3D printer nozzle for direct printing of composite sandwich plate and printing method of 3D printer nozzle

Abstract

The invention discloses a 3D printer spray head for direct printing of a composite sandwich plate and a printing method of the 3D printer spray head. The 3D printer spray head comprises a resin wire feeding assembly, a resin wire material, a fiber wire feeding assembly, long fiber prepreg wires, a first heating assembly, a second heating assembly, a first fused deposition head and a second fused deposition head. The at least one resin wire feeding assembly and the multiple fiber wire feeding assemblies are installed on the 3D printing equipment, the first heating assembly is installed at the bottom of each resin wire feeding assembly, the second heating assembly is installed at the bottom of each fiber wire feeding assembly, the first fused deposition head is installed at the bottom of the first heating assembly, and the second fused deposition head is installed at the bottom of the second heating assembly. And the resin wires and the long fiber prepreg filaments form the composite sandwich plate on a printing platform. The invention relates to the technical field of additive manufacturing, and can solve the problem that FDM printing in the prior art is not used for printing various long fiber reinforced sandwich plates.

Description

Technical Field

[0001] The present invention relates to the technical field of additive manufacturing, and in particular to a 3D printer nozzle for directly printing a composite sandwich panel and a printing method thereof. Background Art

[0002] The advanced composite manufacturing method that combines additive manufacturing with continuous carbon fiber and polymer is an emerging technology in recent years. In terms of material extrusion molding, fused deposition modeling (FDM) is the most widely used technology, which can obtain products with certain complexity and previously unattainable performance. Therefore, the fiber-reinforced composite materials produced by this technology are widely used in industrial fields such as aerospace, automobile manufacturing and medical devices. The layered structure of the composite material is generally a composite material composed of three layers of materials. The upper and lower layers of the sandwich composite material are high-strength and high-modulus materials, and the middle layer is a thick and lightweight material.

[0003] The sandwich structure is used to improve the effective utilization rate of materials and reduce the weight of the structure. Taking beams and plate components as an example, during use, they must meet the strength requirements and the stiffness requirements. The characteristics of fiber-reinforced composite materials are high strength and low modulus. Therefore, when the beams and plates made of a single FRP material meet the strength requirements, the deflection is often large. If it is designed according to the allowable deflection, it will greatly exceed the strength, resulting in waste. Only the design of the sandwich structure can reasonably solve this contradiction. This is also the main reason for the development of the sandwich structure. Due to its advantages of high strength, light weight, high stiffness, corrosion resistance, electrical insulation and microwave penetration, FRP sandwich structures have been widely used in aircraft, missiles, spacecraft and samples, roof panels, etc. in the aviation and aerospace industries, which can greatly reduce the weight of buildings and improve their use functions. Transparent FRP sandwich panels have been widely used in cold areas such as industrial plants, large public buildings and greenhouse lighting roofs. In the field of shipbuilding and transportation, fiberglass sandwich structures are widely used in many parts of fiberglass submarines, minesweepers and yachts. The fiberglass sandwich structures designed and manufactured domestically, such as pedestrian bridges, highway bridges, and automobile and train insulation, meet the performance requirements of light weight, high strength, high rigidity, heat insulation, and thermal insulation. In lightning protection shields that require microwave transmission, fiber-reinforced composite sandwich structures have become special materials that other materials cannot match.

[0004] At present, material extrusion has been successfully applied to the preparation of continuous fiber reinforced resin composite materials. However, due to the limitations of the characteristics of a single fiber material, the prepared composite material can usually only obtain a single performance enhancement. Combining the advantages of two or more fibers in the sandwich panel will give full play to the synergistic performance between the fibers and play a beneficial role in the development of sandwich panel performance, application, cost and other aspects. At present, there is no printing technology that applies FDM printing to a variety of long fiber reinforced sandwich panels. Therefore, it is necessary to provide a 3D printer nozzle and a printing method for directly printing composite sandwich panels, which can solve the problem that FDM printing is not used to print a variety of long fiber reinforced sandwich panels in the prior art. Summary of the invention

[0005] The purpose of the present invention is to provide a 3D printer nozzle for directly printing a composite sandwich panel and a printing method thereof, which can solve the problem in the prior art that FDM printing is not used for printing a variety of long fiber reinforced sandwich panels.

[0006] The present invention is achieved in that:

[0007] A 3D printer nozzle for direct printing of a composite sandwich panel comprises a resin wire feeding assembly, a resin filament, a fiber wire feeding assembly, a long fiber prepreg, a first heating assembly, a second heating assembly, a first molten deposition head, a second molten deposition head and a mounting plate; at least one group of resin wire feeding assemblies and multiple groups of fiber wire feeding assemblies are respectively mounted on a 3D printing device through mounting plates, a first heating assembly is mounted at the bottom of each group of resin wire feeding assemblies, so that the resin filament is fed into the first heating assembly through the resin wire feeding assembly and heated and melted, a second heating assembly is mounted at the bottom of each group of fiber wire feeding assemblies, so that the long fiber prepreg is fed into the second heating assembly through the fiber wire feeding assembly and heated and melted; the first molten deposition head is mounted at the bottom of the first heating assembly, so that the heated and melted resin filament is deposited by the first molten deposition head and then extruded onto a printing platform, a second molten deposition head is mounted at the bottom of the second heating assembly, so that the heated and melted long fiber prepreg is deposited by the second molten deposition head and then extruded onto the printing platform, and the resin filament and the long fiber prepreg form a composite sandwich panel on the printing platform.

