3D printing polymer powder system based on microwave heating and 3D printing method

Abstract

The invention discloses a 3D printing polymer powder system based on microwave heating and a 3D printing method, and relates to the technical field of 3D printing. Comprising a 3D printing lifting platform, a powder supply and laying system for laying or spraying powder on the 3D printing lifting platform, a mounting frame arranged on the 3D printing lifting platform in a sliding mode, an SSPPs waveguide welding module arranged below the mounting frame and a spraying assembly for spraying a wave absorbing agent. The SSPPs waveguide welding module comprises a first microwave source, a second microwave source and a gradually-changed bent waveguide component; the first microwave source and the second microwave source are arranged at the two ends of the gradually-changed bent waveguide component respectively, and the gradually-changed bent waveguide component is a gradually-changed upwards-convex bent waveguide assembly; and the gradually-changed bent waveguide component is a gradually-changed upwards-convex bent waveguide component. The 3D printing and stacking device has the advantages of quicker and more efficient heating and more uniform heating in the 3D printing and stacking process.

Description

Technical Field

[0001] This invention relates to the field of 3D printing technology, and more specifically to a 3D printing polymer powder system and 3D printing method based on microwave heating. Background Technology

[0002] 3D printing, also known as additive manufacturing, is a technology that constructs three-dimensional objects by stacking materials layer by layer. A 3D printer extends this planar printing principle to the third dimension. Following instructions generated by slicing software, the printer begins printing layer by layer, ultimately stacking these thin layers into a solid, three-dimensional object. There are various 3D printing technologies suitable for different materials and applications. The most common ones include: Fused Deposition Modeling (FDM): A roll of thermoplastic filament (such as PLA or ABS) is fed into a heated printhead, melted, and then extruded layer by layer onto a printing platform, forming a 3D model. The advantages of this 3D printing method are low machine and material costs, simple operation, wide variety of materials, and safety and environmental friendliness. The disadvantages are surface texture, relatively low precision, and slow speed. It is the most popular consumer-grade 3D printing technology, commonly used for prototyping, education, and DIY creation.

[0003] Stereolithography (SLA): This technology uses a liquid resin sensitive to specific wavelengths of light (photosensitive resin). A laser beam or ultraviolet light spot precisely scans the surface of the resin liquid; the resin in the illuminated area solidifies, and the platform gradually rises, thus pulling out the entire object. Advantages include extremely high printing precision, smooth surface, and strong detail. Disadvantages include higher material costs, the resin's toxicity requiring careful handling, the printed parts being typically brittle, and the need for post-curing. It is used in fields requiring high precision, such as jewelry casting, dentistry, and figurine model making.

[0004] Powder sintering refers to the process of fusing and bonding solid micro-powder particles into a monolithic structure through heating. Fused Deposition Modeling (FDM) works by melting thermoplastic material through a heated nozzle, extruding it layer by layer onto a build platform, and then solidifying it upon cooling. The physical process involves melting followed by deposition, not sintering. Stereolithography (SLA) works by using ultraviolet lasers or projection light sources to irradiate liquid photosensitive resin, initiating a photochemical reaction; it is not a thermally driven sintering process.

[0005] Some high-end or custom-made printers also use independent infrared heaters to irradiate the top of the part being printed, in order to reduce interlayer cooling stress during the printing process, further improve print quality, and prevent warping (especially when printing easily shrinkable materials such as ABS).

[0006] Infrared heaters have weak penetration ability in polymer powders, resulting in slow penetration speed and low interlayer strength. Infrared heaters have long energy transfer paths and high thermal inertia, leading to excessive overall energy consumption in order to maintain local high temperatures and easily introducing thermal stress. Infrared heaters do not support high temperatures; for example, PEEK materials cannot be heated to the corresponding temperature.

[0007] Therefore, developing a new molding technology that can achieve precise local heating, improve efficiency from the energy conversion source, has strong selectivity and penetration, and is suitable for high temperatures has become the key to breaking through the high energy consumption dilemma of existing technologies. Summary of the Invention

[0008] The purpose of this invention is to solve the above-mentioned technical problems by providing a 3D printing polymer powder system and 3D printing method based on microwave heating. This invention uses microwave heating technology and relies on the characteristics of bulk heating to make heating faster, more efficient and uniform during the 3D printing deposition process.

[0009] To achieve the above objectives, the present invention specifically adopts the following technical solution: The first aspect of the present invention provides a microwave-heated 3D printing polymer powder system, including a 3D printing lifting platform, a powder supply and laying system for laying or spraying powder on the 3D printing lifting platform, a mounting frame slidably disposed on the 3D printing lifting platform, and an SSPPs waveguide welding module and a spraying component for spraying microwave absorbing agent disposed below the mounting frame. The SSPPs waveguide welding module includes a first microwave source, a second microwave source, and a gradually curved waveguide component; the first microwave source and the second microwave source are respectively located at both ends of the gradually curved waveguide component, which is a gradually convex-bent waveguide assembly; the gradually curved waveguide component is a gradually convex-bent waveguide assembly.

[0010] In one embodiment, the SSPPs waveguide heating module further includes a phase modulation system, which fixes the phase of a first microwave source or a second microwave source; when the phase of the first microwave source is fixed, the phase modulation system causes the phase of the second microwave source to change periodically; when the phase of the second microwave source is fixed, the phase modulation system causes the phase of the first microwave source to change periodically, thereby improving the uniformity of the transverse electric field.

