Composite material in-situ melt mixing printing device and method

Abstract

The present invention relates to an in-situ melt mixing printing device and method for composite materials. The device includes a first feed section and a second feed section that are interconnected. The bottoms of the first feed section and the second feed section are both connected to a mixing and melting chamber, which is connected to a nozzle. The first feed section heats and melts plastic granules according to a set corresponding control instruction and then transports them to the mixing and melting chamber; the second feed section heats and melts chopped fiber pellets according to a set corresponding control instruction and then transports them to the mixing and melting chamber; the mixing and melting chamber is used to evenly mix the plastic granules and chopped fiber pellets and transport the mixed materials to the nozzle under the action of the chamber pressure. Compared with the existing technology, the present invention can achieve the filling of different performance materials in a specific area, and the carbon content in different positions can change in real time according to the stress information of the part, under the premise that the part meets the functional requirements, to obtain a part with a functional gradient material.

Description

Technical Field

[0001] The present invention relates to the technical field of chopped carbon fiber printing, and in particular to a composite material in-situ melt mixing printing device and method thereof. Background Art

[0002] With the development of 3D printing technology, carbon fiber can now be used for 3D printing. There are currently two main carbon fiber printing methods: short-cut carbon fiber filled thermoplastics and continuous carbon fiber reinforced materials. Among them, short-cut carbon fiber filled thermoplastics are printed by standard FFF (FDM) printers, and the main components are thermoplastics (PLA, ABS or nylon) and fine short-cut carbon fibers.

[0003] However, the content of traditional chopped carbon fiber printing filaments is generally below 30%, and the printed carbon fiber content is a fixed value. It is impossible to adjust the carbon fiber content of the corresponding area according to the changes in the stress information of the part, and it is impossible to reliably process parts with functional gradient materials. Summary of the Invention

[0004] The purpose of the present invention is to overcome the defects of the above-mentioned prior art and to provide an in-situ melt mixing printing device and method for composite materials, which can achieve the filling of fixed areas with materials of different performances and the real-time change of carbon content at different positions according to the stress information of the parts, so as to obtain parts with functional gradient materials, on the premise that the parts meet the functional requirements.

[0005] The objectives of the present invention can be achieved by the following technical solutions: A composite material in-situ melting and mixing printing device includes a first feeding part and a second feeding part that are interconnected, wherein the bottom of the first feeding part and the bottom of the second feeding part are both connected to a mixing and melting chamber, wherein the mixing and melting chamber is connected to a nozzle, and the first feeding part heats and melts plastic particles according to a set corresponding control instruction and then transports the heated plastic particles to the mixing and melting chamber;

[0006] The second feeding part heats and melts the chopped fiber pellets according to the corresponding control instructions and then feeds them to the mixing and melting chamber;

[0007] The mixing and melting chamber is used to uniformly mix the plastic granules and the chopped fiber granules, and to transport the mixed materials to the nozzle under the action of the chamber pressure.

[0008] Furthermore, the first feeding part and the second feeding part both include a stepper motor with controllable speed, the stepper motor is connected to a screw, the screw is arranged in a conduit, and the stepper motor drives the screw to move in the conduit according to the set corresponding control instructions. The top end of the conduit is connected to a feed port, and the bottom end of the conduit is provided with a heating block. The internal space of the heating block constitutes a heating and melting chamber, and the heating and melting chamber is connected to the mixing and melting chamber.

[0009] Furthermore, the stepper motor is connected to the screw rod through a first coupling, the stepper motor is connected to a first bolt through a first fixing plate, and the first bolt is connected to the conduit.

[0010] Furthermore, a second fixing plate is connected between the first bolt and the conduit.

[0011] Furthermore, a heat dissipation pipe is provided on the outside of the conduit, and the bottom of the heat dissipation pipe is connected to the heating block via a spring.

[0012] Furthermore, a locking sleeve is provided between the outside of the conduit and the heat dissipation pipe.

[0013] Furthermore, a stirrer is provided in the mixing and melting chamber, and the stirrer is connected and installed at the output end of the stirring motor.

[0014] Furthermore, the stirring motor is connected to the stirrer through a second coupling.

[0015] Furthermore, the stirring motor is connected to a second bolt via a third fixing plate, and the second bolt is connected to the heating block via a connecting plate.