[0008] Each group of the resin wire feeding assembly comprises a first servo motor, a bidirectional wire feeding gear and a first wire feeding driven wheel; the first servo motor is fixedly mounted on the mounting plate, the bidirectional wire feeding gear is mounted on the first servo motor, and the first wire feeding driven wheel is rotatably mounted on the first servo motor; the resin wire is fed out from the gap between the first wire feeding driven wheel and the bidirectional wire feeding gear;

[0009] The resin wire feeding assembly also includes a heat dissipation pipe and a throat; the upper end of the heat dissipation pipe is fixedly connected to the bottom of the first front sheet metal of the first servo motor, the throat is installed in the lower part of the heat dissipation pipe, and the lower end of the throat extends to the bottom of the heat dissipation pipe and is connected to the first heating assembly; the resin wire is sent out from the gap between the first wire feeding driven wheel and the bidirectional wire feeding gear and enters the first heating assembly through the heat dissipation pipe and the throat.

[0010] Each group of the fiber wire feeding components includes a second servo motor, a one-way wire feeding gear, a second wire feeding driven wheel and a fiber guide tube; the second servo motor is fixedly mounted on the mounting plate, the one-way wire feeding gear is mounted on the second servo motor, and the second wire feeding driven wheel is rotatably mounted on the second servo motor; the fiber guide tube is connected between the bottom of the gap between the second wire feeding driven wheel and the one-way wire feeding gear and the second heating component, so that the long fiber prepreg is sent out from the gap between the second wire feeding driven wheel and the one-way wire feeding gear through the middle fiber guide tube to the second heating component.

[0011] The fiber wire feeding assembly also includes a pneumatic cutter assembly, which is installed on the second servo motor so that the cutter of the pneumatic cutter assembly can be horizontally movably arranged between the gap between the second wire feeding driven wheel and the one-way wire feeding gear and the upper end of the fiber guide tube and can cut the long fiber prepreg.

[0012] The first heating assembly and the second heating assembly each include a heat-conducting block, a heating rod and a temperature sensor; a heat-conducting cavity is formed on one side of the interior of the heat-conducting block, the heating rod is inserted into the heat-conducting cavity, and a heating cavity is formed on the other side of the interior of the heat-conducting block; the temperature sensor is arranged on the heat-conducting block and is located above the first molten deposition head or the second molten deposition head.

[0013] The upper end of the heating chamber of the first heating assembly is connected to the lower end of the throat of the resin wire feeding assembly, so that the resin wire enters the heating chamber of the first heating assembly and is heated and melted; the lower end of the heating chamber of the first heating assembly is connected to the first molten deposition head, so that the heated and melted resin wire is deposited in the first molten deposition head;

[0014] The upper end of the heating chamber of the second heating component is connected to the lower end of the fiber guide tube of the fiber feeding component, so that the long fiber prepreg enters the heating chamber of the second heating component and is heated and melted; the lower end of the heating chamber of the second heating component is connected to the second melting deposition head, so that the long fiber prepreg after heating and melting is deposited in the second melting deposition head; the heat conductive block of the second heating component is fixedly connected to the second servo motor through a receiving column.

[0015] The first molten deposition head comprises a first deposition chamber and a first nozzle, the first deposition chamber is connected to the heating chamber of the first heating assembly and the first nozzle, and the first nozzle is arranged facing the printing platform; the internal cavity of the first nozzle is an inverted cone structure that is wide at the top and narrow at the bottom, and the lower end diameter of the first nozzle is 0.4 mm;

[0016] The second fused deposition head includes a second deposition chamber and a second nozzle. The second deposition chamber connects the heating chamber of the second heating assembly and the second nozzle. The second nozzle is arranged facing the printing platform. The internal cavity of the second nozzle is a straight cylindrical structure. The diameter of the second nozzle is 1.0 mm.

[0017] A printing method for a 3D printer nozzle for direct printing of a composite sandwich panel comprises the following steps:

[0018] Step 1: Receive the three-dimensional solid model in the 3D printing device and define the plane printing trajectory;

[0019] Step 2: generating an actuator command in the 3D printing device, and controlling the resin wire feeding assembly or the fiber wire feeding assembly to move along the planar printing trajectory according to the actuator command;

[0020] Step 3: The resin wire feeding assembly extrude resin filaments to the printing platform through the first molten deposition head, and the fiber wire feeding assembly extrude long fiber prepreg filaments to the printing platform through the second molten deposition head to form a composite sandwich panel on the printing platform.

[0021] In the step 1, the plane printing trajectory includes a first nozzle trajectory of a first nozzle of a first fused deposition head and a second nozzle trajectory of a second nozzle of a second fused deposition head; wherein the first nozzle trajectory includes the area where the filling shell, the bottom layer, the top layer, and the contour shell of the composite sandwich panel are located, and the second nozzle trajectory includes the area where the long fiber interlayer of the composite sandwich panel is located.