[0011] In one embodiment, the powder supply and placement system includes a powder supply system and a powder recovery system arranged laterally on both sides of the 3D printing lifting platform, a powder placement module that spreads the powder in the powder supply system onto the 3D printing lifting platform laterally, and a spraying component that is mounted on a mounting frame and sprays a microwave absorbing agent onto the 3D printing lifting platform. The mounting bracket is slidably mounted longitudinally on the 3D printing lifting platform; The powder supply system includes a powder supply box with an opening at the top. The powder supply box includes a powder supply box side wall and a powder supply box bottom plate that is movably sealed inside the powder supply box side wall. A vertical lifting mechanism is provided at the bottom of the powder supply box bottom plate to drive the powder supply box bottom plate to rise and lower and control the lifting stroke. The powder spreading module includes two transverse guide rails arranged horizontally on both sides of the powder supply box and the 3D printing lifting platform, a powder spreading mounting frame set on the two transverse guide rails and reciprocating along the two transverse guide rails, and a powder spreading roller installed longitudinally on the powder spreading mounting frame. The mounting bracket includes a gantry-shaped mounting base that slides longitudinally, two longitudinal mounting plates mounted on the gantry-shaped mounting base via a lifting module, a first transverse mounting rod and a second transverse mounting rod connected between the two longitudinal mounting plates, a spraying assembly that slides on the first transverse mounting rod, and an SSPPs waveguide welding module that is fixedly mounted on the bottom of the second transverse mounting rod.

[0012] In one embodiment, the mounting frame includes two guide rails arranged longitudinally on both sides of the 3D printing lifting platform, a movable frame arranged above the 3D printing lifting platform and reciprocating along the two guide rails, a first linear drive mechanism for driving the movable frame to move horizontally, a work mounting frame capable of lifting and lowering along the vertical direction of the movable frame, and a second linear drive mechanism for driving the work mounting frame to lift and lower vertically. The powder supply and application system includes a powder spraying module and a spraying assembly mounted on a work mounting frame; The SSPPs waveguide welding module is mounted on the work mounting frame; The powder spraying module, spraying components, and SSPPs waveguide welding module are arranged longitudinally on the work mounting frame.

[0013] In one embodiment, the gradually convex bend waveguide assembly includes a U-shaped shell, microwave feed inlets disposed at both ends of the U-shaped shell, and a metal array evenly distributed within the U-shaped shell. The top position of the metal array located within the two straight edge segments of the U-shaped shell gradually rises along the microwave transmission direction, while the bottom position of the metal array located within the two straight edge segments of the U-shaped shell is on the same horizontal line. The U-shaped shell includes a wedge-shaped raised area at the bottom, a left bend and a right bend symmetrically arranged at both ends of the wedge-shaped raised area, a left transition section connected to the left bend, a right transition section connected to the right bend, a left microwave feed port located at the end of the left transition section, and a right microwave feed port located at the end of the right transition section. The wedge-shaped raised area is a strong electric field area for heating. The top positions of the metal arrays installed in the left and right transition sections gradually rise along the microwave transmission direction, while the bottom positions of the metal arrays installed in the left and right transition sections are on the same horizontal line. The bottom positions of the metal arrays in the left and right bends are on the same horizontal line, and the top positions of the metal arrays in the left and right bends are on the same horizontal line.

[0014] A second aspect of the present invention provides a microwave-heated planar powder 3D printing method, employing the microwave-heated 3D printing system of claim 3, comprising the following steps: S1. The powder supply system raises a layer of powder, and the powder spreading module spreads a layer of powder on the 3D printing lifting platform. S2. The spraying component then sprays adhesive or microwave absorber onto the powder on the 3D printing lifting platform; S3. Turn on the SSPPs waveguide heating module. The SSPPs waveguide heating module moves longitudinally to the adhesive area that needs to be heated and heats that area. S4. Monitor the local temperature through a temperature sensor array or infrared imager array and feed it back to the main control unit; S5. The main control unit adjusts the activation, power, and phase of the SSPPs waveguide heating module according to the heating requirements to achieve local heating and avoid stress concentration. The S6 and SSPPs waveguide heating modules move longitudinally with the spraying components, achieving dynamic heating along the 3D printing trajectory. S7. Repeat steps S1 to S6, printing layer by layer until the part is complete.

[0015] In one implementation, in step S5, the main control unit regulates the input power of the SSPPs waveguide heating module using a PID algorithm: when the temperature is lower than or reaches the target temperature, the input power is kept constant at 150W; when the temperature exceeds the target temperature, the input power is reduced.

[0016] A third aspect of the present invention provides a microwave-heated powder spraying 3D printing method, employing the aforementioned microwave-heated 3D printing system, comprising the following steps: S1. The powder spraying module first sprays a layer of powder onto the 3D printing lifting platform; S2. The spraying component then sprays adhesive or microwave absorber onto the powder on the 3D printing lifting platform; S3. Turn on the SSPPs waveguide heating module. The SSPPs waveguide heating module moves longitudinally to the adhesive area that needs to be heated and heats that area. S4. Monitor the local temperature using a temperature sensor or infrared imaging and feed it back to the control system; S5. The control system adjusts the activation, power, and phase of the SSPPs waveguide heating module according to the heating requirements to achieve local heating and avoid stress concentration. The S6 and SSPPs waveguide heating modules move longitudinally with the spraying components, achieving dynamic heating along the 3D printing trajectory. S7. Repeat steps S1 to S6, printing layer by layer until the part is complete.

