A 3D printing system for thermoplastic alloys based on Joule heat

Abstract

The present invention discloses a 3D printing system for thermoplastic alloys based on Joule heat, in which the wire feeding device and the hot roller are relatively fixed in position, the wire feeding port of the wire feeding device is located on one side of the hot roller, the hot roller and the forming substrate are respectively connected to the negative and positive electrodes of the Joule heat power supply, the wire feeding device and the forming substrate can move relative to each other, the wire feeding device is used to convey the printing wire to the forming substrate, and then the wire to be printed is pressed tightly onto the forming substrate by the hot roller. The hot roller and the forming substrate form a circuit, and the conductive wire softens the material instantaneously at the contact end between the hot roller and the substrate. The device has a simple structure, can realize the additive manufacturing of metal parts with high utilization rate, high quality, low cost and environmental friendliness, is a metal additive manufacturing method integrating materials, machinery, measurement and control technology and information processing, and realizes good density inside the formed sample by rolling the wire to be printed instantaneously when it melts through the hot roller.

Description

Technical Field

[0001] The present invention relates to the field of metal additive manufacturing, and particularly to a 3D printing system for thermoplastic alloys based on Joule heat. Background Art

[0002] Additive manufacturing technology, commonly known as 3D printing technology, is characterized by the rapid and free fabrication of three-dimensional structures and is widely used in new product development and single-piece small-batch manufacturing. Among them, direct metal forming is both a difficult and hot topic in additive manufacturing technology.

[0003] Due to its unique amorphous structure, amorphous alloys have significantly better mechanical, physical, and chemical properties than traditional crystalline alloys, such as high strength, good wear resistance, and corrosion resistance. Moreover, they exhibit superplasticity in the supercooled liquid region and can be thermoplastically formed, so they are also called thermoplastic alloys. Amorphous alloys have broad potential prospects in many fields such as aerospace, precision instruments, and military chemical industries.

[0004] Currently, the preparation methods of amorphous alloy parts mainly include thermoplastic forming method, powder sintering method, welding assembly method, and additive manufacturing method, etc. The thermoplastic forming method (such as die pressing, blow molding, etc.) is difficult to manufacture large-sized parts with complex shapes; although the latter three methods have overcome the problem of size limitation, the powder sintering method requires molds and sintering furnaces, and the forming process is relatively cumbersome; during welding assembly, the performance difference between the welded part and the matrix limits the application range of the manufactured parts; in the forming process of additive manufacturing (such as selective laser melting of amorphous powder), high-energy beam additive manufacturing methods represented by lasers have problems such as high equipment cost, complex equipment, large volume, radiation pollution, and slow forming speed under the same power. Therefore, a new low-cost and high-efficiency forming method for large-sized and complex amorphous alloy parts is particularly important.

[0005] For example, patent document CN108080638A discloses a laser 3D printing forming system and forming method for amorphous alloy foils, and specifically discloses that the excess sample material of the amorphous alloy foil is cut by a laser, and then the amorphous alloy is heated to the superplastic state in the supercooled liquid region, and then preheated rollers are used to roll, combined with the action of ultrasonic vibration, to make the upper and lower layers of amorphous alloy foils have atomic connections and rapidly cool down, so as to form large-sized and complex-shaped amorphous alloy parts with a cavity structure. It overcomes the limitations of the traditional amorphous alloy preparation method on the size and shape of alloy parts, but the process of the amorphous alloy 3D printing forming system disclosed in this patent is relatively complex. Since the laser device requires a large amount of energy, and the device occupies a relatively large volume of space, the system cost is high.

[0006] As disclosed in the patent document CN109434112A.pdf, a space 3D printing system based on amorphous alloy superplastic welding is suitable for the space environment. However, the internal structure of the prepared non-metallic alloy parts is not dense enough, and phenomena such as delamination and warping will occur. Summary of the Invention

[0007] The purpose of the present invention is to provide a 3D printing system for thermoplastic alloys based on joule heat to overcome the deficiencies of the prior art.

