Continuous fiber composite 3D printer tail end heating extrusion device

Abstract

The invention belongs to the technical field of fiber reinforced composite material additive manufacturing, and discloses a continuous fiber composite material 3D printer tail end heating extrusion device. Aiming at the problems of poor fiber impregnation degree of a resin matrix, low process flexibility of a mode of directly printing pre-impregnated composite filaments and incapability of changing the fiber content in a composite material structure by adjusting process parameters in real time in an in-situ impregnation printing mode, the invention designs an in-situ impregnation printing method capable of ensuring the printing process flexibility and improving the printing efficiency. According to the tail end heating extrusion device, the continuous fiber reinforced composite material structure can be formed in a high-quality mode, the fiber impregnation degree can be remarkably improved, and the structure of a printing nozzle is optimally designed. Through the structural design of the internal channel and the outlet nozzle of the tail end heating device, the impregnation effect of a resin matrix on continuous fibers can be improved, scraping of the nozzle on the continuous fibers is relieved, and the quality of a printing component can be effectively improved.

Description

Technical Field

[0001] The invention belongs to the field of additive manufacturing of continuous fiber reinforced resin-based composite materials, and relates to a terminal heating extrusion device of a continuous fiber reinforced resin-based composite material 3D printer. Background Art

[0002] The additive manufacturing (also known as "3D printing") technology of continuous fiber reinforced resin-based composite materials is an advanced manufacturing technology that realizes component forming by stacking materials layer by layer. Compared with traditional manufacturing technologies, it has the characteristics of high design freedom, high material utilization, reduced processing steps, and freedom from dependence on tooling and molds. It is used in aerospace, automobile, energy and other fields. This technology is based on fused filament fabrication (FFF) technology, and its core component is the end-heating extruder of the 3D printer. The specific process is: first, the resin matrix is ​​heated to a molten state and the continuous fiber is impregnated / blended, and then the impregnated fiber-resin material is extruded from the nozzle, and the printing is completed according to the planned path to achieve the preparation of composite materials and the formation of the structure.

[0003] According to different material characteristics, continuous fiber reinforced resin-based composite 3D printing can be divided into two methods: in-situ impregnation printing using dry fiber and polymer matrix in-situ material extrusion and direct printing of pre-impregnated composite filaments. The former has the advantage of arbitrary selection of fiber and resin matrix types and fiber tow sizes, but there are problems such as poor fiber impregnation degree of resin matrix and low printing efficiency; compared with the in-situ impregnation printing method, the latter can ensure the impregnation quality of the resin matrix to the fiber and achieve higher mechanical properties of the printed structure. However, there is low process flexibility, and it is impossible to change the fiber content in the composite structure by adjusting the process parameters in real time. In order to improve the mechanical properties of the printed structure, some scholars have proposed a variety of nozzle design schemes. For example, Cheng Lijin and others from Hebei University of Technology invented "a continuous fiber reinforced resin-based composite material 3D printing terminal and printing method" (application / patent number: CN202310739444.6). The terminal is mainly composed of two nozzles, a blending nozzle and a fiber nozzle. The blending nozzle also contains a pressurized screw to improve the degree of infiltration between the continuous fiber and the molten resin and improve the mechanical properties of the printed structure. However, compared with the single nozzle terminal, it is necessary to consider the fiber cutting caused by nozzle conversion and nozzle switching during the printing process. Ye Wenguang and others from Northwestern Polytechnical University invented "a multi-matrix continuous fiber composite material 3D printing nozzle and use method" (application / patent number: CN202111357271.9). This invention solves the problem that the existing 3D printing continuous fiber composite material cannot select different matrices, and realizes the mutual switching of multiple matrix materials. However, the problem of resin matrix impregnation of continuous fibers is not considered, and the problem of low impregnation degree in in-situ impregnation printing cannot be overcome. Liu Jun and others from Jiangsu Mingya Technology Co., Ltd. invented "A continuous fiber reinforced composite material 3D printer nozzle device" (application / patent number: CN202111115482.1). This invention solves the problem that the current printer nozzle is in an exposed state for a long time and is easily contaminated by dust when not in use by setting dust-proof and anti-blocking components. After long-term use, the inside of the nozzle is prone to blockage, affecting the normal operation of the nozzle. However, the nozzle printing component is designed based on the printing pre-impregnated composite filament process, which cannot avoid the low process flexibility of the process and the inability to change the fiber content in the composite material structure by adjusting the process parameters in real time.

