A cross-scale porous structure, 3D printing forming method and device

Abstract

The present invention discloses a cross-scale porous structure, a 3D printing forming method, and an apparatus, belonging to the field of polymer 3D printing technology. The method of the present invention comprises heating and melting a polymer filament, injecting a gas into the molten polymer to form bubbles in the molten polymer, and extruding the bubbles in the molten polymer into a vacuum environment for 3D printing into a lattice structure. The lattice structure has microscopic pores formed by the bubbles expanding and solidifying under vacuum conditions. The microscopic pores are combined with the macroscopic lattice structure to form a cross-scale porous structure. The present invention utilizes the pressure differential enhancement effect of a vacuum environment to overcome the high surface tension of high-performance polymers, combining the microscopic pores formed by the thermal expansion growth of vacuum micropores with the macroscopic pores of the lattice structure to form a cross-scale effect.

Description

Technical Field

[0001] The present invention relates to the field of polymer 3D printing technology, and in particular to a cross-scale porous structure, a 3D printing forming method and a device. Background Art

[0002] Porous polymer materials and structures boast lightweight, high specific strength, excellent thermal insulation and sound absorption, and superior impact resistance. They are widely used in lightweight components, wave-absorbing materials, thermal insulation, and other fields to meet demands for lightweight and multifunctional integration. Cross-scale porous materials, in particular, combine macroscale and microscale pores, leveraging the synergistic macro- and microscale effects to further enhance the load-bearing and functionality of porous materials. However, traditional porous materials are often prepared using microporous foaming technology, which makes it difficult to freely form complex porous structures and precisely control the macro- and micro-pore morphology, limiting the application of porous structures.

[0003] 3D printing technology has the ability to form complex structures in an integrated manner, which broadens the freedom of design and manufacturing of porous structures. However, at present, high-performance polymers represented by special engineering plastics such as polyetheretherketone and polyimide are mainly manufactured by 3D printing processes such as material extrusion and powder bed fusion. Due to the limitations of the forming accuracy of such processes, porous structures are mainly composed of macroscopic structural pores, making it difficult to prepare microscopic pore structures. The manufacture of microscopic pores mainly relies on high-resolution 3D printing technologies such as digital light processing, photocuring, and ink direct writing. However, such processes mainly use low-viscosity and low-surface tension polymers such as photocurable resins as raw materials. Although they can realize the manufacture of cross-scale porous structures, their mechanical properties are often relatively poor. 3D printing technology for cross-scale porous structures of high-performance polymers is still under development. Summary of the Invention

[0004] The purpose of the present invention is to overcome the problems in the prior art and provide a cross-scale porous structure, 3D printing forming method and device, which uses a vacuum environment to drive bubble growth to realize the manufacture of microscopic pore structures, and then integrates the microscopic pore structures into the macroscopic lattice structure to realize the manufacture of cross-scale porous structures.

[0005] The present invention provides a method for 3D printing a cross-scale porous structure. After heating and melting a polymer filament, gas is injected into the molten polymer to form bubbles in the molten polymer. The bubbles in the molten polymer are extruded along with the molten polymer into a vacuum environment and 3D printed into a lattice structure. The lattice structure has microscale pores formed by the bubbles expanding and solidifying under vacuum conditions. The lattice structure is macroscale pores. A porous structure having macroscale pores and the microscale pores is a cross-scale porous structure.

[0006] Preferably, the injected gas is injected into the molten polymer in multiple gas streams, and the number of the multiple gas streams and the gas flow rate are adjusted according to the size of the porosity inside the melt and the distribution of micro-scale pores.

[0007] Preferably, the polymer filaments are thermoplastic polymer filaments or composite polymer filaments containing chopped and continuous fibers.

[0008] Preferably, the polymer filament comprises polylactic acid, nylon, polycarbonate, polyurethane, polyetheretherketone or polyimide.

[0009] Preferably, the injected gas is air, nitrogen or helium.

[0010] The present invention also discloses a cross-scale porous structure prepared by the above-mentioned cross-scale porous structure 3D printing forming method. The cross-scale porous structure includes a skin and a lattice structure located on the skin. The skin is 3D printed under vacuum conditions, and no gas is injected during 3D printing; the lattice structure includes a plurality of unit cells, and the plurality of unit cells are periodically arranged in an array to form macro-scale pores of the cross-scale porous structure, and each of the unit cells has micro-scale pores.

