A device for secondary utilization of heat from a vacuum FDM printer nozzle on a substrate

Abstract

The present invention provides a device for reusing heat from a vacuum FDM printer nozzle at the substrate. The device comprises a base, a printer arm disposed on one side of the base; a substrate support disposed on the base, wherein the substrate support is provided with a substrate; the printer arm and a material tray box are connected to the printer arm; a Z-axis lead screw motor assembly and a Y-axis lead screw motor assembly are located at the upper and left portions of the printer arm, respectively; a nozzle without a heat sink is mounted at the lower portion of the printer arm; substrate heat transfer wires are embedded within the printer arm and the printer arm; the substrate heat transfer wires are connected to the nozzle and then to the substrate via the printer arm and the printer arm; and a routing groove for the heat transfer wires is designed within the substrate. The present invention recycles heat from the nozzle, utilizing the heat while eliminating substrate heating, reducing the amount of heat input into the vacuum system and effectively mitigating damage to the machine caused by heat accumulation during prolonged vacuum printing.

Description

Technical Field

[0001] The present invention belongs to the field of vacuum additive manufacturing equipment, in particular to a device for reusing the heat at the nozzle of a vacuum FDM printer at a printer substrate. Background Art

[0002] In-orbit additive manufacturing (OAM) involves launching raw materials and AM equipment into orbit via a carrier rocket for in-space manufacturing and assembly. It is essential for future deep space exploration. FDM printing uses filament as the raw material, softening it with heat. This material is then mechanically extruded through a nozzle, where it accumulates layer by layer as the nozzle moves. A vacuum FDM printer, based on FDM technology, is a device capable of performing additive manufacturing in space environments.

[0003] The high vacuum environment of space orbit significantly impacts the operation of FDM printers. Due to the lack of a heat transfer medium, the heat generated by the printhead during operation cannot be dissipated by convection. This ultimately causes the filament above the printhead to soften and clog, severely impacting printer efficiency. Currently, heat can be removed from the printer by installing a heat exchanger on the printer's exterior, utilizing liquid circulation. However, this results in a significant amount of heat being wasted at the printhead through thermal circulation. Furthermore, the heat dissipation system, typically consisting of a circulation pump, radiator, and heat dissipation piping, is bulky and heavy, making it unsuitable for firing. Furthermore, over time, there is a risk of leakage, preventing long-term stable operation. During operation, the printhead temperature of an FDM printer reaches 400°C, while the substrate temperature is typically around 100°C, resulting in a 300°C temperature gradient between the two. Therefore, in a vacuum environment, the residual heat from the printhead can be transferred to the substrate for secondary use.

[0004] In view of this, a device is needed that can dissipate heat stably for a long time in a vacuum environment and reuse the residual heat at the nozzle on the printer substrate. Summary of the Invention

[0005] In response to the problems that vacuum FDM printers cannot use gas for convection heat dissipation, liquid circulation heat dissipation has the risk of leakage, and high-temperature nozzle heat is wasted, the present invention invents a device for secondary utilization of the heat of the vacuum FDM printer nozzle on the printer substrate.

[0006] The principle of the present invention is to use heat conduction to transfer the heat at the high-temperature nozzle of the FDM printer to the printer substrate where a lower temperature is required through heat transfer wires, while meeting the heat dissipation requirements of the vacuum FDM printer. The temperature gradient on the printer substrate is reduced by designing the arrangement of the heat transfer wires on the printer substrate.

[0007] A device for secondary utilization of heat from a vacuum FDM printer nozzle at a substrate, comprising a base, one side of which is provided with a printer arm; a substrate support located above the base, wherein the substrate support is provided with a substrate; a printer fork arm and a material tray box are connected to the printer arm; a Z-axis lead screw motor group and a Y-axis lead screw motor group are located at the upper and left parts of the printer arm, respectively, the Z-axis lead screw motor group controls the up and down movement of the printer fork arm on the printer arm, and the Y-axis lead screw motor group can control the forward and backward movement of the printer fork arm on the printer arm; a nozzle motor is installed at the upper right part of the printer fork arm, which can control the left and right movement of the nozzle on the printer fork arm; the printer fork arm filament is drawn out from the material tray box and enters the nozzle through an extruder from a filament inlet; a nozzle without a heat sink is installed at the lower part of the printer fork arm; substrate heat transfer wires are embedded in the interior of the printer arm and fork arm; the substrate heat transfer wires are connected to the nozzle and are connected to the substrate through the printer fork arm and the printer arm; and an arrangement groove for the heat transfer wires is designed inside the substrate.