[0022] The step 3 comprises the following sub-steps:

[0023] Step 3.1: When the resin wire feeding assembly moves, the molten deposited resin wire is extruded through the first molten deposition head to form an outer shell of the composite sandwich panel; the outer shell includes a filling shell, a bottom layer and a contour shell;

[0024] Step 3.2: When the fiber feeding assembly moves, the molten-deposited long fiber prepreg is extruded through the second molten deposition head and embedded in the outer shell to form a long fiber sandwich;

[0025] In the step 3.2, the long fiber prepreg is cut by moving the pneumatic cutter assembly, the long fiber prepregs of the multiple groups of fiber feeding assemblies are switched, and filling and printing are performed on different areas in the long fiber interlayer to form a long fiber interlayer with multiple long fibers coordinated; between different long fiber prepreg filling areas, a filling shell is formed by resin filaments;

[0026] Step 3.3: When the resin wire feeding assembly moves, the molten deposited resin wire is extruded through the first nozzle of the first molten deposition head to form a top layer of the composite sandwich panel, thereby completing the 3D printing of the composite sandwich panel.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] 1. The present invention applies FDM printing technology to the 3D printing manufacturing of various long fiber reinforced sandwich panels, providing a new additive manufacturing method for composite sandwich panels.

[0029] 2. Since the present invention is provided with multiple groups of fiber wire feeding assemblies and pneumatic cutter assemblies, the long fiber prepreg filaments are cut by the pneumatic cutter assemblies, and different long fiber prepreg filaments can be switched when the long fiber interlayer is printed. Different long fiber prepreg filaments can be arranged independently in the long fiber interlayer, so that the synergistic advantages of various long fibers can be fully exerted, and a beneficial guide is provided for the development of performance coordination, application, cost and other aspects of composite sandwich panels. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 It is a schematic structural diagram of a 3D printer nozzle for direct printing of a composite sandwich panel according to the present invention.

[0031] In the figure, 101 is a first servo motor, 102 is a bidirectional wire feeding gear, 103 is a first wire feeding driven wheel, 104 is a heat dissipation pipe, 105 is a throat, 106 is a first front sheet metal, 2 is a resin wire, 301 is a second servo motor, 302 is a unidirectional wire feeding gear, 303 is a second wire feeding driven wheel, 304 is a fiber guide tube, 305 is a pneumatic cutter assembly, 306 is a second front sheet metal, 307 is a receiving column, 4 is a long fiber prepreg, 501 is a heat conducting block, 502 is a heating rod, 503 is a heat conducting cavity, 504 is a heating cavity, 505 is a temperature sensor, 601 is a first deposition cavity, 602 is a first nozzle, 701 is a second deposition cavity, 702 is a second nozzle, and 8 is a mounting plate. DETAILED DESCRIPTION

[0032] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments.

[0033] Please see attached Figure 1A 3D printer nozzle for direct printing of a composite sandwich panel comprises a resin wire feeding assembly, a resin filament 2, a fiber wire feeding assembly, a long fiber prepreg filament 4, a first heating assembly, a second heating assembly, a first molten deposition head, a second molten deposition head and a mounting plate 8; at least one group of resin wire feeding assemblies and multiple groups of fiber wire feeding assemblies are respectively mounted on the 3D printing device through the mounting plate 8, a first heating assembly is mounted at the bottom of each group of resin wire feeding assemblies, so that the resin filament 2 is fed into the first heating assembly through the resin wire feeding assembly and heated and melted, a second heating assembly is mounted at the bottom of each group of fiber wire feeding assemblies, so that the long fiber prepreg filament 4 is fed into the second heating assembly through the fiber wire feeding assembly and heated and melted; the first molten deposition head is mounted at the bottom of the first heating assembly, so that the heated and melted resin filament 2 is deposited by the first molten deposition head and then extruded onto a printing platform, the second molten deposition head is mounted at the bottom of the second heating assembly, so that the heated and melted long fiber prepreg filament 4 is deposited by the second molten deposition head and then extruded onto the printing platform, and the resin filament 2 and the long fiber prepreg filament 4 form a composite sandwich panel on the printing platform.

[0034] The number of resin wire feeding assemblies and fiber wire feeding assemblies can be adaptively adjusted according to actual printing requirements. Preferably, one group of resin wire feeding assemblies is provided, and two groups of fiber wire feeding assemblies are provided. The structure of each group of fiber wire feeding assemblies is the same and can be used to convey different long fiber prepreg filaments 4. The number of first heating assemblies and the number of first molten deposition heads are consistent with the number of resin wire feeding assemblies, and the number of second heating assemblies and the number of second molten deposition heads are consistent with the number of fiber wire feeding assemblies. The resin wire feeding assemblies and the fiber wire feeding assemblies can share a mounting plate 8, or they can be installed using an independent mounting plate 8.

[0035] The resin wire feeding assembly is used to convey the resin wire 2, which is used for printing and laying the top layer, bottom layer, contour shell, and internal filling of the composite sandwich panel. The fiber wire feeding assembly is used to convey the long fiber prepreg 4, which is used for printing and laying between the internal filling to form a long fiber sandwich.

[0036] The first heating component is used to heat the molten resin filament 2, and deposit the heated and molten resin filament 2 through the first molten deposition head, and then extrude it onto the printing platform to form the top layer, bottom layer, contour shell, and internal filling of the composite sandwich panel. The second heating component is used to heat the molten long fiber prepreg filament 4, and deposit the heated and molten long fiber prepreg filament 4 through the second molten deposition head, and then extrude it onto the printing platform to form the long fiber sandwich of the composite sandwich panel.