[0011] Preferably, the unit cell configuration in the lattice structure is a combination of one or more of body-centered cubic, honeycomb, and cross grid.

[0012] The present invention also provides a device using the above-mentioned cross-scale porous structure 3D printing forming method, including a 3D printer, the 3D printer including a polymer filament feeding unit, the 3D printer being placed in a vacuum box, the nozzle of the 3D printer being a bubble injection nozzle, the bubble injection nozzle including;

[0013] The heating and melting head has a first flow channel and a second flow channel connected to each other in an upper and lower manner, wherein the first flow channel is located above the second flow channel and has an inner diameter larger than an inner diameter of the second flow channel. A plurality of air inlet channels are connected to the outer periphery of the top of the first flow channel, and the polymer filament enters the heating and melting head from the top of the first flow channel through the feeding unit;

[0014] A plurality of air cores, corresponding to the number of the air inlet channels, wherein the air cores are provided with air channels, a microporous array plate is provided at the inlet of the gas channels, and the gas channels are connected to the air inlet channels;

[0015] A gas delivery unit comprises a gas supply assembly, a gas preheating pipe, and a gas diverter connected in sequence, wherein a pressure monitoring module and a flow monitoring module are provided on the connecting pipeline between the gas supply assembly and the gas diverter, and the gas diverter has a plurality of gas outlets, each gas outlet being connected to the gas channel of the gas core one by one;

[0016] The temperature control device is arranged outside the heating and melting head and is used for heating the heating and melting head and regulating the temperature inside the heating and melting head.

[0017] Preferably, the temperature control device includes a heating block sleeved on the heating and melting head, and a heating rod and a temperature sensor located on the periphery of the heating and melting head, and the heating rod and the temperature sensor are evenly distributed on the periphery of the heating and melting head.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] The present invention utilizes the pressure difference enhancement effect of the vacuum environment to overcome the large surface tension of high-performance polymers, realizes the expansion and growth of micropores, and at the same time combines the vacuum slow heating effect to provide a longer time for micropore growth, ensuring that the micropores have a certain size, breaking through the limitations of the forming accuracy of polymer 3D printing methods such as material extrusion, and providing a new method for the preparation of high-performance polymer porous structures. The cross-scale porous structure prepared by the vacuum micropore thermal expansion 3D printing method of the present invention has a significantly improved porosity, high tensile strength and modulus retention rate, and high mechanical properties.

[0020] The cross-scale porous structure 3D printing forming method proposed in the present invention combines the microscopic pores formed by vacuum microporous thermal expansion growth with the macroscopic pores of the lattice structure to form a cross-scale effect, so that the porous structure achieves load-bearing-function integration. At the same time, due to the characteristics of 3D printing discrete forming, the distribution and morphology of macroscale pores and microscale pores can be dynamically adjusted, thereby controllably manufacturing the performance of the cross-scale porous structure.

[0021] The cross-scale porous structure of the present invention can regulate crack deflection through microscale pore distribution, and combined with the macroscopic lattice structure metamaterial characteristics, it is not only expected to achieve excellent mechanical properties such as impact resistance and shock absorption, but also has functionality in terms of heat insulation, sound absorption, electromagnetic shielding, etc. In addition, the polymer used can be characteristic engineering plastics such as polyetheretherketone and polyimide, which also perform well in high and low temperature resistance and corrosion resistance. Therefore, the prepared cross-scale porous structure has excellent comprehensive performance and has potential application prospects in aerospace, automobile transportation, biomedicine and other fields. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 Schematic diagram of the vacuum microporous thermal expansion 3D printing method of the present invention.

[0023] Figure 2 This is a schematic diagram of the bubble injection nozzle device of the present invention.

[0024] Figure 3 Schematic diagram of the gas delivery unit device of the present invention.

[0025] Figure 4 This is a schematic diagram of the heating and melting head device of the present invention.

[0026] Figure 5 Schematic diagram of the air core device of the present invention.

[0027] Figure 6 Schematic diagram of the temperature control device of the present invention.

[0028] Figure 7 Schematic diagram of the cross-scale porous structure of the present invention.

[0029] Figure 8 The microstructure diagrams of the vacuum 3D printing and normal pressure 3D printing samples of the present invention.

[0030] Figure 9 This is a diagram of the mechanical properties of vacuum 3D printing and normal pressure 3D printing samples of the present invention.

