A three-dimensional printing method combined with laser cleaning

Abstract

The present invention relates to three-dimensional printing technology, and in particular to a three-dimensional printing method combined with laser cleaning, and belongs to the field of additive manufacturing technology. The present invention can print high-strength metal parts directly in an atmospheric environment without using any protective gas, which can save the cost of inert protective gas; since it can be printed in an open atmospheric environment, large metal parts can be printed, and integrated high-strength large metal components that are difficult to manufacture with traditional technologies can be manufactured in an integrated manner, which has great social value; since it can be printed in an open atmospheric environment, it is conducive to reducing the manufacturing difficulty of three-dimensional printing equipment, has the advantage of flexible integration with other production lines, is conducive to the popularization of three-dimensional printing technology, and also has good user-friendliness. The beneficial effects of the present invention are remarkable and represent substantial progress.

Description

Technical Field

[0001] The invention relates to three-dimensional printing technology, in particular to a three-dimensional printing method combined with laser cleaning, and belongs to the technical field of additive manufacturing. Background Art

[0002] 3D printing technology originated in the United States. Common mainstream 3D printing technologies, such as Stereo Lithography Apparatus (SLA), Fused Deposition Modeling (FDM), Selective Laser Sintering (SLS), and Three Dimensional Printing and Gluing (3DP), were commercialized in the United States and Europe in the 1980s and 1990s. Among the metal 3D printing technologies that use metal as printing materials, the common ones are Selective Laser Melting (SLM), Laser Engineered Net Shaping (LENS), Electron Beam Melting (EBM), and Wire and Arc Additive Manufacture (WAAM). All of them require the solid metal raw materials to be melted during the 3D molding process, and at the same time, the area where the molten metal raw materials are being deposited needs to be heated and melted (the printed body is formed by cooling the molten raw materials after deposition) so that the printed body and the molten raw materials are combined together by melting. These common metal 3D printing technologies require a protective atmosphere or vacuum isolation of air during the 3D molding process to protect the molten raw materials and high-temperature parts such as the molten pool, so as to prevent the metal oxides or metal nitrides generated under high temperature conditions from affecting the 3D molding and material properties. For example, argon or vacuum protection is generally used when printing titanium alloys.There are many ways to isolate the air, for example: using a sealed box to wrap the molding environment of 3D printing and establish a high-purity argon atmosphere in the box or evacuating the space in the box into a high vacuum environment, but this type of box isolation method has limitations such as small molding space (smaller parts that can be printed) and high cost of use; another example: not using a sealed box, printing in an open environment, but during the printing process, it is necessary to spray protective gas into the area where the molten metal raw material is being deposited. The protective gas removes or blows away the air in the area around the molten metal raw material and the molten pool, but this type of spraying protective gas also has the problem of high gas consumption, especially when printing large metal parts. The amount of gas consumed is huge, the gas cost is high, and the method of spraying shielding gas cannot completely protect the high-temperature parts from being oxidized, because it takes time for the high-temperature metal to cool to a temperature where oxidation does not occur. The nozzle for spraying shielding gas always moves with the movement of the area where the molten metal raw material is currently deposited. The sprayed shielding gas can only protect the molten metal raw material and the molten pool, and cannot cover the area where the molten metal raw material has been deposited but has not yet cooled. Moreover, the method of spraying shielding gas cannot completely eliminate the air in the area around the molten metal raw material and the molten pool, but only reduces the air concentration to a level that does not cause significant oxidation and the concentration is unstable. Spraying shielding gas to establish a small dynamic protective atmosphere in the area around the molten metal raw material and the molten pool is commonly used in metal 3D printing technologies such as wire arc melting and wire laser melting, and is also used in tungsten inert gas arc welding (TIG), such as common argon arc welding.

[0003] Therefore, how to overcome the defects of the above-mentioned method of using a box to isolate the air and the method of using a protective gas to perform three-dimensional printing is a technical problem that needs to be solved urgently in the field of three-dimensional printing technology. Summary of the invention

[0004] The inventor has found through practice that in the three-dimensional printing process, if the surface layer of the molten metal raw material that is about to fuse with the molten pool is removed, and the surface layer of the molten pool that is about to fuse with the molten metal raw material is removed, it is possible to print high-strength metal parts directly in the atmospheric environment without using any protective gas. The inventor further found that the use of laser cleaning technology can reliably and effectively remove the surface layer of the molten metal raw material that is about to fuse with the molten pool, and can also reliably and effectively remove the surface layer of the molten pool that is about to fuse with the molten metal raw material. The laser cleaning (Laser ablation), also called laser ablation or photoablation, is a process of removing solid (or sometimes liquid) surface material by irradiating it with a laser beam, and the surface material is heated by the absorbed laser energy and evaporates or sublimates.

[0005] To this end, an object of the present invention is to provide a 3D printing method that can be used in an open atmospheric environment and does not use a protective gas, in particular a metal 3D printing method.

[0006] In order to achieve the above-mentioned invention object, the technical solution adopted by the present invention is: a three-dimensional printing method combined with laser cleaning, the main process of which is: heating energy is used to melt the solid raw material to obtain a molten raw material, the molten raw material is placed in a molding area used by a three-dimensional printing device, the molten raw material is deposited in the molding area and converted into a printing body after cooling, and the newly generated molten raw material is deposited on the basis of the printing body until the object to be printed is formed; wherein: in the process of depositing the molten raw material, the position where the molten raw material is placed is determined by the shape and structure of the object to be printed; the molding area used by the three-dimensional printing device refers to the space used by the three-dimensional printing device when printing an object;

[0007] Features:

[0008] During the deposition of the molten raw material, a laser beam is used to clean the surface of the printed body and / or the molten raw material being deposited, and the surface layer of the printed body and / or the surface layer of the molten raw material being deposited is removed by laser cleaning.

[0009] (Note: There are many optional types of heating energy for melting the solid raw material to obtain the molten raw material, and the heating method is one or a combination of at least two of the heating methods such as laser heating, electron beam heating, arc heating, plasma beam heating, resistance heating, electromagnetic induction heating, microwave heating, chemical combustion heating, and mechanical friction heating; the present invention does not limit the type of heating energy for melting the solid raw material to obtain the molten raw material.)

[0010] Optionally:

[0011] The interface between the printed body surface and the molten raw material being deposited is laser heated by a laser beam to laser clean the interface.

[0012] Optionally:

[0013] The laser beam is used to perform laser heating on the interface between the surface of the printed body and the molten raw material being deposited in the molten raw material deposition direction, so as to laser clean the interface.

[0014] Optionally:

[0015] Using a laser beam to laser clean the molten pool on the surface of the printed body, wherein the molten pool is a liquefied area formed by heating and melting on the surface of the printed body for depositing molten raw materials;

[0016] The molten pool has been formed on the surface of the printed body before the laser cleaning, or the molten pool is formed on the surface of the printed body at the same time as the laser cleaning (for example: laser cleaning is performed using a high-power density continuous laser, and a molten pool is simultaneously generated on the surface of the printed body during laser cleaning, that is, laser cleaning and the generation of the molten pool occur synchronously).