[0037] Each group of the resin wire feeding components includes a first servo motor 101, a bidirectional wire feeding gear 102 and a first wire feeding driven wheel 103; the first servo motor 101 is fixedly mounted on the mounting plate 8, the bidirectional wire feeding gear 102 is mounted at the keyway of the first servo motor 101, and the first wire feeding driven wheel 103 is rotatably mounted on the first front sheet metal part 106 of the first servo motor 101 through a wheel axle; the resin wire 2 is fed out from the gap between the first wire feeding driven wheel 103 and the bidirectional wire feeding gear 102.

[0038] Preferably, the first servo motor 101 can adopt a servo motor with a bidirectional rotation function in the prior art. The servo motor has the characteristic of high control accuracy and is used to control the forward or reverse rotation of the bidirectional wire feeding gear 102 .

[0039] Preferably, the bidirectional wire feeding gear 102 can adopt a ratchet with sharp teeth on the surface, and the first wire feeding driven wheel 103 can adopt a wheel body with a smooth surface. A certain gap is formed between the bidirectional wire feeding gear 102 and the first wire feeding driven wheel 103, and the gap is smaller than the thickness of the resin wire 2, so that a certain extrusion and friction are generated between the resin wire 2 and the surface of the first wire feeding driven wheel 103, so that when the bidirectional wire feeding gear 102 rotates, the friction force is used to drive the first wire feeding driven wheel 103 to rotate synchronously, thereby ensuring the stable wire feeding of the resin wire 2.

[0040] The resin wire feeding assembly also includes a heat dissipation pipe 104 and a throat 105; the upper end of the heat dissipation pipe 104 is fixedly connected to the bottom of the first front sheet metal part 106 of the first servo motor 101 by screws, and the throat 105 is installed in the lower part of the heat dissipation pipe 104, and the lower end of the throat 105 extends to the bottom of the heat dissipation pipe 104 and is connected to the first heating assembly; the resin wire 2 is sent out from the gap between the first wire feeding driven wheel 103 and the bidirectional wire feeding gear 102 and enters the first heating assembly through the heat dissipation pipe 104 and the throat 105.

[0041] Preferably, the top of the heat dissipation pipe 104 can be screwed together with the bottom of the first front sheet metal part 106 through a thread, and a channel for feeding the resin wire 2 is formed in the heat dissipation pipe 104, and the upper end of the channel is located at the bottom of the gap between the first wire feeding driven wheel 103 and the bidirectional wire feeding gear 102, and the throat 105 is embedded in the lower part of the channel, and the lower end of the throat 105 is screwed together with the first heating component through a thread, thereby ensuring that the resin wire 2 passes through the gap between the first wire feeding driven wheel 103 and the bidirectional wire feeding gear 102, the heat dissipation pipe 104, and the throat 105 and is fed into the first heating component for heating and melting.

[0042] During the fused deposition printing process, a retraction action is involved, that is, the first servo motor 101 drives the bidirectional wire feeding gear 102 to rotate in the opposite direction, so that the resin wire is retracted upward. At this time, the first fused deposition head will stop discharging materials. At the same time, since the heat dissipation tube 104 is very close to the first heating component, in order to prevent the upwardly conducted heat from causing the retracted resin wire 2 to adhere to the inner wall of the heat dissipation tube 104 and affect the subsequent wire feeding action, a Teflon throat 105 is built in to prevent the retracted resin wire 2 from adhering to the inner wall of the heat dissipation tube 104, effectively avoiding the blockage problem.

[0043] The retraction action is a common action in fused deposition printing, and its working process and working principle will not be described here.

[0044] Each group of the fiber wire feeding components includes a second servo motor 301, a one-way wire feeding gear 302, a second wire feeding driven wheel 303 and a fiber guide tube 304; the second servo motor 301 is fixedly mounted on the mounting plate 8, the one-way wire feeding gear 302 is mounted at the keyway of the second servo motor 301, and the second wire feeding driven wheel 303 is rotatably mounted on the second front sheet metal part 306 of the second servo motor 301 through a wheel axle; the fiber guide tube 304 is connected between the bottom of the gap between the second wire feeding driven wheel 303 and the one-way wire feeding gear 302 and the second heating component, so that the long fiber prepreg 4 is sent out from the gap between the second wire feeding driven wheel 303 and the one-way wire feeding gear 302 through the middle fiber guide tube 304 to the second heating component.

[0045] Preferably, the second servo motor 301 can be a servo motor with a unidirectional rotation function in the prior art, which has the characteristics of high control accuracy and is used for the unidirectional rotation of the unidirectional wire feeding gear 302. The fiber guide tube 304 can be made of stainless steel, and the inner diameter of the fiber guide tube 304 is larger than the diameter of the long fiber prepreg 4, and is used to transport the long fiber prepreg 4.

[0046] Preferably, the one-way wire feeding gear 302 can adopt a ratchet with fine small teeth on the surface, and the second wire feeding driven wheel 303 can adopt a wheel body with a smooth surface. A certain gap is formed between the one-way wire feeding gear 302 and the second wire feeding driven wheel 303, and the gap is smaller than the thickness of the long fiber prepreg yarn 4, so that a certain amount of extrusion and friction is generated between the long fiber prepreg yarn 4 and the surface of the second wire feeding driven wheel 303, so that when the one-way wire feeding gear 302 rotates, the friction force is used to drive the second wire feeding driven wheel 303 to rotate synchronously, thereby ensuring the stable wire feeding of the resin wire 2.