[0017] In one implementation, the longitudinal movement of the SSPPs waveguide heating module in step S6 is specifically as follows: S61. Input waveguide length L and phase adjustment frequency f, calculate electric field scanning speed V-scan, V-scan=L×f; S62. Input the electric field scanning speed V-scan and the desired number of scanning cycles N, and calculate the longitudinal moving speed range of the SSPPs waveguide heating module: V-move < V < V-scan / N, where V-move is the initial longitudinal moving speed of the SSPPs waveguide heating module; S63. Start the longitudinal movement and phase modulation of the SSPPs waveguide heating module to monitor the electric field uniformity and temperature in real time. S64. Determine whether the heating effect meets the requirements. If the heating effect meets the requirements, complete the heating and stop moving. If the heating effect does not meet the requirements, adjust the initial longitudinal moving speed V-move or the phase adjustment frequency f, and then return to step S63.

[0018] The beneficial effects of this invention are as follows: 1. This invention offers a speed advantage over single-layer printing, moving from layer-by-layer scanning to volumetric manufacturing, specifically as follows: The speed advantage of microwaves stems from their unique volumetric heating (or "volume heating") mechanism. Traditional infrared 3D printing relies on heat conduction, with energy transferred from the material surface inwards. This heating method limits the melting or sintering of each powder layer to the layers directly irradiated by infrared light and the interface with the already solidified portion below, essentially making it a layer-by-layer process. Microwaves, however, can penetrate the material's interior, directly converting electromagnetic energy into heat energy throughout the entire powder area. This means that in a microwave field, energy can act simultaneously on multiple newly laid powder layers, not just the surface layers. This capability enables microwave 3D printing to achieve "volume manufacturing," that is, solidifying a three-dimensional volume in a single step, thus overcoming the efficiency bottleneck of traditional point-by-point scanning and layer-by-layer accumulation, and providing potential for the rapid prototyping of large-sized parts.

[0019] 2. The present invention features low energy consumption and improved efficiency, with precise energy utilization as follows: The superior performance of microwaves in terms of energy consumption is mainly attributed to two characteristics: selective heating and volume heating.

[0020] Selective Heating and Power Requirements: Microwave energy is not uniformly absorbed by all materials; it is primarily absorbed by materials or components with specific dielectric losses (high loss factors), such as polar molecules, moisture, or specific additives within the material. This selectivity means that energy can be used efficiently when heating such materials without first heating the entire build cavity or surrounding environment. Therefore, to raise materials to the same processing temperature, microwave systems typically require less effective power than infrared-based systems, where a significant amount of energy is consumed in heating the surrounding environment, cavity, or gaseous environment, rather than being used entirely for the target material.

[0021] Highly efficient energy conversion and low heat loss: Microwave heating is a "bulk heat source" where electromagnetic energy causes the molecules inside the material to oscillate at high frequencies, generating heat directly within the material itself. In contrast, traditional methods such as infrared heating require high-temperature heat sources, and energy is transferred from the outside to the inside through thermal radiation and conduction. During this process, a considerable portion of the energy is dissipated in the heating environment, carrier gas, or equipment components.

[0022] 3. Compared to infrared heating technology, this invention is suitable for high-temperature printing, specifically as follows: Infrared technology faces multiple limitations when reaching high temperatures, mainly due to its energy transfer method and the inherent characteristics of material interactions. Infrared heating relies on electromagnetic radiation for heat transfer, and the achievable temperature is highly dependent on the power density of the emission source and the absorption efficiency of the heated material for a specific infrared wavelength. If the wavelength of the infrared radiation does not match the optimal absorption band of the material, a large amount of energy will be reflected or transmitted instead of being absorbed and converted into heat energy, which directly limits the heating potential. Even with the use of higher-power near-infrared technology, if the surface of the heated object is smooth, light-colored, or has poor thermal conductivity and rapid heat dissipation, it will be difficult to accumulate heat, making it difficult to achieve and maintain a stable high-temperature state. Theoretically, by greatly increasing the power, the upper limit of infrared heating temperature can be very high, but in practical industrial applications, due to limitations in equipment cost, safety, and material tolerance, achieving a uniform, efficient, and controllable ultra-high temperature environment remains a challenge. Microwaves can achieve ultra-high temperature processing mainly due to their volumetric heating mechanism. Microwave energy can penetrate materials and be directly converted into heat energy inside the material, thereby achieving rapid overall heating.

[0023] 4. The present invention achieves better interlayer bonding quality and deep fusion, as detailed below: Penetrating heating improves adhesion: In powder bed 3D printing, infrared heating, due to its limited penetration depth, concentrates heat primarily on the surface of the newly laid powder layer. This may result in insufficient temperature at the interface between the new powder layer and the underlying solidified solid to achieve adequate molecular diffusion and fusion, leading to relatively weak interlayer adhesion (e.g., ...). Figure 15 (As shown).

[0024] Interfacial co-fusion and improved mechanical properties: Microwaves, with their strong penetrating power, can simultaneously heat the new powder layer and the area near the interface of the solidified solid. This heating method allows for more complete interdiffusion and fusion of materials on both sides of the interface at the molecular level, forming a denser and stronger interface. From a mechanical property perspective, this strong interfacial bonding helps to significantly improve the interlaminar shear strength and tensile properties of the part, reduce anisotropy caused by incomplete interlaminar fusion, and make the part approach the overall density and mechanical property consistency of a monolithic solid. Figure 16 (As shown).