[0008] The vacuum FDM printer described in this invention places the FDM printer under normal pressure in a vacuum tank. The Z-axis leadscrew motor assembly controls the vertical movement of the printer arm on the main arm; the Y-axis leadscrew motor assembly controls the forward and backward movement of the printer arm on the main arm; and the X-axis leadscrew motor assembly controls the left and right movement of the printer nozzle on the printer arm.

[0009] Furthermore, the nozzle is composed of an insulation board, a heating resistor, a wire channel, and a substrate heat transfer wire. The substrate heat transfer wire is connected to the outer wall of the wire channel. The heat at the bottom of the insulation board is transferred to the substrate by the substrate heat transfer wire in the heat transfer wire channel.

[0010] When the printer is working in a vacuum environment, the temperature at the nozzle rises rapidly, and the temperature at the heat insulation plate above the nozzle also rises rapidly. The heat transfer wire is connected to the heat insulation plate above the nozzle, and the heat at the nozzle is transferred by heat conduction through the heat transfer wire channel inside the printer's upper and lower arms to the bottom entrance of the printer baseboard. The heat is almost evenly transferred to the entire baseboard through the specific heat transfer wire arrangement at the bottom of the printer baseboard, achieving the effect of secondary utilization of the nozzle heat on the baseboard and a small temperature gradient on the baseboard.

[0011] Furthermore, after the substrate heat transfer wire is connected to the substrate from the substrate heat transfer wire inlet, it is divided into four wires with a width of 10 mm, respectively, in the upper left, lower left, upper right, and lower right directions. In each transmission direction, there are three substrate heat transfer wires with different widths that are parallel to the outer contour of the substrate. The width of the substrate heat transfer wire from the center of the substrate to the edge of the substrate is 3 mm, 5 mm, and 10 mm respectively.

[0012] Beneficial effects of the present invention:

[0013] 1. The present invention uses wires with excellent thermal conductivity to transfer heat from the nozzle to the bottom of the vacuum printer's substrate through the principle of heat conduction. By arranging the heat transfer wires on the printer substrate at the bottom of the substrate, a uniform heat distribution is achieved on the printed substrate. The temperature distribution of the printer substrate affects the degree of deformation of the printed part during molding, ultimately affecting the printer's printing accuracy and product qualification rate. Taking fiber-reinforced resin-based composite materials as an example, during the printing process, due to the presence of temperature gradients at different locations on the substrate, the resin temperature varies at different locations on the structural component, affecting the movement range and speed differences of the polymer chains at different locations, ultimately causing warping and even interlaminar cracking in some areas of the printed part. The present invention achieves this by setting a specific wire arrangement pattern at the bottom of the substrate, creating grooves in the substrate, and then filling the grooves with silver metal. This ensures that the heat transferred from the wires to the interface is distributed as evenly as possible across the substrate surface, reducing the temperature gradient on the substrate and improving the printer's molding accuracy.

[0014] 2. This invention uses heat transfer wires to transfer heat from the hot end of the printhead through the wires on the printer's upper and lower arms to the heat transfer wire interface at the bottom of the substrate. The wires are then connected to the interface. This allows the heat transfer capacity of the wires to be varied by changing their cross-sectional area, thereby controlling the amount of heat transferred from the printhead to the substrate. Once the heat in the vacuum system reaches equilibrium, a constant substrate temperature is achieved.

[0015] 3. The present invention utilizes the large temperature gradient between the printer nozzle and the printer substrate to transfer heat from the nozzle to the printer substrate via metal wires for secondary use. To address the varying temperature gradients between the nozzle and substrate when printing different materials, the temperature requirements of both the nozzle and the substrate can be met by replacing wires with different thermal conductivity properties, allowing heat from the high-temperature nozzle to be reused on the lower-temperature substrate. This reduces or eliminates the need to heat the printer substrate during operation, reducing heat input into the vacuum system, lowering the printer's operating power, and alleviating the heat dissipation pressure of the vacuum FDM printer.