[0008] To achieve the above purpose, the present invention adopts the following technical solutions:

[0009] A 3D printing system for thermoplastic alloys based on joule heat includes a joule heat power supply, a wire feeding device, a hot roller press wheel, and a forming substrate;

[0010] The wire feeding device and the hot roller press wheel are relatively fixed in position. The wire feeding port of the wire feeding device is located on one side of the hot roller press wheel. The hot roller press wheel is connected to the positive or negative pole of the joule heat power supply, and the forming substrate is connected to the negative or positive pole of the joule heat power supply. The wire feeding device and the forming substrate can move relative to each other.

[0011] Further, the wire feeding device includes a wire feeding frame and a wire feeding disk arranged on the wire feeding frame. A wire feeding driving wheel is arranged on one side of the wire feeding disk. The surface of the wire feeding disk is in contact with the surface of the wire feeding driving wheel. A wire guiding head is arranged at the lower end of the wire feeding frame, and the wire outlet of the wire guiding head is close to the hot roller press wheel.

[0012] Further, the hot roller press wheel includes a rolling wheel body and a rolling wheel body frame. The rolling wheel body is fixed to the rolling wheel body frame through a rotating shaft. A brush box is arranged on one side of the rolling wheel body frame. A brush is arranged in the brush box, and the brush is in contact with the surface of the rolling wheel body.

[0013] Further, a spring is arranged between the brush and the brush box. A power supply interface for electrically connecting with the joule heat power supply is arranged on the brush box side of the rolling wheel body frame.

[0014] Further, the rolling wheel body frame is fixed to the moving frame through a preloading telescopic rod. The rolling wheel body frame is fixed to the lower end of the preloading telescopic rod. The upper end of the preloading telescopic rod is connected to the moving frame through a bolt. The length of the preloading telescopic rod is adjustable. A compression spring is arranged between the preloading telescopic rod and the moving frame.

[0015] Further, the wire feeding disk is fixed to the wire feeding frame through a wire feeding adjusting frame. The wire feeding adjusting frame and the wire feeding disk are respectively located on both sides of the wire feeding adjusting frame. An adjusting rod hole is arranged on the wire feeding adjusting frame. An adjusting rod is arranged in the adjusting rod hole. A compression spring is sleeved on the adjusting rod. A driven wheel shaft is fixed at the end of the adjusting rod hole. The wire feeding disk is installed on the driven wheel shaft. A sliding groove for the movement of the driven wheel shaft is arranged on the wire feeding frame.

[0016] Further, a pressing wheel fixed to the wire feeding frame is also provided on one side of the wire feeding disc, and the pressing wheel is fixed to the wire feeding frame through a pressing bracket.

[0017] Further, a pressing spring is provided on the pressing bracket, a blocking portion is provided on one side of the pressing bracket, the pressing wheel is always in contact with the surface of the wire feeding disc under the action of the compression spring, and an adjusting bolt is provided on the other side of the pressing bracket for adjusting the pre-tightening force of the pressing bracket.

[0018] Further, the wire feeding device, the hot roll pressing wheel and the forming substrate are all placed in a sealed cavity.

[0019] Further, the forming substrate is fixed on a moving platform, a radiator is provided at the upper end of the moving platform, a heating plate is fixed to the upper end of the radiator through a heat dissipation bracket, and the forming substrate is fixed on the heating plate; the heating plate is connected with a heating power supply.

[0020] Compared with the prior art, the present invention has the following beneficial technical effects:

[0021] The present invention relates to a thermoplastic alloy 3D printing system based on Joule heat, which uses a Joule heat power supply, a wire feeding device, a hot roll pressing wheel and a forming substrate to form a Joule heat printing system. The positions of the wire feeding device and the hot roll pressing wheel are relatively fixed, and the wire feeding port of the wire feeding device is located on one side of the hot roll pressing wheel. The hot roll pressing wheel and the forming substrate are respectively connected to the negative electrode and the positive electrode of the Joule heat power supply. The wire feeding device and the forming substrate can move relative to each other. The wire feeding device is used to convey the printing wire to the forming substrate, and then the hot roll pressing wheel presses the wire to be printed onto the forming substrate, so that the hot roll pressing wheel and the forming substrate form a circuit. The conductive wire material is instantaneously softened at the contact end between the hot roll pressing wheel and the substrate, and additive manufacturing of the thermoplastic alloy is realized based on Joule heat. The device has a simple structure and can realize additive manufacturing of metal parts with high utilization rate, high quality, low cost and environmental protection. It is a metal additive manufacturing method that integrates materials, machinery, measurement and control technology and information processing. Moreover, the forming sample has good density inside by rolling the wire to be printed melted instantaneously by the hot roll pressing wheel, which is beneficial to the combination between layers and between the layer and the substrate, and realizes high-quality metal 3D forming; the Joule heat power supply directly heats the material and the substrate without passing through heat conduction, and has high energy utilization rate.

