A multi-nozzle air-assisted 3D printing nozzle

Abstract

This invention discloses an integrated multi-nozzle air-assisted 3D printing nozzle, comprising an upper horizontal plate, a lower horizontal plate, m material feed cylinders, and a heating element, where m is 3-100. The upper horizontal plate is located above the lower horizontal plate, and the two together form an air chamber. An air inlet is provided on the air chamber. The top wall of the air chamber has m material feed cylinder channels, and the bottom wall has m gas channels. The m material feed cylinder channels and m gas channels are all vertically arranged and simultaneously connected to the air chamber. The m material feed cylinders are vertically arranged, and each material feed cylinder has a discharge port at its lower end. The m material feed cylinder channels, m gas channels, and m material feed cylinders correspond one-to-one. The top of the i-th material feed cylinder is located within and sealed to the i-th material feed cylinder channel, and its bottom is located within the i-th gas channel, with a gap between them for gas passage, i = 1, 2, ..., m. This invention has a simple structure and effectively solves the problems of existing technologies that cannot achieve multi-nozzle printing and simultaneous air-assisted 3D printing of multiple materials and colors.

Description

Technical Field

[0001] This invention belongs to the field of 3D technology and relates to an integrated multi-nozzle air-assisted 3D printing nozzle. Background Technology

[0002] In conventional 3D printing technology, the friction between the polymer melt and the inner wall of the metal nozzle in the micron-sized nozzle channel causes the melt to exhibit a mold expansion effect after leaving the nozzle. This results in a large filament diameter after 3D printing, a large layer thickness of the printed part, poor dimensional accuracy, and high surface roughness.

[0003] To address the issues of large filament diameter, poor dimensional accuracy, and surface finish in existing 3D printing technologies caused by mold bulging, patent CN105235220A discloses a gas-assisted extrusion head for an FDM 3D printer. However, the technical solution of this patent still has some shortcomings: ① It cannot achieve multi-nozzle printing, and it cannot achieve simultaneous printing of multiple materials and colors; ② The dimensional accuracy and surface finish of FDM printed parts are low; ③ The length of the gas-assisted section is fixed and cannot be adjusted. Summary of the Invention

[0004] The purpose of this invention is to solve the problems existing in the prior art and provide an integrated multi-nozzle gas-assisted 3D printing nozzle. The integrated multi-nozzle gas-assisted 3D printing nozzle of this invention can realize intelligent printing of multiple materials and multiple colors at the same time, which helps to improve printing efficiency, color design of printed parts, material gradient design of each part of the printed parts, etc. The FDM printed parts have high dimensional accuracy and surface smoothness, and the length of the gas-assisted section is adjustable.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0006] A multi-nozzle air-assisted 3D printing nozzle assembly includes an upper horizontal plate, a lower horizontal plate, m material delivery cylinders, and a heating element, where m is 3-100.

[0007] The upper horizontal plate is located above the lower horizontal plate, and the two together form an air chamber;

[0008] An air inlet is provided on the air chamber;

[0009] The top wall of the air chamber is provided with m material conveying cylinder channels, and the bottom wall of the air chamber is provided with m gas channels; both the m material conveying cylinder channels and the m gas channels are arranged vertically and are simultaneously connected to the air chamber.

[0010] m conveying cylinders are arranged vertically. Each conveying cylinder consists of sections a, b, c, d, and e arranged from top to bottom. Each conveying cylinder has a discharge port at its lower end.

[0011] There are m material conveying cylinder channels, m gas channels, and m material conveying cylinders in a one-to-one correspondence. Section a of the i-th material conveying cylinder is located inside the i-th material conveying cylinder channel and is sealed to it. Section b of the i-th material conveying cylinder is located inside the gas chamber. The upper part of section c of the i-th material conveying cylinder is located inside the gas chamber. The lower part of section c, section d, and section e of the i-th material conveying cylinder are all located inside the i-th gas channel, and there is a gap between them for gas to pass through. i = 1, 2, ..., m;

[0012] The distance between the discharge port and the lower end of the gas channel is 1-2mm. This setting is conducive to the merging of gas and melt to form gas-assisted molding. The gas and melt flow begin to merge in the lower horizontal plate. The gas-liquid two-phase flow flows parallel along the microchannel in the lower horizontal plate. The gas wraps around the consumable to form a thin gas film, forming a stable gas-assisted 3D printing.

