A retractable multi-material 3D printing head

Abstract

This invention discloses a retractable multi-material 3D printing head, which includes an extrusion structure, a first feeding structure, a second feeding structure, and a third feeding structure. By connecting the three feeding structures with one extrusion structure, the extrusion retraction problem in 3D printing of multiple materials is solved. The extrusion structure has three meshing screws, resulting in high mixing efficiency during slurry mixing. Simultaneously, each of the three feeding structures has a screw, allowing for better control of the amount of high-viscosity material added to the extrusion structure. Furthermore, the three screws inside the extrusion structure are specially designed irregular-shaped screws. While achieving conventional mixing, they not only better control the material extrusion amount but also work together with the screws in the feeding structures to achieve slurry retraction when printing high-viscosity materials, improving the forming effect and allowing for a wider solid content range in the formed ceramic slurry.

Description

Technical Field

[0001] This invention relates to the field of 3D printer technology, and in particular to a retractable multi-material 3D printing head. Background Technology

[0002] Additive manufacturing technology, also known as 3D printing, is an advanced manufacturing technology encompassing mechanics, electronics, control, and materials. Single-material 3D printing technology is becoming increasingly sophisticated. However, there are still certain technical limitations in printing high-viscosity materials such as ceramics, clay, high-solids-content materials, and viscous polymers. Meanwhile, existing multi-material 3D printers generally use multiple extruders to achieve multi-material printing. This type of printer has many problems during the printing process. Regarding printing materials, each additional material requires a corresponding extruder, which greatly limits the number of material types that can be printed and increases the complexity of the printer structure. When using multiple extruders to print multiple materials, switching extruders requires switching the extruder for each new material, causing inconvenience in terms of program control, mechanical structure, and equipment maintenance. Furthermore, this structure makes it difficult to print gradient composite materials. In the process of printing gradient materials, most current equipment uses passive material mixing, which cannot achieve automatic mixing of multiple materials and components or precise control of the mixing ratio. Moreover, the mixing efficiency and mixing effect of multiple components and materials during the printing process are low. Existing multi-material 3D printers generally cannot use the retraction function when printing high-viscosity materials, resulting in severe burrs when printing discontinuous materials, significant material leakage during the printing process, and inability to accurately control the material extrusion amount, leading to a narrow range of solid content in printed ceramics. Summary of the Invention

[0003] To address the shortcomings of existing additive manufacturing technologies in multi-material, multi-scale 3D printing, this invention aims to design a retractable multi-material 3D printing head to achieve integrated manufacturing of multiple materials and multiple scales.

[0004] This invention is achieved through the following technical solution: a retractable multi-material 3D printing head, characterized in that the 3D printing head includes an extrusion structure, a first feeding structure, a second feeding structure, and a third feeding structure; the extrusion structure comprises a lower extrusion head, an upper extrusion head, a mixing chamber, an extrusion head support, a right-end gear, a middle gear, a left-end gear, an extrusion motor, a coupling, a supporting copper column, a right-end screw, a middle screw, and a left-end screw;

[0005] The top of the lower extruder is installed on the inner side of the bottom of the upper extruder via a threaded structure, and the upper part of the upper extruder is installed on the inner side of the bottom of the mixing chamber via a threaded structure. The lower extruder, the upper extruder, and the mixing chamber are assembled in such a way that the vertical central axis of their internal cavities coincides.

[0006] An extruder head bracket is mounted on the top of the mixing chamber. A locking block is horizontally positioned outward on one side of the upper part of the extruder head bracket for mounting in a slot on the 3D printer frame. Three through holes are located in the middle of the top of the extruder head bracket, and the line connecting the centers of the three through holes forms an isosceles triangle. The right-end screw, middle screw, and left-end screw have the same basic structure, each including a gear mounting section, a feeding section, a mixing section, a pressurized extrusion section, and a conical end, arranged from top to bottom. The gear mounting section of the middle screw is longer than that of the right-end screw, and the gear mounting section of the right-end screw is the same length as that of the left-end screw. The structure and dimensions of the feeding section, mixing section, pressurized extrusion section, and conical end of the three screws are identical. The lower parts of the right-end screw, middle screw, and left-end screw are located in the cavity formed by the upper extruder head and the mixing chamber. The three screws mesh with each other to form a three-screw mechanism, and their tops pass through the three through holes on the top of the extruder head bracket.

[0007] Above the three through holes at the top of the extruder head support are respectively a right-end gear, a middle gear, and a left-end gear. The top end of the right-end screw is set inside the right-end gear and fixedly connected by a set screw. The top end of the left-end screw is set inside the left-end gear and fixedly connected by a set screw. The top end of the middle screw passes through the middle gear and is connected to the output shaft of the extrusion motor located directly above it by a coupling. The middle gear is fixed to the middle screw by a set screw. The right-end gear, middle gear, and left-end gear are at the same horizontal height and mesh with each other to form a fixed-axis gear train for mutual meshing and transmission.

[0008] The extrusion head support has a row of supporting copper pillars on both the left and right sides, and the extrusion motor is fixed at the top of the two rows of supporting copper pillars; the output shaft of the extrusion motor is set downwards, and the output shaft is connected to the top of the central screw through a coupling.

[0009] Three horizontal feed holes are evenly arranged circumferentially in the upper middle part of the mixing chamber. These three feed holes correspond to the feed sections of the right screw, the middle screw, and the left screw, respectively. The three feed holes are respectively threaded to the No. 1 extrusion hose connector of the No. 1 feeding structure, the No. 2 extrusion hose connector of the No. 2 feeding structure, and the No. 3 extrusion hose connector of the No. 3 feeding structure. The No. 1 extrusion hose connector is connected to the main body of the No. 1 feeding structure through the No. 1 feeding hose, the No. 2 extrusion hose connector is connected to the main body of the No. 2 feeding structure through the No. 2 feeding hose, and the No. 3 extrusion hose connector is connected to the main body of the No. 3 feeding hose.