[0047] Since the materials and rigidities of the resin filament 2 and the long fiber prepreg filament 4 are different, the long fiber prepreg filament 4 is easy to break. The gap between the bidirectional wire feeding gear 102 and the first wire feeding driven wheel 103 and the gap between the unidirectional wire feeding gear 302 and the second wire feeding driven wheel 303 can be adaptively adjusted according to the actual material to ensure a tight bite effect and stable wire feeding action.

[0048] The fiber wire feeding assembly also includes a pneumatic cutter assembly 305, which is mounted on the second front sheet metal part 306 of the second servo motor 301, so that the cutter of the pneumatic cutter assembly 305 can be horizontally movably arranged between the gap between the second wire feeding driven wheel 303 and the one-way wire feeding gear 302 and the upper end of the fiber guide tube 304 and can cut the long fiber prepreg 4.

[0049] Preferably, the pneumatic cutter assembly 305 can adopt the pneumatic cutter composed of a cylinder and a cutter in the prior art. The cylinder uses air pressure changes to control the extension or retraction of the piston rod, and the cutter is installed on the piston rod. Therefore, the cutter can be controlled by the cylinder to make rapid reciprocating motion perpendicular to the wire feeding direction of the long fiber prepreg yarn 4, thereby achieving the purpose of cutting the long fiber prepreg yarn 4.

[0050] When two or more long fiber prepreg yarns 4 are used, the pneumatic cutter assembly 305 can perform instant shearing on the long fiber prepreg yarns 4, which is convenient for switching different long fiber prepreg yarns 4 in different areas and printing the reinforced areas inside the long fiber interlayer respectively. It is also convenient for switching between the long fiber prepreg yarns 4 and the resin filaments 2, and can be independently arranged according to performance, cost and other requirements.

[0051] The first heating assembly and the second heating assembly each include a heat conducting block 501, a heating rod 502 and a temperature sensor 505; a heat conducting cavity 503 is formed on one side of the heat conducting block 501, the heating rod 502 is inserted into the heat conducting cavity 503, and a heating cavity 504 is formed on the other side of the heat conducting block 501; the temperature sensor 505 is arranged on the heat conducting block 501 and is located above the first molten deposition head or the second molten deposition head.

[0052] Preferably, the heating rod 502 can be an electric heating rod of the prior art, and the heating rod 502 heats the heat conducting block 501 through an external power supply, and the heat conducting block 501 conducts heat to the heating chamber 504, so that the resin filament 2 / long fiber prepreg filament 4 is heated and melted in the heating chamber 504. The size of the heat conducting chamber 503 can be adaptively adjusted according to the size of the heating rod 502, and the size of the heating chamber 504 can be adaptively adjusted according to the feeding and melting requirements of the resin filament 2 / long fiber prepreg filament 4.

[0053] The heating temperature of the heating rod 502 can be adaptively adjusted according to the actual conditions such as the material of the wire, printing parameters, etc. The temperature sensor 505 is provided to more accurately control the temperature of the wire of the melt deposition.

[0054] The upper end of the heating chamber 504 of the first heating component is connected to the lower end of the throat 105 of the resin wire feeding component, so that the resin wire 2 enters the heating chamber 504 of the first heating component and is heated and melted; the lower end of the heating chamber 504 of the first heating component is connected to the first molten deposition head, so that the heated and melted resin wire 2 is deposited in the first molten deposition head.

[0055] The upper end of the heating chamber 504 of the second heating component is connected to the lower end of the fiber guide tube 304, so that the long fiber prepreg yarn 4 enters the heating chamber 504 of the second heating component and is heated and melted; the lower end of the heating chamber 504 of the second heating component is connected to the second melting deposition head, so that the long fiber prepreg yarn 4 after heating and melting is deposited in the second melting deposition head; the heat conductive block 501 of the second heating component is fixedly connected to the bottom of the second front sheet metal part 306 of the second servo motor 301 through the supporting column 307.

[0056] The receiving column 307 is used to improve the connection strength between the heat conducting block 501 and the second front sheet metal component 306 . One or more receiving columns 307 may be provided according to actual connection requirements.

[0057] The first molten deposition head includes a first deposition chamber 601 and a first nozzle 602. The first deposition chamber 601 connects the heating chamber 504 of the first heating component and the first nozzle 602. The nozzle of the first nozzle 602 is arranged facing the printing platform. The internal cavity of the first nozzle 602 is an inverted cone structure that is wide at the top and narrow at the bottom. The lower end diameter of the first nozzle 602 is 0.4 mm.

[0058] The second molten deposition head includes a second deposition chamber 701 and a second nozzle 702. The second deposition chamber 701 connects the heating chamber 504 of the second heating assembly and the second nozzle 702. The nozzle of the second nozzle 702 is arranged facing the printing platform. The internal cavity of the second nozzle 702 is a straight cylindrical structure, and the diameter of the second nozzle 702 is 1.0 mm.

[0059] All the first fused deposition heads and the second fused deposition heads are located in the same straight line, for example, in the Y direction, and can be adaptively arranged according to actual printing requirements.

[0060] Please see attached Figure 1 , a printing method for a 3D printer nozzle for direct printing of a composite sandwich panel, comprising the following steps:

[0061] Step 1: Receive the three-dimensional solid model in the 3D printing device and define the plane printing trajectory.

[0062] Specifically, in a machine-implemented method for generating three-dimensional tool path instructions for a three-dimensional printer, a three-dimensional solid model is received, and a planar printing trajectory is defined when slicing and editing executable code.