[0013] The heating element is used to heat m feed cylinders.

[0014] One of the objectives of this invention is to solve the problems of CN105235220A, which cannot achieve multi-nozzle printing and simultaneous printing of multiple materials and colors. The nozzle of this invention contains m(3-100) pairs of feed cylinders and gas channels. Under the control of the 3D printer software, they can achieve the same movement, enabling simultaneous printing of multiple nozzles, which improves printing efficiency compared to a single nozzle. Each feed cylinder can be inserted with 3D printing consumables of different materials or different colors, enabling simultaneous printing of multiple materials and colors, thus enriching 3D printing technology.

[0015] As a preferred technical solution:

[0016] As described above, this invention provides a multi-nozzle gas-assisted 3D printing nozzle. By rationally designing the structure of the gas channel, the high-pressure gas achieves a more stable flow velocity and a gradual change in flow direction during the downward flow process. Finally, it wraps around the 3D printing filament to achieve simultaneous extrusion of gas-assisted melt two-phase flow. Specifically, the gas channel consists of a series of coaxial sections arranged from top to bottom: an inverted frustum-shaped section I, a cylindrical section I, an inverted frustum-shaped section II, a cylindrical section II, an inverted frustum-shaped section III, and a cylindrical section III.

[0017] The small end diameter of the inverted frustum I segment, the diameter of the cylindrical I segment, and the large end diameter of the inverted frustum II segment are the same. The small end diameter of the inverted frustum II segment, the diameter of the cylindrical II segment, and the large end diameter of the inverted frustum III segment are the same. The small end diameter of the inverted frustum III segment and the diameter of the cylindrical III segment are the same.

[0018] The angle between the generatrix of the inverted frustum-shaped sections I, II, and III and the central axis is in the range of 45-60°. This range is set so that the cross-section of the gas channel gradually decreases and contracts. Ultimately, it is necessary to ensure that the gas flow direction is parallel to the flow direction of the consumable to achieve the effect of gas-assisted extrusion molding. The actual gas flow velocity can be decomposed into two components: the velocity parallel to the consumable flow velocity and the velocity perpendicular to the consumable flow velocity. When the angle is too large, the intake gas flow velocity is mainly perpendicular to the consumable flow velocity; when the angle is too small, the corresponding length of the inverted frustum-shaped section is too large, resulting in a low proportion of cylindrical section length, which is not conducive to stable gas flow.

[0019] The cylindrical sections I, II, and III decrease in length. This design aims to optimize fluid dynamics (by reducing the channel length, higher fluid flow velocity and greater flow rate can be achieved, thereby improving gas transmission efficiency), increase pressure (when gas flows through a long pipe, a certain pressure loss occurs; by reducing the channel length, pressure loss can be reduced, and the required pressure increase can be achieved in applications where increased pressure is needed), and avoid turbulent gas flow at high speeds.