[0010] The upper part of the upper extrusion head is a cylindrical cavity with the same diameter as the upper cavity of the mixing chamber, and the lower part is a conical cavity with the apex pointing downwards. The lower ends of the right end screw, the middle screw, and the left end screw are located inside the conical cavity of the upper extrusion head.

[0011] The main structures of feeding structures No. 1, No. 2, and No. 3 are all identical. Taking feeding structure No. 1 as an example, the structure is described as follows: The main body of feeding structure No. 1 includes a feeding hose connector, a hopper, a hopper support, a feeding screw, a feeding motor, a worm gear coupling, a worm gear bearing, a worm gear, a worm wheel fixing nut, a worm wheel fixing key, a worm wheel, a worm wheel bushing, and a feeding screw bearing. One end of the feeding hose connector is connected to the feeding hose, and the other end is connected to the bottom of the hopper. The top of the hopper is connected to the inner wall of the lower part of the hopper support. The hopper support is a hollow cylindrical container with openings at both ends. The lower opening is connected to the lower outer wall of the hopper, and the upper opening is fixedly connected to the bottom of the motor mounting bracket.

[0012] The motor mounting bracket includes at least one bottom surface and vertical plates connected to the left and right sides of the bottom surface. A bearing mounting hole is provided on the left vertical plate, and a stepped hole is provided on the right vertical plate. The inner diameter of the stepped hole is the same as the bearing mounting hole on the left side and is directly opposite it. The outer diameter of the stepped hole is larger than its inner diameter. A first-generation feeding motor is fixedly mounted on the outer side of the right vertical plate of the motor mounting bracket, and its output shaft is located within the outer portion of the stepped hole on the right vertical plate. Two first-generation transmission worm gear bearings are respectively installed in the bearing mounting hole on the left vertical plate and the inner portion of the stepped hole on the right vertical plate of the motor mounting bracket. A first-generation transmission worm gear is positioned above a first-generation feeding screw via these two first-generation transmission worm gear bearings. The first-generation transmission worm gear is connected to the output shaft of the first-generation feeding motor via a first-generation worm gear coupling.

[0013] The main body of the No. 1 feeding screw is set inside the No. 1 hopper support. Its top end passes through the bearing hole of the bottom surface of the motor mounting bracket, which is provided with two No. 1 feeding screw bearings, and is then fixed in the central through hole of the No. 1 transmission turbine. The interior of the No. 1 hopper is a conical cavity with the apex facing downwards. The lower end of the No. 1 feeding screw is set inside the No. 1 hopper. The No. 1 transmission turbine is meshed with the No. 1 transmission worm gear.

[0014] The feed section, mixing section and pressurized extrusion section of the left screw are all equipped with threaded structures, and the thread helix angle of the three sections decreases in sequence, while the inner diameter of the pressurized extrusion section gradually increases from top to bottom.

[0015] Compared with existing technologies, the advantages of this invention are as follows: The retractable multi-material 3D printing head of this invention solves the problem of adding multiple materials in 3D printing by using a structure connecting three feeding structures and one extrusion structure as the 3D printing head. The extrusion structure contains three meshing screws, and the three screws are directly opposite the outlets of the three feeding structures, resulting in high mixing efficiency during slurry mixing. Simultaneously, each of the three feeding structures contains a screw, which allows for better control of the amount of material added to the extrusion structure. Furthermore, the three screws inside the extrusion structure are specially designed irregularly shaped screws. While achieving conventional mixing, they not only better control the material extrusion amount but also work together with the screws in the feeding structures to achieve slurry retraction when printing high-viscosity materials, improving the forming effect. Moreover, both the feeding structure and the extrusion structure are screw extrusion designs. Screw extrusion designs can form ceramic slurries with high solid content, while the irregularly shaped screws in the extrusion structure can also form slurries with low solid content, thus resulting in a wide range of solid content in the formed ceramic slurries. Attached Figure Description

[0016] To more clearly illustrate the prior art solutions of this invention, the drawings used in the description of the embodiments or prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this invention. For those skilled in the art, other drawings can be obtained from these drawings without any creative effort or labor.

[0017] Figure 1 This is an assembly diagram of one embodiment of a retractable multi-material 3D printing head according to the present invention.

[0018] Figure 2 This is a schematic diagram of the extrusion structure of an embodiment of a retractable multi-material 3D printing head of the present invention (some parts are in cross-section; the upper extrusion head 202, mixing chamber 203, right end gear 205, No. 1 extrusion hose connector 315, and No. 3 extrusion hose connector 515 are in cross-section along the longitudinal symmetrical plane; the extrusion head support 204 and the middle gear 206 are in cross-section of the right side).

[0019] Figure 3 This is a schematic diagram of the assembly of the central screw and the extrusion motor in one embodiment of a retractable multi-material 3D printing head of the present invention (the right side of the central gear 206, the right side of the coupling 209, and the right side of the extrusion head support 204 are in cross-section).

[0020] Figure 4 This is a schematic diagram of the right-end screw of an embodiment of a retractable multi-material 3D printing head.

[0021] Figure 5This is a schematic diagram of the first feeding structure 3 of an embodiment of a retractable multi-material 3D printing head (the first hopper 303, the first hopper support 304, the motor mounting bracket, the first feeding screw bearing 314, and the first transmission worm bearing 308 are cross-sectional views along the longitudinal symmetry plane, and the first transmission worm 312 is a partial cross-sectional view). Detailed Implementation

[0022] The invention will now be further described in conjunction with the accompanying drawings.

[0023] This invention provides a retractable multi-material 3D printing head (hereinafter referred to as a 3D printing head, see below). Figures 1-5 The system includes an extrusion structure 2, a first feeding structure 3, a second feeding structure 4, and a third feeding structure 5. The extrusion structure 2 consists of a lower extrusion head 201, an upper extrusion head 202, a mixing chamber 203, an extrusion head support 204, a right-end gear 205, a middle gear 206, a left-end gear 207, an extrusion motor 208, a coupling 209, a support copper column 210, a right-end screw 211, a middle screw 212, and a left-end screw 213.