[0025] 5. This invention designs an artificial surface plasmon polariton (SSPP) waveguide composed of a periodic metal array. This waveguide enhances the microwave power absorbed by the material by strengthening the electric field and improves heating uniformity through its periodic structure. Due to the high localization of the electromagnetic field by the SSPP structure, the designed waveguide can be used for heating in open spaces, making it particularly suitable for 3D printing of polymer powders. Furthermore, the surface waves formed by the metal array possess a wide-range, strong electric field region, which can be used as a "line source" in 3D printing. The second part first presents the dispersion principle of SSPPs and the governing equations for microwave heating. Secondly, it establishes a heating model based on a three-dimensional SSPP waveguide and the optimization process for bending and lifting treatments. In the third part, based on a multiphysics model, the heating effect of the SSPP waveguide in 3D printing of polymer powders is demonstrated. Attached Figure Description

[0026] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained from these drawings without creative effort.

[0027] Figure 1 This is a schematic diagram of the structure of a microwave-heated 3D printing polymer powder system (powder spreading type) according to the present invention; Figure 2 This is a schematic diagram of the structure of a microwave-heated 3D printing polymer powder system (powder spraying type) according to the present invention; Figure 3 This is a schematic diagram of the structure of a gradually convex bend waveguide assembly; Figure 4 This is a schematic diagram of a one-dimensional subwavelength groove periodic structure; Figure 5 The optimization process diagram shows that the height of the metal unit is kept constant and the lower wall of the waveguide is set to a wedge-shaped gradient. Figure 6The process involves changing the curvature of the metal array to improve transmission efficiency, as shown in the diagram. Figure 7 This is a waveform field distribution diagram of SSPPs under bending and lifting. Figure 8 This is a diagram showing the electric field distribution in the load and waveguide; Figure 9 yes Figure 8 The result after heating for 30 seconds; Figure 10 This is a simulation diagram comparing temperature distribution with and without phase change (the upper part has a constant phase, while the lower part has a changing phase). Figure 11 It is a curve comparing the temperature distribution with and without phase change; Figure 12 This is a diagram showing the heating effect of SSPPs waveguides sweeping across a carrier plate sprayed with absorbing agent; Figure 13 The figure shows the heating effect of the SSPPs waveguide during longitudinal movement when the port phase changes; Figure 14 This is a flowchart of the longitudinal movement control of the SSPPs waveguide heating module; Figure 15 This is a schematic diagram illustrating the penetration depth of infrared heating and microwave heating; Figure 16 This is a schematic diagram of the temperature distribution for infrared heating and microwave heating; Reference numerals: 1. Powder recovery system; 2. SSPPs waveguide heating module; 3. Spraying assembly; 4. Second microwave source; 5. Mounting bracket; 6. Powder spreading module; 7. Powder supply system; 8. 3D printing lifting platform; 9. First microwave source; 10. Powder spraying module; 21. Left microwave feed port; 22. Left transition section; 23. Left bend section; 24. Wedge-shaped lifting area; 25. Right bend section; 26. Right transition section; 27. Right microwave feed port. Detailed Implementation

[0028] To make the technical problems, technical solutions, and technical effects of the present invention clearer, 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. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0029] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0030] It should be noted that similar reference numerals and letters in the following figures indicate similar items; therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures. Furthermore, the terms "first," "second," etc., are used only to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0031] In the description of the embodiments of the present invention, it should be noted that the terms "inner", "outer", "upper", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship in which the product of the invention is usually placed when in use. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limiting the present invention.

[0032] Example 1 like Figure 1 As shown, this embodiment provides a 3D printing polymer powder system based on microwave heating, including a 3D printing lifting platform 8, a powder supply and laying system for laying or spraying powder on the 3D printing lifting platform 8, a mounting frame 5 slidably disposed on the 3D printing lifting platform 8, and an SSPPs waveguide welding module and a spraying component 3 for spraying microwave absorbing agent disposed below the mounting frame 5. The SSPPs waveguide welding module includes a first microwave source 9, a second microwave source 4, and a gradually curved waveguide component; the first microwave source 9 and the second microwave source 4 are respectively disposed at both ends of the gradually curved waveguide component, which is a gradually convex curved waveguide assembly; the gradually curved waveguide component is a gradually convex curved waveguide assembly.

[0033] The SSPPs waveguide heating module 2 also includes a phase control system, which fixes the phase of the first microwave source 9 or the second microwave source 4; when the phase of the first microwave source 9 is fixed, the phase control system causes the phase of the second microwave source 4 to change periodically; when the phase of the second microwave source 4 is fixed, the phase control system causes the phase of the first microwave source 9 to change periodically, in order to improve the uniformity of the transverse electric field.

[0034] The powder supply and laying system includes a powder supply system 7 and a powder recovery system 1 arranged laterally on both sides of the 3D printing lifting platform 8, a powder laying module 6 that lays the powder in the powder supply system 7 onto the 3D printing lifting platform 8 laterally, and a spraying component 3 that is mounted on the mounting frame 5 and sprays the microwave absorbing agent onto the 3D printing lifting platform 8. The mounting bracket 5 is slidably mounted on the 3D printing lifting platform 8 along the longitudinal direction; The powder supply system 7 includes a powder supply box with an opening at the top. The powder supply box includes a powder supply box side wall and a powder supply box bottom plate that is movably sealed inside the powder supply box side wall. A vertical lifting mechanism is provided at the bottom of the powder supply box bottom plate to drive the powder supply box bottom plate to rise and lower and control the lifting stroke. The powder spreading module 6 includes two transverse guide rails arranged horizontally on both sides of the powder supply box and the 3D printing lifting platform 8, a powder spreading mounting frame set on the two transverse guide rails and reciprocating along the two transverse guide rails, and a powder spreading roller installed longitudinally on the powder spreading mounting frame. Mounting bracket 5 includes a gantry mounting base that slides longitudinally, two longitudinal mounting plates mounted on the gantry mounting base via a lifting module, a first transverse mounting rod and a second transverse mounting rod connected between the two longitudinal mounting plates, a spraying assembly 3 that slides on the first transverse mounting rod, and an SSPPs waveguide welding module that is fixedly mounted on the bottom of the second transverse mounting rod.