[0022] Further, the wire feeding device includes a wire feeding frame and a wire feeding disc arranged on the wire feeding frame. A wire feeding driving wheel is provided on one side of the wire feeding disc, the surface of the wire feeding disc is in contact with the surface of the wire feeding driving wheel, and a wire guiding head is provided at the lower end of the wire feeding frame. The wire outlet of the wire guiding head is close to the hot roll pressing wheel, with a simple structure and convenient replacement of the wire to be printed.

[0023] Further, the hot roll press wheel includes a rolling wheel body and a rolling wheel body frame. The rolling wheel body is fixed to the rolling wheel body frame through a rotating shaft. A brush box is provided on one side of the rolling wheel body frame. A brush is provided in the brush box, and the brush contacts the surface of the rolling wheel body to ensure good conductivity of the rolling wheel body during the printing process.

[0024] Further, a pressing wheel fixed to the wire feeding frame is also provided on one side of the wire feeding disk. The pressing wheel is fixed to the wire feeding frame through a pressing bracket to prevent the wire to be printed from loosening and improve the printing stability.

[0025] Further, the wire feeding device, the hot roll press wheel and the forming substrate are all placed in a sealed cavity.

[0026] Further, the forming substrate is fixed to a moving platform. A radiator is provided at the upper end of the moving platform. A heating plate is fixed to the upper end of the radiator through a heat dissipation bracket, and the forming substrate is fixed to the heating plate; the heating plate is connected to a heating power supply, which can realize temperature control of the forming substrate and solve the problems of cracking, warping, deformation, etc. caused by excessive temperature gradient during the metal 3D printing process. Brief Description of the Drawings

[0027] Figure 1 It is a schematic structural diagram of the wire feeding device of the present invention.

[0028] Figure 2 It is a schematic structural diagram of the present invention.

[0029] Figure 3 It is a schematic structural diagram of the wire feeding adjustment frame of the present invention.

[0030] Figure 4 It is a cross-sectional view of the rolling wheel body frame.

[0031] Among them, 1. Joule heat power supply; 2. Wire feeding device; 3. Hot roll press wheel; 4. Forming substrate; 5. Moving platform; 6. Radiator; 7. Heating plate; 8. Heating power supply; 9. Wire feeding frame; 10. Wire feeding disk; 11. Wire feeding driving wheel; 12. Pressing wheel; 13. Pressing bracket; 14. Pressing spring; 15. Wire feeding adjustment frame; 16. Adjusting rod hole; 17. Compression spring; 18. Driven wheel shaft; 19. Wire guiding head; 20. Rolling wheel body; 21. Rolling wheel body frame; 22. Brush; 23. Spring; 24. Power interface; 25. Moving frame; 26. Pre-pressing telescopic rod; 27. Sealed cavity; 28. Anti-oxidation device; 29. Control system. Detailed Embodiment

[0032] The following further describes the present invention in detail with reference to the drawings:

[0033] Such as Figure 1 、 Figure 2As shown in the figure, a 3D printing system for thermoplastic alloys based on Joule heat includes a Joule heat power supply 1, a wire feeding device 2, a hot rolling wheel 3, and a forming substrate 4;

[0034] The wire feeding device 2 and the hot rolling wheel 3 are relatively fixed in position. The wire outlet of the wire feeding device 2 is located on one side of the hot rolling wheel 3. The hot rolling wheel 3 is connected to the positive or negative pole of the Joule heat power supply 1, and the forming substrate 4 is connected to the negative or positive pole of the Joule heat power supply 1. The wire feeding device 2 and the forming substrate 4 can move relative to each other, and the hot rolling wheel 3 can roll and contact the surface of the forming substrate 4.

[0035] Specifically, the forming substrate 4 is fixed on a moving platform 5. A radiator 6 is provided at the upper end of the moving platform 5. A heating plate 7 is fixed to the upper end of the radiator 6 through a heat dissipation bracket, and the forming substrate 4 is fixed on the heating plate 7; the heating plate 7 is connected to a heating power supply 8; it is used for auxiliary heating of the forming substrate 4 to improve the heating and forming efficiency.