[0024] The top of the lower extruder 201 is installed on the inner side of the bottom of the upper extruder 202 via a threaded structure. The upper part of the upper extruder 202 is installed on the inner side of the bottom of the mixing chamber 203 via a threaded structure. The lower extruder 201, the upper extruder 202, and the mixing chamber 203 are assembled in such a way that the vertical central axis of their internal cavities coincides.

[0025] An extruder support 204 is mounted on the top of the mixing chamber 203. A locking block is horizontally positioned outward on one side of the upper part of the extruder support 204 for mounting in a slot on the 3D printer frame 1. Three through holes are located in the center of the top of the extruder support 204, and the line connecting the centers of the three through holes forms an isosceles triangle. The right screw 211, the middle screw 212, and the left screw 213 have the same basic structure, each including a gear mounting section, a feeding section, a mixing section, a pressurized extrusion section, and a conical end, arranged from top to bottom. The gear mounting section of the middle screw 212 is longer than that of the right screw 211, and the gear mounting section of the right screw 211 is the same length as that of the left screw 213. The structure and dimensions of the feeding section, mixing section, pressurized extrusion section, and conical end of all three are identical. The lower parts of the right end screw 211, the middle screw 212, and the left end screw 213 are located in the cavity formed by the upper extrusion head 202 and the mixing chamber 203. The three screws mesh with each other to form a three-screw mechanism, and the tops of the three screws pass through the three through holes at the top of the extrusion head support 204.

[0026] Above the three through holes at the top of the extruder head support 204 are respectively a right-end gear 205, a middle gear 206, and a left-end gear 207. The top end of the right-end screw 211 is located inside the right-end gear 205 and is fixedly connected to it by a set screw. The top end of the left-end screw 213 is located inside the left-end gear 207 and is fixedly connected to it by a set screw. The top end of the middle screw 212 passes through the middle gear 206 and is connected to the output shaft of the extrusion motor 208 located directly above it by a coupling 209. The middle gear 206 is fixed to the middle screw 212 by a set screw. The right-end gear 205, middle gear 206, and left-end gear 207 are at the same horizontal height and mesh with each other, forming a fixed-axis gear train for mutual meshing and transmission.

[0027] The left and right sides of the extruder head support 204 are provided with a row of supporting copper columns 210, and the extrusion motor 208 is fixed at the top of the two rows of supporting copper columns 210. The output shaft of the extrusion motor 208 is set downward, and the output shaft is connected to the top of the central screw 212 through a coupling 209.

[0028] Three horizontal feed holes are evenly arranged circumferentially (i.e., horizontally) in the upper middle part of the mixing chamber 203. These three feed holes correspond to the feed sections of the right screw 211, the middle screw 212, and the left screw 213, respectively. The three feed holes are respectively threaded to the first extrusion hose connector 315 of the first feeding structure 3, the second extrusion hose connector of the second feeding structure 4, and the third extrusion hose connector 515 of the third feeding structure 5. The first extrusion hose connector 315 is connected to the main body of the first feeding structure 3 through the first feeding hose 301, the second extrusion hose connector is connected to the main body of the second feeding structure 4 through the second feeding hose 401, and the third extrusion hose connector 515 is connected to the main body of the third feeding structure 5 through the third feeding hose 501.

[0029] The upper part of the upper extrusion head 202 is a cylindrical cavity with the same diameter as the upper cavity of the mixing chamber 203, and the lower part is a conical cavity with the apex pointing downwards. The lower ends of the right end screw 211, the middle screw 212, and the left end screw 213 are located inside the conical cavity of the upper extrusion head 202.

[0030] Taking the left-end screw 213 as an example, the left-end screw 213, from top to bottom, includes a gear mounting section, a feeding section 2131, a mixing section 2132, a pressure extrusion section 2133, and a tapered end. The left-end screw 213's gear mounting section is fixedly connected to the left-end gear 207 via an internal set screw. The feeding section 2131 (thread helix angle a), the mixing section 2132, and the pressure extrusion section 2133 (thread helix angle b) all have threaded structures, and the thread helix angle decreases sequentially across these three sections. Specifically, the threads on the feeding section 2131 and the pressure extrusion section 2133 are regular, continuous sawtooth thread structures, while the thread on the mixing section 2132 is a regular, intermittent sawtooth thread structure. The thread on the pressure extrusion section 2133 is a regular, continuous sawtooth thread structure, and the inner diameter of this section of the screw (i.e., the diameter of the rod inside the thread) gradually increases from top to bottom. The screw inner diameter is d1 at the initial position of the pressurized extrusion section and d2 at the end position of the pressurized extrusion section. d2 is greater than d1. The angle between the line connecting the initial position and the end position of the pressurized extrusion section and the inner surface of the screw (i.e. the surface of the rod inside the thread) at the initial position of the pressurized extrusion section is called the deflection angle c.

[0031] The main structures of feeding structures 3 (No. 1), 4 (No. 2), and 5 (No. 3) are all identical. Taking feeding structure 3 (No. 1) as an example, the structure is described as follows: The main body of feeding structure 3 (No. 1) includes a feeding hose connector 302, a hopper 303, a hopper support 304, a feeding screw 305, a feeding motor 306, a worm gear coupling 307, a worm gear bearing 308, a worm gear 309, a worm wheel fixing nut 310, a worm wheel fixing key 311, a worm wheel 312, and a worm gear coupling 312. The moving turbine shaft sleeve 313, the first feeding screw bearing 314, and the feeding hose connector 302 are connected at one end to the first feeding hose 301 and at the other end to the bottom of the first hopper 303. The top of the first hopper 303 is connected to the inner wall of the lower part of the first hopper support 304. The first hopper support 304 is a hollow cylindrical container with openings at both ends. Its lower opening is connected to the lower outer wall of the first hopper 303, and its upper opening is fixedly connected to the bottom surface of the motor mounting bracket (fixed by sealant or other means).