[0035] The gradually convex bend waveguide assembly includes a U-shaped shell, microwave feed inlets located at both ends of the U-shaped shell, and a metal array evenly distributed within the U-shaped shell. The top position of the metal array located within the two straight edge segments of the U-shaped shell gradually rises along the microwave transmission direction, while the bottom position of the metal array located within the two straight edge segments of the U-shaped shell is on the same horizontal line. The U-shaped shell includes a wedge-shaped raised area 24 at the bottom, a left bend 23 and a right bend 25 symmetrically arranged at both ends of the wedge-shaped raised area 24, a left transition section 22 connected to the left bend 23, a right transition section 26 connected to the right bend 25, a left microwave feed port 21 provided at the end of the left transition section 22, and a right microwave feed port 27 provided at the end of the right transition section 26. The wedge-shaped raised area 24 is a strong electric field area for heating. The top positions of the metal arrays provided in the left transition section 22 and the right transition section 26 gradually rise along the microwave transmission direction, while the bottom positions of the metal arrays provided in the left transition section 22 and the right transition section 26 are on the same horizontal line. The bottom positions of the metal arrays within the left bend 23 and the right bend 25 are on the same horizontal line, and the top positions of the metal arrays within the left bend 23 and the right bend 25 are on the same horizontal line.

[0036] A planar powder 3D printing method based on a microwave-heated polymer powder system includes the following steps: S1. The powder supply system 7 raises a layer of powder, and the powder spreading module 6 spreads a layer of powder on the 3D printing lifting platform 8. S2, Spraying component 3 then sprays adhesive or microwave absorber onto the powder on the 3D printing lifting platform 8; S3. Turn on the SSPPs waveguide heating module 2. The SSPPs waveguide heating module 2 moves longitudinally to the adhesive area that needs to be heated and heats that area. S4. Monitor the local temperature through a temperature sensor array or infrared imager array and feed it back to the main control unit; S5. The main control unit adjusts the activation, power and phase of the SSPPs waveguide heating module 2 according to the heating requirements to achieve local heating and avoid stress concentration. S6, SSPPs waveguide heating module 2 moves longitudinally with spray component 3 to achieve dynamic heating along the 3D printing trajectory; S7. Repeat steps S1 to S6, printing layer by layer until the part is complete.

[0037] In one implementation, in step S5, the main control unit regulates the input power of the SSPPs waveguide heating module 2 using a PID algorithm: when the temperature is lower than or reaches the target temperature, the input power is kept constant at 150W; when the temperature exceeds the target temperature, the input power is reduced.

[0038] Specifically, in recent years, microwave-assisted or direct microwave sintering has been considered a potential enhancement technology, especially demonstrating unique advantages in energy saving and uniform heating. First, microwave heating is highly selective; in a microwave field, only absorbing materials absorb microwaves, generating electromagnetic loss and thus being heated. Other materials that do not absorb microwaves or have low loss are hardly heated. Adding a small amount of absorbing materials (such as carbon black or carbon nanotubes) to ordinary polymers allows these fillers to preferentially absorb microwaves and generate heat, driving the matrix to soften and sinter, achieving "on-demand heating" and controlling the sintering area. This high selectivity also improves energy utilization efficiency, making 3D printing equipment more energy-efficient. Second, compared to lasers, microwaves have stronger penetrating power in polymer powders, which can significantly increase the heating rate and shorten the sintering process time. Furthermore, microwave heating converts microwave energy into heat energy through the absorption of microwave energy by polar molecules within the material. This bulk heating from the inside out, compared to the surface treatment of laser sintering, reduces reliance on traditional heat conduction, reduces temperature gradients, and obtains a more uniform temperature field. In summary, microwave heating sintering of polymer powders has advantages such as low energy consumption, fast heating rate, and low temperature gradient, providing a new approach for polymer powder sintering 3D printing technology.

[0039] Example 2 like Figure 2 As shown, this embodiment provides a 3D printing polymer powder system based on microwave heating, including a 3D printing lifting platform 8, a powder supply and laying system for laying or spraying powder on the 3D printing lifting platform 8, a mounting frame 5 slidably disposed on the 3D printing lifting platform 8, and an SSPPs waveguide welding module and a spraying component 3 for spraying microwave absorbing agent disposed below the mounting frame 5. The SSPPs waveguide welding module includes a first microwave source 9, a second microwave source 4, and a gradually curved waveguide component; the first microwave source 9 and the second microwave source 4 are respectively disposed at both ends of the gradually curved waveguide component, which is a gradually convex curved waveguide assembly; the gradually curved waveguide component is a gradually convex curved waveguide assembly.

[0040] The SSPPs waveguide heating module 2 also includes a phase control system, which fixes the phase of the first microwave source 9 or the second microwave source 4; when the phase of the first microwave source 9 is fixed, the phase control system causes the phase of the second microwave source 4 to change periodically; when the phase of the second microwave source 4 is fixed, the phase control system causes the phase of the first microwave source 9 to change periodically, in order to improve the uniformity of the transverse electric field.