[0017] Optionally:

[0018] The laser beam is used to heat the interface between the molten pool on the surface of the printed body and the molten raw material being deposited, so as to laser clean the interface. (Note: The "molten pool on the surface of the printed body" here can be the molten pool that has been generated before laser cleaning, or the molten pool that is generated on the surface of the printed body when continuous laser is used for laser cleaning, that is, laser cleaning and the generation of the molten pool occur simultaneously.)

[0019] Optionally:

[0020] Laser cleaning is performed on the interface between the molten pool on the surface of the printed body and the molten raw material being deposited in the direction of molten raw material deposition using a laser beam. (Note: Here, the "molten pool on the surface of the printed body" can be a molten pool that has been generated before laser cleaning, or a molten pool that is generated on the surface of the printed body when continuous laser cleaning is used, that is, laser cleaning and the generation of the molten pool occur simultaneously.)

[0021] Optionally:

[0022] The molten pool is generated by laser heating, arc heating, electromagnetic induction heating, electron beam heating, plasma beam heating, mechanical friction heating, or resistance heating on the surface of the printed body.

[0023] Optionally:

[0024] The molten raw material is obtained by heating a solid raw material by resistance heating, laser heating, arc heating, electromagnetic induction heating, electron beam heating, plasma beam heating, or chemical reaction heating (such as combustion heat generation);

[0025] The molten raw material is obtained by melting a solid raw material on the surface of the printing body; or the molten raw material is melted in a heating device and then output to the surface of the printing body (for example, the solid raw material is melted in a micro furnace and then sprayed onto the surface of the printing body).

[0026] Optionally:

[0027] Using the same laser beam to heat the printed body to generate the molten pool and perform laser cleaning (for example, using a high-power density continuous laser for laser cleaning can generate a thin layer of molten pool on the solid surface of the cleaning area while laser cleaning);

[0028] Alternatively, when the number of laser beams projected simultaneously is two or more, part of the laser beams is used to heat the printed body to generate a molten pool, and part of the laser beam is used for laser cleaning (for example, a low-power density continuous laser is used to heat the surface of the printed body to generate a molten pool, and a pulsed laser is used for laser cleaning);

[0029] Alternatively, when the number of laser beams projected simultaneously is two or more, part of the laser beams is used to heat the printed body to generate a molten pool and to heat the solid raw material to generate a molten raw material, and part of the laser beams is used for laser cleaning.

[0030] Optionally:

[0031] The laser beam used in the laser cleaning adopts scanning irradiation to perform laser scanning heating, and the laser beam uses continuous laser or pulsed laser;

[0032] Alternatively, the laser beam used in the laser cleaning adopts non-scanning pulse irradiation for laser pulse heating. The laser beam uses pulsed laser (pulsed laser has the characteristics of very high peak power (e.g., 100,000 watts), very short pulse width (e.g., nanosecond laser pulse width is nanoseconds, femtosecond laser pulse width reaches femtoseconds), but average power is often much smaller than peak power (e.g., average power is less than 400 watts), which can vaporize the surface of the object in a very short time without damaging the structure below the surface). (Note: During laser cleaning, the thickness of the vaporized surface is affected by many factors, such as power density, beam dwell time, material type, laser wavelength, laser pulse peak power, etc.)

[0033] Optionally:

[0034] The laser cleaning described above uses a continuous laser or a pulsed laser. When a continuous laser is used, the thermal effect is very serious due to the excessively high energy of the continuous laser, for example, the solid metal surface will be remelted, that is, a molten pool (thin molten pool) will be generated while ablation is performed. Therefore, the continuous laser is suitable for scanning laser heating to avoid overheating the surface of the printed body or the surface of the molten raw material. When a continuous laser is used, a molten pool can be generated while laser cleaning is performed, and the molten pool does not need to be formed before laser cleaning. When a pulsed laser is used, the pulsed laser will only remove a thin layer of material on the surface of the object, but will not damage the structure below the surface of the object (for example, in the prior art: a pulsed laser is used to clean cultural relics, and pollutants on the surface of the cultural relics are removed, but the cultural relics are not damaged). Therefore, the pulsed laser will only remove the surface of the cleaned target, and will not generate a "molten pool" on the surface of the printed body. When this method of laser cleaning is used, the molten pool can be formed before laser cleaning. The pulsed laser is suitable for both scanning laser cleaning and non-scanning laser cleaning.

[0035] Optionally:

[0036] The laser cleaning described above can be performed with an adjustable laser spot power density value and / or an adjustable spot area size. (Note: The laser beam power density value and the duration of laser irradiation are key factors in determining whether the heated area is melted or vaporized, or vaporized and melted at the same time)

[0037] Optionally:

[0038] The laser beam does not heat the molten raw material after it is deposited and before it solidifies. (Note: Avoid overheating the molten raw material that has just been deposited)

[0039] Optionally:

[0040] The molten pool is obtained by laser scanning and heating, and the molten raw material is obtained by applying an electric current between the printing body and the solid raw material to generate a resistance heating effect to heat and melt the solid raw material located on the surface of the printing body; the laser beam that generates the molten pool heats the area on the surface of the printing body where the molten raw material is to be deposited to generate the molten pool, and also scans and heats the molten raw material being deposited;

[0041] Alternatively, the molten pool is obtained by laser scanning heating, and the molten raw material is obtained by applying an electric current between the printing body and the solid raw material to generate resistive heating to heat and melt the solid raw material located on the surface of the printing body; a laser beam independent of (different from) the laser beam used to generate the molten pool is used to scan and heat the molten pool and the molten raw material being deposited to vaporize the molten pool and the surface of the molten raw material being deposited.

[0042] Optionally:

[0043] A magnetic field is applied to the depositing molten raw material and the molten pool, and the magnetic field interacts with the current flowing through the depositing molten raw material and the molten pool to generate electromagnetic force, which stirs or vibrates the depositing molten raw material and the molten pool.

[0044] Optionally:

[0045] The laser beam used for laser cleaning is controlled by a laser beam moving mechanism to perform scanning heating on the interface between the printed body surface and the molten raw material being deposited;

[0046] The laser beam moving mechanism is an optical device that can change the projection position of the laser beam. (Explanation: For example, a rotatable or movable reflector, or a rotatable or movable lens, has the function of moving the laser beam)

[0047] Optionally:

[0048] The laser beam moving mechanism is mainly composed of a rotatable and / or movable reflector, or mainly composed of a rotatable and / or movable lens, or mainly composed of a combination of a rotatable and / or movable reflector and a rotatable and / or movable lens.

[0049] The present invention uses a laser beam to perform laser cleaning on the surface of the printed body and / or the molten raw material being deposited during the process of depositing the molten raw material. The surface layer of the printed body and / or the surface layer of the molten raw material being deposited is removed by laser cleaning, so that high-strength metal parts can be printed directly in an atmospheric environment without using any protective gas. The best way is to use a laser beam to simultaneously perform laser cleaning on the surface of the printed body and the molten raw material being deposited, so that the quality of the obtained metal parts can be better.