[0032] The motor mounting bracket includes at least one bottom surface and vertical plates connected to the left and right sides of the bottom surface. A bearing mounting hole is provided on the left vertical plate, and a stepped hole is provided on the right vertical plate. The inner portion of the stepped hole (with the position closest to the two vertical plates as the innermost) has the same diameter as the bearing mounting hole on the left and is directly opposite it. The outer portion of the stepped hole has a larger diameter than its inner portion. A first-generation feed motor 306 is fixedly mounted on the outer surface of the right vertical plate of the motor mounting bracket, with its output shaft located within the outer portion of the stepped hole on the right vertical plate. Two first-generation drive worm gear bearings 308 are respectively installed in the bearing mounting hole on the left vertical plate and within the inner portion of the stepped hole on the right vertical plate. A first-generation drive worm gear 309 is positioned above a first-generation feed screw 305 via these two first-generation drive worm gear bearings 308. The first-generation drive worm gear 309 is connected to the output shaft of the first-generation feed motor 306 via a first-generation worm gear coupling 307.

[0033] The main body of the first feeding screw 305 is housed within the first hopper support 304. Its top end passes through the bearing holes of two first feeding screw bearings 314 on the bottom surface of the motor mounting bracket and is then fixed within the central through hole of the first transmission turbine 312. The interior of the first hopper 303 is a conical cavity with its apex pointing downwards, and the lower end of the first feeding screw 305 is located inside the first hopper 303. The first transmission turbine 312 is meshed with the first transmission worm gear 309.

[0034] The No. 1 feeding screw 305 includes a top mounting section, a feeding section and a tapered end. Its top mounting section is a stepped shaft section with a diameter that gradually increases from top to bottom. Its feeding section is provided with a rectangular thread structure. The bottom of its tapered end is located inside the No. 1 hopper 303.

[0035] In one embodiment, the outer peripheral end face of the top mounting section of the first feeding screw 305 is provided with threads and a positioning groove; the upper inner side of the central through hole of the first transmission turbine 312 is provided with a ring of horizontally inward mounting parts, and the inner side of the mounting parts is provided with a horizontally inward first transmission turbine fixing key 311; the lower part of the first transmission turbine 312 is a first transmission turbine bushing 313; after the top end of the top mounting section of the first feeding screw 305 passes through the first transmission turbine bushing 313, its positioning groove engages with the first transmission turbine fixing key 311, and its top end is mounted on the mounting part inside the first transmission turbine 312 by a first transmission turbine fixing nut 310. The first transmission turbine 312 and the first feeding screw 305 are circumferentially fixedly connected by the first transmission turbine fixing key 311, and axially fixed by the first transmission turbine fixing key 311, the first transmission turbine bushing 313, and the stepped shoulder of the first feeding screw 305 itself.

[0036] The working principle and process of the retractable multi-material 3D printing head are as follows: Material feeding structures 3, 4, and 5 are connected to the extrusion structure 2 via corresponding feeding hoses and extrusion hose connectors. Material feeding structures 3, 4, and 5 are fixedly mounted near the 3D printer frame 1 using brackets. The extrusion structure 2 is fixed to the 3D printer frame 1. Depending on the application requirements, appropriate materials are added to material feeding structures 3, 4, and 5. The proportion of material entering the extrusion structure 2 is controlled by adjusting the rotation speed of the corresponding material feeding motors. The extrusion motor 208 controls the right screw 211, middle screw 212, and left screw 213 to mix the material entering the mixing chamber 203. The mixture is then extruded into the application environment through the upper extrusion head 202 and lower extrusion head 201. The movement trajectory of the 3D printing head is controlled by the motion mechanism of the 3D printer and is not within the scope of this invention. The working principle of the 3D printing head of this invention will be explained in detail below with reference to several specific application scenarios.

[0037] Application Scenario 1

[0038] The process of printing a full-color structure using the 3D printing head of this invention includes the following steps:

[0039] 1) Zirconia ceramic slurry preparation

[0040] 1.1 Use an electronic balance to accurately weigh 70% red zirconium oxide powder, 25% anhydrous ethanol, and 5% methylcellulose by mass ratio.

[0041] 1.2 The above materials were placed in a ball mill jar and ball milled at 500 r / min for 5 hours to obtain red zirconia ceramic slurry.

[0042] 1.3 Using the slurry preparation methods in steps 1.1 and 1.2, the red zirconium oxide powder was replaced with yellow zirconium oxide powder and blue zirconium oxide powder, respectively, to obtain yellow zirconium oxide ceramic slurry and blue zirconium oxide ceramic slurry.

[0043] 2) Colorful Structure 3D Printing

[0044] 2.1 First, place the red zirconia ceramic slurry in hopper 1 (303), the yellow zirconia ceramic slurry in hopper 2, and the blue zirconia ceramic slurry in hopper 3. Then, perform ultrasonic vibration on hoppers 1 (303), hopper 2, and hopper 3 to improve the density of the zirconia slurry. When the desired printing paste color is orange, start the first feeding motor 306 and the second feeding motor 406, ensuring that the extrusion directions and pulse frequencies of the first feeding motor 306 and the second feeding motor 406 are the same. The first feeding motor 306 transmits power to the first transmission worm gear 309, which in turn transmits power to the first transmission turbine 312, driving the first feeding screw 305 to rotate and extruding the red zirconia paste. The second feeding motor 406 transmits power to the second transmission worm gear 409, which in turn transmits power to the second transmission turbine 412, driving the second feeding screw 405 to rotate and extruding the yellow zirconia paste. The red and yellow zirconia pastes enter the mixing chamber 203 through the first extrusion hose connector 315, the first feeding hose 301, the second extrusion hose connector, and the second feeding hose 401, respectively.