[0016] A composite material in-situ melt mixing printing method comprises the following steps:

[0017] S1. Perform finite element analysis on the part to be printed under the corresponding working conditions to obtain stress information data of the mesh nodes corresponding to the part;

[0018] S2. Processing stress information data in stress visualization software to obtain multiple different stress contour lines;

[0019] S3, dividing the area between two different stress contour lines into stress contour areas, where different stress contour areas correspond to different carbon fiber contents;

[0020] S4, determining the corresponding feeding hysteresis of the first feeding part and the second feeding part according to the corresponding volumes of the first feeding part and the second feeding part, and the preset printing wire output speed;

[0021] According to the relationship between feeding speed and motor speed, the speed of the stepper motor corresponding to different carbon fiber contents is determined;

[0022] S5. Add the feeding lag and the stepper motor speed information to the G code of the existing printer. Through the G code instructions, control the printing of printing filaments with different carbon fiber contents in different areas to complete the printing process of the functional gradient material.

[0023] Compared with the prior art, the present invention proposes an in-situ melt mixing printing device for composite materials, which is provided with a first feeding part and a second feeding part that are interconnected, and the bottom of the first feeding part and the bottom of the second feeding part are both connected to a mixing and melting chamber, and the mixing and melting chamber is connected to a nozzle. The first feeding part is used to heat and melt the plastic granules according to the corresponding control instructions set, and then transport them to the mixing and melting chamber; the second feeding part is used to heat and melt the chopped fiber pellets according to the corresponding control instructions set, and then transport them to the mixing and melting chamber; the mixing and melting chamber is used to evenly mix the plastic granules and the chopped fiber pellets, and the mixed materials are transported to the nozzle under the action of the cavity pressure. In this way, the plastic granules and the chopped carbon fibers can be mixed in a heated and molten state, and a mixed printing filament of pure plastic and chopped carbon fibers can be extruded through the same nozzle, so that the carbon fiber content of the filament output from the print head can be controlled, and the automatic integrated process of feeding, heating and melting, mixing and filament extrusion is completed.

[0024] The present invention provides a stepper motor in both the first feeding part and the second feeding part, connects the stepper motor to the screw, and according to the relationship between the feeding speed and the speed of the stepper motor, controls the speed of the stepper motor to drive the screw to move in the conduit accordingly, thereby correspondingly controlling the feeding speed of the chopped fibers and the plastic granules, thereby ensuring the accuracy of the feeding.

[0025] The present invention performs finite element analysis on the parts to be printed, obtains stress information, and then draws stress contour lines to determine different stress isovalue areas, that is, to clarify the short-cut carbon fiber content corresponding to different areas; in addition, the present invention determines the feeding lag amount based on the volume of the two feeding parts and the printing wire speed, and on the other hand, determines the stepper motor speed corresponding to different short-cut carbon fiber contents based on the relationship between the feeding speed and the stepper motor speed. Therefore, combined with the G code of the existing printing equipment, the carbon fiber content of the in-situ melted printing wire can be accurately controlled, so that the carbon fiber content in the printing wire is increased in the area where the part is subjected to greater stress; in the area with less stress, the content of plastic pellets is increased, thereby strengthening the part in a fixed area and range according to the design, and finally obtaining a part with functional gradient material. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 Schematic diagram of the device structure of the present invention;

[0027] Figure 2 Schematic diagram of the cross-sectional structure of the device of the present invention;

[0028] Figure 3 Schematic diagram of the method flow of the present invention;

[0029] Figure 4 Schematic diagram of the loading method of the plate in the embodiment;

[0030] Figure 5 Schematic diagram of the stress isovalue region division result in the embodiment;

[0031] Explanation of the marks in the figure: 1. Stepper motor, 2. First fixed plate, 3. First bolt, 4. First coupling, 5. Screw, 6. Second fixed plate, 7. Feed port, 8. Locking sleeve, 9. Conduit, 10. Heat pipe, 11. Spring, 12. Bolt hole, 13. Heating block, 14. Nozzle, 15. Stirring motor, 16. Third fixed plate, 17. Second coupling, 18. Second bolt, 19. Connecting plate, 20. Agitator, 21. Heating and melting chamber, 22. Mixing and melting chamber. DETAILED DESCRIPTION

[0032] The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0033] Example

[0034] like Figure 1 and Figure 2 As shown, a composite material in-situ melting and mixing printing device includes a first feeding part and a second feeding part that are interconnected. The bottom of the first feeding part and the bottom of the second feeding part are both connected to a mixing and melting chamber 22. The mixing and melting chamber 22 is connected to a nozzle 14. The first feeding part heats and melts the plastic particles according to the corresponding control instructions set, and then transports them to the mixing and melting chamber 22.