[0031] Description of reference numerals:

[0032] 1. Skin; 2. Lattice structure; 21. Unit cell; 3. Bubble injection nozzle; 4. Feed unit; 5. Heating and melting head; 51. First flow channel; 52. Second flow channel; 53. Air inlet channel; 6. Air core; 61. Gas channel; 62. Microporous array plate; 7. Gas delivery unit; 71. Gas supply assembly; 72. Gas preheating pipe; 73. Gas diverter; 8. Temperature control device; 81. Heating block; 82. Heating rod; 83. Temperature sensor; 9. Melting section; 10. Solidification section; 11. Vacuum box; 12. Microscale pores; 13. Polymer filament. DETAILED DESCRIPTION

[0033] To make the purpose, technical solutions, and advantages of the embodiments of the present disclosure more clear, the technical solutions of the embodiments of the present disclosure will be clearly and completely described below in conjunction with the accompanying drawings of the embodiments of the present disclosure. Obviously, the described embodiments are part of the embodiments of the present disclosure, not all of the embodiments. Based on the described embodiments of the present disclosure, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present disclosure.

[0034] Unless otherwise defined, the technical or scientific terms used herein shall have the ordinary meaning understood by persons of ordinary skill in the field to which the present disclosure pertains. The terms "first", "second" and similar words used in the present disclosure do not indicate any order, quantity or importance, but are merely used to distinguish different components. The terms "include" or "comprise" and similar words mean that the elements or objects appearing before "include" or "comprise" encompass the elements or objects listed after "include" or "comprise" and their equivalents, and do not exclude other elements or objects. The terms "connect" or "connected" and similar words are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect. The terms "upper", "lower", "left", "right" and the like are only used to indicate relative positional relationships. When the absolute position of the object being described changes, the relative positional relationship may also change accordingly.

[0035] The cross-scale porous structure 3D printing method proposed in the present invention places the material extrusion forming 3D printing process in a vacuum environment. When the polymer filament 13 is molten, microporous bubbles are injected into the interior. During extrusion deposition, the pressure difference between the microporous bubbles and the vacuum environment is used to drive the bubble growth. The vacuum slow heating effect is combined to increase the bubble growth temperature window. Under the drive of heat-pressure coupling, the surface tension of the high-viscosity polymer is overcome to achieve microscopic pore preparation. At the same time, the microscopic pore characteristics are integrated into the macroscopic lattice structure to design a cross-scale porous structure, realizing the multifunctional integrated manufacturing of high-performance polymer porous insulation structures. Based on the vacuum microporous thermal expansion 3D printing method, the customized preparation of cross-scale porous structures represented by high-performance polymers such as polyetheretherketone and polyimide is realized, achieving structural-functional integration, and has application potential in the fields of biomimetic bone, thermal insulation structures, and sound insulation structures.

[0036] This embodiment provides a method for 3D printing a cross-scale porous structure, which includes heating and melting a polymer filament 13, injecting gas into the molten polymer to form bubbles in the molten polymer, and the bubbles in the molten polymer are squeezed out along with the molten polymer into a vacuum environment to be 3D printed into a lattice structure 2. The lattice structure 2 has microscale pores 12 formed by the bubbles expanding and solidifying under vacuum conditions. The lattice structure 2 is a macroscale pore, and a porous structure having the macroscale pores and the microscale pores 12 is a cross-scale porous structure. In this embodiment, after the polymer filament 13 is heated and melted, gas is injected into the molten polymer. The injected gas forms bubbles in the molten polymer, and the bubbles are squeezed out into the vacuum environment together with the melt. The vacuum environment can have two effects on the melt. On the one hand, there is a pressure difference enhancement effect. There is a large pressure difference between the gas inside the bubble and the external vacuum environment, which can drive the bubble to expand and grow outward. On the other hand, there is a vacuum slow-heating effect. In the vacuum environment, there is no air medium, and the convective heat dissipation of the melt disappears. The heat can only be dissipated outward through radiation heat dissipation. The heat dissipation speed is slow, and the melt solidification rate slows down. Compared with the normal pressure environment, there is a longer melting section 9, which ensures that the bubbles have a longer expansion and growth time, and are shaped in the solidification section 10 to form microscopic pores.

[0037] As a preferred embodiment, the gas is divided into multiple groups of gas flows and injected into the molten polymer. The number of the multiple groups of gas flows and the gas flow rate are adjusted according to the size of the porosity inside the melt and the distribution of the micro-scale pores 12.