[0045] 2.2 The extrusion motor 208 provides power, which is transmitted to the central screw 212 via the coupling 209. The right-end gear 205, the central gear 206, and the left-end gear 207 are fixed to the right-end screw 211, the central screw 212, and the left-end screw 213, respectively. The right-end screw 211, the central screw 212, and the left-end screw 213 are ensured to move at the same speed in opposite directions through the fixed-axis gear train of the right-end gear 205, the central gear 206, and the left-end gear 207. The yellow zirconia slurry and the red zirconia slurry enter the mixing chamber 203 under the action of the first feeding screw 305 and the second feeding screw 405. They first enter the feed section 2131 of the central screw 213. The feed section 2131 has a larger thread helix angle α than the mixing section 2132 and the pressure extrusion section 2133. The larger thread helix angle effectively ensures that the slurry can smoothly enter the mixing section 2132. Meanwhile, the larger thread helix angle α makes it less likely for the slurry to move in the opposite direction of the extruder head even under greater pressure, effectively reducing the problem of slurry leakage. The thread structure on the mixing section 2132 is a special-shaped thread, which can improve the slurry mixing rate while ensuring slurry extrusion. The yellow zirconia slurry and red zirconia slurry are fully mixed in this section. After mixing, the orange slurry enters the pressurized extrusion section 2133. The pressurized extrusion section 2132 has a smaller thread helix angle b, which can provide a larger component force in the extrusion direction. The above features ensure that the slurry solid content that can be printed by a retractable multi-material 3D printing head is also higher, which increases the range of ceramic slurry solid content that can be printed by this structure to a certain extent. The fact that the screw diameter d1 at the initial position of this section is smaller than the screw diameter d2 at the end position increases the pressure of the slurry during extrusion, and also increases the density of the slurry to a certain extent. Orange zirconia slurry is collected at the upper extrusion head 202 and then extruded through the lower extrusion head 201 with a diameter of 0.5 mm. The mixing chamber 203 is fixed on the extrusion head support 204, which completes its trajectory movement by connecting to the 3D printer frame 1, thereby obtaining an orange molded part.

[0046] 2.3 When different materials need to be printed, refer to step 2.2 and adjust the No. 1 feeding motor 306, No. 2 feeding motor 406 and No. 3 feeding motor 506. By changing their speed, different proportions of zirconia slurry can be obtained to achieve 3D printing of colorful structures.

[0047] 2.4 When the printed model is a discontinuous model, when passing through the discontinuous position, the extrusion motor 208, the first feeding motor 306, the second feeding motor 406, and the third feeding motor 506 simultaneously reverse. When the extrusion motor 208 reverses, it drives the middle screw 213 to reverse as well. The helix angle b of the pressure extrusion section 2133 is small, and its downward force due to gravity is small under the same weight. At the same time, the screw diameter d1 at the initial position of this section is smaller than the screw diameter d2 at the end position, which makes the upper pressure of the pressure extrusion section 2133 smaller than the lower pressure. The helix angle a of the feeding section 2131 is large, which can provide greater lift during the reverse conveying of material by the middle screw 213, assisting in the slurry back-drawing. When the middle screw 213 rotates in reverse, the above structure allows the zirconia slurry of various colors to move upwards relatively easily; Driven by the feed motors 306, 406, and 506 respectively, the No. 1 feed screw 305, No. 2 feed screw 405, and No. 3 feed screw 505 rotate in opposite directions. During this reverse rotation, the feed screws exert a certain force on the alumina slurry, which can reduce the pressure on the upper end of the middle screw 213 to some extent. Simultaneously, after the middle screw 213 retracts the slurry, it can be placed. The slurry completes the retraction process under the reversing action of the screws. During the forward extrusion process, the screw mechanism effectively controls the retraction amount and prevents air bubbles from being introduced into the slurry during retraction, thus ensuring the material's density during extrusion and resulting in high precision and quality of the printed parts.

[0048] Application Scenario 2

[0049] Printing material type transformation gradient structural parts using the 3D printing head of this invention includes the following steps:

[0050] 1) Slurry preparation

[0051] 1.1 Accurately weigh 60% zirconium oxide powder and 40% anhydrous ethanol using an electronic balance. Place the above materials in a ball mill jar and ball mill at 500 r / min for 5 hours to obtain zirconium oxide ceramic slurry.

[0052] 1.2 Accurately weigh 65% alumina powder and 35% anhydrous ethanol using an electronic balance. Place the above materials in a ball mill jar and ball mill at 500 r / min for 5 hours to obtain alumina ceramic slurry.

[0053] 1.3 Accurately weigh 15% by mass of methylcellulose powder and 85% by mass of deionized water using an electronic balance. Place the above materials in a ball mill jar and ball mill at 500 r / min for 5 hours to obtain methylcellulose slurry.

[0054] 2) 3D printing of gradient structural components with material type transformation

[0055] 2.1 First, place the zirconia ceramic slurry in hopper 1 (303), the alumina ceramic slurry in hopper 2, and the methylcellulose slurry in hopper 3. Perform ultrasonic vibration on hoppers 1 (303), 2 (406), and 3 (506) to improve the slurry density. When the required printing material is a gradient material, start the first feeding motor (306), second feeding motor (406), and third feeding motor (506), ensuring that the extrusion directions of the first feeding motor (305), second feeding motor (406), and third feeding motor (506) are the same. The pulse frequency is controlled by the percentage of the required printing gradient. Power is transmitted from the first feeding motor (306) to the first transmission worm gear (309), and then to the first transmission turbine (312), driving the first feeding screw (305) to rotate and extrude the zirconia slurry. Power is transmitted from the second feeding motor (406) to the second transmission worm gear (409), and then to the second transmission turbine (412), driving the alumina slurry to rotate and extrude the zirconia slurry. The slurry is extruded; power is transmitted from the No. 3 feeding motor 506 to the No. 3 transmission worm gear 509, and then to the No. 3 transmission turbine 512, which drives the No. 3 feeding screw to rotate, thus extruding the methylcellulose slurry. The extruded zirconia slurry, alumina slurry, and methylcellulose slurry enter the mixing chamber 203 through feeding hoses 301, 401, and 501, respectively. Because the alumina and zirconia composite slurry has shear-thinning properties, the maximum solid content and maximum shear force achievable during printing change when different proportions of alumina and zirconia slurries are mixed. At this time, the input flow rate of the binder is changed by changing the pulse frequency of the feeding motor. The rotation speed is proportionally increased by changing the pulse frequency of the No. 1 feeding motor 306, the No. 2 feeding motor 406, and the extrusion motor 208, so as to adjust the rheological effect of the alumina and zirconia slurry.