[0016] 4. This invention connects the printer nozzle and substrate via heat transfer wires, using a temperature gradient as a driving force for heat transfer. This device dissipates heat from the nozzle and recycles it back onto the printer substrate. To achieve a greater temperature gradient, this device eliminates the need for heat sinks on the nozzle, thereby reducing the size of the nozzle and increasing its mobility within the fixed printer chamber, thus increasing the size of the printer.

[0017] 5. The heat at the print head is reused. While utilizing the heat, the heating of the substrate can be eliminated, which reduces the amount of heat input into the vacuum system and effectively alleviates the occurrence of machine damage caused by heat accumulation during long-term vacuum printing. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 Schematic diagram of the device for secondary utilization of heat from the nozzle of a vacuum FDM printer;

[0019] Figure 2 Structure diagram of the printhead without heat sink;

[0020] Figure 3 Substrate conductor layout diagram;

[0021] List of reference numerals:

[0022] 1. Z-axis lead screw motor assembly; 2. Y-axis lead screw motor assembly; 3. Material tray box; 4. Heat transfer wire; 5. Printer arm; 6. Base; 7. Filament; 8. Filament inlet; 9. Extruder; 10. X-axis lead screw motor assembly; 11. Print head; 12. Base plate; 13. Base plate bracket; 14. Printer arm; 15. Heat shield; 16. Heating resistor; 17. Filament channel; 18. Base plate heat transfer wire inlet; 19. Base plate heat transfer wire. DETAILED DESCRIPTION

[0023] The present invention will be further described below with reference to the accompanying drawings and specific embodiments. It should be understood that the following specific embodiments are intended only to illustrate the present invention and are not intended to limit the scope of the present invention. It should be noted that the terms "front," "rear," "left," "right," "up," and "down" used in the following description refer to directions in the accompanying drawings, and the terms "inward" and "outward" refer to directions toward or away from the geometric center of a particular component, respectively.

[0024] This embodiment Figure 1As shown, a device for secondary utilization of heat from a vacuum FDM printer nozzle at a substrate comprises a base 6, a printer arm 5 is provided on one side of the base 6; a substrate support 13 is located on the base 6, wherein a substrate 12 is provided on the substrate support 13; a printer arm 14 and a material tray box 3 are connected to the printer arm 5; a Z-axis lead screw motor group 1 and a Y-axis lead screw motor group 2 are respectively located at the upper part and the left part of the printer arm 5, the Z-axis lead screw motor group 1 controls the up and down movement of the printer arm 14 on the printer arm 5, and the Y-axis lead screw motor group 2 can control the printer arm 14 to move up and down on the printer arm 5 forward and backward movement; a nozzle motor 10 is installed on the upper right part of the printer arm 14, which can control the left and right movement of the nozzle 11 on the printer arm 14; the filament 7 of the printer arm 14 is led out from the material tray box 3, and enters the nozzle 11 from the filament inlet 8 through the extruder 9; wherein the lower part of the printer arm 14 is equipped with a nozzle 11 without a heat sink; a substrate heat transfer wire 19 is embedded in the inside of the printer arm and the arm; the substrate heat transfer wire 19 is connected to the nozzle 11 and is connected to the substrate 12 through the printer arm 14 and the printer arm 5; wherein the arrangement groove of the heat transfer wire is designed inside the substrate 12.

[0025] When the printer is operating, the temperature at the nozzle 11 rises rapidly, and so does the temperature of the heat transfer wire 4 connected to the nozzle 11. Heat is then transferred from the printer arm 14 and the printer arm 5 to the base plate 12 via the heat transfer wire 4, where it is evenly distributed across the base plate. This device's heat dissipation is unaffected by the absence of a heat transfer medium in a vacuum environment, resulting in a relatively stable heat transfer effect.