[0050] A laser beam is used to laser heat the interface between the surface of the printed body and the molten raw material being deposited so as to laser clean the interface. Thus, while the surface of the interface is being laser cleaned, the interface is also fused, thereby counteracting the oxidation or nitridation (i.e., poisoning) of the molten metal raw material being deposited and the surface of the printed body by air. In particular, the higher the printing rate and the faster the laser cleaning rate, the faster the rate at which the molten raw material being deposited fuses with the printed body, and the better the effect of counteracting oxidation or nitridation.

[0051] The present invention can directly print high-strength metal parts in an atmospheric environment without using any protective gas, such as parts made of titanium alloy, aluminum alloy, steel, stainless steel and other materials, and can save the cost of inert gas (protective gas); because it can be printed in an open atmospheric environment, large metal parts can be printed, and integrated high-strength large metal components that are difficult to manufacture with traditional technology can be manufactured in an integrated manner, which has great social value, such as integrated manufacturing of large high-pressure containers of nuclear power plants and integrated manufacturing of titanium alloy keels of aircraft; because it can be printed in an open atmospheric environment, it is conducive to reducing the manufacturing difficulty of three-dimensional printing equipment; because it can be printed in an open atmospheric environment, it has the advantage of being flexibly integrated with other production lines, which is conducive to the popularization of three-dimensional printing technology and has good user-friendliness. The beneficial effects of the present invention are remarkable and have substantial progress. BRIEF DESCRIPTION OF THE DRAWINGS

[0052] Figure 1 is a three-dimensional schematic diagram for illustrating a first specific embodiment of a three-dimensional printing method combined with laser cleaning according to the present invention;

[0053] Figures 2 to 7 is a two-dimensional schematic diagram for illustrating the principle of the first specific embodiment of the present invention, Figure 5 yes Figure 4 The enlarged view of the dotted box AA in the figure shows the part indicated by the dashed line, wherein arrows D1 and D2 indicate the moving direction, arrow D1 is also the deposition direction of the molten raw material, and arrows D3 and D4 indicate the scanning direction of the laser beam;

[0054] Figure 8 is a three-dimensional schematic diagram for illustrating a second specific embodiment of a three-dimensional printing method combined with laser cleaning according to the present invention;

[0055] Fig. 9 yes Figure 8 Bottom view of

[0056] Figures 10 to 12 is a two-dimensional schematic diagram for illustrating the principle of the second specific embodiment of the present invention, wherein arrows D5 and D6 indicate the moving directions, arrow D5 is also the deposition direction of the molten raw material, and arrow D7 indicates the scanning direction of the laser beam;

[0057] Fig.13 is a two-dimensional schematic diagram for illustrating a third specific embodiment of a three-dimensional printing method combined with laser cleaning according to the present invention, wherein arrow D8 indicates a moving direction (also a deposition direction of molten raw materials), and arrow D9 indicates a laser beam scanning direction;

[0058] Fig.14is a two-dimensional schematic diagram for illustrating a fourth specific embodiment of a three-dimensional printing method combined with laser cleaning according to the present invention, wherein arrow D10 indicates a moving direction (also a deposition direction of molten raw materials), and arrow D11 indicates a laser beam scanning direction;

[0059] Fig.15 is a two-dimensional schematic diagram for illustrating a fifth specific embodiment of a three-dimensional printing method combined with laser cleaning according to the present invention, wherein an arrow D12 indicates a moving direction (also a deposition direction of the molten raw material);

[0060] Fig.16 and Fig.17 is a two-dimensional schematic diagram for illustrating the optional form of the laser scanning area of ​​the present invention, wherein arrow D13 is the deposition direction of the molten raw material;

[0061] The labels are:

[0062] 1-galvanometer 1, 2-galvanometer 2, 3-laser beam 1, 4-laser beam 2, 5-solid material guiding mechanism 1, 6-linear solid material 1, 7-magnetic field generating device 1, 8-substrate 1, 9-resistance heating power supply 1, 10-printing body 1, 10A-previous molding body of printing body 1, 10B-current molding layer of printing body 1, 11-molten pool 1, 12-focusing mirror 1, 13-focusing mirror 2, 14-area where molten material is being deposited, 15-area scanned by laser beam 1, 16-area scanned by laser beam 2, 17-current working laser beam 1, 19-molten pool 2, 20-molten material being deposited, 21-molten material that has just been deposited, 22-overlapping area between current laser scanning area and molten material being deposited, 23-current laser scanning area;

[0063] 30-laser beam moving mechanism array 2, 31-laser beam 3, 32-laser beam 4, 33-laser beam 5, 34-laser beam 6, 35-solid raw material guiding mechanism 2, 36-linear solid raw material 2, 37-magnetic field generating device 2; 38-currently working laser beam 2, 39-currently working laser beam 3, 40A-previously formed body of printing body 2, 40B-currently formed layer of printing body 2, 41-substrate 2, 42-resistance heating power supply 2, 43-molten pool 3, 44-molten raw material 2 being deposited, 45-laser melting scanning area 1, 46-laser cleaning scanning area 1, 47-overlapping area between laser cleaning scanning area and molten raw material being deposited;

[0064] 48-molten raw material 3 being deposited, 49-arc-shaped light spot 1, 50-overlapping area of ​​the arc-shaped light spot 1 and the arc-shaped light spot 2, 51-overlapping area of ​​the arc-shaped light spot 2 and the molten raw material being deposited;

[0065] 60-molten raw material being deposited VI, 61-laser scanning area shape 1, 62-overlapping area 4 between the laser scanning area and the molten raw material being deposited, 63-laser scanning area shape 2, 64-overlapping area 5 between the laser scanning area and the molten raw material being deposited;

[0066] 68-molten raw material 4 being deposited, 69-arc-shaped light spot 2, 70-overlapping area of ​​arc-shaped light spot 2 and annular light spot 1, 71-overlapping area of ​​annular light spot 1 and the molten raw material being deposited, 72-annular light spot 1;

[0067] 78-molten raw material five being deposited, 79-annular light spot two, 80-overlapping area of ​​annular light spot two and annular light spot three, 81-overlapping area of ​​annular light spot three and the molten raw material being deposited;

[0068] Arrow D1-deposition direction one of molten raw material, arrow D2-advancing direction one of solid raw material, arrow D3-scanning direction of laser beam one, arrow D4-scanning direction of laser beam two, arrow D5-deposition direction two of molten raw material, arrow D6-advancing direction two of solid raw material, arrow D7-scanning direction two, arrow D8-deposition direction three of molten raw material, arrow D9-scannable direction one of arc-shaped light spot, arrow D10-deposition direction four of molten raw material, arrow D11-scannable direction two of arc-shaped light spot, arrow D12-deposition direction five of molten raw material, arrow D13-deposition direction six of molten raw material, arrow D101-advancing direction one of raw material deposition trajectory, arrow D102-advancing direction two of raw material deposition trajectory, arrow D103-advancing direction three of raw material deposition trajectory. DETAILED DESCRIPTION

[0069] Preferred specific embodiments of the present invention are listed below and the present invention is described in detail with reference to the accompanying drawings.