[0056] 2.2 The extrusion motor 208 provides power, which is transmitted to the middle screw 212 via the coupling 209. The right-end gear 205, the middle gear 206, and the left-end gear 207 are respectively fixed to the right-end screw 211, the middle screw 212, and the left-end screw 213. The right-end screw 211, the middle screw 212, and the left-end screw 213 are connected by a fixed-axis gear train via the right-end gear 205, the middle gear 206, and the left-end gear 207. To demonstrate their opposing and uniform velocity motion, the zirconia slurry, alumina slurry, and methylcellulose slurry, under the action of the No. 1 feeding screw 305, No. 2 feeding screw 405, and No. 3 feeding screw 505, enter the mixing chamber 203 and first enter the feed section 2131 of the middle screw 213. The feed section 2131 has a larger thread helix angle α than the mixing section 2132 and the pressure extrusion section 2133, effectively ensuring that the slurry can smoothly enter the mixing section 2133. In section 32; simultaneously, the larger thread helix angle α makes it less likely for the slurry to move in the opposite direction of the extruder head even under greater pressure, effectively reducing the problem of slurry leakage; the mixing section 2132 has a special thread, which can improve the slurry mixing rate while ensuring slurry extrusion. Zirconia slurry and zirconia slurry are fully mixed with methylcellulose slurry in this section. After mixing, the gradient ceramic slurry enters the pressure extrusion section 2133. The pressure extrusion section 2132 has a smaller thread helix angle b, which can provide a larger component force in the extrusion direction; the above features ensure that the slurry solid content that can be printed by a retractable multi-material 3D printing head is also higher, which increases the range of ceramic slurry solid content that can be printed by this structure to a certain extent. The fact that the screw diameter d1 at the initial position of this section is smaller than the screw diameter d2 at the end position increases the pressure of the slurry during the extrusion process, and the density of the slurry is also increased to a certain extent. The gradient ceramic slurry is collected at the upper extrusion head 202 and then extruded through the lower extrusion head 201 with a diameter of 0.5 mm. The mixing chamber 203 is fixed on the extrusion head support 204, which is connected to the 3D printer frame 1 to complete its trajectory movement, thereby obtaining a ceramic gradient shaped part.

[0057] 2.3 When the printed model is a discontinuous model, when passing through the discontinuous position, the extrusion motor 208, the first feeding motor 306, the second feeding motor 406, and the third feeding motor 506 all reverse simultaneously. When the extrusion motor 208 reverses, it drives the central screw 213 to reverse as well. The helix angle b of the pressure extrusion section 2133 is relatively small, and its downward force due to gravity is relatively small under the same weight. At the same time, the deflection angle c makes the upper pressure of the pressure extrusion section 2133 smaller than the lower pressure. The helix angle a of the feeding section 2131 is relatively large, and it can provide greater lift during the reverse conveying of the material by the central screw 213, assisting in the slurry back-drawing. When the central screw 213 rotates in reverse, the above structure allows the alumina, zirconium oxide, and methylcellulose slurry to move upwards relatively easily. At the same time, the first feeding screw... The No. 305, No. 2 feeding screw 405, and No. 3 feeding screw 505 rotate in opposite directions under the drive of the No. 1 feeding motor 306, No. 2 feeding motor 406, and No. 3 feeding motor 506, respectively. When the No. 1 feeding screw 305, No. 2 feeding screw 405, and No. 3 feeding screw 505 rotate in reverse, they exert a certain force on the slurry, which can reduce the pressure on the upper end of the middle screw 213 to a certain extent. At the same time, after the middle screw 213 pulls the slurry back, it can be placed. The slurry completes the back-pulling work under the action of the screws rotating in reverse. At the same time, during the forward extrusion process, since the back-pulling is carried out by the screw mechanism, the back-pulling amount can be effectively controlled, and air bubbles can be prevented from being introduced into the slurry during the back-pulling process. This ensures the density of the material during the extrusion process, resulting in high forming accuracy and good quality of the printed parts.

[0058] Application Scenario 3

[0059] Printing toughening material content gradient structural parts using the 3D printing head of this invention includes the following steps:

[0060] 1) Slurry preparation

[0061] 1.1 Accurately weigh 60% zirconium oxide powder and 40% anhydrous ethanol using an electronic balance. Place the above materials in a ball mill jar and ball mill at 500 r / min for 5 hours to obtain zirconium oxide ceramic slurry.

[0062] 1.2 Accurately weigh 60% alumina powder and 40% anhydrous ethanol using an electronic balance. Place the above materials in a ball mill jar and ball mill at 500 r / min for 5 hours to obtain alumina ceramic slurry.

[0063] 1.3 Accurately weigh 60% silicon carbide powder and 40% deionized water using an electronic balance, place the above materials in a ball mill jar, and ball mill at 500 r / min for 5 hours to obtain methylcellulose slurry.

[0064] 2) 3D printing of structural components with varying toughening material content

[0065] 2.1 First, place the zirconia ceramic slurry in hopper 1 (303), the alumina ceramic slurry in hopper 2, and the silicon carbide slurry in hopper 3. Then, perform ultrasonic vibration on hoppers 1 (303), hopper 2, and hopper 3 to improve the density of the slurry. When the required printing material is a gradient material, the first feeding motor 306, the second feeding motor 406, and the third feeding motor 506 are started, ensuring that the extrusion directions of the first feeding motor 306, the second feeding motor 406, and the third feeding motor 506 are the same. The pulse frequency is controlled by the percentage of the required printing gradient. Power is transmitted from the first feeding motor 306 to the first transmission worm gear 309, and then to the first transmission turbine 312, driving the first feeding screw 305 to rotate and extrude the zirconia slurry. Power is transmitted from the second feeding motor 406 to the second transmission worm gear 409, and then to the second transmission turbine 412, to extrude the alumina slurry. Power is transmitted from the third feeding motor 506 to the third transmission worm gear 509, and then to the third transmission turbine 512, driving the third feeding screw 305 to rotate and extrude the zirconia slurry. The screw 505 rotates to extrude silicon carbide slurry. The extruded zirconia slurry, alumina slurry, and silicon carbide slurry enter the mixing chamber 203 through feeding hoses 301, 401, and 501, respectively. Because the content of alumina and zirconia in the composite slurry varies, the addition of zirconia ceramic to the alumina ceramic results in a composite material with excellent mechanical and thermodynamic properties. However, the fracture toughness and flexural strength differ to some extent depending on their relative content. Adding silicon carbide slurry further enhances the flexural strength and fracture toughness of the mixed slurry. By changing the pulse frequency of the first feeding motor 306, the second feeding motor 406, and the third feeding motor 506, the slurry input flow rate can be altered, resulting in ceramic slurries with different mechanical properties. The overall extrusion speed is adjusted by proportionally increasing the rotational speed of the extrusion motor 208 by changing its pulse frequency.