[0036] The wire feeding device 2 includes a wire feeding frame 9 and a wire feeding disk 10 arranged on the wire feeding frame 9. A wire feeding driving wheel 11 is provided on one side of the wire feeding disk 10. The surface of the wire feeding disk 10 is in contact with the surface of the wire feeding driving wheel 11. A wire guiding head 19 is provided at the lower end of the wire feeding frame 9, and the wire outlet of the wire guiding head 19 is close to the hot rolling wheel 3.

[0037] As Figure 4 shown in the figure, the hot rolling wheel 3 includes a rolling wheel body 20 and a rolling wheel body frame 21. The rolling wheel body 20 is fixed to the rolling wheel body frame 21 through a rotating shaft. A brush box is provided on one side of the rolling wheel body frame 21. A brush 22 is provided in the brush box, and the brush 22 is in contact with the surface of the rolling wheel body 20. A spring 23 is provided between the brush 22 and the brush box. A power supply interface 24 is provided on the side of the brush box of the rolling wheel body frame 21 for electrical connection with the Joule heat power supply 1.

[0038] Both the rolling wheel body frame 21 and the wire feeding frame 9 are fixed on a moving frame 25; the rolling wheel body frame 21 is fixed on the moving frame 25 through a preloading telescopic rod 26. The rolling wheel body frame 21 is fixed to the lower end of the preloading telescopic rod 26. The upper end of the preloading telescopic rod 26 is connected to the moving frame 25 through a bolt. The length of the preloading telescopic rod 26 is adjustable. A compression spring is provided between the preloading telescopic rod 26 and the moving frame 25 for adjusting the height and preloading force of the preloading telescopic rod 26.

[0039] As Figure 3As shown in the figure, the wire feeding reel 10 is fixed on the wire feeding machine frame 9 through the wire feeding adjusting frame 15. The wire feeding adjusting frame 15 is connected to the wire feeding machine frame 9 by bolts. The wire feeding adjusting frame 15 and the wire feeding reel 10 are respectively located on both sides of the wire feeding adjusting frame 15. The wire feeding adjusting frame 15 is provided with an adjusting rod hole 16. An adjusting rod is arranged in the adjusting rod hole 16. A compression spring 17 is sleeved on the adjusting rod. A driven wheel shaft 18 is fixed at the end of the adjusting rod hole 16. The wire feeding reel 10 is installed on the driven wheel shaft 18. A sliding groove for the movement of the driven wheel shaft 18 is opened on the wire feeding machine frame 9; the good contact between the wire feeding reel 10 and the wire feeding driving wheel 11 is realized through the wire feeding machine frame 9.

[0040] On one side of the wire feeding reel 10, there is also a pressing wheel 12 fixed on the wire feeding machine frame 9. The pressing wheel 12 is fixed on the wire feeding machine frame 9 through a pressing bracket 13. A pressing spring 14 is arranged on the pressing bracket 13. A blocking part is arranged on one side of the pressing bracket 13. Under the action of the compression spring, the pressing wheel 12 is always in contact with the surface of the wire feeding reel 10. An adjusting bolt is arranged on the other side of the pressing bracket 13 for adjusting the pre-tightening force of the pressing bracket 13.

[0041] The wire feeding device 2, the hot roll pressing wheel 3 and the forming substrate 4 are all placed in the sealed cavity 27, and the printing atmosphere is provided by the anti-oxidation device 28; the Joule heat power supply 1, the heating power supply 8 and the wire feeding device 2 are all controlled by the control system 29, and the control system provides control parameters and printing atmosphere parameters.

[0042] The principle of the present invention is based on the fact that the alloy material will generate Joule heat after being electrified, and the thermoplastic cladding forming of the material is realized through the Joule heat. The alloy material is fed into the hot roll pressing wheel through the automatic feeding system. The hot roll pressing wheel is connected to the positive or negative pole of the Joule heat power supply through a brush. The printing substrate is connected to the positive or negative pole of the Joule heat power supply. A circuit is formed between the brush and the forming substrate. When an electric current is passed, the conductive wire material is instantaneously softened at the contact end of the hot roll pressing wheel and the substrate. For example, the amorphous material also exhibits superplasticity in the supercooled liquid phase region, and thermoplastic forming can be realized. With the movement of the substrate and the continuous delivery of the material, a stacked metal part can be formed on the substrate, realizing metal additive manufacturing.

