A modular, multi-functional FDM printhead for space additive manufacturing

Abstract

This invention relates to the field of FDM printing, and in particular to a modular, multifunctional FDM printhead for space additive manufacturing. It includes a coaxial extrusion component, a heat dissipation component, and a printhead switching component. One end of the printhead switching component is fixedly connected to the end of a motion mechanism, and the other end is fixedly connected to the heat dissipation component. The coaxial extrusion component is fixed to the heat dissipation component. The coaxial extrusion component includes a heating block, an outer nozzle, and an inner nozzle. An inner nozzle connecting pipe is located at the center of the upper end of the heating block, and the inner nozzle is fixed to the lower end of the inner nozzle connecting pipe. The outer nozzle is coaxially sleeved around the inner nozzle and fixedly connected to the lower end of the heating block. An inner throat communicating with the outer nozzle is located at an eccentric position on the upper end of the heating block. The outer nozzle has a large downward-pointing conical shape, and the inner nozzle has a slender needle-like structure. The lower ends of the outer and inner nozzles are flush. This invention enables recessed structure printing, modular switching, and prevents backflow of composite materials.

Description

Technical Field

[0001] This invention relates to the field of FDM printing, and in particular to a modular, multifunctional FDM printhead for space additive manufacturing. Background Technology

[0002] Addressing the urgent need for highly integrated, rapid manufacturing, and highly customized advanced structures in numerous fields such as aerospace, electronics manufacturing, and military equipment, the multifunctional integrated additive manufacturing method of fused deposition modeling (FDM) has become the mainstream development trend for advanced functional equipment due to its excellent space additive manufacturing capabilities, multi-material switching capabilities, and composite material additive manufacturing capabilities. However, as research and application have deepened, the single structure, limited functionality, and poor reliability of multi-degree-of-freedom / multi-axis / spatial FDM printheads, coupled with insufficient control methods for the FDM process, have become increasingly inadequate to meet current stringent manufacturing and market demands. These shortcomings include: First, existing spatial FDM printheads are designed for covering structures with raised or small-curvature recesses. The bulky printheads make it difficult for multi-functional integrated additive manufacturing devices to penetrate narrow spaces, hindering the printing of large-curvature recessed structures. Second, existing material-switching FDM printheads typically employ internal filament switching or parallel multi-nozzle arrangements for multi-material printing. The former is only suitable for single-filament printing, while the latter limits printhead arrangement and wastes space, restricting expandability and degrees of freedom. Third, existing composite material FDM printheads typically use layered roller pressing or coaxial extrusion. The former is unsuitable for large-curvature spatial surfaces, while the latter suffers from resin matrix backflow issues, making stable printing and high-precision molding at high temperatures difficult. Therefore, a multi-functional FDM printhead integrating recessed structure printing, modular switching, and anti-backflow composite material processing is urgently needed. Summary of the Invention

[0003] The purpose of this invention is to provide a modular, multifunctional FDM printhead for space additive manufacturing, capable of printing recessed structures, modular switching, and preventing backflow of composite materials.

[0004] The objective of this invention is achieved through the following technical solution:

[0005] A modular multifunctional FDM printhead for space additive manufacturing includes a coaxial extrusion component, a heat dissipation component, and a printhead switching component. One end of the printhead switching component is fixedly connected to the end of the motion mechanism, and the other end is fixedly connected to the heat dissipation component. The coaxial extrusion component is fixed on the heat dissipation component.

[0006] The coaxial extrusion component includes a heating block, an outer nozzle, and an inner nozzle. The upper center of the heating block is provided with an inner nozzle connecting pipe for conveying continuous phase material. The inner nozzle is fixed to the lower end of the inner nozzle connecting pipe. The outer nozzle is coaxially sleeved outside the inner nozzle and fixedly connected to the lower end of the heating block. An inner throat is provided at the eccentric position of the upper end of the heating block, which communicates with the outer nozzle. The inner throat is used to convey resin matrix material. The outer nozzle has a large downward-pointing pointed cone shape. The inner nozzle has a slender needle tube structure. The lower ends of the outer nozzle and the inner nozzle are flush.