[0020] The second objective of this invention is to address the issues of low dimensional accuracy and surface finish of FDM printed parts in CN105235220A. In CN105235220A, the gas and melt flow are perpendicular at the point where they meet. At this point, the 3D printing filament is in a viscous flow state (low modulus, easily deformable). The vertical high-pressure gas flow exerts a significant normal force on the melt flow, making it prone to surface roughness or cracking, thus negatively impacting the dimensional accuracy and surface finish of the printed parts. In this invention, the high-pressure gas undergoes a gradual change in flow direction as it passes through a gas channel, with the cross-section of the gas channel gradually decreasing. At the outlet, the gas and melt flow converge, and the gas-liquid two-phase flow is extruded in a parallel state. On one hand, the gas friction coefficient is 10... -5 The shear force exerted by the airflow on the melt flow approaches zero; on the other hand, the airflow exerts no normal force perpendicular to the melt flow. Enveloped in gas, the melt is in a completely stress-free state, with macromolecular chains in a state of random entanglement. Stress and strain rapidly decrease to zero, achieving stable gas-assisted 3D extrusion. The melt surface is smooth after leaving the gas-assisted nozzle, maintaining its shape and size within the nozzle, eliminating mold expansion. Compared to traditional 3D printing nozzles, the gas layer enveloping the melt flow occupies part of the channel, resulting in a smaller melt flow channel diameter and a thinner printed layer. Therefore, the dimensional accuracy and surface finish of the 3D printed parts are higher. Compared to CN105235220A, the melt flow changes from a rough surface to a smooth surface, and from a high normal force to a completely stress-free state, thus resulting in higher dimensional accuracy and surface finish of the printed parts.

[0021] As described above, in a multi-nozzle air-assisted 3D printing nozzle, the feed cylinder is a rotating body, and the i-th feed cylinder is coaxial with the i-th gas channel.

[0022] As described above, in a multi-nozzle gas-assisted 3D printing nozzle, n fixing modules are provided on the outer wall of the c-th section of the i-th feed cylinder, where n = 2-4. The n fixing modules are evenly distributed around the c-th section of the i-th feed cylinder and are in contact with the inner walls of the cylindrical II-th section and the inverted frustum III-th section of the i-th gas channel. This allows the outlet of the feed cylinder to be centered, positioned, and secured in the gas channel, preventing it from tilting under the impact of high-pressure gas flow / melt, thus improving stability.

[0023] The multi-nozzle air-assisted 3D printing nozzle described above also includes m hollow dome feed bolts; each of the m hollow dome feed bolts corresponds one-to-one with a m feed cylinder, with the nut on top and the screw on the bottom of the i-th hollow dome feed bolt, the screw being inserted into section a of the i-th feed cylinder and threadedly connected to it, and the hollow part of the i-th hollow dome feed bolt communicating with the hollow part of the i-th feed cylinder; the dome groove design at the top of the hollow dome feed bolt facilitates the removal of the screwdriver, and the hollow part is used to pass in the 3D printing filament.

[0024] As described above, in a multi-nozzle air-assisted 3D printing nozzle, the diameter of segment b of the i-th feed cylinder is larger than the diameter of the i-th feed cylinder channel; the nut of the hollow dome feed bolt and segment b of the feed cylinder together clamp the upper horizontal plate, realizing the centering, positioning and fastening of the feed cylinder within the upper horizontal plate.

[0025] As described above, the multi-nozzle gas-assisted 3D printing nozzle consists of an upper lower horizontal plate A and a lower lower horizontal plate B. The lower horizontal plate A is detachably connected to both the upper and lower horizontal plates B. A portion of the cylindrical III section of the gas channel is located inside the lower horizontal plate A, and the other portion is located inside the lower horizontal plate B, with a length equal to the thickness of the lower horizontal plate B. This allows for easy adjustment of the length of the cylindrical III section of the gas channel, and replacement with lower horizontal plates B of different thicknesses is possible. The discharge port is located inside the lower horizontal plate B, and the small distance between the discharge port and the lower end of the gas channel prevents the melt flow from overflowing from the gap between the lower horizontal plates A and B.

[0026] The third objective of this invention is to solve the problem of the fixed length of the air-assisted section in CN105235220A, which cannot be adjusted. This invention processes the lower horizontal plate B into plates of different heights and fixes them together with the upper horizontal plate and the lower horizontal plate A to form a whole, which is convenient for disassembly and replacement, and realizes the flexible adjustment of the core dimension - the length of the air-assisted section.

[0027] As described above, the air inlet of the multi-nozzle air-assisted 3D printing nozzle is located on the top wall of the air chamber.

