rotating spindle 5 and detaches from the shaft. The folding blade 3 unfolds to the foaming working position under the action of the push rod assembly 4. Seal the outlet with the plug 16, and add a measured amount of ultrapure water into the foaming chamber 2 through the feed port. Adjust the rotation speed of the rotating spindle 5 to 300 r / min, and slowly add the weighed zirconia ceramic particles to form a ceramic suspension. After adding 5 wt% sodium dodecyl sulfate solution, increase the rotation speed of the rotating spindle 5 sequentially to 1000 r / min and 1500 r / min, and maintain each speed for 10 s. Adjust the pH value by adding hydrochloric acid or potassium hydroxide according to the foaming state. Finally, increase the speed to 2000 r / min for full foaming until the volume of the foam ink no longer increases, forming a stable foam ink. The staged speed increase method is beneficial for the ceramic particles to be fully wetted and dispersed in the low-speed stage, and then achieve uniform foaming in the high-speed stage, avoiding uneven particle distribution or coarse foam structure caused by one-time high-speed rotation.

[0038] Exhaust Phase: The active finger coupling assembly 11 is switched to the position where it engages with the finger teeth of the worm gear 15 coupling. The servo motor drives the rack plunger 10 downward through the worm gear 15 transmission mechanism. After the rack plunger 10 moves down and contacts the foam ink, excess gas in the cavity is discharged through the damping hole of the exhaust plunger 601 and the exhaust port of the upper housing 607 of the air valve. The damping hole is designed to allow the gas to be discharged slowly, avoiding excessive exhaust speed that could cause disturbance to the foam ink and damage to the foam structure. As the foam ink gradually blocks the damping hole, the cavity pressure continues to rise. The exhaust plunger 601 moves upward against the elastic force of the control spring 602 until the lower magnet 604 and the upper magnet 606 are attracted together. The rubber ring 603 seals the exhaust port, and the exhaust channel remains closed.

[0039] Printing Stage: The plug 16 at the discharge port is replaced with the printing needle 1. The servo motor drives the rack plunger 10 to continue moving downwards. The stop block 401 moves downwards with the rack plunger 10, pushing the push rod 403 to retract the folding blade 3. As the rack plunger 10 continues to move downwards, the stop block 401 pushes into the first fixed spindle 14. During the downward movement of the rack plunger 10, the foam ink is stably extruded through the printing needle 1 under the pressure of the rack plunger 10. By coordinating the movement speed of the rack plunger 10 and the movement speed of the printing needle 1, continuous 3D printing of particle-stabilized foam ink is achieved. Since foaming, venting, and extrusion are all completed in the same sealed cavity, air introduction and mechanical disturbance during material transfer are avoided, the loss of volatile components such as ethanol and ammonia is reduced, and the rheological properties of the foam ink are effectively maintained, thereby ensuring the continuity of extrusion pressure and the dimensional accuracy of the printed filaments.

[0040] Reset Phase: After printing, the printing needle 1 at the outlet is replaced with the plug 16. The servo motor reverses to drive the rack plunger 10 upward, creating negative pressure in the foaming chamber 2. Under this negative pressure, the lower magnet 604 and the upper magnet 606 disconnect and engage. The exhaust plunger 601 resets and moves downward under the action of the air control spring 602, reopening the exhaust channel and depressurizing the chamber. Simultaneously, the rack plunger 10 moves upward, causing the stop block 401 and push rod 403 to move in the opposite direction, and the folding blade 3 unfolds back to the foaming working position. After the rack plunger 10 returns to its highest position, the device returns to the initial foaming state and enters the next foaming and printing cycle. During the reset process, the exhaust valve 6 automatically triggers the magnet to disconnect using the negative pressure in the chamber, eliminating the need for manual intervention. This achieves automatic reset of the device after printing, providing an equipment foundation for continuous and automated printing.

[0041] After printing is complete, loosen the set screw 13 and disassemble the second fixed spindle 8, along with the rotating spindle 5 and related components in contact with the material, for cleaning. Special attention should be paid to cleaning the damping hole of the exhaust valve 6, preferably using ultrasonic cleaning to remove residual ceramic particles and foamy ink, to ensure smooth exhaust during the next cycle of printing.

[0042] While the specific embodiments of the present invention have been described above in conjunction with the accompanying drawings, this is not intended to limit the scope of protection of the present invention. Those skilled in the art should understand that various modifications or variations that can be made by those skilled in the art without creative effort based on the technical solutions of the present invention are still within the scope of protection of the present invention.

Claims

1. An integrated 3D printing device for in-situ foaming and extrusion, characterized in that, The device includes a foaming chamber, a rack and pinion plunger, a rotating spindle, a worm gear, and a finger coupling assembly. The finger coupling assembly has two shifting positions, which are respectively engaged with the rotating spindle and the worm gear for transmission. The lower end of the foaming chamber has a discharge port. The rotating spindle is located inside the foaming chamber and is equipped with folding blades that can switch between an unfolded and a retracted position. The rotating spindle is also equipped with a rack and pinion plunger, which is coaxially engaged with the rotating spindle and is driven by a worm gear transmission mechanism to reciprocate axially. An exhaust valve is installed on the rack plunger. The exhaust valve is provided with an exhaust channel. The exhaust channel is in the open state when the pressure in the foaming chamber is lower than the set value, and switches to the closed state when the pressure in the foaming chamber rises to the set value. The rotating spindle is equipped with a push rod assembly, which is mechanically linked to the rack plunger. When the rack plunger moves axially, it drives the push rod assembly to switch the folding blade between the unfolded position and the retracted position. The finger coupling assembly is connected to the rotating spindle drive when it is engaged with the finger teeth of the rotating spindle coupling, and is connected to the worm drive when it is engaged with the finger teeth of the worm coupling.