[0007] The lower ends of both the outer and inner nozzles are smoothly transitioned.

[0008] The lower end of the inner nozzle's inner hole has a trumpet-shaped outward structure.

[0009] The upper end of the heating block is further extended inward with two heating rods and a temperature sensor. The two heating rods are arranged opposite each other with the inner nozzle connecting pipe as the center, and the temperature sensor and the inner throat are arranged opposite each other with the inner nozzle connecting pipe as the center. The distance between the two heating rods and the inner throat and the temperature sensor is the same.

[0010] The heat dissipation component includes a round tube fitted on the upper end of the inner throat tube. The upper end of the round tube is connected to an outer throat tube. A connecting flange is fixed to the upper end of the outer throat tube. Two cooling fans are suspended and opposite at both ends of the connecting flange, forming a cooling fan that blows air onto multiple heat sinks that are spaced apart and eccentrically fixed on the round tube.

[0011] There is a gap between the two cooling fans and the heat sink.

[0012] The printhead switching component includes a fixed flange fixed to the end of the motion mechanism, and two sets of magnetic head-changing devices are provided between the fixed flange and the connecting flange.

[0013] The magnetic head-changing device includes a female connector, a demagnetizing magnet, and a male connector. The upper end of the male connector is fixed to the lower end of the fixed flange. The lower end of the male connector is hollow and a demagnetizing magnet is inserted therein. The female connector is made of magnetic material and fixed to the connecting flange.

[0014] It also includes a vision inspection device that is fixed to a fixed flange via a vision inspection bracket, used for monitoring the entire printing and switching process.

[0015] It also includes an auxiliary heater fixed to the connecting flange via an auxiliary heating bracket to preheat the area to be printed.

[0016] The beneficial effects of this invention are:

[0017] 1. The large tilt angle design of the external nozzle enables the integration of multiple functions in a small space. It can achieve printing at any angle of 45° with the vertical nozzle as the central axis, and 60° when the depth does not exceed 20mm, that is, printing with the central axis at a 30° angle to the printing plane, thereby achieving the printing of concave structures.

[0018] 2. High temperature and high pressure anti-backflow is achieved through three measures: the inner nozzle is a thin needle tube, the inner nozzle has an outward-opening flared mouth, and the tips of the inner and outer nozzles are flush.

[0019] 3. Real-time switching of the printhead is achieved by deactivating the electromagnet, ensuring modular switching and functional expansion of the multi-composite material printhead. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the modular multi-functional FDM printhead.

[0021] Figure 2 This is a schematic diagram for printing angles;

[0022] Figure 3 This is a schematic diagram of the printhead dimensions;

[0023] Figure 4 This is a schematic diagram of the structure of the outer nozzle and the inner nozzle.

[0024] Figure 5 This is a schematic diagram of the coaxial extrusion component;

[0025] Figure 6 This is a schematic diagram of the heat dissipation component;

[0026] Figure 7 This is a structural diagram of the printhead switching component;

[0027] Figure 8 This is a flowchart of the printing process.

[0028] In the picture:

[0029] 1. Fixed flange; 2. Magnetic head-changing device; 3. Connecting flange; 4. Visual inspection device; 5. Auxiliary heating bracket; 6. Auxiliary heater; 7. Cooling fan; 8. Heat sink; 9. Heating block; 10. External nozzle; 11. Internal nozzle; 12. Internal nozzle connecting pipe; 13. Internal throat pipe; 14. External throat pipe; 15. Female connector; 16. Electromagnet; 17. Male connector. Detailed Implementation

[0030] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0031] like Figure 1-7 As shown, a detailed description of the modular, multi-functional FDM printhead for space additive manufacturing is provided:

[0032] A modular, multifunctional FDM printhead for space additive manufacturing includes a coaxial extrusion component, a heat dissipation component, an auxiliary heater, a printhead switching component, and a vision inspection device.