[0028] As described above, a multi-nozzle air-assisted 3D printing nozzle has a groove with a downward-facing opening on the lower surface of the upper horizontal plate, the top wall of the air chamber is the bottom of the groove, and the bottom wall of the air chamber is the lower horizontal plate.

[0029] As described above, the multi-nozzle air-assisted 3D printing nozzle has an upper and lower horizontal plate that are both circular, and a cylindrical groove. The air inlet, groove, upper horizontal plate, and lower horizontal plate are coaxial. m gas channels are distributed concentrically around the central axis of the lower horizontal plate. The air inlet is located at the center of the upper horizontal plate and connects to the air chamber, which helps to balance the flow rate and velocity of the gas in each gas channel.

[0030] As described above, the heating element of the multi-nozzle air-assisted 3D printing nozzle is a thermocouple, which is installed in the upper and lower horizontal plates.

[0031] Beneficial effects:

[0032] (1) The present invention is equipped with multiple pairs of feeding cylinders and gas channels, which are evenly distributed on the upper and lower horizontal plates, so as to achieve high-speed and uniform printing effect, improve printing efficiency, and realize multi-material printing and multi-color printing.

[0033] (2) The gas channel of the present invention helps the high pressure airflow to be more stable during the downward flow process. A fixing module is added above the outlet to make the conveying cylinder more stable under the impact of the high pressure gas and liquid flow, and enhances the overall vertical stability of the conveying cylinder and the centering of the outlet.

[0034] (3) The hollow dome feed bolt of the present invention has the dual functions of fixing and conveying. The top dome groove design makes it easy to disassemble with a screwdriver. The external thread is tightly connected and fixed with the internal thread on the upper part of the feed cylinder, and forms a strong groove buckle connection with the clamped upper horizontal plate, realizing the centering, positioning and fastening of the top of the feed cylinder in the upper horizontal plate of the mold.

[0035] (4) The thickness of the lower horizontal plate B of the present invention is designed and processed in multiple dimensions, and can be flexibly replaced by bolt connection, which is beneficial to the flexible control of the length of the gas-assisted 3D printing nozzle. Attached Figure Description

[0036] Figure 1 This is a longitudinal cross-sectional view of the integrated multi-nozzle air-assisted 3D printing nozzle of the present invention (the lower horizontal plate B is omitted in the figure);

[0037] Figure 2 This is a longitudinal cross-sectional view of the connection structure of the hollow dome feeding bolt, the conveying cylinder, and the fixing module in this invention, where a and b correspond to different viewing directions;

[0038] Figure 3 c is Figure 1 A partially enlarged schematic diagram, where d is a cross-sectional view of the integrated multi-nozzle air-assisted 3D printing nozzle of the present invention;

[0039] Figure 4 In the diagram, e is the top view of the upper horizontal plate, and f is the longitudinal section view of the upper horizontal plate.

[0040] Figure 5 In the diagram, h is the top view of the lower horizontal plate A, i is the bottom view of the lower horizontal plate A, and g is the longitudinal section view of the lower horizontal plate A.

[0041] Figure 6 This is a longitudinal cross-sectional view of the integrated multi-nozzle air-assisted 3D printing nozzle of the present invention;

[0042] Among them, 1-lower horizontal plate A, 2-upper horizontal plate, 3-dome feed bolt, 4-feed hole, 5-air inlet, 6-air chamber, 7-gas channel, 8-nozzle embedding hole, 9-fixed module, 10-discharge port, 11-round nut, 12-thread, 13-feeding cylinder, 14-material channel, 15-lower horizontal plate B. Detailed Implementation

[0043] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings illustrating the embodiments of the present invention. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the contents of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims.

[0044] A type of integrated multi-nozzle air-assisted 3D printing nozzle, such as Figure 6 As shown, it includes an upper horizontal plate 2, a lower horizontal plate A1, a lower horizontal plate B15, m material conveying cylinders 13, m hollow dome feeding bolts 3 and heating elements, where m is 3-100;

[0045] like Figure 1 As shown, the upper horizontal plate 2, the lower horizontal plate A1, and the lower horizontal plate B15 are arranged in order from top to bottom, and the lower horizontal plate A1 is detachably connected to the upper horizontal plate 2 and the lower horizontal plate B15 respectively.

