Laser additive manufacturing system and additive manufacturing method

Abstract

The present invention discloses a system and method for laser additive manufacturing, and relates to the field of additive manufacturing technology. The system for laser additive manufacturing includes an infrared laser generator, an infrared light collimating lens, a blue light laser generator, a blue light collimating lens, a dichroic mirror and a focusing lens, and the other parts are common supporting systems of the laser additive manufacturing system. The present invention adopts the idea of ​​multi-wavelength light beams for composite processing, that is, multiple low-power pulsed blue light lasers are used to combine the beams at the focus to increase the actual processing area and the energy density of the laser output. While reducing the energy loss rate of the blue light laser in the optical fiber and increasing the laser absorption rate of the high-reflectivity material, a large spot infrared laser is used to expand and maintain its molten pool, so as to achieve the purpose of improving additive efficiency and reducing energy consumption. It is an excellent means for laser processing of high-reflectivity materials such as copper and aluminum.

Description

Technical Field

[0001] The present invention relates to the technical field of additive manufacturing, and in particular to a laser additive manufacturing system and an additive manufacturing method. Background Art

[0002] Laser additive manufacturing (LAM), which uses high-energy laser beams as energy sources, is a new type of manufacturing technology based on the principle of layered manufacturing. It uses the method of accumulating materials layer by layer to directly manufacture digital models into physical parts. The F42 International Committee of the American Society for Testing and Materials (ASTM) defines additive manufacturing as follows: Additive manufacturing is the process of connecting materials to form objects based on three-dimensional model data. Compared with subtractive manufacturing, it is usually a layer-by-layer accumulation process. Additive manufacturing technology integrates multiple disciplines such as digital technology, manufacturing technology, laser technology, and new material technology. It can directly manufacture CAD digital models into three-dimensional physical parts quickly and accurately, realizing true "free manufacturing". Compared with traditional manufacturing technology, additive manufacturing technology has a series of advantages such as high flexibility, no molds, short cycle, and no restrictions on part structure and materials. It has been widely used in aerospace, automotive, electronics, medical, military and other fields.

[0003] At present, the materials used in laser additive manufacturing technology have covered titanium alloys, high-temperature alloys, iron-based alloys, aluminum alloys, refractory alloys, amorphous alloys, ceramics, and gradient materials, etc., and have significant advantages in the manufacture of high-performance complex components in the aerospace field and porous complex structures in the field of biomanufacturing. Laser additive manufacturing technology is classified according to its forming principle. The most representative ones are selective laser melting (SLM) with powder bed laying as the technical feature and laser solid forming (Laser solid forming) with synchronous powder feeding as the technical feature. However, no matter which laser additive manufacturing technology is used, the most commonly used one at this stage is still the near-infrared laser in the 960-1100nm band as the processing source, which makes it difficult to melt and form high-reflectivity metals (such as gold, silver, copper, and aluminum) with low red light absorption.

[0004] To solve this problem, in the construction of laser additive manufacturing processing systems, it is proposed to use a short-wavelength (450nm) blue laser with a high laser absorption rate as the energy source for laser additive manufacturing. However, due to the high absorption rate of optical fiber to blue laser, it will cause at least 15% energy loss after fiber coupling and easily burn the optical fiber. The existing technology also integrates dual-wavelength lasers in the form of blue light / red light laser optical paths, so as to achieve the effect of large-size red light preheating and small-size blue light fine processing through galvanometer adjustment. However, when the red and blue lasers use the same galvanometer for optical path adjustment, it will inevitably interfere with the blue laser, and the expected effect cannot be achieved. In addition, the energy density of the blue laser generated is still in Gaussian mode (TEM). 00 ) is the main method, which cannot reduce the keyhole effect produced in the laser additive process, and there are still many pores and cracks formed.

[0005] Therefore, in order to solve the processing difficulties caused by the low infrared laser absorption rate of high-reflectivity metal materials, the damage problem of blue laser to optical fiber during continuous transmission, and the keyhole phenomenon easily generated by Gaussian single-mode laser, the present invention is specially proposed. Summary of the invention

[0006] The purpose of the present invention is to provide a laser additive manufacturing system and an additive manufacturing method, which not only solves the problem that extremely high energy density is required when processing high-reflectivity materials with a simple infrared laser, but also solves the problem that the blue light laser has low output energy and cannot melt the material and the molten pool well.