[0033] The coaxial extrusion component includes a heating block 9, an outer nozzle 10, an inner nozzle 11, an inner nozzle connecting pipe 12, an inner throat 13, heating rods, and a temperature sensor. The heating block 9 has mounting holes for the inner nozzle connecting pipe, the inner throat, the temperature sensor, and two heating rods at its upper end. The inner nozzle connecting pipe mounting hole is located at the center of the heating block 9, while the inner throat and temperature sensor mounting holes are located to the left and right of the center. The two heating rod mounting holes are located to the front and rear of the center, ensuring that the distance between the heating rods and the inner throat 13 and the temperature sensor is the same. The rod and temperature sensor are installed in the corresponding mounting holes by the side of the set screw. The inner throat tube mounting hole is connected to the lower end of the inner throat tube 13 by thread. The inner nozzle connecting tube mounting hole is connected to the inner nozzle connecting tube 12 by thread. The lower end of the inner nozzle connecting tube 12 is connected to the inner nozzle 11 by thread. The lower end of the heating block 9 has an outer nozzle thread, which is connected to the outer nozzle 10 by thread. The outer nozzle 10 is coaxially sleeved outside the inner nozzle 11. The tips of the outer nozzle 10 and the inner nozzle 11 are kept flush. If necessary, Teflon tape or other materials are used to seal the threads of the heating block 9 at high temperature.

[0034] It should be noted that during processing, in order to ensure that the nozzles of the outer nozzle 10 and the inner nozzle 11 at the bottom are as concentric as possible after installation, the coaxiality of the inner nozzle connecting pipe mounting thread hole, the inner nozzle mounting thread hole and the outer nozzle mounting thread hole needs to be greater than 0.03. If the coaxiality is less than 0.03, the outer surface of the inner nozzle 11 will be in contact with the inner wall of the outer nozzle 10 on one side, resulting in no resin flowing out in that direction.

[0035] Most printheads currently on the market are designed for general commercial flatbed printers. Except for the protruding nozzles, all other modules, including the heating element, are placed parallel around the printhead, making it difficult for the printhead to form an angle with the printing surface. Therefore, as... Figure 2As shown, the multi-functionality is integrated in a small space through the 10-angle design of the external nozzle. It can achieve printing at any angle of 45° with the nozzle vertical as the central axis, and 60° when the depth does not exceed 20mm, that is, printing at a 30° angle between the central axis and the printing plane, thereby achieving the purpose of printing concave structures.

[0036] Printhead design requirements for achieving the above spatial printing functions, such as Figure 3 The dimensions of the external nozzle 10 are described below:

[0037] Let the position one layer height away from the center of the print nozzle be denoted as o(0,0). Let a straight line rotate around o as its center, and let a(Xa,Ya) be the intersection point where the line reaches its maximum rotation angle with the print head. Then, Ya / Xa ≥ tan(60°). Let the position of the auxiliary heating device head be b(Xb,Yb), then Yb / Xb ≥ tan(45°). Simultaneously, to achieve print head heating and temperature measurement functions, Xa ≥ 10mm (…). Figure 3 (Xa = 10 mm); to achieve the penetration depth Z, Yb ≥ Z ( Figure 3 (Yb=30mm, Z=25mm).

[0038] Additionally, to achieve a greater depth of penetration at an angle of 45° to 60°, the auxiliary temperature control device can adjust the spacing S between points b and c. Figure 3 With S=20mm, the auxiliary temperature control device is moved upwards. If necessary, the power of the auxiliary heating device can be increased accordingly to ensure printing quality. Regarding the potential issue of the auxiliary heating device being blocked when printing at large tilt angles of 45° to 60°, since the distance between the heating head and the printing surface is extremely small, the unprinted areas should be directly heated by heat radiation from nearby heating blocks. Figure 2 The left printing surface is in close contact with the heating head.