[0046] like Figure 1 As shown, the upper horizontal plate 2 and the lower horizontal plate A1 are both circular plates and together form an air chamber 6. The lower surface of the upper horizontal plate 2 is provided with a cylindrical groove with the groove opening facing downwards. The top wall of the air chamber 6 is the bottom of the groove, and the bottom wall of the air chamber 6 is the lower horizontal plate A1.

[0047] An air inlet 5 is provided on the top wall of the air chamber 6. The air inlet 5 is coaxial with the groove, the upper horizontal plate 2, and the lower horizontal plate A1.

[0048] like Figure 4 , 5 As shown, the top wall of the air chamber 6 is provided with m material conveying cylinder channels, and the bottom wall of the air chamber 6 is provided with m gas channels 7; the m material conveying cylinder channels and the m gas channels 7 are all arranged vertically and are simultaneously connected to the air chamber 6.

[0049] The gas channel 7 consists of three coaxial segments arranged from top to bottom: an inverted frustum-shaped segment I, a cylindrical segment I, an inverted frustum-shaped segment II, a cylindrical segment II, an inverted frustum-shaped segment III, and a cylindrical segment III.

[0050] The small end diameter of the inverted frustum I segment, the diameter of the cylindrical I segment, and the large end diameter of the inverted frustum II segment are the same. The small end diameter of the inverted frustum II segment, the diameter of the cylindrical II segment, and the large end diameter of the inverted frustum III segment are the same. The small end diameter of the inverted frustum III segment and the diameter of the cylindrical III segment are the same.

[0051] The angle between the generatrix of the inverted frustum I segment, inverted frustum II segment, and inverted frustum III segment and the central axis ranges from 45° to 60°.

[0052] The lengths of cylindrical segment I, cylindrical segment II, and cylindrical segment III decrease in that order.

[0053] One part of the cylindrical section III is set inside the lower horizontal plate A1, and the other part is set inside the lower horizontal plate B15 with a length equal to the thickness of the lower horizontal plate B15.

[0054] like Figure 5 As shown, m gas channels 7 are arranged in concentric circles around the central axis of the lower horizontal plate A1;

[0055] m feeding cylinders 13 are rotating bodies and arranged vertically, such as Figure 2 As shown, the conveying cylinder 13 is composed of sections a, b, c, d and e arranged from top to bottom, and each conveying cylinder 13 is provided with a discharge port 10 at its lower end.

[0056] There are m material conveying cylinder channels, m gas channels 7, and m material conveying cylinders 13 in a one-to-one correspondence. The a section of the i-th material conveying cylinder 13 is located inside the i-th material conveying cylinder channel and is sealed to it.

[0057] Section b of the i-th conveying cylinder 13 is located inside the air chamber 6, and its diameter is larger than the diameter of the i-th conveying cylinder channel;

[0058] like Figure 3As shown, n fixed modules 9 are provided on the outer wall of the c section of the i-th conveying cylinder 13, n = 2-4. The n fixed modules 9 are evenly distributed around the c section of the i-th conveying cylinder 13 and are in contact with the inner wall of the cylindrical II section and the inner wall of the inverted frustum III section of the i-th gas channel 7. The upper part is located in the gas chamber 6. The lower part of the c section, the d section and the e section of the i-th conveying cylinder 13 are all located in the i-th gas channel 7, and the two are coaxial and have a gap for gas to pass through, i = 1, 2, ..., m;

[0059] m hollow dome feed bolts 3 correspond one-to-one with m feed cylinders 13. The nut of the i-th hollow dome feed bolt 3 is on top and the screw is on the bottom. The screw is inserted into section a of the i-th feed cylinder 13 and is threadedly connected to it. The hollow part of the i-th hollow dome feed bolt 3 is connected to the hollow part of the i-th feed cylinder 13.