[0066] 2.2 The extrusion motor 208 provides power, which is transmitted to the central screw 212 via the coupling 209. The right-end gear 205, the central gear 206, and the left-end gear 207 are fixed to the right-end screw 211, the central screw 212, and the left-end screw 213, respectively. The right-end screw 211, the central screw 212, and the left-end screw 213 are ensured to move at the same speed in opposite directions through the fixed-axis gear train of the right-end gear 205, the central gear 206, and the left-end gear 207. The zirconia slurry, alumina slurry, and silicon carbide slurry enter the mixing chamber 203 under the action of the first feeding screw 305, the second feeding screw, and the third feeding screw, and first enter the feed section 2131 of the central screw 213. The feed section 2131 has a larger thread helix angle α than the mixing section 2132 and the pressure extrusion section 2133, which effectively ensures that the slurry can smoothly enter the mixing section 2132. Meanwhile, the larger thread helix angle α makes it less likely for the slurry to move in the opposite direction of the extruder head even under greater pressure, effectively reducing the problem of slurry leakage. The mixing section 2132 has a special-shaped thread, which can improve the slurry mixing rate while ensuring slurry extrusion. Zirconia slurry, zirconia slurry and silicon carbide slurry are fully mixed in this section. After mixing, the gradient ceramic slurry enters the pressure extrusion section 2133. The pressure extrusion section 2132 has a smaller thread helix angle b, which can provide a larger component force in the extrusion direction. The above features ensure that the slurry solid content that can be printed by a retractable multi-material 3D printing head is also higher, which increases the range of ceramic slurry solid content that can be printed by this structure to a certain extent. The fact that the screw diameter d1 at the initial position of this section is smaller than the screw diameter d2 at the end position increases the pressure of the slurry during the extrusion process, and the density of the slurry is also increased to a certain extent. The gradient ceramic slurry is collected at the upper extrusion head 202 and then extruded through the lower extrusion head 201 with a diameter of 0.5 mm. The mixing chamber 203 is fixed on the extrusion head support 204, which is connected to the 3D printer frame 1 to complete its trajectory movement, thereby obtaining a ceramic gradient shaped part.

[0067] 2.3 When the printed model is a discontinuous model, when passing through the discontinuous position, the extrusion motor 208, the first feeding motor 306, the second feeding motor, and the third feeding motor all reverse simultaneously. When the extrusion motor 208 reverses, it drives the central screw 213 to reverse as well. The pressure extrusion section 2133 has a smaller helix angle b, resulting in a smaller downward force due to gravity for the same weight. At the same time, the deflection angle c makes the upper pressure of the pressure extrusion section 2133 lower than the lower pressure. The feeding section 2131 has a larger helix angle a, which can provide greater lift during the reverse conveying of materials by the central screw 213, assisting in the slurry retraction. When the central screw 213 rotates in the reverse direction, the above structure allows the alumina, zirconium oxide, and silicon carbide slurries to move upwards relatively easily. Meanwhile, the first feeding screw 305... The No. 2 feeding screw 405 and the No. 3 feeding screw 505 rotate in opposite directions under the drive of the No. 1 feeding motor 306, the No. 2 feeding motor 406, and the No. 3 feeding motor 506. When the No. 1 feeding screw 305, the No. 2 feeding screw 405, and the No. 3 feeding screw 505 rotate in reverse, they exert a certain force on the slurry, which can reduce the pressure on the upper end of the middle screw 213 to a certain extent. At the same time, after the middle screw 213 pulls the slurry back, it can be placed. The slurry completes the back-pulling work under the action of the screws rotating in reverse. At the same time, during the forward extrusion process, since the back-pulling is carried out by the screw mechanism, the back-pulling amount can be effectively controlled, and air bubbles can be prevented from being introduced into the slurry during the back-pulling process. This ensures the density of the material during the extrusion process, resulting in high forming accuracy and good quality of the printed parts.

[0068] Any aspects not covered in this invention are applicable to existing technologies.