[0039] FDM essentially involves continuously pressing molten thermoplastic resin matrix into a nozzle at high temperatures, extruding it from the nozzle and allowing it to cool and solidify. Therefore, the pressure within the heating chamber is typically high. In contrast, coaxial extrusion uses a two-in-one-out feeding method. If the pressure at the two inlets is uneven or if non-dense materials, such as continuous fibers, are present, the resin matrix material is highly likely to be extruded from the other inlet. Continuous reinforcing materials, such as continuous fibers, are prone to backflow. Therefore, the outer nozzle 10, coaxially fitted around the inner nozzle 11, allows for initial separation of the two materials and mixing outside the nozzle, effectively preventing backflow. Even if a small amount of resin is forced into the inner nozzle 11 during printing, it can still be carried out by the continuous fibers within the thin tube at the front of the inner nozzle 11. The rounded corners and flared nozzle design further enhance the anti-backflow capability, and the smooth nozzle transition minimizes damage to the continuous phase reinforcement, effectively improving print quality.

[0040] The heat dissipation components include a radiator, a cooling fan 7, an outer throat 14, and a connecting flange 3. The radiator consists of a circular tube and multiple heat dissipation fins 8 eccentrically fixed on the circular tube. The lower end of the circular tube has a stepped hole for positioning the inner throat 13, which is tightened by a set bolt. The upper end of the circular tube is threaded with the outer throat 14, and the connecting flange 3 is fitted onto the upper end of the outer throat 14 and fixed to the outer throat by set screws. Spacers are provided at the four corners of the connecting flange 3 for installing the cooling fan 7, so that the cooling fan 7 hangs on both sides of the multiple heat dissipation fins 8, which is more conducive to the airflow carrying away heat. The cooling fan 7 is close to the middle of the heat dissipation fins 8 and maintains a certain gap with the heat dissipation fins 8 to prevent heat from being directly conducted from the radiator to the cooling fan 7, which would cause damage to the cooling fan 7.

[0041] The printhead switching component is fixed to the fixed flange 1 at the end of the motion mechanism. Two sets of magnetic head-changing devices 2 are provided between the fixed flange 1 and the connecting flange 3. The magnetic head-changing device 2 includes a female connector 15, a demagnetizing magnet 16, and a male connector 17. The male connector 17 is hollow and houses the demagnetizing magnet 16, and is fixed to the lower end of the fixed flange 1 with bolts. The female connector 15 is made of magnetic material, such as industrial pure iron, and is fixed to the lower end of the connecting flange 3 with bolts. The upper end of the fixed flange 1 is fixed to the end of the motion mechanism such as a three-axis motion mechanism or a robotic arm.

[0042] By setting up the printhead switching component, the matrix material can be switched through internal consumables; for reinforcing materials such as continuous fibers that cannot be switched, the printhead can be replaced through the magnetic head-changing device 2, thus enabling real-time switching of the printhead and ensuring modular switching and functional expansion of the multi-composite material printhead.

[0043] The auxiliary heater 6 is installed at the end of the auxiliary heating bracket 5. Its heating area should illuminate the printing path to preheat the area to be printed. The other end of the auxiliary heating bracket 5 is bolted to the connecting flange 3 and is switched when the print head is switched.

[0044] The visual inspection device 4 is fixed to the visual inspection device bracket by bolts, and the other end of the visual inspection device bracket is fixed to the fixed flange 1 by bolts. It does not switch with the printhead, thus realizing full printing and switching process monitoring.

[0045] The principle of this invention:

[0046] When printing composite materials, the outer nozzle 10 and the inner nozzle 11 are coaxially extruded. The annular nozzle formed by the outer nozzle 10 and the inner nozzle 11 extrudes the resin matrix material fed into the inner throat tube 13. Under the high temperature of the heating block 9, the resin material melts at the bottom of the inner throat tube 13 and flows into the outer chamber in a liquid state. As the material is continuously fed in, the pressure increases and eventually flows out from the annular nozzle. Since the inner nozzle 11 is funnel-shaped and faces outward, the material will not enter the inner nozzle 11, thus preventing the inner nozzle 11 from becoming clogged. A very small amount of resin that does enter the inner nozzle 11 will also be extruded along with the material in the inner nozzle 11 during the printing process due to the long needle structure of the inner nozzle 11, making it difficult to form a blockage. The circular nozzle of the inner nozzle 11 extrudes continuous phase material, such as continuous fiber or metal wire, fed through the middle inner nozzle connecting pipe 12. The outer annular nozzle ensures that when printing in any direction, the resin extruded in front of the travel path is pressed under the continuous phase material, and the resin extruded behind the travel path is spread on top of the continuous phase material, forming a good encapsulation effect; the entire nozzle end should ensure a smooth transition.