[0060] The discharge port 10 is located 1-2 mm above the lower end of the gas channel 7;

[0061] The heating element is a thermocouple, which is installed in the upper horizontal plate 2 and the lower horizontal plate A1, and is used to heat the m conveying cylinders 13.

[0062] Example 1

[0063] A multi-nozzle air-assisted 3D printing nozzle with the same structure as above, wherein m is 3, the angle between the generatrix of the inverted frustum I, inverted frustum II, and inverted frustum III sections and the central axis is 45°, n = 2, the discharge port is located 2mm above the lower end of the gas channel, the length of cylindrical I section is 8mm, the length of cylindrical II section is 6mm, the length of cylindrical III section is 2mm, the thickness of the lower horizontal plate B is 5mm, and the diameter of the discharge port is 1.0mm.

[0064] A 3D printing method employs the aforementioned multi-nozzle gas-assisted 3D printing nozzle and uses PLA material (Aulco Technology Co., Ltd.) with a diameter of 1.75 mm for printing; wherein the heating temperature is 210℃, the gas flow rate is 1.75L / min, the gas pressure is 0.40MPa, the gas temperature is 210℃, the printing speed is 30mm / s, the infill rate is 100%, the infill pattern is linear, the printing platform temperature is 50℃, and the deposition direction is 45 / -45°.

[0065] The gas-assisted 3D printed parts produced using the above method have a dimensional shrinkage rate of less than 0.13% and a surface roughness of 3.433 μm.

[0066] Comparative Example 1

[0067] A 3D printing method is basically the same as in Example 3, except that the printing nozzle used is a gas-assisted extrusion head for an FDM 3D printer disclosed in CN105235220A.

[0068] The gas-assisted 3D printed part produced using the above method has a dimensional shrinkage rate of 0.82% and a surface roughness of 6.451 μm.

[0069] Comparing Example 1 with Comparative Example 1, it can be seen that the present invention solves the problems of low dimensional accuracy and surface finish of FDM printed parts existing in CN105235220A.

[0070] Example 2

[0071] A multi-nozzle air-assisted 3D printing nozzle with the same structure as above, wherein m is 50, the angle between the generatrix of the inverted frustum I section, inverted frustum II section, and inverted frustum III section and the central axis is 50°, n=3, the discharge port is located 2mm above the lower end of the gas channel, the length of cylindrical I section is 8mm, the length of cylindrical II section is 6mm, the length of cylindrical III section is 2mm, the thickness of the lower horizontal plate B is 5mm, and the diameter of the discharge port is 1.0mm.

[0072] A 3D printing method employs the aforementioned multi-nozzle gas-assisted 3D printing nozzle and uses PLA material (Aulco Technology Co., Ltd.) with a diameter of 1.75 mm for printing; wherein the heating temperature is 210℃, the gas flow rate is 1.75L / min, the gas pressure is 0.40MPa, the gas temperature is 210℃, the printing speed is 30mm / s, the infill rate is 100%, the infill pattern is linear, the printing platform temperature is 50℃, and the deposition direction is 45 / -45°.

[0073] The gas-assisted 3D printed parts produced using the above method have low dimensional shrinkage and low surface roughness.

[0074] Example 3

[0075] A multi-nozzle air-assisted 3D printing nozzle with the same structure as above, wherein m is 100, the angle between the generatrix of the inverted frustum I section, inverted frustum II section, and inverted frustum III section and the central axis is 60°, n=4, the discharge port is located 2mm above the lower end of the gas channel, the length of cylindrical I section is 8mm, the length of cylindrical II section is 6mm, the length of cylindrical III section is 2mm, the thickness of the lower horizontal plate B is 5mm, and the diameter of the discharge port is 1.0mm.