[0063] In the step 1, the plane printing trajectory includes a first nozzle trajectory of the first nozzle 602 of the first fused deposition head and a second nozzle trajectory of the second nozzle 702 of the second fused deposition head; wherein the first nozzle trajectory includes the area where the filling shell, the bottom layer, the top layer, and the contour shell of the composite sandwich panel are located, and the second nozzle trajectory includes the area where the long fiber interlayer of the composite sandwich panel is located.

[0064] Step 2: Generate an actuator command in the 3D printing device, and control the resin wire feeding assembly or the fiber wire feeding assembly to move along the planar printing trajectory according to the actuator command.

[0065] Specifically, the planar printing trajectory includes a path that can be interpreted as an actuator command, generating actuator commands (including position switching, heating, heat dissipation, shearing, etc.) and g-codes, which are interpreted by the controller to control the actuator (such as servo motors in the X, Y, and Z directions, cutters, and heating rods, etc.) to move the molten deposition head along the nozzle trajectory (i.e., "track" the nozzle trajectory) to melt the material and build the model, so as to deposit the resin filament 2 as the outer shell, and deposit the long fiber prepreg filament 4 to embed the resin into the outer shell.

[0066] Step 3: The resin wire feeding assembly extrude resin wire 2 to the printing platform through the first molten deposition head, and the fiber wire feeding assembly extrude long fiber prepreg wire 4 to the printing platform through the second molten deposition head to form a composite sandwich panel on the printing platform.

[0067] The step 3 comprises the following sub-steps:

[0068] Step 3.1: When the resin wire feeding assembly moves, the molten deposited resin wire material 2 is extruded through the first molten deposition head to form an outer shell of the composite sandwich panel.

[0069] The outer shell may include a filling shell, a base layer and a contour shell.

[0070] The resin filament 2 uses polyamide resin: polyamide resin has high strength, rigidity and heat resistance, and can provide excellent bonding and reinforcement effects during the impregnation of carbon fibers, so that the composite sandwich panel has excellent strength, rigidity and durability.

[0071] Step 3.2: When the fiber feeding assembly moves, the molten-deposited long fiber prepreg filaments 4 are extruded through the second molten-deposition head and embedded in the outer shell to form a long fiber sandwich.

[0072] The long fiber prepreg filaments 4 are filled in the filling layer, and the shape of the filling layer can be designed to realize the autonomous arrangement of the long fiber prepreg filaments 4 inside the external shell, thereby constructing various features, internal honeycomb or lattice structures and other structural forms to meet the printing requirements of different components.

[0073] Preferably, the long fiber prepreg yarn 4 can use continuous carbon fiber and continuous glass fiber produced by Markfoged Company of the United States. The long fiber prepreg yarn 4 can also use semi-continuous prepreg filaments, including resin-embedded fibers arranged along the longitudinal direction of the filaments when the filaments are in one of the solidified, melted or resolidified forms. The diameter of the long fiber prepreg yarn 4 is between 0.3-0.8 mm.

[0074] In the step 3.2, the pneumatic cutter assembly 305 is used to move and cut the long fiber prepreg filaments 4, and the long fiber prepreg filaments 4 of multiple groups of fiber wire feeding assemblies are switched to fill and print different areas in the long fiber interlayer to form a long fiber interlayer with multiple long fibers working together.

[0075] Preferably, a filling shell may be formed between different filling areas of the long fiber prepreg yarns 4 by the resin yarns 2 .

[0076] Due to the unique rigidity and thermal properties of the long fiber prepreg 4, it is impossible to feed the wire by a single melt extrusion method, but a passive pulling process needs to be added. During the printing and laying process, a section of the wire will be reserved so that the long fiber prepreg 4 is completely laid on the printing platform after being cut off by the pneumatic cutter assembly 305 at the top of the fiber guide tube 304 before the next section of printing begins. This action is repeated every time the long fiber interlayer is printed and laid, ensuring that no excess long fiber prepreg 4 is left in the fiber guide tube 304. That is, the laying process of the long fiber prepreg 4 is not completed after the cutting action, but continues to lay a reserved distance, and the printing and laying of this section of the long fiber interlayer is completed only after all the long fiber prepreg 4 in the fiber guide tube 304 are pulled out.

[0077] After the long fiber prepreg yarn 4 is cut off, due to the bonding between the long fiber prepreg yarn 4 that has been printed and laid before and the external shell, a pulling force is formed on the remaining long fiber prepreg yarn 4 in the fiber guide tube 304, and the subsequent long fiber prepreg yarn 4 can be pulled out to complete the printing and laying of the reserved distance, ensuring that there is no residual long fiber prepreg yarn 4 in the fiber guide tube 304.

[0078] Step 3.3: When the resin wire feeding assembly moves, the molten deposited resin wire material 2 is extruded through the first nozzle 602 of the first molten deposition head to form a top layer of the composite sandwich panel, thereby completing the 3D printing of the composite sandwich panel.

[0079] The printed resin filament 2 forms the top layer, bottom layer and contour shell of the composite sandwich panel, so that the composite sandwich panel has good surface accuracy.