[0035] The second feeding part heats and melts the chopped fiber pellets according to the corresponding control instructions and then feeds them to the mixing and melting chamber 22;

[0036] The mixing and melting chamber 22 is used to uniformly mix the plastic granules and the chopped fiber granules, and to deliver the mixed materials to the nozzle 14 under the action of the chamber pressure.

[0037] Among them, the first feeding part and the second feeding part both include a stepper motor 1 with controllable speed, the stepper motor 1 is connected to a screw 5, the screw 5 is arranged in a conduit 9, and the stepper motor 1 drives the screw 5 to move in the conduit 9 according to the set corresponding control instructions. The top of the conduit 9 is connected to the feed port 7, and the bottom end of the conduit 9 is provided with a heating block 13. The internal space of the heating block 13 constitutes a heating and melting chamber 21, and the heating and melting chamber 21 is connected to the mixing and melting chamber 22.

[0038] The stepper motor 1 is connected to the screw 5 through a first coupling 4 . The stepper motor 1 is connected to a first bolt 3 through a first fixing plate 2 . The first bolt 3 is connected to the guide tube 9 through a second fixing plate 6 .

[0039] The outer sleeve of the conduit 9 is provided with a heat dissipation pipe 10, and the bottom of the heat dissipation pipe 10 is connected to the heating block 13 through a spring 11. A locking sleeve 8 is provided between the outer portion of the conduit 9 and the heat dissipation pipe 10.

[0040] A stirrer 20 is provided in the mixing and melting chamber 22 and is connected to the output end of the stirring motor 15. The stirring motor 15 is connected to the stirrer 20 via a second coupling 17. The stirring motor 15 is connected to a second bolt 18 via a third fixing plate 16. The second bolt 18 is connected to the heating block 13 via a connecting plate 19.

[0041] The above device is used to realize an in-situ melt mixing printing method of composite materials, such as Figure 3 As shown, the following steps are included:

[0042] S1. Perform finite element analysis on the part to be printed under the corresponding working conditions to obtain stress information data of the mesh nodes corresponding to the part;

[0043] S2. Processing stress information data in stress visualization software to obtain multiple different stress contour lines;

[0044] S3, dividing the area between two different stress contour lines into stress contour areas, where different stress contour areas correspond to different carbon fiber contents;

[0045] S4, determining the corresponding feeding hysteresis of the first feeding part and the second feeding part according to the corresponding volumes of the first feeding part and the second feeding part, and the preset printing wire output speed;

[0046] According to the relationship between feeding speed and motor speed, the speed of the stepper motor corresponding to different carbon fiber contents is determined;

[0047] S5. Add the feeding lag and the stepper motor speed information to the G code of the existing printer. Through the G code instructions, control the printing of printing filaments with different carbon fiber contents in different areas to complete the printing process of the functional gradient material.

[0048] Thus, the present technical solution realizes a print head device for in-situ melting of a composite material with controllable chopped carbon fiber content. The screw 5 and the stirrer 20 rotate under the drive of the stepper motor 1 and the stirring motor 15, respectively. The plastic granules and the chopped fiber granules enter from their respective corresponding feed ports 7, and move to the heating and melting chamber 21 inside the heating block 13 under the drive of the screw 5, and then stir and mix in the mixing and melting chamber 22, and finally print from the nozzle 14. The print head device can mix the plastic granules and the chopped carbon fibers in a heated and molten state, and extrude a mixed printing filament of pure plastic and chopped carbon fibers through the same nozzle, so as to realize controllable carbon fiber content of the filaments output by the print head; and realize the automatic integrated process of feeding, heating and melting, mixing and filament extrusion.