[0038] As a preferred embodiment, the polymer filaments 13 are thermoplastic polymer filaments or composite polymer filaments containing short-cut and continuous fibers. As a preferred embodiment, the polymer filaments 13 include polylactic acid, nylon, polycarbonate, polyurethane, polyetheretherketone or polyimide.

[0039] As a preferred embodiment, the injected gas is air, nitrogen or helium.

[0040] This embodiment also discloses a cross-scale porous structure prepared by the above-mentioned cross-scale porous structure 3D printing forming method. The cross-scale porous structure includes a skin 1 and a lattice structure 2 located on the skin 1. In this embodiment, the skin 1 is not injected with gas during 3D printing under a vacuum environment; the lattice structure 2 includes a plurality of unit cells 21, and the plurality of unit cells 21 are arranged in a periodic array to form macro-scale pores of the cross-scale porous structure, and each of the unit cells 21 has a micro-scale pore 12. Figure 7The skin 1 of this embodiment adopts a solid structure. No bubbles are injected during 3D printing under vacuum conditions to ensure certain mechanical properties. The lattice structure 2 is composed of unit cells 21 in a periodic array, forming macro-scale pores of a cross-scale porous structure. When printing each unit cell 21, a bubble injection nozzle 3 is used to print in a vacuum environment with polymer filament 13 as raw material. During the printing process, bubbles are injected into the melt. Under the dual effects of vacuum pressure difference enhancement and vacuum slow heating, the bubbles are driven to expand and grow, forming micro-scale pores 12 inside the polymer, and finally completing the preparation of the cross-scale porous structure.

[0041] Reference Figure 1 The porosity of the cross-scale porous structure of this embodiment can be changed by adjusting the macro-scale pores and the micro-scale pores 12. The ratio of the macro-scale pores can be changed by adjusting the size and density of the unit cells 21. The micro-scale pores 12 can be changed by changing the number of gas channels 61, the gas flow rate and other parameters. The distribution of pores in the cross-scale porous structure can be uniform or gradient distributed, which is mainly achieved by adjusting the morphology of the macro-scale pores and the micro-scale pores 12 in real time during the 3D printing process.

[0042] As a preferred embodiment, the unit cell 21 in the lattice structure 2 has a configuration of one or more combinations of body-centered cubic, honeycomb, and cross grid.

[0043] This embodiment also provides an apparatus using the above-mentioned cross-scale porous structure 3D printing forming method, including a 3D printer, the 3D printer including a feeding unit 4 for a polymer filament 13, the 3D printer being placed in a vacuum box 11, the nozzle of the 3D printer of this embodiment being a bubble injection nozzle 3, the bubble injection nozzle 3 including a heating and melting head 5, the heating and melting head 5 having a first flow channel 51 and a second flow channel 52 connected to each other in an upper and lower manner, the first flow channel 51 being located above the second flow channel 52, and the inner diameter of the first flow channel 51 being larger than the inner diameter of the second flow channel 52, the top periphery of the first flow channel 51 being connected to a plurality of air inlet channels 53, the polymer filament 13 entering the heating and melting head 5 from the top of the first flow channel 51 through the feeding unit 4;

[0044] A plurality of air cores 6, corresponding to the number of the air inlet channels 53, a gas channel 61 is provided inside the air core 6, a microporous array plate 62 is provided at the entrance of the gas channel 61, and the gas channel 61 is connected to the air inlet channel 53;

[0045] The gas delivery unit 7 includes a gas supply assembly 71, a gas preheating pipe 72, and a gas diverter 73 connected in sequence. A pressure monitoring module and a flow monitoring module are provided on the connecting pipeline between the gas supply assembly 71 and the gas diverter 73. The gas diverter 73 has multiple gas outlets, each gas outlet is connected to the gas channel 61 of each gas core 6 one by one.

[0046] The temperature control device 8 is disposed outside the heating and melting head 5 and is used to heat the heating and melting head 5 and regulate the temperature inside the heating and melting head 5 .

[0047] Reference Figure 2 The 3D printer of this embodiment is a material extrusion forming 3D printer. The material extrusion forming 3D printer is placed in a vacuum environment. The polymer filament 13 is fed into the heating and melting head 5 through the feeding unit 4 to be heated and melted inside. The temperature control device 8 heats and melts the polymer filament 13 on the heating and melting head 5. At the same time, the gas delivery unit 7 feeds external gas into the heating and melting head 5 through the pipeline and the gas core 6. In order to ensure that the gas enters the heating and melting head 5 evenly, a uniformly distributed multi-channel pipeline is used to inject gas into the interior, and each gas core 6 is connected to the heating and melting head 5.