[0043] The roller press wheel and the ball bearing in the middle of the roller press wheel realize the rolling of alloy materials. The pre-pressing telescopic rod is used to adjust the magnitude of the rolling pressure for different materials and different processes. The roller press wheel is in good contact with the conductive wire through the spring 23 and the brush. The roller press wheel conducts electricity to the conductive wire through the brush, and realizes hot rolling forming through the rolling device. There are electrode terminals on the brush to connect to the Joule heat power supply. The Joule heat control power supply part provides the main electric energy for the thermoplastic forming of the conductive wire. According to the thermoplastic forming process characteristics of different alloy materials, it can be in the form of direct current, alternating current or pulse, or in the form of voltage source or current source. The Joule heat generated by the short circuit between the conductive wire and the substrate instantaneously makes the alloy material have viscoplasticity, without conduction heating, which is internal heating of the material, with high thermal efficiency, high efficiency and energy saving. According to different materials and different forming efficiencies, the printing parameters are set; the conductive wire is made of metal strip or alloy wire.

[0044] The forming substrate heating power supply part makes the printing area achieve a constant temperature environment, which can reduce the warping and deformation of the printed object caused by stress and improve the forming quality. The forming substrate heating power supply can adopt various heating and temperature control methods, such as resistance heating or induction heating, etc., and a temperature sensor needs to be added to achieve PID temperature control. And according to the different heat treatment processes of different metal materials, different temperatures can be set. Considering that the moving platform cannot bear high temperatures for a long time, resulting in deformation and misalignment of movement, a radiator needs to be added. According to different conditions, air cooling, water cooling, semiconductor refrigeration, etc. can be selected. If the substrate requires a low temperature, the radiator can also not be added, or if the substrate needs to be cooled, direct cooling and heat dissipation can be added to achieve a constant temperature environment for the substrate.

[0045] The feeding of the conductive wire is completed by the wire feeding reel 10, the pressing wheel, and the wire feeding driving wheel 11. The printing material is installed on the driven wheel of the conductive wire reel. However, the alloy material is relatively easy to loosen, so a pressing wheel is needed to prevent the material from loosening and causing the feeding to fail.

[0046] The anti-oxidation part can design atmosphere protection according to different metal materials, including a gas purification system, a circulation system and a gas temperature control system. It requires the in and out control of a water oxygen sensor, a pressure sensor, a temperature sensor, a gas tank, a gas pump and a gas valve. It can also be designed according to a vacuum sealed cavity and requires a vacuum pump. If large parts need to be formed, the anti-oxidation system can also be designed in a local atmosphere protection mode.

[0047] The energy input part, that is, the power control part, the spatial motion control part, the print head and the feeding control part, and the anti-oxidation part all need to be connected to the computer overall control system of the printer and are uniformly coordinated and controlled through special software according to the process characteristics of different metal materials.

[0048] The working steps of a thermoplastic alloy 3D printing system based on Joule heat of the present invention are as follows:

[0049] 1) Loading of the model. Model slicing actually translates a 3D model described by triangular patches into a set of G-code instructions that can be executed by a 3D printer through a specific algorithm, that is, converting a 3D model in *.stl format into G-code that can be used by a 3D printer;

[0050] 2) Before starting printing, first install the conductive wire material, start the anti-oxidation system, and preheat the substrate to a certain temperature;

[0051] 3) Start the motion system, level the platform, deliver the conductive wire material under the hot roller, turn on the Joule heat power supply. After the alloy material is softened by efficient Joule heat, the alloy material is deposited on the high-temperature substrate through the hot rolling device to achieve good metallurgical bonding between the substrate and the first layer. Subsequently, further hot pressing and plastic accumulation forming are carried out to achieve good bonding between layers, layer by layer accumulation, and part stacking forming;

[0052] 4) During printing, the temperature measuring element detects the temperature of the hot roller and the substrate temperature and transmits the temperature signal to the temperature control system. The temperature control system adjusts the heating power in real time by comparing the magnitude of the feedback temperature with the preset temperature value.