[0049] The print head device is provided with two feed ports, one for chopped carbon fiber pellets and the other for plastic pellets. The feed port adopts a proximal feeding method, which can timely adjust the feeding speed of the pellets according to the printing information, thereby controlling the carbon fiber content. The pellets are fed downward under the rotation of the screw 5. The screw 5 has high precision and can achieve accurate feeding within a certain range. In this embodiment, the inner shaft cylinder of the screw 5 is a variable diameter cylinder, which gradually reduces the space and increases the pressure during the pellet conveying process, and can further achieve better fusion of the plastic and chopped carbon fibers in the mixed melting chamber 22.

[0050] The feed ratio is achieved by the stepper motor 1 that controls the feed. To obtain printing filaments with different carbon fiber contents and stable filament output, this embodiment uses a length path calculation method. That is, before the print head is ready to print a section, the feed ratio of plastic and chopped fiber filaments is set in the corresponding printing code G-code of the existing printer. Within this section of the path, the mixing ratio and total mixing amount of the two pellets remain unchanged, ensuring a relatively stable extrusion rate at the discharge port at every moment of printing. After the feeding of this section of the path is completed, the speed of the stepper motor 1 is adjusted to print the next gradient section. The G-code contains the speed code for controlling the stepper motor 1 of the plastic pellets and chopped fiber. It is used to control the feed speed of the chopped fiber and plastic pellets, thereby controlling the carbon fiber content of the in-situ melted printing filament, and thus effectively controlling the strength of the printed area.

[0051] In addition, considering that after the pellets enter the screw 5, there is a certain distance from the mixing of the pellets and the extrusion of the material, there is a certain lag between the feeding and the printing of the filament (the printing start time is delayed relative to the feeding start time, and the printing operation is performed only after the feeding fills the cavity). Therefore, this technical solution adjusts and sets the lag parameters according to the space between the screw 5 and the conduit 9, and the volume of the heating and melting cavity 21. By adding the lag parameters to the G-code, that is, controlling the advance time of pellet feeding before printing, precise printing control is achieved.

[0052] As screw 5 rotates, the filament enters heating and melting chamber 21. The plastic pellets reach a molten state under the action of heating block 13, while the chopped fibers remain in a wet, high-temperature state. The two materials then enter mixing and melting chamber 22. During pressure release, the speed of stirring motor 15 in mixing and melting chamber 22 is regulated to achieve an appropriate stirring rate, thereby ensuring uniform mixing of the two materials. The fully mixed molten materials then pass through a heated pipe to nozzle 14, where they are printed onto the platform or pre-printed area through the filament outlet, ultimately resulting in a designed part with a functionally gradient material.

[0053] This embodiment is for printing on a two-dimensional plate. First, the plate is loaded. The loading method is as follows: Figure 4 As shown in the figure, the stress information data of the node is extracted through finite element analysis.

[0054] Stress contours are then processed in the visualization interface. The density of these contours is controllable and can be adjusted using parameters. The areas between different stress contours are approximated as stress isovalue regions. Regions with higher stress are represented by darker colors in the image.

[0055] Based on the stress isovalue area, the material distribution is redesigned. In different areas, as the stress increases, the carbon fiber content increases, showing a gradient functional material distribution state.

[0056] like Figure 5 As shown, in this embodiment, the number of stress contour lines is controlled to be 17, and the 17 stress contour lines divide the part into 16 stress isovalue areas. Within a region, the ratio of printed plastic and chopped carbon fiber filaments is consistent. Between different regions, as the stress increases, the chopped carbon fiber content increases. The specific percentage of chopped carbon fiber in the printed filament and the difference in control in different intervals depend on the number of divided areas. Among the 17 areas divided in this embodiment, the chopped carbon fiber content is set to 53% in the maximum stress area, and the remaining areas decrease by 3% in turn. The chopped carbon fiber content in the area with the lowest stress is 0%, and finally the chopped carbon fiber content is enhanced in a certain area, achieving efficient utilization of chopped carbon fibers and obtaining a design structure of functional gradient materials.