[0047] Four channels are evenly distributed on a concentric circle with the inner nozzle connecting pipe 12 as the axis. These channels are the first heating rod, the resin flow channel (where the inner throat is installed), the second heating rod, and the temperature sensor. The two heating rods are symmetrically arranged and equidistant from the temperature sensor and the resin flow channel, respectively. Therefore, the thermocouple can accurately measure the temperature conducted from the two heating rods to the resin flow channel, thereby achieving precise control of the FDM process temperature.

[0048] The main function of the heat dissipation components is to prevent heat from the heating head from being conducted to the top of the throat tube, causing premature resin melting and blockage. They have two main functions: reducing heat conduction and increasing heat convection. Reducing heat conduction means decreasing the heat conducted to the top of the inner throat tube 13 (i.e., the radiator section). The inner throat tube 13 is made of multiple materials; the part below the radiator is made of titanium alloy to reduce thermal conductivity and minimize heat entry. The radiator connection part is made of copper alloy to improve heat dissipation. A thin-walled structure is also used at the connection between the heating block 9 and the radiator to reduce the heat transfer area. Increasing heat convection means reducing the heat already conducted to the top of the inner throat tube 13 (i.e., the radiator section). A copper heat sink 8 is used in conjunction with air cooling technology. The two fans have the same airflow direction, and the fans are positioned close to the center of the heat sink, maintaining a certain gap to prevent heat from being directly conducted from the radiator to the fans, which could damage them. The fans are suspended on both sides of the heat sink, making it easier for the airflow to carry away the heat.

[0049] The male connector 17 of the magnetic head-changing device 2 is equipped with a demagnetizing electromagnet 16, and the female connector 15 is made of a magnetic material, such as industrial pure iron. When no power is applied, the demagnetizing electromagnet 16 firmly attracts the magnetic material. When power is applied, the demagnetizing electromagnet 16 demagnetizes, and the male connector 17 separates from the female connector 15. Devices for the current printhead are all installed on the female connector 15 side, such as auxiliary heating devices, while devices for the entire printing / processing process are all installed on the male connector 17 side, such as vision inspection devices.

[0050] The method steps for printing using a modular, multi-functional FDM printhead designed for space additive manufacturing are as follows:

[0051] 1. When starting printing, enter a global print path file containing all FDM parameter information such as material, temperature, and printing speed;

[0052] 2. Based on the different composite materials or single materials mentioned in the material information in the document, determine the corresponding printhead for each material and break the path into paths corresponding to each printhead;

[0053] 3. Arrange the print heads in the path order and load the corresponding materials to facilitate subsequent preheating;

[0054] 4. Load the current printhead path, record the printhead preheating time as j, calculate the remaining time i of the current first path segment, and start preheating the printhead corresponding to the current path. At the same time, turn on laser-assisted heating to provide auxiliary heating to the area in front of the path to be printed.

[0055] 5. After preheating is complete, the path code is executed line by line. It is determined whether the path code of the current print head has ended. If it has not ended, the time spent on the current path is calculated and the remaining time of the current print head is updated to i = i - t. The remaining time is compared with the preheating time of the next print head. When i < j, the next print head is heated in the order of the arranged print heads. Otherwise, the subsequent path code is executed.

[0056] 6. If the path code of the current print head has ended, determine whether the entire path has been printed. If not, execute the print head switching procedure.

[0057] 7. First, move the printhead to the current printhead installation position. Then, power on the de-energized magnet to eliminate its magnetic force. The printhead will automatically fall off to its installation position. Next, move the fixing flange above the preheated next printhead, disconnect the de-energized electromagnet circuit, and move the magnet down to the new printhead. The new printhead will automatically be attracted and return to the previous node. The printhead replacement is complete.