[0004] Therefore, in order to meet the requirements of continuous fiber reinforced composite 3D printing for fiber impregnation quality and printing process flexibility, it is necessary to develop a terminal heating extrusion device for continuous fiber reinforced resin-based composite 3D printer that comprehensively considers improving the fiber impregnation degree and ensuring the flexibility of the printing process, so as to realize the manufacturing of high-performance 3D printed structures. Summary of the invention

[0005] The purpose of the present invention is to solve the problems of low fiber impregnation degree faced by the in-situ impregnation printing method in the current 3D printing of continuous fiber reinforced resin-based composite materials and poor printing process flexibility faced by the method of directly printing pre-impregnated composite filaments. The present invention proposes a 3D printing end heating extrusion device that can achieve double impregnation of fibers. Specifically, a necking structure with a diameter significantly smaller than the material channel and similar to the nozzle outlet diameter is designed at the end of the melting cavity of the heating unit, and rounded corners are processed to form a gradient change in diameter. During the printing process, the diameter difference at the necking structure is used to generate additional pressure to enhance the impregnation effect on the continuous fiber. When the heating unit is assembled with the nozzle, the material channel undergoes two diameter changes at the necking and the nozzle outlet, achieving double impregnation of the fiber and significantly improving the degree of fiber impregnation. In addition, the gradient change in the diameter of the material channel at the necking point causes the channel to narrow rapidly, which restricts the flow of molten resin, so that the resin can pass through and be extruded smoothly only under sufficient feed pressure. This feature allows the user to control the amount of resin extrusion by adjusting the feed parameters of the resin wire (such as pressure, speed, etc.), thereby achieving flexible regulation of the fiber content in the printed structure and improving the design flexibility and mechanical properties of the 3D printed structure.

[0006] The technical solution of the present invention:

[0007] A terminal heating extrusion device for a continuous fiber composite material 3D printer comprises a resin feeding unit A, a continuous fiber feeding unit B, a heating unit C and a nozzle D; the terminal heating extrusion device for a continuous fiber composite material 3D printer takes the heating unit C as the core, and the resin feeding unit A, the continuous fiber feeding unit B and the nozzle D are connected to the heating unit C through threads to form the terminal heating extrusion device for a continuous fiber composite material 3D printer;

[0008] Among them, the resin feeding unit A and the continuous fiber feeding unit B transport low-viscosity molten resin and continuous fiber reinforcement phase to the melting chamber in the heating unit C, so that the two can complete the impregnation of the fiber by the resin wire in the melting chamber, and then deposit it on the printing platform through the nozzle D; the melting chamber outlet is designed with a necking structure to increase the impregnation pressure of the resin matrix on the fiber, so as to improve the degree of fiber impregnation; the necking structure at the melting chamber outlet can also effectively limit the flow of the molten resin, and the resin extrusion amount during the printing process is controlled by adjusting the printing parameters, so as to realize the regulation of the fiber content in the printed structure.

[0009] The resin feeding unit A is mainly composed of a Teflon tube A1, a radiator A2 and a metal conduit A3. The Teflon tube A1 is inserted into the metal conduit A3, and the metal conduit A3 is connected to the heating unit C through a thread. The resin wire is transported to the resin channel of the heating unit C through the Teflon tube A1, and is finally heated to a molten state in the melting chamber. The radiator A2 has a heat dissipation effect on the resin wire in the metal conduit A3, so as to avoid the resin wire from melting prematurely due to the excessively high temperature of the metal conduit A3 and causing blockage.

[0010] The continuous fiber feeding unit B is mainly composed of a metal conduit B1 and a Teflon tube B2. The Teflon tube B2 is inserted into the metal conduit B1. The metal conduit B1 is connected to the heating unit C through a thread. The continuous fiber is transported to the fiber channel of the heating unit C through the Teflon tube B2, and finally enters the melting chamber to mix with the resin wire heated to a molten state to achieve impregnation of the fiber.