[0053] 5) After printing is completed, continue heat preservation treatment for a period of time according to the heat treatment requirements of various materials to eliminate internal stress. After printing is finished, take out the workpiece.

Claims

1. A thermoplastic alloy 3D printing system based on Joule heat, characterized in that, it includes a Joule heat power supply (1), a wire feeding device (2), a hot rolling wheel (3) and a forming substrate (4); The wire feeding device (2) and the hot rolling wheel (3) are relatively fixed in position. The wire feeding port of the wire feeding device (2) is located on one side of the hot rolling wheel (3). The hot rolling wheel (3) is connected to the positive or negative pole of the Joule heat power supply (1), and the forming substrate (4) is connected to the negative or positive pole of the Joule heat power supply (1). The wire feeding device (2) and the forming substrate (4) can move relative to each other. The hot rolling wheel (3) can roll and contact the surface of the forming substrate (4). The wire feeding device (2) includes a wire feeding frame (9) and a wire feeding disk (10) arranged on the wire feeding frame (9). A wire feeding driving wheel (11) is arranged on one side of the wire feeding disk (10). The surface of the wire feeding disk (10) is in contact with the surface of the wire feeding driving wheel (11). A wire guiding head (19) is arranged at the lower end of the wire feeding frame (9). The wire outlet of the wire guiding head (19) is close to the hot rolling wheel (3). The hot rolling wheel (3) includes a rolling wheel body (20) and a rolling wheel body frame (21). The rolling wheel body (20) is fixed to the rolling wheel body frame (21) through a rotating shaft. A brush box is arranged on one side of the rolling wheel body frame (21). A brush (22) is arranged in the brush box. The brush (22) is in contact with the surface of the rolling wheel body (20). The rolling wheel body frame (21) is fixed to a moving frame (25) through a preloading telescopic rod (26). The rolling wheel body frame (21) is fixed to the lower end of the preloading telescopic rod (26). The upper end of the preloading telescopic rod (26) is connected to the moving frame (25) through a bolt. The length of the preloading telescopic rod (26) is adjustable. A compression spring is arranged between the preloading telescopic rod (26) and the moving frame (25).

2. The thermoplastic alloy 3D printing system based on Joule heat according to claim 1, characterized in that, the wire feeding disk (10) is fixed to the wire feeding frame (9) through a wire feeding adjusting frame (15). The wire feeding adjusting frame (15) and the wire feeding disk (10) are respectively located on both sides of the wire feeding frame (9). An adjusting rod hole (16) is arranged on the wire feeding adjusting frame (15). An adjusting rod is arranged in the adjusting rod hole (16). A compression spring (17) is sleeved on the adjusting rod. A driven wheel shaft (18) is fixed at the end of the adjusting rod hole (16). The wire feeding disk (10) is installed on the driven wheel shaft (18). A sliding groove for the movement of the driven wheel shaft (18) is arranged on the wire feeding frame (9).

3. The thermoplastic alloy 3D printing system based on Joule heat according to claim 1, characterized in that, a pressing wheel (12) fixed to the wire feeding frame (9) is further arranged on one side of the wire feeding disk (10). The pressing wheel (12) is fixed to the wire feeding frame (9) through a pressing bracket (13).

4. The thermoplastic alloy 3D printing system based on Joule heat according to claim 3, characterized in that, A pressing spring (14) is provided on the pressing bracket (13). A blocking portion is provided on one side of the pressing bracket (13). Under the action of the compression spring, the pressing bracket (13) makes the pressing wheel (12) always in contact with the surface of the wire feeding disc (10). An adjusting bolt is provided on the other side of the pressing bracket (13) for adjusting the pre-tightening force of the pressing bracket (13).

5. A thermoplastic alloy 3D printing system based on Joule heat according to claim 1, characterized in that, The wire feeding device (2), the hot rolling wheel (3) and the forming substrate (4) are all placed in the sealed cavity (27).

6. A thermoplastic alloy 3D printing system based on Joule heat according to claim 1, characterized in that, The forming substrate (4) is fixed on the moving platform (5). A radiator (6) is provided at the upper end of the moving platform (5). A heating plate (7) is fixed to the upper end of the radiator (6) through a heat dissipation bracket. The forming substrate (4) is fixed on the heating plate (7); the heating plate (7) is connected to a heating power supply (8).

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