[0080] Please see attached Figure 1 , taking a set of resin wire feeding assemblies (left side of the figure) and two sets of fiber wire feeding assemblies (middle and right side of the figure) as an example, the printing and laying process of the composite sandwich panel is as follows:

[0081] When the first fused deposition head is driven to track the trajectory of the first nozzle, the first servo motor 101 feeds the wire according to the printing speed at the same time. After the bottom layer is printed by the resin filament 2, the second fused deposition head tracks the trajectory of the second or third nozzle to deposit part of the long fiber interlayer. After the construction of this part of the long fiber interlayer is completed, it is switched to the first fused deposition head, and the resin is deposited at the contour position of this part of the long fiber interlayer to form a filling shell. Thereafter, it is switched to the second fused deposition head, and the subsequent part of the long fiber interlayer of the sandwich board is deposited by tracking the trajectory of the second or third nozzle. Repeat the above process to manufacture the long fiber interlayer layer by layer. Optionally, during the printing and laying process of the long fiber interlayer, the second nozzles 702 of the two groups of fiber wire feeding assemblies can independently choose whether to switch according to the trajectory requirements. Finally, the first fused deposition head drives to track the trajectory of the first nozzle to print and lay the top layer to form a sandwich sandwich board, that is, a composite sandwich board.

[0082] In this embodiment, the resin filament 2 may include a thermoplastic resin having an unmelted ultimate tensile strength of about 30-100 MPa, and the fiber is formed of a fiber material having an ultimate tensile strength of about 3000-7000 MPa. Optionally, the long fiber prepreg filament 4 may be supplied as a filament having a cross-sectional area greater than 0.07 square millimeters and less than 0.785 square millimeters, and include 100 to 6000 parallel continuous axial strands in any cross-sectional area.

[0083] In this embodiment, two types of long fiber prepreg yarns 4 are used to realize additive manufacturing of two continuous fiber sandwich panels, and obtain sandwich panels that combine the advantages of two types of fibers, which is a new manufacturing method for composite sandwich panels. According to different composite sandwich panel manufacturing requirements, the types and quantities of long fiber prepreg yarns 4 can also be flexibly increased or decreased to obtain sandwich panels with different fiber advantages.

[0084] As an apparatus, the described process can be performed by any apparatus disclosed herein, including but not limited to each fused deposition head and a build plate, the deposition head being associated with a servo motor drive for relatively moving the fused deposition head and a printing substrate supporting a 3D printed part in at least three degrees of freedom, and a controller configured to control the electric drive and the fused deposition head operatively connected to the controller to build a 3D printed part by depositing a resin filament and a long fiber prepreg filament along a nozzle trajectory, respectively.

[0085] The above are only preferred embodiments of the present invention and are not intended to limit the scope of protection of the invention. Therefore, any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A 3D printer nozzle for direct printing of composite sandwich panels, characterized by: The invention comprises a resin wire feeding assembly, a resin filament (2), a fiber wire feeding assembly, a long fiber prepreg (4), a first heating assembly, a second heating assembly, a first molten deposition head, a second molten deposition head and a mounting plate (8); at least one group of resin wire feeding assemblies and multiple groups of fiber wire feeding assemblies are respectively mounted on a 3D printing device via the mounting plate (8); a first heating assembly is mounted at the bottom of each group of resin wire feeding assemblies, so that the resin filament (2) is fed into the first heating assembly through the resin wire feeding assembly and heated and melted; a second heating assembly is mounted at the bottom of each group of fiber wire feeding assemblies, so that the long fiber prepreg (4) is fed into the second heating assembly through the fiber wire feeding assembly and heated and melted; the first molten deposition head is mounted at the bottom of the first heating assembly, so that the heated and melted resin filament (2) is deposited through the first molten deposition head and then extruded onto a printing platform; the second molten deposition head is mounted at the bottom of the second heating assembly, so that the heated and melted long fiber prepreg (4) is deposited through the second molten deposition head and then extruded onto the printing platform; the resin filament (2) and the long fiber prepreg (4) form a composite sandwich panel on the printing platform.

2. The 3D printer nozzle for direct printing of composite sandwich panels according to claim 1, characterized in that: Each group of the resin wire feeding components comprises a first servo motor (101), a bidirectional wire feeding gear (102) and a first wire feeding driven wheel (103); the first servo motor (101) is fixedly mounted on the mounting plate (8), the bidirectional wire feeding gear (102) is mounted on the first servo motor (101), and the first wire feeding driven wheel (103) is rotatably mounted on the first servo motor (101); the resin wire (2) is fed out from the gap between the first wire feeding driven wheel (103) and the bidirectional wire feeding gear (102); The resin wire feeding assembly further comprises a heat dissipation pipe (104) and a throat pipe (105); the upper end of the heat dissipation pipe (104) is fixedly connected to the bottom of the first front sheet metal part (106) of the first servo motor (101), the throat pipe (105) is installed in the lower part of the heat dissipation pipe (104), and the lower end of the throat pipe (105) extends to the bottom of the heat dissipation pipe (104) and is connected to the first heating assembly; the resin wire (2) is fed out from the gap between the first wire feeding driven wheel (103) and the bidirectional wire feeding gear (102), and then enters the first heating assembly through the heat dissipation pipe (104) and the throat pipe (105).

3. The 3D printer nozzle for direct printing of composite sandwich panels according to claim 1, characterized in that: Each group of the fiber wire feeding components comprises a second servo motor (301), a one-way wire feeding gear (302), a second wire feeding driven wheel (303) and a fiber guide tube (304); the second servo motor (301) is fixedly mounted on the mounting plate (8), the one-way wire feeding gear (302) is mounted on the second servo motor (301), and the second wire feeding driven wheel (303) is rotatably mounted on the second servo motor (301); the fiber guide tube (304) is connected between the bottom of the gap between the second wire feeding driven wheel (303) and the one-way wire feeding gear (302) and the second heating component, so that the long fiber prepreg (4) is sent out from the gap between the second wire feeding driven wheel (303) and the one-way wire feeding gear (302) through the middle fiber guide tube (304) into the second heating component.