[0011] The heating unit C is mainly composed of a continuous fiber delivery channel C1, a melting chamber C2, a heating rod socket C3, a thermistor socket C4 and a resin delivery channel C5; the upper end of the continuous fiber delivery channel C1 is connected to the continuous fiber feeding unit B by a thread; the upper end of the resin delivery channel C5 is connected to the resin feeding unit A by a thread, the ends of the continuous fiber delivery channel C1 and the resin delivery channel C5 merge into the melting chamber C2, and the end of the melting chamber C2 is connected to the nozzle D by a thread; a necking structure is designed at the end of the melting chamber C2, and the diameter of the necking structure is the same as the diameter d of the nozzle D, so as to increase the impregnation pressure of the resin wire on the continuous fiber, and after being combined with the nozzle D, the effect of double impregnation of the continuous fiber is achieved, thereby improving the impregnation effect between the fiber and the resin wire; at the same time, the flow of the molten resin can be restricted to achieve effective regulation of the resin extrusion amount during the printing process; the heating unit C is also provided with a heating rod socket C3 and a thermistor socket C4;

[0012] The nozzle D is mainly composed of an upper end face D1, a material channel D2, a nozzle D outlet D3 and a lower end face D4, and is connected to the heating unit C through a thread, and the upper end face D1 is in contact with the end face of the threaded hole of the heating unit C to form a seal. After the continuous fiber is impregnated in the melting chamber, it is extruded through the material channel D2 and the nozzle D outlet D3 and deposited on the printing surface. The lower end face D4 plays a role in ironing and compacting the printing surface to improve the quality of the printing surface.

[0013] The diameter of the material channel of the heating unit C is designed to match the matching material. The angle between the resin delivery channel C5 and the continuous fiber delivery channel C1 is 30-45°. The channel outlets converge at the melting cavity, so that the resin wire and the continuous fiber are mixed in the melting cavity to achieve impregnation of the continuous fiber. The resin delivery channel C5 is larger than the wire diameter of the resin matrix material, and its diameter D resinThe diameter D of the resin wire is set to 1.1 to 1.3D; the diameters of the continuous fiber delivery channel C1 and the nozzle D outlet D3 are determined according to the diameter of the continuous fiber. The diameter D of the continuous fiber delivery channel C1 is fiber Need to meet D fiber =2~2.5d, d is the outlet diameter of nozzle D; the diameter d of nozzle D is determined according to the specifications of continuous fibers.

[0014] The channel ports of each unit are rounded with a radius of r = 0.3 to 0.5d to avoid scratching the continuous fibers at the inlet and outlet of each channel during the printing process and to prevent the fibers from breaking due to friction and shearing.

[0015] The nozzle D material channel D2 is designed with targeted size structure according to the different processes and materials of 3D printing to meet the needs of continuous fiber-resin mixed material passing through. The nozzle D material channel D2 is 2 to 2.5 times the diameter d of the nozzle D outlet. That is, D comp =2~2.5d; the size of the end surface D4 is set to 1.5~2.5d.

[0016] The size of the end surface of the lower end surface D4 is set to 1.5-2d according to different printing structures. The larger nozzle end surface plays a role in ironing and compacting the printed component to ensure that the printed part has good surface quality.

[0017] Beneficial effects of the present invention: The present invention specifically optimizes the internal material channel, nozzle outlet and terminal end face of the terminal heating extruder, while ensuring the advantage of flexible material selection for the in-situ impregnation process, significantly improving the impregnation effect of the resin matrix on the continuous fibers, and can change the fiber content in the composite material structure by adjusting the process parameters in real time, while reducing the scraping of the continuous fibers by the nozzle, improving the fiber breakage phenomenon during printing and the uniformity of heating of the printed material, making the material extrusion smoother, increasing the extrusion force on the printed component, and greatly improving the quality of the printed component. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 This is a schematic structural diagram of the components of a terminal heating extrusion device of a continuous fiber composite 3D printer of the present invention;

[0019] Figure 2 This is a schematic diagram of the assembly structure of a terminal heating extrusion device of a continuous fiber composite 3D printer of the present invention;

[0020] Figure 3 It is a cross-sectional structural schematic diagram of the equipment state of a terminal heating extrusion device of a continuous fiber composite 3D printer of the present invention;

[0021] Figure 4The present invention is a schematic diagram of the cross-sectional structure of a heating unit and a nozzle of a terminal heating extruder of a continuous fiber composite 3D printer; (a) is a schematic diagram of the cross-sectional structure of the heating unit, and (b) is a schematic diagram of the cross-sectional structure of the nozzle;