[0070] In the descriptions of all specific embodiments of the present invention, terms such as "up", "down", "left", "right", etc., orientation or positional relationships are based on the orientation or positional relationships shown in the accompanying drawings and are only for the convenience of description and simplification of operation, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation.

[0071] like Figures 1 to 7The first specific embodiment of the three-dimensional printing method combined with laser cleaning of the present invention is shown, a three-dimensional printing method combined with laser cleaning, the main process of which is: heating energy is used to melt the solid raw material to obtain a molten raw material, the molten raw material is placed in a molding area used by a three-dimensional printing device (not shown in the drawings), the molten raw material is deposited in the molding area and converted into a printing body after cooling, and the newly generated molten raw material is deposited on the basis of the printing body until the object to be printed is formed; wherein: in the process of depositing the molten raw material, the position where the molten raw material is placed is determined by the shape and structure of the object to be printed; the molding area used by the three-dimensional printing device refers to the space used by the three-dimensional printing device when printing an object;

[0072] The key points are:

[0073] During the process of molten raw material deposition, a laser beam is used to laser clean the molten pool (i.e., molten pool 11) on the surface of the printed body and / or the molten raw material being deposited (i.e., molten raw material 20 being deposited), and the surface layer of the molten pool and / or the surface layer of the molten raw material being deposited is removed by laser cleaning to promote the fusion of the deposited molten raw material with the molten pool; the molten pool is a liquefied area formed by the heated and melted surface of the printed body. The molten pool may have been formed on the surface of the printed body before the laser cleaning, or the molten pool may be formed on the surface of the printed body at the same time as the laser cleaning. In order to improve the quality of the printed body, it is preferred in this embodiment that a laser beam is used to simultaneously laser clean the molten pool on the surface of the printed body and the molten raw material being deposited.

[0074] In this embodiment, preferably, laser cleaning is performed on the junction of the deposited molten metal raw material and the molten pool located on the molten raw material deposition path (printing path), so as to remove the surface layer of the molten metal raw material at the junction that is about to be fused with the molten pool, and the surface layer of the molten pool that is about to be fused with the molten metal raw material (including harmful substances such as oxide film or nitride film); while the surface of the junction is being laser cleaned, the junction is fused at the same time, thereby counteracting the poisonous effects of air such as oxidation or nitridation on the deposited molten metal raw material and the molten pool.

[0075] In the first specific embodiment of the present invention, the core part of the three-dimensional printing device used is as follows Figure 1 and Figure 2As shown in the figure: a motion platform (not shown in the figure), a laser (not shown in the figure), an optical path, a solid raw material conveying mechanism (not shown in the figure), a solid raw material guiding mechanism (i.e., a solid raw material guiding mechanism-5), a control circuit (not shown in the figure), and a power supply are provided; wherein: the control circuit controls the movement of the motion platform, and the movement of the motion platform determines the deposition position of the molten raw material formed after the solid raw material is melted in the molding area; the control circuit controls the solid raw material conveying mechanism to move the solid raw material (i.e., the linear solid raw material-6) to the molding area via the solid raw material guiding mechanism (i.e., the solid raw material guiding mechanism-5), and the front end of the solid raw material is melted in the molding area to form a molten raw material, and the molten raw material is melted. The raw material is deposited in the forming area to form a printing body (i.e., printing body 10); the control circuit controls the working state of the laser, and the laser generated by the laser forms a laser beam through the optical path and is transmitted to the forming area; the laser adopts a continuous laser type fiber laser (outputting continuous laser) with a central wavelength of 1064nm; the power supply provides power to each electrical component of the three-dimensional printing system; the forming area refers to the space used by the three-dimensional printing system when printing parts, and the parts are formed in this space; the laser beam (i.e., laser beam 3, laser beam 4) is projected onto the printing body from the surrounding space of the solid raw material (i.e., linear solid raw material 6, using Ti-6Al-4V (TC4) titanium alloy wire).

[0076] The optical path includes a laser beam moving mechanism, which is an optical device capable of changing the projection position of the laser beam. The laser beam moving mechanism is mainly composed of a rotatable and / or movable reflector, or mainly composed of a rotatable and / or movable lens, or mainly composed of a rotatable and / or movable reflector and a rotatable and / or movable lens. The laser beam moving mechanism of this embodiment includes a galvanometer 1 and a galvanometer 2, which form a laser beam moving mechanism array. Among them, the galvanometer 1 and the galvanometer 2 are standardized laser scanning devices, which use a rotatable reflector inside, and the reflector is connected to the shaft of a galvanometer motor (also called a galvanometer motor), and the motor controls the deflection angle of the reflector, thereby controlling the projection position of the laser beam.

[0077] The laser beam moving mechanism controls the laser beam to scan and heat the area on the surface of the printing body (i.e., the printing body 10) where the molten raw material is to be deposited (located on the deposition path / printing path and in front of the molten raw material being deposited). That is, the laser cleaning of this embodiment adopts continuous laser scanning irradiation to perform laser scanning heating. The power density of the laser beam spot on the surface of the printing body is higher than 10 6 W / cm 2, the scanning rate is 6m / s. Since the laser type used is a continuous laser (non-pulsed laser), the energy of the continuous laser is too high (relative to the pulsed laser), and the thermal effect is very serious, which will cause the solid metal surface to remelt. Therefore, a thin layer of molten pool can be generated while laser cleaning the surface of the printed body (the depth of the molten pool is affected by factors such as material type, heat dissipation conditions, spot power density, and scanning rate). This specific embodiment just takes advantage of the characteristic that the continuous laser can generate a molten pool when used as a laser cleaning heat source. That is, the laser beam of this embodiment forms a molten pool on the surface of the printed body while performing laser cleaning. The laser beam simultaneously laser cleans the surface of the molten pool and the surface of the molten raw material being deposited. When the laser spot power density is higher than 10 6 W / cm 2 , producing a significant gasification effect, which is very beneficial for material removal processing such as drilling, cutting and engraving. The laser spot power density is 10 4 Up to 10 6 W / cm 2 When the temperature is between 0.5 and 1.5 °C, the molten pool vaporization is not obvious, which is suitable for heat conduction laser welding.

[0078] The number of laser beams projected by the laser beam moving mechanism is two (i.e., laser beam 1 3, laser beam 2 4), and each laser beam can be independently controlled (e.g., laser intensity, laser beam projection position, whether the laser beam is turned on); the number of laser beams projected at the same time is controllable (e.g., one beam, zero beams, or two beams); the number of lasers is two. During implementation, the same laser beam can be used to heat the printed body to generate the molten pool and perform laser cleaning; when the number of laser beams projected simultaneously is two or more, part of the laser beams can be used to heat the printed body to generate the molten pool, and part of the laser beams can be used for laser cleaning; or, when the number of laser beams projected simultaneously is two or more, part of the laser beams can be used to heat the printed body to generate the molten pool and to heat the solid raw material to generate the molten raw material, and part of the laser beams can be used for laser cleaning.