4. The 3D printer nozzle for direct printing of composite sandwich panels according to claim 3, characterized in that: The fiber wire feeding assembly also includes a pneumatic cutter assembly (305), which is mounted on the second servo motor (301), so that the cutter of the pneumatic cutter assembly (305) can be horizontally movably arranged between the gap between the second wire feeding driven wheel (303) and the one-way wire feeding gear (302) and the upper end of the fiber guide tube (304) and can cut the long fiber prepreg (4).

5. The 3D printer nozzle for direct printing of composite sandwich panels according to claim 1, characterized in that: The first heating assembly and the second heating assembly both comprise a heat conducting block (501), a heating rod (502) and a temperature sensor (505); a heat conducting cavity (503) is formed on one side of the interior of the heat conducting block (501), the heating rod (502) is inserted into the heat conducting cavity (503), and a heating cavity (504) is formed on the other side of the interior of the heat conducting block (501); the temperature sensor (505) is arranged on the heat conducting block (501) and is located above the first molten deposition head or the second molten deposition head.

6. The 3D printer nozzle for direct printing of composite sandwich panels according to claim 5, characterized in that: The upper end of the heating chamber (504) of the first heating component is connected to the lower end of the throat (105) of the resin wire feeding component, so that the resin wire (2) enters the heating chamber (504) of the first heating component and is heated and melted; the lower end of the heating chamber (504) of the first heating component is connected to the first molten deposition head, so that the heated and melted resin wire (2) is deposited in the first molten deposition head; The upper end of the heating chamber (504) of the second heating component is connected to the lower end of the fiber guide tube (304) of the fiber feeding component, so that the long fiber prepreg (4) enters the heating chamber (504) of the second heating component and is heated and melted; the lower end of the heating chamber (504) of the second heating component is connected to the second melting deposition head, so that the long fiber prepreg (4) after heating and melting is deposited in the second melting deposition head; the heat conductive block (501) of the second heating component is fixedly connected to the second servo motor (301) through the receiving column (307).

7. The 3D printer nozzle for direct printing of composite sandwich panels according to claim 6, characterized in that: The first molten deposition head comprises a first deposition chamber (601) and a first nozzle (602), wherein the first deposition chamber (601) is connected to the heating chamber (504) of the first heating assembly and the first nozzle (602), and the first nozzle (602) is arranged facing the printing platform; the internal cavity of the first nozzle (602) is an inverted cone structure that is wide at the top and narrow at the bottom, and the diameter of the lower end of the first nozzle (602) is 0.4 mm; The second molten deposition head comprises a second deposition chamber (701) and a second nozzle (702); the second deposition chamber (701) is connected to the heating chamber (504) of the second heating component and the second nozzle (702); the second nozzle (702) is arranged facing the printing platform; the internal cavity of the second nozzle (702) is a straight cylindrical structure, and the diameter of the second nozzle (702) is 1.0 mm.

8. A printing method for a 3D printer nozzle for direct printing of a composite sandwich panel according to claim 1, characterized in that: The following steps are involved: Step 1: Receive the three-dimensional solid model in the 3D printing device and define the plane printing trajectory; Step 2: generating an actuator command in the 3D printing device, and controlling the resin wire feeding assembly or the fiber wire feeding assembly to move along the planar printing trajectory according to the actuator command; Step 3: The resin wire feeding assembly extrude resin filaments (2) to the printing platform through the first molten deposition head, and the fiber wire feeding assembly extrude long fiber prepreg filaments (4) to the printing platform through the second molten deposition head, thereby forming a composite sandwich panel on the printing platform.

9. The printing method according to claim 8, characterized in that: In the step 1, the plane printing trajectory includes a first nozzle trajectory of a first nozzle (602) of a first fused deposition head and a second nozzle trajectory of a second nozzle (702) of a second fused deposition head; wherein the first nozzle trajectory includes the area where the filling shell, the bottom layer, the top layer, and the contour shell of the composite sandwich panel are located, and the second nozzle trajectory includes the area where the long fiber sandwich of the composite sandwich panel is located.

10. The printing method according to claim 8, characterized in that: The step 3 comprises the following sub-steps: Step 3.1: When the resin wire feeding assembly moves, the molten deposited resin wire (2) is extruded through the first molten deposition head to form an outer shell of the composite sandwich panel; the outer shell includes a filling shell, a bottom layer and a contour shell; Step 3.2: When the fiber feeding assembly moves, the molten-deposited long fiber prepreg (4) is extruded through the second molten-deposition head and embedded in the outer shell to form a long fiber sandwich; In the step 3.2, the long fiber prepreg (4) is cut by moving the pneumatic cutter assembly (305), the long fiber prepreg (4) of the plurality of fiber feeding assemblies is switched, and filling and printing are performed on different areas in the long fiber interlayer to form a long fiber interlayer with multiple types of long fibers coordinated; a filling shell is formed between different long fiber prepreg (4) filling areas by using the resin filament (2); Step 3.3: When the resin wire feeding assembly moves, the molten deposited resin wire (2) is extruded through the first nozzle (602) of the first molten deposition head to form a top layer of the composite sandwich panel, thereby completing the 3D printing of the composite sandwich panel.

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