[0041] Mounting frame 5 includes two guide rails arranged longitudinally on both sides of 3D printing lifting platform 8, a mobile frame arranged above 3D printing lifting platform 8 and reciprocating along the two guide rails, a first linear drive mechanism for driving the mobile frame to move horizontally, a working mounting frame that can be raised and lowered along the vertical direction of the mobile frame, and a second linear drive mechanism for driving the working mounting frame to rise and fall vertically. The powder supply and application system includes a powder spraying module 10 and a spraying assembly 3 mounted on a work mounting frame; The SSPPs waveguide welding module is mounted on the work mounting frame; The powder spraying module 10, the spraying component 3, and the SSPPs waveguide welding module are arranged longitudinally on the work mounting frame.

[0042] The gradually convex bend waveguide assembly includes a U-shaped shell, microwave feed inlets located at both ends of the U-shaped shell, and a metal array evenly distributed within the U-shaped shell. The top position of the metal array located within the two straight edge segments of the U-shaped shell gradually rises along the microwave transmission direction, while the bottom position of the metal array located within the two straight edge segments of the U-shaped shell is on the same horizontal line. The U-shaped shell includes a wedge-shaped raised area 24 at the bottom, a left bend 23 and a right bend 25 symmetrically arranged at both ends of the wedge-shaped raised area 24, a left transition section 22 connected to the left bend 23, a right transition section 26 connected to the right bend 25, a left microwave feed port 21 provided at the end of the left transition section 22, and a right microwave feed port 27 provided at the end of the right transition section 26. The wedge-shaped raised area 24 is a strong electric field area for heating. The top positions of the metal arrays provided in the left transition section 22 and the right transition section 26 gradually rise along the microwave transmission direction, while the bottom positions of the metal arrays provided in the left transition section 22 and the right transition section 26 are on the same horizontal line. The bottom positions of the metal arrays within the left bend 23 and the right bend 25 are on the same horizontal line, and the top positions of the metal arrays within the left bend 23 and the right bend 25 are on the same horizontal line.

[0043] The powder-spraying 3D printing method, using the aforementioned microwave-heated 3D printing system, includes the following steps: S1. The powder spraying module 10 sprays a layer of powder onto the 3D printing lifting platform 8; S2, Spraying component 3 then sprays adhesive or microwave absorber onto the powder on the 3D printing lifting platform 8; S3. Turn on the SSPPs waveguide heating module 2. The SSPPs waveguide heating module 2 moves longitudinally to the adhesive area that needs to be heated and heats that area. S4. Monitor the local temperature using a temperature sensor or infrared imaging and feed it back to the control system; S5. The control system adjusts the activation, power and phase of the SSPPs waveguide heating module 2 according to the heating requirements to achieve local heating and avoid stress concentration. S6, SSPPs waveguide heating module 2 moves longitudinally with spray component 3 to achieve dynamic heating along the 3D printing trajectory; S7. Repeat steps S1 to S6, printing layer by layer until the part is complete.

[0044] In one embodiment, the specific method of longitudinal movement of the SSPPs waveguide heating module 2 in step S6 is as follows, see below. Figure 14 : S61. Input waveguide length L and phase adjustment frequency f, calculate electric field scanning speed V-scan, V-scan=L×f; S62. Input the electric field scanning speed V-scan and the desired number of scanning cycles N, and calculate the longitudinal moving speed range V-move < V < V-scan / N of the SSPPs waveguide heating module 2, where V-move is the initial longitudinal moving speed of the SSPPs waveguide heating module 2; S63. Start the longitudinal movement and phase modulation of SSPPs waveguide heating module 2 to monitor the electric field uniformity and temperature in real time; S64. Determine whether the heating effect meets the requirements. If the heating effect meets the requirements, complete the heating and stop moving. If the heating effect does not meet the requirements, adjust the initial longitudinal moving speed V-move or the phase adjustment frequency f, and then return to step S63.

[0045] The principle analysis of the SSPPs waveguide structure in Embodiments 1 and 2 is as follows: The fundamental properties of SSPPs: SSPPs based on three-dimensional subwavelength periodic structures possess excellent characteristics such as high confinement, low loss, and super-strong focusing. This section provides a theoretical analysis of the fundamental properties of SSPPs based on one-dimensional subwavelength groove periodic structures. For example... Figure 4 As shown, h Indicates the height of the metal unit. a Indicates the thickness of the metal unit. d Let represent the spacing between the metal elements (i.e., the period of the metal array). Then, the dispersion relation of the SSPPs of the one-dimensional subwavelength groove periodic structure can be given by the following equation: (1) (2) (3) in, Representing the periodic structure n Wave number of spatial harmonics; Indicates the attenuation constant; Used to simplify expressions; The free-space wavenumber is given. The dispersion equation reflects the modulation of the equivalent dielectric constant of SSPPs, through... a , d and h Adjusting the dispersion characteristics of periodic structures. The dispersion curves of SSPPs structures at different sizes obtained from simulation calculations are shown below. Figure 4 As shown. Metal height h The effect is most pronounced on dispersion characteristics. a and d It will also affect the dispersion characteristics, but the impact is small. Therefore, we can determine it first. h The value is then fine-tuned. a and d Obtain the desired structure.

[0046] The simulation of the heating system involves the coupling of electromagnetic fields and solid heat transfer fields. The distribution of the electromagnetic field is calculated using the following Helmholtz equations: (4) (5) in It is the electric field strength. Represents the free space wavenumber. Represents angular frequency. It is electrical conductivity. It is the relative permeability. Represents the relative permittivity. It is the relative permittivity of vacuum. It represents the vacuum permeability.