[0079] The scanning range of the laser beam around the area where the molten raw material is being deposited on the surface of the printed body is as follows: Figure 3 As shown: laser beam 13 and laser beam 24 are respectively in charge of the area 180° around the area 14 where the molten raw material is being deposited, namely: the area 15 scanned by laser beam 1 and the area 16 scanned by laser beam 2; the galvanometer 1 moves the laser beam 13 to be focused by focusing lens 12, and the light spot moves in the direction indicated by the double-headed arrow D3 in the area 15 scanned by laser beam 1; the galvanometer 2 moves the laser beam 24 to be focused by focusing lens 2 13, and the light spot moves in the direction indicated by the double-headed arrow D4 in the area 16 scanned by laser beam 2.

[0080] Applying electric current between the solid raw material and the printing body generates a resistive heating effect, and under the effect of the resistive heating, a molten raw material is generated between the solid raw material and the printing body; the electric current is generated by a resistive heating power supply 9, and is connected to the linear solid raw material 6 and the printing body 10 through a substrate 8 and a solid raw material guiding mechanism 5.

[0081] like Figure 2 , Figure 4 and Figure 5 As shown, the laser beam always scans and heats the area on the surface of the printed body where the molten raw material is to be deposited, and does not heat the molten raw material that has just been deposited (to avoid overheating the molten raw material that has just been deposited, causing adverse effects such as increased fluidity and aggravated oxidation), ensuring that the scanning heating area is always located on the deposition path and in front of the molten raw material being deposited. Since the linear solid raw material 16 always progresses in the direction indicated by the arrow D2 (the progressive direction of the solid raw material 12), the linear solid raw material 16 simultaneously moves in the direction indicated by the arrow D1 (the deposition direction of the molten raw material 11) (for example, a moving speed of 50 mm / s), the molten raw material immediately generated by the electric heating effect always deposits in the direction indicated by the arrow D1, and the cooling of the molten pool takes time. When the molten raw material being deposited quickly moves above the previously generated molten pool (i.e., molten pool 11), the molten pool still remains in a molten state. Under the action of resistance heating, there is still a molten pool (i.e., molten pool 219) directly below the molten raw material 20 being deposited. This molten pool is both a successor to the molten pool 11 and superimposed with resistance heat.

[0082] like Figure 5 , Figure 6 and Figure 7 As shown, while the laser beam (current working laser beam 17) is scanning and cleaning the area on the surface of the printed body where the molten raw material is to be deposited, the scanning range of the laser beam (i.e., the current laser scanning area 23) always covers the part of the molten raw material 20 being deposited, which is located on the side of the deposition path forward direction (i.e., the direction indicated by the arrow D1) close to the molten pool 11 (i.e., the overlapping area 22 of the current laser scanning area and the molten raw material being deposited), and the surface of this part is laser cleaned, that is, the laser cleaning range includes the intersection of the molten raw material being deposited and the molten pool in the deposition path (printing path) forward direction. Since it takes time for the molten raw material to cool and solidify, the molten raw material 21 that has just been deposited remains in a molten state for a short time, and forms the current molding layer 10B of the printed body 1 after solidification. The current molding layer 10B of the printed body 1 is based on the previous molding body 10A of the printed body 1.

[0083] The laser beam (currently working laser beam 17) performs laser cleaning on the interface between the depositing molten metal raw material and the molten pool on the deposition path (printing path), removing the surface layer of the molten metal raw material that is about to fuse with the molten pool, and the surface layer of the molten pool that is about to fuse with the molten metal raw material, that is, removing the oxide film or nitride film that is immediately generated; while the surface of the interface is being cleaned, the interface is fused, counteracting the oxidation or nitridation of the depositing molten metal raw material and the molten pool by air. Once the molten metal raw material fuses with the molten pool, the contact surface between the molten metal raw material and the molten pool is no longer in contact with the air, and cannot be oxidized or nitrided by the air. Since the junction of the depositing molten metal raw material and the molten pool on the deposition path (printing path) is quickly cleaned, the time that the junction is exposed to the air is very short. For example, assuming that the diameter of the projection of the depositing molten raw material on the molding plane is 1.0 mm, the scanning rate of the laser cleaning is 6 m / s, the cleaning part is on the side of the depositing molten raw material on the deposition path, the laser spot diameter is 1.0 mm, and the center distance between the center of the laser spot and the projection of the molten raw material on the molding plane is 0.95 mm (the width of the overlapping area 22 between the current laser scanning area and the depositing molten raw material is 0.05 mm). The laser cleaning reciprocates and scans with a semicircle of 1.9 mm diameter as the path. The arc length of the semicircle of 1.9 mm diameter is about 2.98 mm, so it is cleaned approximately every 0.5 ms (milliseconds). For common metal materials, the oxidation or nitridation produced in such a short time of 0.5 ms is very weak. The process of "melting-->laser cleaning-->fusion" is repeated until the deposition of the molten raw material is suspended or the printing is completed. Since the molten raw material itself is in a high temperature state, the superposition of high-power density laser energy will cause the temperature of the molten raw material to rise sharply instantly and produce significant vaporization. Therefore, the overlapping area 22 between the current laser scanning area and the molten raw material being deposited must be as small as possible to reduce the range of action of the laser on the molten raw material. The area of ​​the overlapping area 22 between the current laser scanning area and the molten raw material being deposited can be obtained through multiple actual tests and can also be considered as an empirical value. When printing the current layer, it is printed based on the surface of the previously formed layer, and the surface of the previously formed layer is laser cleaned.

[0084] In this embodiment, a magnetic field is applied to the molten raw material and the molten pool being deposited, and the magnetic field interacts with the current flowing through the molten raw material and the molten pool being deposited to generate electromagnetic force, which stirs or vibrates the molten raw material and the molten pool being deposited. Specifically, a static magnetic field is generated by setting a magnetic field generating device (i.e., a magnetic field generating device 7). The air gap magnetic field generated by the magnetic field generating device 7 acts on the molten raw material 20 being deposited, the molten pool, the molten raw material 21 that has just been deposited, and the surrounding areas. The current flowing through the molten raw material 20 being deposited, the molten pool, and the molten raw material 21 that has just been deposited is 50kHz alternating current. The alternating current interacts with the magnetic field to generate ultrasonic-level strong magnetic vibrations inside the areas where the alternating current passes, such as the molten raw material 20 being deposited, the molten pool, and the molten raw material 21 that has just been deposited. In addition to further promoting the fusion of the molten raw material 20 being deposited and the molten pool, it can also modulate the grain growth process inside these areas, and the dendrites are strongly sheared to obtain fine grains and improve material properties.