[0022] In the figure: A-resin feeding unit, B-continuous fiber feeding unit, C-heating unit, D-nozzle, A1-Teflon tube, A2-radiator, A3-metal conduit, B1-metal conduit, B2-Teflon tube, C1-continuous fiber delivery channel, C2-melting chamber, C3-heating rod socket, C4 thermistor socket, C5-resin delivery channel, D1-upper end face, D2-material channel, D3-nozzle outlet, D4-lower end face. DETAILED DESCRIPTION

[0023] The specific implementation of the present invention is further described below in conjunction with the accompanying drawings and technical solutions.

[0024] like Figure 1-Figure 4 As shown, a continuous fiber composite 3D printer end heating extruder includes its working state, including a resin matrix feed channel C5, a continuous fiber feed channel C1, a heating unit C, and a nozzle D. Each part is connected by a thread to ensure that the contact surface is in a closed state to avoid resin leakage in the melting cavity; when machining is performed by a machining method, the inlet and outlet of each material channel should be rounded, and the size of the rounded corners should be designed according to the selected printing process and the characteristics of the printing path. The rounded corners of the parts for which the specific design standards are not given are printed as r = 0.5mm. For example, the nozzle outlet is rounded (rounded corner R = 0.3~0.5d) to reduce the scratching of the continuous fiber by the nozzle outlet and improve the surface quality of the printed component.

[0025] To further illustrate the specific implementation of the present invention, nylon resin (PA, wire diameter is 1.75mm) and continuous carbon fiber dry filaments with a specification of T300-1K are used as printing materials to carry out the structural design of the terminal heating extrusion device. Figure 4 As shown in the figure, different diameters need to be set for the material channel in the nozzle according to the selected printing process: the diameter D of the resin feed material channel C5 resin It can be set to 2mm according to the wire diameter of the resin matrix; the continuous fiber material feeding channel C1 can be set to 2.3mm according to the specifications of the printed continuous fiber to ensure the effective impregnation of the molten resin matrix into the continuous fiber bundle.

[0026] The nozzle diameter d is set to 1mm, and the diameter of the material channel D2 is set to be equal to the diameter of the continuous fiber delivery channel C1 in the heating unit to meet the passage of the continuous fiber-resin mixed material. Its diameter should be set to 2.3mm; the size of the end surface D4 is set to 2mm to play the role of ironing and compacting the printed component to ensure that the printed part has good surface quality.

[0027] The above embodiments are only descriptions of the preferred implementation modes of the present invention, and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary engineering and technical personnel in the field should fall within the protection scope determined by the claims of the present invention.

Claims

1. A terminal heating extruder for a continuous fiber composite material 3D printer, characterized in that: The terminal heating extrusion device of the continuous fiber composite material 3D printer comprises a resin feeding unit (A), a continuous fiber feeding unit (B), a heating unit (C) and a nozzle (D); the terminal heating extrusion device of the continuous fiber composite material 3D printer takes the heating unit (C) as the core, and the resin feeding unit (A), the continuous fiber feeding unit (B) and the nozzle (D) are connected with the heating unit (C) through threads to form the terminal heating extrusion device of the continuous fiber composite material 3D printer; Among them, the resin feeding unit (A) and the continuous fiber feeding unit (B) transport low-viscosity molten resin and continuous fiber reinforcement phase to the melting chamber in the heating unit (C), so that the two can complete the impregnation of the fiber with the resin wire in the melting chamber, and then deposit it on the printing platform through the nozzle (D); the melting chamber outlet is designed with a necking structure to increase the impregnation pressure of the resin matrix on the fiber, so as to improve the degree of fiber impregnation; the necking structure at the melting chamber outlet can also effectively limit the flow of the molten resin, and the resin extrusion amount during the printing process is controlled by adjusting the printing parameters, so as to realize the regulation of the fiber content in the printed structure.