2. The in-situ foaming and extrusion integrated 3D printing device according to claim 1, characterized in that, The exhaust valve includes a lower valve housing, an upper valve housing, an exhaust plunger, a control spring, a lower magnet, and an upper magnet. The lower valve housing is threadedly connected to the rack plunger, with four springs evenly distributed on the plunger. The control spring is connected between the lower end of the lower valve housing and the exhaust plunger. The exhaust plunger has a damping hole, and the lower magnet and a rubber ring are fitted onto the exhaust plunger. The upper valve housing is connected above the lower valve housing and has an exhaust port. The upper magnet is installed inside the upper valve housing. Under the elastic force of the control spring, the exhaust plunger remains in a downward position, keeping the exhaust passage in an open position. The upper magnet and the lower magnet are arranged opposite each other, and when the exhaust plunger moves upward to the position where the two magnets are attracted to each other, the exhaust passage remains closed.

3. The in-situ foaming and extrusion integrated 3D printing device according to claim 1, characterized in that, The push rod assembly includes a push rod, a stop block, and a stop block spring. The stop block has a limiting groove that mates with the push rod. The stop block spring provides an elastic force that causes the stop block to extend outward. When the stop block is extended, its arc-shaped end contacts the inner wall of the rack plunger. The push rod is connected to the folding blade. When the stop block is axially displaced under the drive of the inner wall of the rack plunger, the push rod drives the folding blade to switch between an unfolded position and a retracted position. The stop block has a dead point position. After reaching the dead point position, the stop block can be pressed into the interior of the rotating spindle.

4. The in-situ foaming and extrusion integrated 3D printing device according to claim 1, characterized in that, The inner wall of the rack plunger is provided with an upper sealing ring and a lower sealing ring; the installation height of the upper sealing ring is higher than the highest height of the end of the folding blade when it is in the retracted position; the installation height of the lower sealing ring is higher than the shoulder of the rotating spindle when the rack plunger is at its highest position, so that the lower sealing ring is disengaged from the rotating spindle body.

5. The in-situ foaming and extrusion integrated 3D printing device according to claim 1, characterized in that, The rotating spindle is mounted on the fixed spindle via an angular contact ball bearing. The upper end of the rotating spindle is provided with coupling fingers. When the inter-finger coupling assembly engages with the coupling fingers at the upper end of the rotating spindle, it drives the rotating spindle to rotate. The upper end of the fixed spindle is connected to the worm gear via an angular contact ball bearing. The lower end of the worm gear is provided with coupling fingers. When the inter-finger coupling assembly engages with the coupling fingers at the lower end of the worm gear, it drives the worm gear to rotate.

6. The in-situ foaming and extrusion integrated 3D printing device according to claim 5, characterized in that, The fixed spindle is divided into upper and lower sections, which are detachably connected by a fixed coupling and set screws. The lower section of the fixed spindle, together with the rotating spindle and the parts in contact with the material, constitutes a detachable cleaning unit.

7. The in-situ foaming and extrusion integrated 3D printing device according to claim 1, characterized in that, A detachable closure is connected to the discharge port. The closure includes a plug and a printing needle, and the plug and the printing needle can be interchangeably installed on the discharge port.

8. A printing method using the in-situ foaming and extrusion integrated 3D printing apparatus according to any one of claims 1 to 7, characterized in that, Includes the following steps: Foaming steps: Raise the rack plunger to the highest position, the folding blades unfold during the raising process, the discharge port is closed, ceramic particles, surfactant and solution are added into the foaming cavity, the finger coupling assembly is switched to the first position and connected to the rotating spindle, the rotating spindle is driven to rotate, the material in the cavity is stirred and foamed until a stable foam ink is formed. Exhaust procedure: Switch the finger coupling assembly to the second position and connect it to the worm gear, drive the rack plunger to move downward, and discharge excess gas in the cavity through the exhaust valve. After the cavity pressure increases, the exhaust valve will automatically close. Printing steps: Replace the plug at the discharge port with a printing needle, drive the rack plunger to continue moving downwards, the stop block moves downwards with the rack plunger, pushes the push rod to retract the folding blade, and as the rack plunger continues to move downwards, the stop block is pushed into the main shaft; during the downward movement of the rack plunger, foam ink is stably extruded through the printing needle, and continuous printing is achieved by coordinating the movement speed of the rack plunger and the movement speed of the printing needle; Reset Steps: After printing is complete, replace the printing needle with a plug, drive the rack plunger to move upward, creating negative pressure in the cavity. The exhaust valve resets and opens under the negative pressure, and the folded blades unfold again as the rack plunger moves upward until the rack plunger returns to its highest position, and the device returns to the initial foaming state.

9. The printing method according to claim 8, characterized in that, In the foaming step, the rotation speed driving the rotating spindle is increased in stages: first, a ceramic particle suspension is formed at the first rotation speed, then a surfactant is added and the speed is increased to the second and third rotation speeds and maintained for a predetermined time. After adjusting the pH value of the system according to the foaming state, the speed is increased to the fourth rotation speed for full foaming until the volume of the foam ink no longer increases.

10. The printing method according to claim 8, characterized in that, In the venting step, after the rack plunger moves down and contacts the foam ink, excess gas is slowly discharged through the damping orifice of the venting valve. When the foam ink blocks the damping orifice of the venting plunger, the cavity pressure continues to rise, and the venting plunger moves up until the upper magnet and the lower magnet are attracted to each other, keeping the venting channel closed. In the reset step, the upward movement of the rack plunger creates a negative pressure in the cavity. Under the action of the negative pressure, the upper magnet and the lower magnet disconnect from each other, and the venting plunger resets under the action of the gas control spring, reopening the venting channel.

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