[0085] In this specific embodiment, the heating energy for generating the molten pool is laser, and the heating energy for generating the molten raw material is resistance heat, and the two are independent of each other. In other embodiments, the molten pool can also be generated by arc heating, or electromagnetic induction heating, or electron beam heating, or plasma beam heating, or mechanical friction heating, or resistance heating of the printed body surface; in other embodiments, the molten raw material can also be obtained by laser heating, or arc heating, or electromagnetic induction heating, or electron beam heating, or plasma beam heating, or chemical reaction heating of solid raw materials;

[0086] In this embodiment, the molten raw material is obtained by melting solid raw material on the surface of the printing body. Of course, in other embodiments, the molten raw material can also be melted in the heating device and then output to the surface of the printing body.

[0087] In this embodiment, the laser cleaning described above has an adjustable laser spot power density value and / or an adjustable spot area, thereby making the control of "laser cleaning" more flexible.

[0088] In this embodiment, the molten raw material is not heated by the laser beam after being deposited and before being solidified.

[0089] In the first specific embodiment, when printing the first layer of a metal part, that is, printing the first layer of a workpiece, printing is performed on a metal base plate. For example, the first layer of a stainless steel part is printed on a stainless steel plate or a metal plate that can be welded with a stainless steel material.

[0090] Among the existing three-dimensional printing technologies based on laser heating, there is a laser heating method that uses more than two laser beams to form a discontinuous annular composite light spot, and the positional relationship between the light spots is fixed. Specifically, a linear solid raw material (such as a metal wire) is centered and perpendicular to the current molding surface of the printing body, and multiple laser beams are used to project from the space around the linear solid raw material to the surface of the printing body, and the front end of the linear solid raw material meets the multiple laser beams on the surface of the printing body; the light spot of the multiple laser beams on the surface of the printing body surrounds the linear solid raw material with the projection of the linear solid raw material on the current molding surface of the printing body as the center, and a part of the light spot is in contact with the front end of the linear solid raw material, and the laser energy diffuses on the surface of the printing body through heat conduction to form a molten pool; while the laser beam melts the surface of the printing body to form a molten pool, it also heats and melts the front end of the linear solid raw material through heat conduction, and the molten raw material generated instantly merges with the molten pool instantly; there are some relevant literature introductions to this existing technology using multiple laser beams, such as the title Annular laser beam based direct metal Deposition (DOI: 10.1016 / j.procir.2018.08.099), and another paper titled "Three-beam internal wire feeding laser cladding temperature field simulation analysis and process optimization (DOI: 10.3788 / CJL201946.1002004, author: Zhang Jiping, etc., journal "Chinese Journal of Lasers")". Since the positional relationship between the laser spots of this technology is fixed, it uses heat conduction to heat, and the laser spot power density is the same as that of traditional heat conduction laser welding (the existing laser fuse metal 3D printing forming basis is essentially laser welding), and the spot power density range is 10 4 Up to 10 6 W / cm 2No significant vaporization can be produced between the two, otherwise it will cause serious harm to the three-dimensional printing process. For example, before the heat in the spot area is transferred to the area without the spot, significant or serious vaporization has already occurred, resulting in a large number of micro holes in the material, and the liquid metal at the front end of the molten pool and the linear solid raw material is seriously splashed to destroy the deposition of the molten raw material and the morphology after deposition. This technology uses a lower laser power density and cannot achieve the function of "laser cleaning". If printing is performed directly in the air without using a protective gas, it will lead to printing failure or poor part quality. Compared with the above-mentioned prior art, the first specific embodiment of the present invention adopts a laser scanning heating method with a high scanning line speed (for example, 6m / s or even more than 15m / s), which can quickly disperse heat over a larger area. The laser spot has moved to a new position before serious vaporization occurs, and the heat can be diffused without relying on the "heat conduction" method. High laser power density can be used to heat and generate a thin layer of molten pool while achieving the function of "laser cleaning"; and, combined with the resistance heating method to generate molten raw materials, metal three-dimensional printing can be achieved in the air without using a protective gas.

[0091] like Figures 8 to 12 The second specific embodiment of the three-dimensional printing method combined with laser cleaning of the present invention is shown, based on the three-dimensional printing device and Figures 1 to 7 The main difference of the three-dimensional printing device used in the first specific embodiment of the present invention shown is that: the laser beam moving mechanism (i.e., the laser beam moving mechanism array 2 30) adopts 4 three-dimensional galvanometers and uses 4 continuous laser lasers to generate at most 4 laser beams (i.e., laser beam 31, laser beam 4 32, laser beam 5 33 and laser beam 6 34); the magnetic field generating device 2 37 is composed of two pairs of electromagnets; the air gap of the magnetic field generating device 2 37 is arranged at the lower end outlet of the solid raw material guiding mechanism 2 35; two-phase alternating current is passed through the magnetic field generating device 2 37; a rotating magnetic field with the linear solid raw material 2 36 as the rotation axis is generated in the surrounding space at the lower end of the outlet of the solid raw material guiding mechanism 2 35 and the front end of the linear solid raw material 26; the magnetic field rotation frequency is 500 Hz; direct current is applied between the linear solid raw material 2 36 and the printing body (not shown in the drawings). The galvanometers in the prior art are divided into two-dimensional galvanometers and three-dimensional galvanometers: the optical components of the two-dimensional galvanometer are composed of two rotatable mirrors, which respectively control the movement of the light beam in the X-axis and Y-axis directions in the plane; the three-dimensional galvanometer is a two-dimensional galvanometer with a set of electric focusing lenses added. The electric focusing lenses control the position of the focal point of the light beam in the Z-axis direction, thereby realizing the position of the focus in the three-dimensional space represented by the XYZ three-axis.

[0092] In a second specific embodiment of a three-dimensional printing method combined with laser cleaning of the present invention, at least two laser beams (i.e., currently working laser beam 2 38 and currently working laser beam 3 39) are used at the same time. The spot power density of the currently working laser beam 2 38 on the surface of the printed body is 10 4 Up to 10 6 W / cm 2 The current working laser beam 2 38 is used to heat the area on the surface of the printed body where the molten raw material is to be deposited to generate a molten pool. The spot area of ​​the current working laser beam 39 on the surface of the printed body is significantly smaller than the spot area of ​​the current working laser beam 2 38 on the surface of the printed body (e.g. Fig.11 As shown), the power density is 10 6 W / cm 2 The current working laser beam 2 38 and the current working laser beam 3 39 are both scanned back and forth in the direction indicated by the double-headed arrow D7 (scanning direction 2 D7), as shown in FIG. Fig.12 As shown, a laser melting scanning area 1 45 and a laser cleaning scanning area 1 46 are always formed in front of the molten raw material 2 44 being deposited on the molten raw material deposition path shown by arrow D5 (deposition direction 2 D5 of the molten raw material). The intersection of the scanning area of ​​the current working laser beam 2 38 and the scanning area of ​​the current working laser beam 3 39 is the laser cleaning scanning area 1 46. The energy of the current working laser beam 3 39 and part of the energy of the current working laser beam 2 38 are superimposed on the laser cleaning scanning area 1 46. The power density of the laser cleaning scanning area 1 46 is greater than 10 6 W / cm 2 There is an overlap area (i.e., overlap area 47 between the laser cleaning scanning area and the molten raw material being deposited) between the scanning area of ​​the currently working laser beam 39 and the side of the molten raw material 2 44 being deposited, which is located in front of the molten raw material deposition path (i.e., the direction indicated by the deposition direction 2 D5 of the molten raw material). Since the molten raw material 2 44 being deposited is already in a molten state, the energy power density in the overlap area 47 between the laser cleaning scanning area and the molten raw material being deposited is also greater than 10 6 W / cm 2 .