[0007] The present invention is achieved in that:

[0008] In a first aspect, the present invention provides a system for laser additive manufacturing, which is used to form a red-blue laser composite processing optical path, including an infrared laser generator, an infrared light collimating lens, a blue light laser generator, a blue light collimating lens, a dichroic mirror and a focusing lens, wherein the infrared laser generator, the infrared light collimating lens, the dichroic mirror and the focusing lens are sequentially connected in an optical path through an optical fiber, and the blue light laser generator, the blue light collimating lens, the dichroic mirror and the focusing lens are sequentially connected in an optical path through an optical fiber;

[0009] The side of the dichroic mirror facing the infrared laser generator is coated with an infrared light-transmitting film layer, and the side facing the blue light laser generator is coated with a blue light total-reflecting film;

[0010] The optical output part of the focusing lens is used for an external galvanometer system or a cladding gun head.

[0011] In an optional embodiment, the dichroic mirror is tilted, and the angle between the dichroic mirror and the horizontal plane is 30-45 degrees;

[0012] The infrared laser generator is located above the dichroic mirror, and the blue laser generator is located on one side of the dichroic mirror.

[0013] In an optional embodiment, the blue light laser generator is a low-power blue light laser with four gallium nitride as pump sources. The blue light laser generator and the focusing lens are configured to excite parallel light beams with energy of Gaussian beams from the blue light laser generator, and the two light beams overlap at the half-peak height of the Gaussian beam.

[0014] In an optional embodiment, the output multiple beams of blue parallel laser light converge at a focusing lens at an angle of 10 to 45 degrees to the incident axis. The convergence result is that 1 / 3 to 2 / 3 of the beam diameter (i.e., the half-peak width height of a single beam of light) will undergo energy superposition, so that the incident center axis converges into a nearly circular or rectangular spot with a diameter 1 to 1.5 times that of the original single beam of blue light, and the converged blue light beam falls completely inside the infrared laser.

[0015] In an optional embodiment, the infrared laser generator is a YAG fiber laser.

[0016] In an alternative embodiment, the optical fiber is a double-clad active optical fiber.

[0017] In an optional embodiment, a control system is further included, and the control system is connected to the infrared laser generator and the blue laser generator.

[0018] In a second aspect, the present invention provides an additive manufacturing method, which uses the laser additive manufacturing system of any one of the aforementioned embodiments to perform additive manufacturing.

[0019] In an optional embodiment, the spot size of the infrared laser generator is 1.2 to 2 times the size of the four blue laser beams after the beam is combined, the infrared laser generator maintains a continuous light emitting state during the laser processing process, and the on / off frequency of the blue laser generator is 1-10HZ;

[0020] Preferably, when the laser additive manufacturing system is used in a powder feeding additive device, the power of the infrared laser generator is 3000-6000W, the power of the blue laser generator is 300-1000W; the laser spot diameter of the blue laser generator is 1-2mm;

[0021] Preferably, when the laser additive manufacturing system is used in a powder-spreading additive device, the power of the infrared laser generator is 500-1000W, the power of the blue laser generator is 50-100W, and the laser spot diameter of the blue laser generator is 30-50μm.

[0022] In an optional embodiment, it includes:

[0023] Use 3D modeling software to build a 3D model based on the target part, and import the virtual model into the additive manufacturing control system to generate the part scanning path;

[0024] Pour the powder to be processed into the powder storage bin and wait for the high-energy laser beam to form the additive manufacturing;

[0025] Under the protection of inert gas, a laser additive manufacturing system is used to form and manufacture the desired parts from high-reflectivity metal powder;

[0026] Preferably, the 3D modeling software is selected from at least one of UG, Solidworks and CATIA;

[0027] Preferably, the powder to be processed is selected from at least one of copper and aluminum;

[0028] Preferably, the powder to be processed is a spherical particle. When used in a powder spreading type additive device, the particle size of the powder to be processed is 15-72 μm; when used in a powder feeding type additive device, the particle size of the powder to be processed is 90-150 μm;

[0029] Preferably, the powder to be processed is dried before being poured into the powder storage bin; more preferably, the powder is dried by vacuum drying, and the drying temperature is controlled to be 120-200° C. and the vacuum degree is -0.080 to -0.1 MPa.