[0047] The temperature field distribution is calculated using the following thermodynamic equation: (6) in , , , and These represent the material's density, constant-pressure heat capacity, thermodynamic temperature, heat source, and thermal conductivity, respectively. This represents the heating time.

[0048] The electromagnetic field and the heat transfer field are coupled through the electromagnetic loss equation: (7) in Represents the imaginary part of the relative permittivity. It is electromagnetic energy loss, which is used as a heat source that causes temperature changes during the heating process.

[0049] The open waveguide design is as follows: To utilize the strong electric field region above the metal array for heating, the upper wall of the waveguide needs to be opened. The strong localization of electromagnetic fields by SSPPs can avoid the rapid attenuation and scattering of electromagnetic fields in an open environment. The lifting treatment ensures that the strong electric field above the metal array is higher than the upper wall of the waveguide, while the bending treatment prevents the lateral dimension of the waveguide from being too long.

[0050] The lifting process is as follows: Keep the height of the metal unit constant, and set the lower wall of the waveguide to a wedge-shaped gradient. The optimization process is as follows: Figure 5 As shown.

[0051] Bending treatment: A 90° arc transition is used to improve transmission efficiency by changing the curvature (thi) of the metal array. The optimization process is as follows: Figure 6 As shown.

[0052] The designed bending-lift SSPPs waveguide field distribution is as follows: Figure 7 As shown, the electric field in the open region decays rapidly in the absence of a metal array.

[0053] 3D printing heating effect, determined by heating effect Figure 8 and Figure 9 It can be seen that the microwave absorbing material heats up rapidly under the action of microwave energy.

[0054] Phase changes improve uniformity; periodic phase changes in the microwave feed at the port improve lateral uniformity, such as... Figure 10 and Figure 11 As shown.

[0055] SPPs waveguide longitudinal movement heating, such as Figure 12 As shown, the rectangular carrier plate is made of polytetrafluoroethylene (non-absorbing), coated with an absorbing agent in the shape of "SCU". The selective heating results during the longitudinal movement of the waveguide are shown in the figure. The absorbing agent experiences a significant temperature rise within a short time, while the PTFE plate remains largely unheated. This fully demonstrates the high selectivity of microwave heating, allowing for arbitrary control of the desired heating area.

[0056] A phase-shift and motion-controlled microwave heating 3D printing system divides the port phase change into 12 segments, with a 30° change every 0.408 seconds. A 360° change takes 4.896 seconds, constituting one cycle. Based on this, the heating effect during the waveguide's longitudinal movement is as follows: Figure 13 As shown. In practical applications, the moving speed can be adjusted based on the real-time monitored temperature rise.

Claims

1. A microwave heating based 3D printing of polymer powder system, characterized in that , including a 3D printing lifting platform (8), a powder supply laying system for laying or spraying powder on the 3D printing lifting platform (8), a mounting frame (5) slidingly arranged on the 3D printing lifting platform (8), and a SSPPs waveguide welding module and a spray assembly (3) for spraying a wave-absorbing agent arranged below the mounting frame (5); The SSPPs waveguide welding module comprises a first microwave source (9), a second microwave source (4), and a tapered bent waveguide component; the first microwave source (9) and the second microwave source (4) are respectively arranged at two ends of the tapered bent waveguide component, and the tapered bent waveguide component is a tapered convex bent waveguide assembly.

2. The microwave heating based 3D printing polymer powder system according to claim 1, wherein, The SSPPs waveguide heating module (2) further comprises a phase control system, which fixes the phase of the first microwave source (9) or the second microwave source (4); when the phase of the first microwave source (9) is fixed, the phase control system changes the phase of the second microwave source (4) periodically; when the phase of the second microwave source (4) is fixed, the phase control system changes the phase of the first microwave source (9) periodically, so as to improve the uniformity of the transverse electric field.

3. The microwave heating based 3D printing polymer powder system according to claim 2, wherein, The powder supply laying system comprises a powder supply system (7) and a powder recycling system (1) arranged on both sides of the 3D printing lifting platform (8) in the transverse direction, a powder laying module (6) for laying powder in the powder supply system (7) to the 3D printing lifting platform (8) in the transverse direction, and a spray assembly (3) arranged on the mounting frame (5) and spraying a wave-absorbing agent on the 3D printing lifting platform (8); The mounting frame (5) is slidingly arranged on the 3D printing lifting platform (8) in the longitudinal direction; The powder supply system (7) comprises a powder supply box with an upper opening, the powder supply box comprises a powder supply box side wall and a powder supply box bottom plate slidingly arranged in the powder supply box side wall, and a vertical lifting mechanism is arranged at the bottom of the powder supply box bottom plate to lift the powder supply box bottom plate and control the lifting stroke; The powder laying module (6) comprises two transverse guide rails arranged on both sides of the powder supply box and the 3D printing lifting platform (8) in the transverse direction, a powder laying mounting frame reciprocally moving on the two transverse guide rails, and a powder laying roller mounted on the powder laying mounting frame in the longitudinal direction; The mounting frame (5) comprises a door-shaped mounting seat slidingly arranged in the longitudinal direction, two longitudinal mounting plates arranged on the door-shaped mounting seat through a lifting module, a first transverse mounting rod and a second transverse mounting rod connected between the two longitudinal mounting plates, the spray assembly (3) slidingly mounted on the first transverse mounting rod, and the SSPPs waveguide welding module fixedly mounted at the bottom of the second transverse mounting rod.