[0093] like Fig.10As shown, the DC power required for resistance heating is connected by the resistance heating power supply 2 42 through the solid material guiding mechanism 2 35 and the substrate 2 41; the linear solid material 2 36 is advanced toward the surface of the previously formed body 40A of the printed body 2 in the direction indicated by the arrow D6 (the progressive direction of the solid material 2 D6). Since the interface resistance between the linear solid material 2 36 and the previously formed body 40A of the printed body 2 is the largest in the entire resistance heating circuit (the resistance heating circuit is mainly composed of the resistance heating power supply 2 42, the solid material guiding mechanism 2 35, the linear solid material 2 36, the previously formed body 40A of the printed body 2, and the substrate 2 41 in series), the junction between the front end of the linear solid material 2 36 and the surface (molten pool) of the previously formed body 40A of the printed body 2 is the generation point of the molten raw material; after the molten raw material is deposited and solidified, the current forming layer 40B of the printed body 2 is formed.

[0094] The rotating magnetic field generated by the magnetic field generating device 2 37 interacts with the direct current, producing a magnetic stirring effect in the molten pool 3 43, the molten raw material 2 44 being deposited, the molten raw material that has just been deposited, and other areas, which not only promotes the fusion of the molten raw material 2 44 being deposited and the molten pool 3 43, but also has a modulating effect on the grains inside the area that has not yet solidified.

[0095] like Fig.13 In the third specific embodiment of the three-dimensional printing method combined with laser cleaning of the present invention, the spot projected by the laser beam on the surface of the printed body is arc-shaped, including arc-shaped spot 1 49 and arc-shaped spot 2; arc-shaped spot 1 49 is generated by continuous laser projection, and arc-shaped spot 1 49 is used to heat the printed body to generate a molten pool; arc-shaped spot 2 is generated by pulsed laser, and the laser pulse width is 100ns, which is used to generate a "laser cleaning" effect, and a "laser cleaning" effect is generated in the overlapping area 50 of the arc-shaped spot 1 and the arc-shaped spot 2 and the overlapping area 51 of the arc-shaped spot 2 and the molten raw material being deposited; the arc-shaped spot and the molten raw material being deposited 3 48 move as a whole in the direction of molten raw material deposition indicated by arrow D8 (deposition direction 3 D8 of molten raw material); arc-shaped spot 1 49 and arc-shaped spot 2 can rotate in the direction indicated by double-headed arrow D9 (scannable direction 1 D9 of the arc-shaped spot) to perform scanning heating. Of course, the arc-shaped spot 2 of this embodiment can also be non-scanning irradiation.

[0096] like Fig.14The fourth specific embodiment of the three-dimensional printing method combined with laser cleaning of the present invention is shown, using an arc-shaped light spot (i.e., arc-shaped light spot 2 69) and an annular light spot (i.e., annular light spot 1 72); the arc-shaped light spot 2 69 is generated by continuous laser projection, and is used to heat the printed body to generate a molten pool; the annular light spot 1 72 is generated by a pulsed laser, and is used to produce a "laser cleaning" effect, and a "laser cleaning" effect is produced in the overlapping area 70 between the arc-shaped light spot 2 and the annular light spot 1 and in the overlapping area 71 between the annular light spot 1 and the molten raw material being deposited; the arc-shaped light spot 2 69 can rotate in the direction indicated by the double-headed arrow D11 (the scannable direction 2 D11 of the arc-shaped light spot) for scanning and heating; the deposited molten raw material 4 68, the arc-shaped light spot 2 69 and the annular light spot 1 72 move as a whole in the molten raw material deposition direction indicated by the arrow D10 (the deposition direction 4 D10 of the molten raw material).

[0097] like Fig.15 The fifth specific embodiment of the three-dimensional printing method combined with laser cleaning of the present invention is shown, using two annular light spots, namely annular light spot 2 79 and annular light spot 3; annular light spot 2 79 is generated by continuous laser projection and is used to heat the printed body to generate a molten pool; annular light spot 3 is generated by pulsed laser and is used to produce a "laser cleaning" effect, producing a "laser cleaning" effect in the overlapping area 80 between the annular light spot 2 and the annular light spot 3 and the overlapping area 81 between the annular light spot 3 and the molten raw material being deposited; the annular light spot 2 79 and the annular light spot 3 are static light spots, and their relative positions with the molten raw material 5 78 being deposited are fixed; the annular light spot 2 79, the annular light spot 3 and the molten raw material 5 78 being deposited move as a whole in the molten raw material deposition direction indicated by the arrow D12 (the deposition direction of the molten raw material 5 D12).

[0098] In the scanning heating of the first and second specific embodiments of the present invention, the shape of the scanning area is set according to the printing requirements, and there are many optional shapes. Fig.16 and Fig.17 For example:

[0099] exist Fig.16 In the figure, arrow D13 indicates the deposition direction of the raw material on the workpiece surface; the laser scanning area shape 1 61 is triangular as a whole; there is an overlapping area between the laser scanning area shape 1 61 and the molten raw material 6 60 being deposited (ie, the overlapping area 4 62 between the laser scanning area and the molten raw material being deposited).

[0100] exist Fig.17In the figure, the scanning area is distributed along the deposition path of the molten raw material on the surface of the printing body and is an area connected to the molten raw material 60 being deposited but the raw material has not yet been deposited (that is, the area where the raw material is about to be deposited). The forward direction 1 D101 of the raw material deposition trajectory, the forward direction 2 D102 of the raw material deposition trajectory, and the forward direction 3 D103 of the raw material deposition trajectory represent the forward vectors of the three sections of the raw material deposition path, and the total length of the three sections of the raw material deposition path can be set in the laser scanning parameters. There is an overlapping area between the laser scanning area form 2 63 and the molten raw material 6 60 being deposited (that is, the overlapping area 5 64 of the laser scanning area and the molten raw material being deposited). The laser scanning area form 2 63 can preheat the area where the raw material is to be deposited in advance, reduce the temperature gradient between the area where the raw material is being deposited and other areas of the workpiece (printing body), inhibit the generation of thermal cracks, and improve the material properties of three-dimensional printed parts or welded parts (mainly mechanical properties, such as fatigue resistance of metal parts). Existing metal 3D printing technologies, especially selective laser melting (SLM) and direct energy deposition (DED) (existing coaxial wire feeding and side-axis wire feeding 3D printing systems based on laser heating, side-axis wire feeding 3D printing systems based on arc heating, coaxial powder feeding and side-axis powder feeding 3D printing systems based on laser heating also belong to DED technologies), generally have the problem of low fatigue resistance of parts, which is also a huge obstacle restricting the application of existing metal 3D printing technologies in industrial production.