[0026] In this embodiment, if Figure 2 As shown, the printhead 11 comprises a heat shield 15, a heating resistor 16, a wire channel 17, and a substrate heat transfer wire 19. The substrate heat transfer wire 19 is connected to the outer wall of the wire channel 17. Heat from the bottom of the heat shield 15 is transferred to the substrate 12 via the substrate heat transfer wire 19 in the heat transfer wire channel. When the printer is operating, the temperature of the heating resistor 16 rises, heating the wire in the wire channel 17 between the heating resistor 16. The heat shield 15 prevents heat from the heating resistor 16 from transferring upward, preventing the wire above from softening and clogging the wire channel 17 above the heat shield 15. The heat transfer wire 4 is connected to the outer wall of the wire channel 17. Heat from the bottom of the heat shield 15 is transferred to the substrate 12 via the heat transfer wire in the heat transfer wire channel. Compared to traditional printheads, this printhead omits the heat sink, resulting in a smaller footprint and increased printer space.

[0027] The arrangement of heat transfer wires is designed inside the substrate 12 of the present invention, such as Figure 3After entering the substrate through the substrate heat transfer wire inlet 18, the substrate heat transfer wire 19 is divided into four 10mm wide wires, extending in the upper left, lower left, upper right, and lower right directions. In each transmission direction, there are three substrate heat transfer wires of different widths, parallel to the outer contour of the substrate. The widths of the substrate heat transfer wires from the center to the edge of the substrate are 3mm, 5mm, and 10mm, respectively.

[0028] The efficiency of heat conduction is closely related to the heat transfer material and its configuration. To ensure that heat is evenly distributed across the bottom of the substrate and to minimize the complexity of the heat transfer structure, the heat transfer wires used in this invention are all made of silver, a material with excellent thermal conductivity. These wires are wrapped with insulation before being connected to the substrate to prevent heat loss.

[0029] The theoretical basis for designing the width of the heat transfer wire at the bottom of the substrate is: the heat conduction equation, α is the thermal diffusivity, u represents temperature, ρ is the density of the heat transfer material, c is the specific heat capacity of the heat transfer material, k is the thermal conductivity coefficient of the heat transfer material, is the time derivative of temperature, is the temperature gradient with respect to position, which shows that heat transfer is related to the heat transfer time t and the heat transfer distance x. This equation describes how the temperature of a small part of a homogeneous conductor changes due to the gradient of heat flow in a small amount of time.

[0030] The heat conduction coefficient is defined as: Take two points with a distance of 1m and an area of 1m perpendicular to the heat conduction direction inside the object. 2 If the temperature difference between the two planes is 1K, the heat transferred from one plane to another in 1 second is the thermal conductivity of the material, which is expressed in watt-meters. -1 ·open -1 .

[0031] For isotropic materials, thermal conductivity is somewhat dependent on their structure. Assuming no heat loss, for a block of parallel sides, Q / t = kS(θ2 - θ1) / L. Here, Q is the energy transferred in time t, S is the cross-sectional area, L is the length, k is the thermal conductivity, and θ2 and θ1 are the temperatures at the two cross-sections, respectively.

[0032] Typically, the heat transfer coefficient k is a constant. When the length L, time t, and cross-sectional temperatures θ2 and θ1 are constant, increasing the heat transfer cross-sectional area S can increase Q, thereby increasing the amount of heat transferred. When the heat transfer time and distance remain constant, increasing the heat transfer cross-sectional area can increase the amount of heat transferred. Therefore, increasing the heat transfer cross-sectional area can improve heat transfer over long distances.

[0033] This example conducted actual measurements by designing substrates of varying sizes, widths, and layout patterns, ultimately selecting the solution with the best heat transfer performance. Based on this design, a three-layer surround extending from the center of the substrate was constructed, with widths of 3mm, 5mm, and 10mm, respectively. With this design, the heat transfer capacity of the three-layer surround, from greatest to least, was ranked as follows: 10mm > 5mm > 3mm. This resulted in a relatively uniform temperature distribution on the substrate during actual heat transfer.

[0034] This embodiment uses silver wire to transfer heat from the hot end of the printhead through wires on the printer's upper and lower arms to a heat transfer wire interface on the bottom of the substrate. The wire is then connected to the interface. This allows the heat transfer capacity of the wire to be varied by changing its cross-sectional area, thereby controlling the amount of heat transferred from the printhead to the substrate. Once the vacuum system reaches thermal equilibrium, a constant substrate temperature is achieved.