4. The microwave heating based 3D printing polymer powder system of claim 2, wherein, The mounting rack (5) comprises two guide rails longitudinally arranged on both sides of the 3D printing lifting platform (8), a moving frame arranged above the 3D printing lifting platform (8) and reciprocating along the two guide rails, a first linear driving mechanism driving the moving frame to move horizontally, a working mounting rack capable of lifting vertically along the moving frame, and a second linear driving mechanism driving the working mounting rack to lift vertically. The powder feeding and laying system comprises a powder spraying module (10) and a spraying assembly (3) arranged on the working mounting rack. The SSPPs waveguide welding module is mounted on the working mounting rack. The powder spraying module (10), the spraying assembly (3) and the SSPPs waveguide welding module are sequentially arranged on the working mounting rack in the longitudinal direction.

5. The microwave heating based 3D printing polymer powder system according to claim 3 or 4, characterized in that, The gradually-upward convex curved waveguide assembly comprises a U-shaped shell, microwave feeding inlets arranged at both ends of the U-shaped shell, and metal arrays uniformly arranged in the U-shaped shell, the top positions of the metal arrays in the two straight edge sections of the U-shaped shell gradually rise along the microwave transmission direction, and the bottom positions of the metal arrays in the two straight edge sections of the U-shaped shell are on the same horizontal line.

6. The 3D printing polymer powder system based on microwave heating according to claim 5, characterized in that, The U-shaped shell comprises a wedge-shaped lifting area (24) at the bottom, a left bending part (23) and a right bending part (25) symmetrically arranged at both ends of the wedge-shaped lifting area (24), a left transition part (22) connected with the left bending part (23), a right transition part (26) connected with the right bending part (25), a left microwave feeding port (21) arranged at the end of the left transition part (22), and a right microwave feeding port (27) arranged at the end of the right transition part (26), and the wedge-shaped lifting area (24) is a strong electric field area for heating; The top positions of the metal arrays arranged in the left transition part (22) and the right transition part (26) gradually rise along the microwave transmission direction, and the bottom positions of the metal arrays arranged in the left transition part (22) and the right transition part (26) are on the same horizontal line; The bottom positions of the metal arrays in the left bending part (23) and the right bending part (25) are on the same horizontal line, and the top positions of the metal arrays in the left bending part (23) and the right bending part (25) are on the same horizontal line.

7. A tiled powder-based 3D printing method based on microwave heating, using the microwave heating-based 3D printing polymer powder system of claim 3, characterized in that, The method comprises the following steps: S1, the powder feeding system (7) rises by one layer of powder, and the powder laying module (6) lays one layer of powder on the 3D printing lifting platform (8); S2, the spraying assembly (3) then sprays the binder or the wave-absorbing agent on the powder on the 3D printing lifting platform (8); S3, the SSPPs waveguide heating module (2) is turned on, and the SSPPs waveguide heating module (2) moves longitudinally to the binder area that needs to be heated to heat the area; S4, the local temperature is monitored by a temperature sensor array or an infrared imager array, and the feedback is fed back to the main control unit. S5, the master unit adjusts the activation, power and phase of the SSPPs waveguide heating module (2) according to the heating requirement, realizes local heating, and avoids stress concentration; S6, the SSPPs waveguide heating module (2) moves longitudinally with the spraying assembly (3), and realizes dynamic heating along the 3D printing track; S7, repeat steps S1 to S6 until the part is completed.

8. The tiled powder type 3D printing method based on microwave heating according to claim 7, in step S5, the master unit controls the input power of the SSPPs waveguide heating module (2) through the PID algorithm: when the temperature is lower than or reaches the target temperature, the input power of 150W is kept unchanged; when the temperature exceeds the target temperature, the input power is reduced.

9. A microwave heating based spray powder type 3D printing method using the microwave heating based 3D printing system according to claim 4, characterized by, The method comprises the following steps: S1, the powder spraying module (10) sprays a layer of powder on the 3D printing lifting platform (8); S2, the spraying assembly (3) sprays the binder or wave-absorbing agent on the powder on the 3D printing lifting platform (8); S3, the SSPPs waveguide heating module (2) is turned on, and the SSPPs waveguide heating module (2) moves longitudinally to the area where the binder needs to be heated to heat the area; S4, the local temperature is monitored by a temperature sensor or infrared imaging and fed back to the control system; S5, the control system adjusts the activation, power and phase of the SSPPs waveguide heating module (2) according to the heating requirement, realizes local heating, and avoids stress concentration; S6, the SSPPs waveguide heating module (2) moves longitudinally with the spraying assembly (3), and realizes dynamic heating along the 3D printing track; S7, repeat steps S1 to S6 until the part is completed.

10. A microwave heating based spray powder type 3D printing method according to claim 9, characterized in that, In step S6, the specific way of longitudinal movement of the SSPPs waveguide heating module (2) is as follows: S61, input the waveguide length L and the phase adjustment frequency f, calculate the electric field scanning speed V-scan, V-scan=Lxf; S62, input the electric field scanning speed V-scan and the expected scanning period number N, calculate the longitudinal movement speed range V-moveVV-scan / N of the SSPPs waveguide heating module (2), wherein V-move is the initial longitudinal movement speed of the SSPPs waveguide heating module (2); S63, start the longitudinal movement and phase modulation of the SSPPs waveguide heating module (2), and monitor the electric field uniformity and temperature in real time; S64, judge whether the heating effect meets the requirements, when the heating effect meets the requirements, complete the heating and stop moving; when the heating effect does not meet the requirements, adjust the initial longitudinal movement speed V-move or the phase adjustment frequency f, and then return to step S63.

Images