[0076] A 3D printing method employs the aforementioned multi-nozzle gas-assisted 3D printing nozzle and uses PLA material (Aulco Technology Co., Ltd.) with a diameter of 1.75 mm for printing; wherein the heating temperature is 210℃, the gas flow rate is 1.75L / min, the gas pressure is 0.40MPa, the gas temperature is 210℃, the printing speed is 30mm / s, the infill rate is 100%, the infill pattern is linear, the printing platform temperature is 50℃, and the deposition direction is 45 / -45°.

[0077] The gas-assisted 3D printed parts produced using the above method have low dimensional shrinkage and low surface roughness.

[0078] Example 4

[0079] A 3D printing method is basically the same as in Example 3, except that the angle between the generatrix of the inverted frustum I, inverted frustum II, and inverted frustum III sections of the gas channel in the integrated multi-nozzle gas-assisted 3D printing nozzle and the central axis is 30°.

[0080] Compared with Example 3, the gas-assisted 3D printed parts printed using the above method have a higher dimensional shrinkage rate and a higher surface roughness.

[0081] Comparing Example 4 and Example 3, it can be seen that the angle between the generatrix of the inverted frustum I, inverted frustum II, and inverted frustum III sections of the gas channel in the multi-nozzle gas-assisted 3D printing nozzle used in Example 4 and the central axis is too small. This will result in the corresponding inverted frustum section length being too large, resulting in a low proportion of cylindrical section length, which is not conducive to stable gas flow and ultimately leads to a higher surface roughness of the printed product.

[0082] Example 5

[0083] A 3D printing method is basically the same as in Example 3, except that the angle between the generatrix of the inverted frustum I, inverted frustum II, and inverted frustum III sections of the gas channel in the integrated multi-nozzle gas-assisted 3D printing nozzle and the central axis is 70°.

[0084] Compared with Example 3, the gas-assisted 3D printed parts printed using the above method have a higher dimensional shrinkage rate and a higher surface roughness.

[0085] Comparing Example 5 and Example 3, it can be seen that the angle between the generatrix of the inverted frustum I, inverted frustum II, and inverted frustum III sections of the gas channel in the multi-nozzle gas-assisted 3D printing nozzle used in Example 5 and the central axis is too large, which will lead to a larger surface roughness and a higher shrinkage rate in the final product.

[0086] Example 6

[0087] A 3D printing method is basically the same as in Example 3, except that the cylindrical I, cylindrical II, and cylindrical III sections of the gas channel in the integrated multi-nozzle gas-assisted 3D printing nozzle have the same length.

[0088] Compared with Example 3, the gas-assisted 3D printed parts printed using the above method have a higher dimensional shrinkage rate and a higher surface roughness.

[0089] Comparing Example 6 and Example 3, it can be seen that the cylindrical I, cylindrical II, and cylindrical III sections of the gas channel in the multi-nozzle gas-assisted 3D printing nozzle used in Example 6 have the same length, which will result in a significant increase in the surface roughness of the final printed part. This is because the vertical high-pressure airflow has a huge normal force on the melt flow, making the melt flow prone to surface roughness or cracking, which in turn has an adverse effect on the dimensional accuracy and surface finish of the printed part.