[0035] Example

[0036] For example, printing a chopped carbon fiber-reinforced PEEK composite at 10 Pa (100 Pa) is performed. A PEEK composite with a 1.75 mm diameter and 10% chopped carbon fiber content is loaded into a tray. Filament is then drawn from the tray, through a filament inlet and into the printhead via a feed mechanism. When the printer is operating, the printhead temperature is maintained at approximately 430°C. Without the heat recovery device and with the substrate heating disabled, the printing substrate temperature remains around 80°C, well below the glass transition temperature of PEEK. As a result, the filament extruded from the printhead rapidly drops below the glass transition temperature due to the low substrate temperature, preventing it from adhering to the substrate and ultimately failing to print. However, with the heat recovery device enabled, even when the substrate heating device is disabled, the printing substrate temperature remains around 150°C, above the glass transition temperature of PEEK, allowing the filament to adhere to the substrate. The heat of the nozzle can be reused on the substrate under vacuum environment, and the substrate heating can be turned off during printing, which greatly reduces the power consumption of the printer.

[0037] The technical means disclosed in the solution of the present invention are not limited to the technical means disclosed in the above-mentioned embodiment, but also include technical solutions composed of any combination of the above technical features.

Claims

1. A device for secondary utilization of heat from a vacuum FDM printer nozzle at a substrate, comprising a base (6), a printer arm (5) being provided on one side of the base (6); a substrate support (13) being located on the base (6), wherein a substrate (12) is provided on the substrate support (13); a printer arm (14) and a material tray box (3) being connected to the printer arm (5); a Z-axis lead screw motor group (1) and a Y-axis lead screw motor group (2) being located at the upper part and the left part of the printer arm (5), respectively; the Z-axis lead screw motor group (1) controlling the printing speed of the printer; and a Y-axis lead screw motor group (2) being provided at the upper part and the left part of the printer arm (5). The printer arm (14) is controlled to move up and down on the printer arm (5), and the Y-axis lead screw motor group (2) can control the forward and backward movement of the printer arm (14) on the printer arm (5); a nozzle motor (10) is installed on the upper right part of the printer arm (14), which can control the left and right movement of the nozzle (11) on the printer arm (14); the filament (7) of the printer arm (14) is drawn out from the material tray box (3), and enters the nozzle (11) from the filament inlet (8) through the extruder (9); the characteristics are: The lower part of the printer arm (14) is provided with a nozzle (11) without a heat sink; a heat transfer wire (4) is embedded inside the printer arm and the lower arm; the heat transfer wire (4) is connected to the nozzle (11) and is connected to the substrate heat transfer wire (19) on the substrate (12) through the printer arm (14) and the printer arm (5); and a layout groove for the heat transfer wire is designed inside the substrate (12).

2. The device for secondary utilization of heat from a vacuum FDM printer nozzle at a substrate according to claim 1, characterized in that: The nozzle (11) is composed of a heat insulation plate (15), a heating resistor (16), a wire channel (17), and a heat transfer wire (4). The heat transfer wire (4) is connected to the outer wall of the wire channel (17). The heat at the bottom of the heat insulation plate (15) is transferred to the substrate (12) by the substrate heat transfer wire (19) in the heat transfer wire channel.

3. The device for secondary utilization of heat from a vacuum FDM printer nozzle at a substrate according to claim 1, characterized in that: The substrate heat transfer wire (19) enters from the bottom of the substrate (12) through the substrate heat transfer wire inlet (18) and is arranged inside the substrate (12) in the manner of a substrate heat transfer wire, so that heat can be transferred to the substrate more evenly.

4. The device for secondary utilization of heat from a vacuum FDM printer nozzle at a substrate according to claim 1, characterized in that: After the substrate heat transfer wire (19) is connected to the substrate from the substrate heat transfer wire inlet (18), it is divided into four wires with a width of 10 mm, respectively, in the upper left, lower left, upper right, and lower right directions. In each transmission direction, there are three substrate heat transfer wires with different widths that are parallel to the outer contour of the substrate. The widths of the substrate heat transfer wires from the center of the substrate to the edge of the substrate are 3 mm, 5 mm, and 10 mm respectively.

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