[0048] Reference Figure 3 The gas delivery unit 7 is composed of a gas supply component 71, a pressure monitoring module, a flow monitoring module, a gas preheating pipe 72, and a gas diverter 73. The gas supply component 71 of this embodiment is supplied by a gas syringe, and the gas is delivered outward by a piston push method. The pressure detection module and the flow detection module are used to achieve stable gas delivery. The gas preheating pipe 72 heats the gas to prevent the cold gas from cooling the melt when entering the heated melting head 5. The gas diverter 73 disperses the gas into multiple paths and delivers them one by one to different pipes and gas cores 6.

[0049] Reference Figure 4 The internal melting cavity of the heating and melting head 5 described in this embodiment adopts a two-section structure. The upper part is a large-diameter flow channel, namely the first flow channel 51, which is used to mix the bubbles and the molten polymer filaments 13. The lower part is a small-diameter flow channel, namely the second flow channel 52. The change in diameter promotes the full flow of the molten polymer filaments 13 and the bubbles to achieve uniform mixing.

[0050] Reference Figure 5 In this embodiment, a gas channel 61 is provided inside the gas core 6, and a microporous array plate 62 is provided at the inlet. There is a uniformly distributed microporous array inside to disperse the gas to form bubbles.

[0051] Reference Figure 6The temperature control device 8 of this embodiment is composed of a heating block 81, a heating rod 82, and a temperature sensor 83. The heating block 81 is covered on the outside of the heating and melting head 5, and the heating rod 82 and the temperature sensor 83 are evenly distributed to achieve precise control of the temperature of different areas of the heating and melting head 5.

[0052] In order to verify the printing effect of the cross-scale porous structure 3D printing forming method described in this embodiment, this embodiment uses short fiber reinforced polyetheretherketone (SCF / PEEK) filaments to carry out experiments. The results are as follows: Figure 8 As shown in the figure, the SCF / PEEK filament has the characteristics of high hardness and high viscosity due to the addition of short carbon fibers, which makes it difficult to flow and compress during the extrusion process. There are many air pores inside the SCF / PEEK filament, and the bubble content in the SCF / PEEK filament reaches about 8%. For the convenience of comparison, in this embodiment, short fiber reinforced polyetheretherketone (SCF / PEEK) filament is 3D printed under normal pressure and vacuum environment respectively. The results show that the microstructure of the sample 3D printed under vacuum environment presents thin-walled porous characteristics, and the porosity reaches more than 20%, which is significantly improved compared with the porosity of 2% of the sample 3D printed under normal pressure environment. In addition, the bubble pore size of the sample 3D printed under vacuum environment increases from 20μm~30μm to about 100μm, which proves the feasibility of the vacuum environment driven microporous bubble expansion growth principle of this embodiment, and as shown in the figure, Figure 9 As shown in the figure, the tensile strength and modulus retention rate of the sample 3D printed under a vacuum environment reached more than 70% and more than 67% respectively, and the good mechanical properties were still maintained. Therefore, the tensile strength and modulus retention rate of the sample 3D printed under a vacuum environment in this embodiment were significantly better than those of the sample 3D printed under a normal pressure environment.

[0053] This embodiment utilizes the pressure difference enhancement and vacuum slow heating effect brought about by the vacuum environment, and breaks through the high surface tension of the polymer melt under the drive of thermal-mechanical coupling to achieve the expansion and growth of bubbles, obtain a microscopic pore structure, and integrate it into the macroscopic lattice structure 2 to form a cross-scale porous structure, providing a new method for the preparation of high-performance polymer porous structures. Under the synergistic effect of macro and micro pore scales, the porous structure-function integrated forming is realized, so that the porous structure has both excellent mechanical properties and special functions.