[0030] The present invention has the following beneficial effects: the infrared laser emitted by the infrared laser generator and the blue laser emitted by the blue laser generator pass through the infrared collimating lens and the blue collimating lens respectively, and then pass through the dichroic mirror and then are focused by the focusing lens, so that the infrared laser and the blue laser of different wavelengths are coupled, but only the energy of the terminal output part is compounded, and the overall optical path system is simple and easy to implement, low in cost, and widely applicable, and can be well promoted in laser additive manufacturing systems such as powder feeding type and powder spreading type. The infrared laser generator continuously emits light during the working process, and the blue laser generator can be a pulsed laser with a low frequency of off / on light. During the blue light off process, the high-energy infrared laser expands and maintains the shape and depth of the molten pool, ensuring that it can achieve effective melting and rapid forming while reducing the high energy consumption caused by the continuous output of blue light, which not only solves the problem that a simple infrared laser needs extremely high energy density when processing high reflectivity materials, but also solves the problem that the blue laser output energy is low and the material and the molten pool cannot be melted well. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments are briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without creative work.

[0032] Figure 1A schematic diagram of the structure of a laser additive manufacturing system provided by an embodiment of the present invention;

[0033] Figure 2 Laser energy distribution: (a) multiple small-sized blue lasers after compounding; (b) large-sized red laser;

[0034] Figure 3 This is the blue light / infrared laser pure copper additive manufacturing of Example 1: (a) surface after laser additive manufacturing; (b) cross section after laser additive manufacturing;

[0035] Figure 4 This is Example 2 blue light / infrared laser additive manufacturing of 7075 aluminum alloy: (a) surface after laser additive manufacturing; (b) cross section after laser additive manufacturing;

[0036] Figure 5 The pure copper laser additive layer processed in Example 3;

[0037] Figure 6 The laser additive layer of 7075 aluminum alloy processed in Example 4;

[0038] Figure 7 For comparative example 1, infrared laser is used to add nickel-based alloy coating on the surface of pure copper substrate;

[0039] Figure 8 For comparative example 2, blue light laser additive manufacturing of 7075 aluminum alloy coating;

[0040] Fig. 9 This is the laser additive layer of 7075 aluminum alloy processed in Comparative Example 3;

[0041] Fig.10 This is the pure copper laser additive layer after processing in comparative example 4.

[0042] Description of the main component symbols: 001-infrared laser generator; 002-optical fiber; 0031-infrared light collimating lens; 0032-blue light collimating lens; 004-dichroic mirror; 005-blue light laser generator; 006-focusing lens. DETAILED DESCRIPTION

[0043] In order to make the purpose, technical scheme and advantages of the embodiments of the present invention clearer, the technical scheme in the embodiments of the present invention will be described clearly and completely below. If the specific conditions are not specified in the embodiments, they are carried out according to conventional conditions or conditions recommended by the manufacturer. If the manufacturer of the reagents or instruments used is not specified, they are all conventional products that can be purchased commercially.

[0044] Please refer to Figure 1The embodiment of the present invention provides a system for laser additive manufacturing, which is used to form a red and blue laser composite processing optical path, including an infrared laser generator 001, an infrared light collimating lens 0031, a blue light laser generator 005, a blue light collimating lens 0032, a dichroic mirror 004 and a focusing lens 006, which couples infrared lasers and blue light lasers of different wavelengths, but only for energy recombination at the terminal output part.