Claims

1. A retractable multi-material 3D printing head, characterized by, The 3D printing head includes an extrusion structure, a first feeding structure, a second feeding structure, and a third feeding structure; the extrusion structure consists of a lower extrusion head, an upper extrusion head, a mixing chamber, an extrusion head support, a right-end gear, a middle gear, a left-end gear, an extrusion motor, a coupling, a support copper column, a right-end screw, a middle screw, and a left-end screw; The top of the lower extruder is installed on the inner side of the bottom of the upper extruder via a threaded structure, and the upper part of the upper extruder is installed on the inner side of the bottom of the mixing chamber via a threaded structure. The lower extruder, the upper extruder, and the mixing chamber are assembled in such a way that the vertical central axis of their internal cavities coincides. An extruder head bracket is mounted on the top of the mixing chamber. A locking block is horizontally positioned outward on one side of the upper part of the extruder head bracket for mounting in a slot on the 3D printer frame. Three through holes are located in the middle of the top of the extruder head bracket, and the line connecting the centers of the three through holes forms an isosceles triangle. The right-end screw, middle screw, and left-end screw have the same basic structure, each including a gear mounting section, a feeding section, a mixing section, a pressurized extrusion section, and a conical end, arranged from top to bottom. The gear mounting section of the middle screw is longer than that of the right-end screw, and the gear mounting section of the right-end screw is the same length as that of the left-end screw. The structure and dimensions of the feeding section, mixing section, pressurized extrusion section, and conical end of the three screws are identical. The lower parts of the right-end screw, middle screw, and left-end screw are located in the cavity formed by the upper extruder head and the mixing chamber. The three screws mesh with each other to form a three-screw mechanism, and their tops pass through the three through holes on the top of the extruder head bracket. Above the three through holes at the top of the extruder head support are respectively a right-end gear, a middle gear, and a left-end gear. The top end of the right-end screw is set inside the right-end gear and fixedly connected by a set screw. The top end of the left-end screw is set inside the left-end gear and fixedly connected by a set screw. The top end of the middle screw passes through the middle gear and is connected to the output shaft of the extrusion motor located directly above it by a coupling. The middle gear is fixed to the middle screw by a set screw. The right-end gear, middle gear, and left-end gear are at the same horizontal height and mesh with each other to form a fixed-axis gear train for mutual meshing and transmission. The extrusion head support has a row of supporting copper pillars on both the left and right sides, and the extrusion motor is fixed at the top of the two rows of supporting copper pillars; the output shaft of the extrusion motor is set downwards, and the output shaft is connected to the top of the central screw through a coupling. Three horizontal feed holes are evenly arranged circumferentially in the upper middle part of the mixing chamber. These three feed holes correspond to the feed sections of the right screw, the middle screw, and the left screw, respectively. The three feed holes are respectively threaded to the No. 1 extrusion hose connector of the No. 1 feeding structure, the No. 2 extrusion hose connector of the No. 2 feeding structure, and the No. 3 extrusion hose connector of the No. 3 feeding structure. The No. 1 extrusion hose connector is connected to the main body of the No. 1 feeding structure through the No. 1 feeding hose, the No. 2 extrusion hose connector is connected to the main body of the No. 2 feeding structure through the No. 2 feeding hose, and the No. 3 extrusion hose connector is connected to the main body of the No. 3 feeding hose. The upper part of the upper extrusion head is a cylindrical cavity with the same diameter as the upper cavity of the mixing chamber, and the lower part is a conical cavity with the apex pointing downwards. The lower ends of the right end screw, the middle screw, and the left end screw are located inside the conical cavity of the upper extrusion head. The main structures of feeding structures No. 1, No. 2, and No. 3 are all identical. Taking feeding structure No. 1 as an example, the structure is described as follows: The main body of feeding structure No. 1 includes a feeding hose connector, a hopper, a hopper support, a feeding screw, a feeding motor, a worm gear coupling, a worm gear bearing, a worm gear, a worm wheel fixing nut, a worm wheel fixing key, a worm wheel, a worm wheel bushing, and a feeding screw bearing. One end of the feeding hose connector is connected to the feeding hose, and the other end is connected to the bottom of the hopper. The top of the hopper is connected to the inner wall of the lower part of the hopper support. The hopper support is a hollow cylindrical container with openings at both ends. The lower opening is connected to the lower outer wall of the hopper, and the upper opening is fixedly connected to the bottom of the motor mounting bracket. The motor mounting bracket includes at least one bottom surface and vertical plates connected to the left and right sides of the bottom surface. A bearing mounting hole is provided on the left vertical plate, and a stepped hole is provided on the right vertical plate. The inner diameter of the stepped hole is the same as the bearing mounting hole on the left side and is directly opposite it. The outer diameter of the stepped hole is larger than its inner diameter. A first-generation feeding motor is fixedly mounted on the outer side of the right vertical plate of the motor mounting bracket, with its output shaft located within the outer portion of the stepped hole on the right vertical plate. Two first-generation transmission worm gear bearings are respectively installed in the bearing mounting hole on the left vertical plate and within the inner portion of the stepped hole on the right vertical plate of the motor mounting bracket. The first-generation transmission worm gear is positioned above the first-generation feeding screw via these two bearings. The first-generation transmission worm gear is connected to the output shaft of the first-generation feeding motor via a worm gear coupling. The main body of the No. 1 feeding screw is set inside the No. 1 hopper support. Its top end passes through the bearing holes of the bottom surface of the motor mounting bracket, which are provided with two No. 1 feeding screw bearings, and is then fixed in the central through hole of the No. 1 transmission worm gear. The interior of the No. 1 hopper is a conical cavity with the apex facing downwards. The lower end of the No. 1 feeding screw is set inside the No. 1 hopper. The No. 1 transmission worm gear is meshed with the No. 1 transmission worm. The feed section, mixing section and pressurized extrusion section of the left screw are all equipped with threaded structures, and the thread helix angle of the three sections decreases in sequence, while the inner diameter of the pressurized extrusion section gradually increases from top to bottom.

2. A retractable multi-material 3D printing head according to claim 1, wherein, The threads on the feed section and the pressure extrusion section of the left screw are regular continuous sawtooth thread structures, while the threads on the mixing section are regular discontinuous sawtooth thread structures; the threads on the pressure extrusion section are regular continuous sawtooth thread structures.

3. The retracting multi-material 3D printing head of claim 1, wherein, The No. 1 feeding screw includes a top mounting section, a feeding section, and a tapered end. The top mounting section is a stepped shaft section with a diameter that gradually increases from top to bottom. The feeding section is equipped with a rectangular thread structure, and the bottom of the tapered end is located inside the No. 1 hopper.

4. A retractable multi-material 3D printing head according to claim 3, wherein, The top end face of the top mounting section of the No. 1 feeding screw is provided with threads and a positioning groove; the upper inner side of the central through hole of the No. 1 transmission worm gear is provided with a ring of horizontally inward mounting parts, and the inner side of the mounting parts is provided with a horizontally inward fixing key for the No. 1 transmission worm gear; the lower part of the No. 1 transmission worm gear is a No. 1 transmission worm gear bushing; after the top end of the top mounting section of the No. 1 feeding screw passes through the No. 1 transmission worm gear bushing, its positioning groove engages with the No. 1 transmission worm gear fixing key, and its top end is installed on the mounting part inside the No. 1 transmission worm gear by the No. 1 transmission worm gear fixing nut.

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