Claims

1. A multi-nozzle air-assisted 3D printing nozzle, characterized in that, It includes an upper horizontal plate (2), a lower horizontal plate, m material conveying cylinders (13) and heating elements, where m is 3-100; The upper horizontal plate (2) is located above the lower horizontal plate, and the two together form an air chamber (6). An air inlet (5) is provided on the air chamber (6); The top wall of the air chamber (6) is provided with m material conveying cylinder channels, and the bottom wall of the air chamber (6) is provided with m gas channels (7); the m material conveying cylinder channels and the m gas channels (7) are all arranged vertically and are connected to the air chamber (6) at the same time. m conveying cylinders (13) are arranged vertically. The conveying cylinders (13) are composed of sections a, b, c, d and e arranged from top to bottom. Each conveying cylinder (13) has a discharge port (10) at its lower end. The gas channel (7) consists of an inverted frustum I section, a cylindrical I section, an inverted frustum II section, a cylindrical II section, an inverted frustum III section, and a cylindrical III section arranged from top to bottom and coaxially. The small end diameter of the inverted frustum I segment, the diameter of the cylindrical I segment, and the large end diameter of the inverted frustum II segment are the same. The small end diameter of the inverted frustum II segment, the diameter of the cylindrical II segment, and the large end diameter of the inverted frustum III segment are the same. The small end diameter of the inverted frustum III segment and the diameter of the cylindrical III segment are the same. The angle between the generatrix of the inverted frustum I segment, inverted frustum II segment, and inverted frustum III segment and the central axis ranges from 45° to 60°. The lengths of cylindrical segment I, cylindrical segment II, and cylindrical segment III decrease in that order. m conveying cylinder channels, m gas channels (7), and m conveying cylinders (13) correspond one-to-one. Section a of the i-th conveying cylinder (13) is located in the i-th conveying cylinder channel and is sealed to it. Section b of the i-th conveying cylinder (13) is located in the gas chamber (6). The upper part of section c of the i-th conveying cylinder (13) is located in the gas chamber (6). The lower part of section c, section d, and section e of the i-th conveying cylinder (13) are all located in the i-th gas channel (7), and there is a gap between them for gas to pass through. i=1,2,…,m; The feed cylinder (13) is a rotating body, and the i-th feed cylinder (13) is coaxial with the i-th gas channel (7); The lower horizontal plate consists of an upper lower horizontal plate A (1) and a lower lower horizontal plate B (15). The lower horizontal plate A (1) is detachably connected to the upper horizontal plate (2) and the lower horizontal plate B (15). A portion of the cylindrical III section of the gas channel (7) is located inside the lower horizontal plate A (1), and the other portion is located inside the lower horizontal plate B (15) with a length equal to the thickness of the lower horizontal plate B (15). The discharge port (10) is located inside the lower horizontal plate B (15). The distance between the discharge port (10) and the lower end of the gas channel (7) is 1-2 mm; The heating element is used to heat m feed cylinders (13).

2. The integrated multi-nozzle air-assisted 3D printing nozzle according to claim 1, characterized in that, The outer wall of the c section of the i-th conveying cylinder (13) is provided with n fixed modules (9), n=2-4. The n fixed modules (9) are evenly distributed around the c section of the i-th conveying cylinder (13) and are in contact with the inner wall of the cylindrical II section and the inverted frustum III section of the i-th gas channel (7).

3. The integrated multi-nozzle air-assisted 3D printing nozzle according to claim 1, characterized in that, It also includes m hollow dome feed bolts (3); the m hollow dome feed bolts (3) correspond one-to-one with the m conveying cylinders (13), the nut of the i-th hollow dome feed bolt (3) is on top and the screw is on the bottom, the screw is inserted into section a of the i-th conveying cylinder (13) and is threadedly connected to it, the hollow part of the i-th hollow dome feed bolt (3) is connected to the hollow part of the i-th conveying cylinder (13).

4. The integrated multi-nozzle air-assisted 3D printing nozzle according to claim 1, characterized in that, The diameter of segment b of the i-th conveying cylinder (13) is greater than the diameter of the channel of the i-th conveying cylinder.

5. A multi-nozzle air-assisted 3D printing nozzle according to claim 1, characterized in that, The air inlet (5) is located on the top wall of the air chamber (6).

6. A multi-nozzle air-assisted 3D printing nozzle according to claim 5, characterized in that, The lower surface of the upper horizontal plate (2) is provided with a groove with the slot facing downwards. The top wall of the air chamber (6) is the bottom of the groove, and the bottom wall of the air chamber (6) is the lower horizontal plate.

7. A multi-nozzle air-assisted 3D printing nozzle according to claim 6, characterized in that, The upper horizontal plate (2) and the lower horizontal plate are both circular plates, and the groove is a cylindrical groove; the air inlet (5), the groove, the upper horizontal plate (2), and the lower horizontal plate are coaxial; m gas channels (7) are distributed in concentric circles around the central axis of the lower horizontal plate.

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