[0054] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A cross-scale porous structure 3D printing method, characterized in that: After heating and melting the polymer filament in a heating and melting head, gas is injected into the molten polymer in the heating and melting head through multiple gas cores to form bubbles in the molten polymer. The bubbles in the molten polymer are extruded along with the molten polymer into a 3D printed lattice structure under a vacuum environment. The lattice structure includes a plurality of unit cells, and the plurality of unit cells are periodically arranged in an array to form macro-scale pores of a cross-scale porous structure. Each of the unit cells has micro-scale pores. The micro-scale pores in the lattice structure are formed by the bubbles expanding and solidifying under vacuum conditions. Among them, when the bubbles in the molten polymer are extruded into a vacuum environment along with the molten polymer, the pressure difference between the microporous bubbles and the vacuum environment is used to drive the bubble growth. Combined with the vacuum slow heating effect, the bubble growth temperature window is increased. Driven by heat-pressure coupling, the surface tension of the high-viscosity polymer is overcome to achieve the preparation of microscale pores. The heating and melting head has a first flow channel and a second flow channel connected to each other in the upper and lower parts. The first flow channel is located above the second flow channel, and the inner diameter of the first flow channel is larger than the inner diameter of the second flow channel. The change in the flow channel diameter promotes the molten polymer filaments and bubbles to fully flow and achieve uniform mixing. The top periphery of the first flow channel is connected to a plurality of air inlet channels, and the polymer filaments enter the heating and melting head from the top of the first flow channel; the plurality of air cores corresponds to the number of the air inlet channels, and a gas channel is arranged inside the air core. A microporous array plate is arranged at the entrance of the gas channel. The microporous array plate is used to disperse the gas to form bubbles, and the gas channel is connected to the air inlet channel.

2. The cross-scale porous structure 3D printing method according to claim 1, characterized in that: The injected gas is divided into multiple groups of gas flows and injected into the molten polymer. The number of the multiple groups of gas flows and the gas flow rate are adjusted according to the size of the porosity inside the melt and the distribution of micro-scale pores.

3. The cross-scale porous structure 3D printing forming method according to claim 1, characterized in that: The polymer filaments are thermoplastic polymer filaments or composite thermoplastic polymer filaments containing short-cut and continuous fibers.

4. The cross-scale porous structure 3D printing method according to claim 1, characterized in that: The polymer filaments include polylactic acid, nylon, polycarbonate, polyurethane, polyetheretherketone or polyimide.

5. The cross-scale porous structure 3D printing method according to claim 1, characterized in that: The injected gas is air, nitrogen or helium.

6. The cross-scale porous structure printed by the cross-scale porous structure 3D printing forming method according to any one of claims 1 to 5, characterized in that: The cross-scale porous structure includes a skin and a lattice structure located on the skin. The skin is formed by 3D printing under vacuum conditions, and no gas is injected during 3D printing.

7. The cross-scale porous structure according to claim 6, wherein The unit cell configuration in the lattice structure is a combination of one or more of body-centered cubic, honeycomb, and cross grid.

8. An apparatus using the cross-scale porous structure 3D printing method according to claim 1, comprising a 3D printer, wherein the 3D printer comprises a polymer filament feeding unit, characterized in that: The 3D printer is placed in a vacuum box, and the nozzle of the 3D printer is a bubble injection nozzle, and the bubble injection nozzle includes: The heating and melting head has a first flow channel and a second flow channel connected in an upper and lower manner. The first flow channel is located above the second flow channel, and the inner diameter of the first flow channel is larger than the inner diameter of the second flow channel. The change in the flow channel diameter promotes the full flow of the molten polymer filaments and the bubbles to achieve uniform mixing. The top periphery of the first flow channel is connected to a plurality of air inlet channels. The polymer filaments enter the heating and melting head from the top of the first flow channel through the feeding unit. A plurality of gas cores, corresponding to the number of the gas inlet channels, a gas channel is provided inside the gas core, a microporous array plate is provided at the entrance of the gas channel, the microporous array plate is used to disperse the gas to form bubbles, and the gas channel is connected to the gas inlet channel; The gas delivery unit includes a gas supply assembly, a gas preheating pipe, and a gas diverter connected in sequence. The gas preheating pipe heats the gas to prevent cold gas from cooling the melt when entering the heated melting head. A pressure monitoring module and a flow monitoring module are provided on the connecting pipeline between the gas supply assembly and the gas diverter. The gas diverter has multiple gas outlets, each gas outlet is connected to the gas channel of each gas core one by one, ensuring that the gas enters the heated melting head evenly. The temperature control device is arranged outside the heating and melting head and is used for heating the heating and melting head and regulating the temperature inside the heating and melting head.

9. The device according to claim 8, wherein The temperature control device includes a heating block sleeved on the outside of the heating and melting head, and heating rods and temperature sensors located on the periphery of the heating and melting head and the heating block. The heating rods and temperature sensors are evenly distributed on the periphery of the heating and melting head.

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