[0057] In summary, the print head device proposed in this technical solution can control the carbon fiber content of the filaments output by the print head by controlling the carbon fiber feeding speed, thereby achieving the printing of filaments with inconsistent carbon fiber content in different areas, realizing a printing process with variable carbon fiber content. Under the premise that the part meets the functional requirements, this technical solution can achieve the filling of different performance materials in a specific area, with inconsistent carbon fiber content in different areas. The carbon content in different positions can change in real time according to the stress information of the part: in areas where the part is subjected to greater stress, the carbon fiber content in the print filament is increased, and in areas with less stress, the content of plastic pellets is increased, thereby strengthening the part in a specific area and range according to the design, and ultimately obtaining a part with a functional gradient material. This technical solution can achieve a higher chopped carbon fiber content than that of general print filaments by in-situ melting of plastic and chopped fibers, realizing effective control of the carbon fiber content according to the design. In addition, the use of chopped carbon fiber in-situ melting printing can also greatly reduce material costs, reduce pollution, and achieve the social benefits of energy conservation and emission reduction.

Claims

1. A composite material in-situ melt mixing printing method, applied to a composite material in-situ melt mixing printing device, characterized in that: The printing device comprises a first feeding portion and a second feeding portion which are interconnected, wherein the bottom of the first feeding portion and the bottom of the second feeding portion are both connected to a mixing and melting chamber (22), the mixing and melting chamber (22) is connected to a nozzle (14), and the first feeding portion heats and melts the plastic granules according to a set corresponding control instruction and then transports the heated plastic granules to the mixing and melting chamber (22); The second feeding part heats and melts the chopped fiber pellets according to the set corresponding control instructions and then feeds them to the mixing and melting chamber (22); The mixing and melting chamber (22) is used to uniformly mix the plastic granules and the chopped fiber granules, and to transport the mixed materials to the nozzle (14) under the action of the chamber pressure; The first feeding part and the second feeding part both include a stepping motor (1) with controllable speed, the stepping motor (1) is connected to a screw (5), the screw (5) is arranged in a conduit (9), the stepping motor (1) drives the screw (5) to move in the conduit (9) according to a set corresponding control instruction, the top end of the conduit (9) is connected to a feed port (7), the bottom end of the conduit (9) is provided with a heating block (13), the internal space of the heating block (13) constitutes a heating and melting chamber (21), and the heating and melting chamber (21) is connected to a mixing and melting chamber (22); The printing method comprises the following steps: S1. Perform finite element analysis on the part to be printed under the corresponding working conditions to obtain stress information data of the mesh nodes corresponding to the part; S2. Processing stress information data in stress visualization software to obtain multiple different stress contour lines; S3, dividing the area between two different stress contour lines into stress contour areas, where different stress contour areas correspond to different carbon fiber contents; S4, determining the corresponding feeding hysteresis of the first feeding part and the second feeding part according to the corresponding volumes of the first feeding part and the second feeding part, and the preset printing wire output speed; According to the relationship between feeding speed and motor speed, the speed of the stepper motor corresponding to different carbon fiber contents is determined; S5. Add the feeding lag and the stepper motor speed information to the G code of the existing printer. Through the G code instructions, control the printing of printing filaments with different carbon fiber contents in different areas to complete the printing process of the functional gradient material.

2. The composite material in-situ melt mixing printing method according to claim 1, characterized in that: The stepper motor (1) is connected to the screw (5) via a first coupling (4), the stepper motor (1) is connected to a first bolt (3) via a first fixing plate (2), and the first bolt (3) is connected to a conduit (9).

3. The composite material in-situ melt mixing printing method according to claim 2, characterized in that: A second fixing plate (6) is connected between the first bolt (3) and the conduit (9).

4. The composite material in-situ melt mixing printing method according to claim 1, characterized in that: The outer portion of the conduit (9) is sheathed with a heat dissipation pipe (10), and the bottom of the heat dissipation pipe (10) is connected to a heating block (13) via a spring (11).

5. The composite material in-situ melt mixing printing method according to claim 4, characterized in that: A locking sleeve (8) is provided between the outside of the conduit (9) and the heat dissipation pipe (10).

6. The composite material in-situ melt mixing printing method according to claim 1, characterized in that: A stirrer (20) is provided in the mixing and melting cavity (22), and the stirrer (20) is connected and installed at the output end of the stirring motor (15).

7. The composite material in-situ melt mixing printing method according to claim 6, characterized in that: The stirring motor (15) is connected to the stirrer (20) via a second coupling (17).

8. The composite material in-situ melt mixing printing method according to claim 6, characterized in that: The stirring motor (15) is connected to a second bolt (18) via a third fixing plate (16), and the second bolt (18) is connected to the heating block (13) via a connecting plate (19).

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