2. The terminal heating extruder of the continuous fiber composite material 3D printer according to claim 1, characterized in that: The resin feeding unit (A) is mainly composed of a Teflon tube (A1), a radiator (A2) and a metal conduit (A3). The Teflon tube (A1) is inserted into the metal conduit (A3). The metal conduit (A3) is connected to the heating unit (C) through a thread. The resin wire is transported to the resin channel of the heating unit (C) through the Teflon tube (A1) and is finally heated to a molten state in the melting chamber. The radiator (A2) dissipates heat for the resin wire in the metal conduit (A3), thereby preventing the resin wire from melting prematurely due to the excessively high temperature of the metal conduit (A3) and causing blockage. The continuous fiber feeding unit (B) is mainly composed of a metal conduit (B1) and a Teflon tube (B2). The Teflon tube (B2) is inserted into the metal conduit (B1). The metal conduit (B1) is connected to the heating unit (C) through a thread. The continuous fiber is transported to the fiber channel of the heating unit (C) through the Teflon tube (B2) and finally enters the melting chamber to mix with the resin wire heated to a molten state, thereby achieving impregnation of the fiber. The heating unit (C) is mainly composed of a continuous fiber delivery channel (C1), a melting chamber (C2), a heating rod socket (C3), a thermistor socket (C4) and a resin delivery channel (C5); the upper end of the continuous fiber delivery channel (C1) is connected to the continuous fiber feeding unit (B) by a thread; the upper end of the resin delivery channel (C5) is connected to the resin feeding unit (A) by a thread, and the ends of the continuous fiber delivery channel (C1) and the resin delivery channel (C5) merge into the melting chamber (C2), and the end of the melting chamber (C2) It is connected to the nozzle (D) by a thread; a necking structure is designed at the end of the melting chamber (C2), and the diameter of the necking structure is the same as the diameter d of the nozzle (D) to increase the impregnation pressure of the resin wire on the continuous fiber. After being combined with the nozzle (D), the continuous fiber can be impregnated twice, thereby improving the impregnation effect between the fiber and the resin wire; at the same time, the flow of the molten resin can be restricted, thereby effectively controlling the amount of resin extrusion during the printing process; the heating unit (C) is also provided with a heating rod jack (C3) and a thermistor jack (C4); The nozzle (D) is mainly composed of an upper end face (D1), a material channel (D2), a nozzle D outlet (D3) and a lower end face (D4), and is connected to a heating unit (C) through a thread, and the upper end face (D1) is in contact with the end face of the threaded hole of the heating unit (C) to form a seal. After the continuous fiber is impregnated in the melting chamber, it is extruded through the material channel (D2) and the nozzle D outlet (D3) and deposited on the printing surface. The lower end face (D4) plays a role in ironing and compacting the printing surface to improve the quality of the printing surface.

3. The terminal heating extruder of the continuous fiber composite material 3D printer according to claim 2 is characterized in that: The diameter of the material channel of the heating unit (C) is designed to match the matching material. The angle between the resin delivery channel (C5) and the continuous fiber delivery channel (C1) is 30-45°. The channel outlets converge at the melting cavity, so that the resin wire and the continuous fiber are mixed in the melting cavity to achieve impregnation of the continuous fiber. The resin delivery channel (C5) is larger than the wire diameter of the resin matrix material, and its diameter D resin The diameter D of the resin wire is set to 1.1 to 1.3D; the diameters of the continuous fiber delivery channel (C1) and the nozzle D outlet (D3) are determined according to the diameter of the continuous fiber. The diameter D of the continuous fiber delivery channel (C1) is fiber Need to meet D fiber =2~2.5d, d is the nozzle (D) outlet diameter; the nozzle (D) diameter d is determined according to the specification of the continuous fiber, and the nozzle (D) diameter d=1mm selected for the continuous carbon fiber of specification T300-1K.

4. The terminal heating extruder device of the continuous fiber composite material 3D printer according to claim 2, characterized in that: Each channel port is rounded, and the radius of the rounded corner is r = 0.3 ~ 0.5d.

5. The terminal heating extruder of the continuous fiber composite material 3D printer according to claim 2, characterized in that: The material channel (D2) of the nozzle (D) is designed with a specific size structure according to the different processes and materials of 3D printing to meet the needs of continuous fiber-resin mixed materials. The material channel (D2) of the nozzle (D) is 2 to 2.5 times the diameter d of the nozzle (D) outlet, that is, D comp =2~2.5d; the size of the end surface D4 is set to 1.5~2.5d.

6. The terminal heating extruder device of the continuous fiber composite material 3D printer according to claim 2, characterized in that: The size of the end surface of the lower end surface (D4) is set to 1.5-2d according to different printing structures.

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