[0058] 8. Calculate the remaining path duration of the printhead after replacement, and repeat steps 5-7;

[0059] 9. If the printing process has been completed, unload the print head to finish printing.

[0060] Of course, the present invention is not limited to the examples above. Any changes, modifications, additions or substitutions made by those skilled in the art within the scope of the present invention are also within the protection scope of the present invention.

Claims

1. A modular, multi-functional FDM printhead for space additive manufacturing, characterized in that: It includes a coaxial extrusion component, a heat dissipation component, and a printhead switching component. One end of the printhead switching component is fixedly connected to the end of the motion mechanism, and the other end is fixedly connected to the heat dissipation component. The coaxial extrusion component is fixed on the heat dissipation component. The coaxial extrusion component includes a heating block (9), an outer nozzle (10), and an inner nozzle (11). The upper center of the heating block (9) is provided with an inner nozzle connecting pipe (12) for conveying continuous phase material. The inner nozzle (11) is fixed at the lower end of the inner nozzle connecting pipe (12). The outer nozzle (10) is coaxially sleeved outside the inner nozzle (11) and fixedly connected to the lower end of the heating block (9). The upper eccentric part of the heating block (9) is provided with an inner throat (13) that communicates with the outer nozzle (10). The inner throat (13) is used to convey resin matrix material. The outer nozzle (10) is a downward pointed cone shape. The angle between the cone surface of the outer nozzle (10) and the horizontal direction is greater than or equal to 45° and less than or equal to 60°. The inner nozzle (11) is a slender needle tube structure. The lower ends of the outer nozzle (10) and the inner nozzle (11) are flush.

2. The modular multi-functional FDM printhead according to claim 1, characterized in that: The lower ends of both the outer nozzle (10) and the inner nozzle (11) are smoothly transitioned.

3. The modular multi-functional FDM printhead according to claim 1, characterized in that: The lower end of the inner hole of the inner nozzle (11) has a trumpet-shaped outward structure.

4. The modular multi-functional FDM printhead according to claim 1, characterized in that: The upper end of the heating block (9) is further extended inward with two heating rods and a temperature sensor. The two heating rods are arranged opposite each other with the inner nozzle connecting pipe (12) as the center. The temperature sensor and the inner throat pipe (13) are arranged opposite each other with the inner nozzle connecting pipe (12) as the center. The two heating rods are at the same distance from the inner throat pipe (13) and the temperature sensor.

5. The modular multi-functional FDM printhead according to claim 1, characterized in that: The heat dissipation component includes a round tube fitted on the upper end of the inner throat tube (13), the upper end of the round tube is connected to an outer throat tube (14), the upper end of the outer throat tube (14) is fixed with a connecting flange (3), and two cooling fans (7) are suspended opposite each other at both ends of the connecting flange (3) to form a pair of heat dissipation fins (8) that are spaced apart and eccentrically fixed on the round tube.

6. The modular multi-functional FDM printhead according to claim 5, characterized in that: There is a gap between the two cooling fans (7) and the heat sink (8).

7. The modular multi-functional FDM printhead according to claim 5, characterized in that: The printhead switching component includes a fixed flange (1) fixed to the end of the motion mechanism, and two sets of magnetic head-changing devices (2) are provided between the fixed flange (1) and the connecting flange (3).

8. The modular multi-functional FDM printhead according to claim 7, characterized in that: The magnetic head-changing device (2) includes a female connector (15), a demagnetizing magnet (16), and a male connector (17). The upper end of the male connector (17) is fixed to the lower end of the fixed flange (1). The lower end of the male connector (17) is hollow and the demagnetizing magnet (16) is inserted therein. The female connector (15) is made of magnetic material and is fixed on the connecting flange (3).

9. The modular multi-functional FDM printhead according to claim 7, characterized in that: It also includes a vision inspection device (4) fixed to the fixed flange (1) via a vision inspection bracket for monitoring the entire printing and switching process.

10. The modular multi-functional FDM printhead according to claim 5, characterized in that: It also includes an auxiliary heater (6) fixed to the connecting flange (3) by an auxiliary heating bracket (5) to preheat the area to be printed.

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