[0101] like Fig.16 and Fig.17 In the scanning heating method shown, the laser scans and heats the surface of the printed body to produce a molten pool. Since the "scanning heating" method can produce a "stirring" effect on the molten pool, it can have a beneficial effect on the performance of the parts finally obtained by 3D printing, such as reducing micropores.

[0102] It should be noted that in each of the above embodiments, a laser beam is used to simultaneously perform laser cleaning on the molten pool and the molten raw material being deposited, so as to obtain a high-quality printed body. Of course, it is also possible to use a laser beam to laser clean only the molten pool or only the molten raw material being deposited, but the quality of the printed body obtained in this way is relatively low. When the quality requirements for the printed body are not high, the latter two methods can be used for printing.

[0103] The above description is only a preferred specific embodiment of the present invention and cannot be used to limit the scope of implementation of the present invention. That is, equivalent changes and modifications made according to the claims and description of the present invention are still within the scope of the present invention.

Claims

1. A three-dimensional printing method combined with laser cleaning, the process of which is: heating energy is used to melt solid raw materials to obtain molten raw materials, the molten raw materials are placed in a molding area used by a three-dimensional printing device, the molten raw materials are deposited in the molding area and transformed into a printing body after cooling, and the newly generated molten raw materials are deposited on the basis of the printing body until the object to be printed is formed; wherein: In the process of depositing the molten raw material, the position where the molten raw material is placed is determined by the shape and structure of the object to be printed; the molding area used by the three-dimensional printing device refers to the space used by the three-dimensional printing device when printing the object; Features: During the process of molten raw material deposition, a laser beam is used to clean the surface of the printed body, and the surface layer of the printed body is removed by laser cleaning; a laser beam is used to clean the molten pool on the surface of the printed body, and the molten pool is a liquefied area formed by heating and melting on the surface of the printed body for depositing the molten raw material; the molten pool has been formed on the surface of the printed body before the laser cleaning, or the molten pool is formed on the surface of the printed body at the same time as the laser cleaning; or, During the process of molten raw material deposition, a laser beam is used to perform laser cleaning on the surface of the printed body and the molten raw material being deposited, and the surface layer of the printed body and the surface layer of the molten raw material being deposited are removed by laser cleaning; a laser beam is used to perform laser cleaning on the molten pool on the surface of the printed body, and the molten pool is a liquefied area formed on the surface of the printed body by heating and melting for depositing the molten raw material; the molten pool has been formed on the surface of the printed body before the laser cleaning, or the molten pool is formed on the surface of the printed body at the same time as the laser cleaning.

2. The three-dimensional printing method combined with laser cleaning according to claim 1, characterized in that: The interface between the molten pool on the surface of the printed body and the molten raw material being deposited is laser heated by a laser beam to laser clean the interface.

3. The three-dimensional printing method combined with laser cleaning according to claim 2, characterized in that: The laser beam is used to laser heat the interface between the molten pool on the surface of the printed body and the molten raw material being deposited in the molten raw material deposition direction, so as to laser clean the interface.

4. The three-dimensional printing method combined with laser cleaning according to claim 1, characterized in that: The molten pool is generated by laser heating, arc heating, electromagnetic induction heating, electron beam heating, plasma beam heating, mechanical friction heating, or resistance heating on the surface of the printed body.

5. The three-dimensional printing method combined with laser cleaning according to claim 1, characterized in that: The molten raw material is obtained by heating a solid raw material by resistance heating, laser heating, arc heating, electromagnetic induction heating, electron beam heating, plasma beam heating, or chemical reaction heating; The molten raw material is obtained by melting solid raw material on the surface of the printing body; or the molten raw material is melted in a heating device and then output to the surface of the printing body.

6. The three-dimensional printing method combined with laser cleaning according to claim 1, characterized in that: Using the same laser beam to heat the printed body to generate the molten pool and perform laser cleaning; Alternatively, when the number of laser beams projected simultaneously is two or more, part of the laser beams is used to heat the printed body to generate a molten pool, and part of the laser beams is used for laser cleaning; Alternatively, when the number of laser beams projected simultaneously is two or more, part of the laser beams is used to heat the printed body to generate a molten pool and to heat the solid raw material to generate a molten raw material, and part of the laser beams is used for laser cleaning.

7. The three-dimensional printing method combined with laser cleaning according to claim 1, characterized in that: The laser beam used in the laser cleaning adopts scanning irradiation to perform laser scanning heating, and the laser beam uses continuous laser or pulsed laser; Alternatively, the laser beam used for the laser cleaning adopts non-scanning pulse irradiation to perform laser pulse heating, and the laser beam uses pulsed laser.

8. The three-dimensional printing method combined with laser cleaning according to claim 1, characterized in that: In the laser cleaning, the power density value of the laser spot used is adjustable, and / or the size of the spot area is adjustable.

9. The three-dimensional printing method combined with laser cleaning according to claim 1, characterized in that: The molten raw material is not heated by the laser beam after it is deposited and before it solidifies.

10. The three-dimensional printing method combined with laser cleaning according to claim 1, characterized in that: The molten pool is obtained by laser scanning and heating, and the molten raw material is obtained by applying an electric current between the printing body and the solid raw material to generate a resistance heating effect to heat and melt the solid raw material located on the surface of the printing body; the laser beam that generates the molten pool heats the area on the surface of the printing body where the molten raw material is to be deposited to generate the molten pool, and also scans and heats the molten raw material being deposited; Alternatively, the molten pool is obtained by laser scanning heating, and the molten raw material is obtained by applying an electric current between the printing body and the solid raw material to generate resistive heating to heat and melt the solid raw material located on the surface of the printing body; a laser beam independent of the laser beam used to generate the molten pool is used to scan and heat the molten pool and the molten raw material being deposited to vaporize the molten pool and the surface of the molten raw material being deposited.

11. The three-dimensional printing method combined with laser cleaning according to claim 10, characterized in that: A magnetic field is applied to the depositing molten raw material and the molten pool, and the magnetic field interacts with the current flowing through the depositing molten raw material and the molten pool to generate electromagnetic force, which stirs or vibrates the depositing molten raw material and the molten pool.

12. The three-dimensional printing method combined with laser cleaning according to claim 1, characterized in that: The laser beam used for laser cleaning is controlled by a laser beam moving mechanism to perform scanning heating on the interface between the printed body surface and the molten raw material being deposited; the laser beam moving mechanism refers to an optical device that can change the projection position of the laser beam.

13. The three-dimensional printing method combined with laser cleaning according to claim 12, characterized in that: The laser beam moving mechanism is mainly composed of a rotatable and / or movable reflector, or mainly composed of a rotatable and / or movable lens, or mainly composed of a combination of a rotatable and / or movable reflector and a rotatable and / or movable lens.

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