[0045] Specifically, the infrared laser generator 001, the infrared light collimating lens 0031, the dichroic mirror 004 and the focusing lens 006 are optically connected in sequence through the optical fiber 002, and the blue light laser generator 005, the blue light collimating lens 0032, the dichroic mirror 004 and the focusing lens 006 are optically connected in sequence through the optical fiber. The dichroic mirror 004 is coated with an infrared light-transmitting film layer on the side facing the infrared laser generator 001 to allow the infrared laser to pass through; and is coated with a blue light total reflection film on the side facing the blue light laser generator 005 to allow the blue light laser to reflect and couple with the infrared laser. For energy recombination at the terminal output part, the overall optical path system is simple, easy to implement, low in cost, and widely applicable, and can be well promoted in laser additive manufacturing systems such as powder feeding and powder spreading.

[0046] Furthermore, the optical path output part of the focusing lens 006 is used for an external galvanometer system or a cladding gun head. For a spreading additive system (SLM), an external galvanometer system is selected, while for a powder feeding additive system (LSF), an external cladding gun head is selected. The other parts are common supporting systems for laser additive manufacturing systems.

[0047] In some embodiments, the dichroic mirror 004 is tilted, and the angle between the dichroic mirror 004 and the horizontal plane is 30-45 degrees; the infrared laser generator 001 is located above the dichroic mirror 004, and the blue laser generator 005 is located on one side of the dichroic mirror 004. The alignment of the infrared laser generator 001 and the dichroic mirror 004, and the alignment of the blue laser generator 005 and the dichroic mirror 004 are both conventional methods, and the angle between the dichroic mirror 004 and the horizontal plane can be controlled to be 30-45 degrees. Specifically, the angle between the dichroic mirror 004 and the horizontal plane can be 30 degrees, 35 degrees, 40 degrees, 45 degrees, etc.

[0048] In some embodiments, the blue laser generator 005 is a low-power blue laser with four gallium nitride as pump sources. The blue laser generator 005 and the focusing lens 006 are configured to excite a Gaussian beam (TEM) from the blue laser generator 005. 00), and the two beams overlap at the half-peak height of the Gaussian beam, so that the four blue laser beams present an energy density distribution similar to that of a flat-top laser after being combined by the focusing lens 006, ensuring that they melt high-reflectivity materials with a higher energy density while reducing the dilution rate and keyhole effect brought by the Gaussian beam, and reducing the possibility of defects such as holes and cracks.

[0049] In some embodiments, the following control means can be used to make the two light beams overlap at the half-peak height of the Gaussian beam: the output multiple blue parallel laser beams converge at a focusing lens that is 10 to 45 degrees to the incident axis, and the convergence result is that 1 / 3 to 2 / 3 of the beam diameter (i.e., the half-peak height of the width of a single beam of light) will undergo energy superposition, so that the incident central axis converges into a nearly circular or rectangular spot that is 1 to 1.5 times the diameter of the original single blue light beam, and the converged blue light beam falls completely inside the infrared laser.

[0050] It should be noted that the 4-beam pulsed blue laser compound method proposed in the embodiment of the present invention not only does not require complicated coupling operations in the optical path system, but also obtains a nearly flat-top laser with large processing size, high energy density and uniform distribution in the formable area. It ensures that the high-reflectivity powder material to be processed can fully absorb the blue laser energy, causing it to melt quickly, while reducing energy loss and alleviating the damage of the blue laser to the optical fiber.

[0051] Furthermore, the infrared laser generator 001 can be, but is not limited to, a YAG fiber laser to improve its transmission efficiency and beam quality in the optical fiber. The beam energy is a Gaussian beam (TEM 00 ) to reduce manufacturing costs.

[0052] In some embodiments, optical fiber 002 can be but is not limited to a double-clad active optical fiber. The use of double-clad active optical fiber is beneficial to reducing the energy loss of blue light laser during transmission. On the other hand, the good thermal conductivity system of the double-clad optical fiber improves its heat dissipation efficiency and reduces the problem of optical fiber burning caused by excessive laser energy.

[0053] In some embodiments, a control system is also included, which is connected to the infrared laser generator 001 and the blue laser generator 005, and controls the operation of the infrared laser generator 001 and the blue laser generator 005 through an external control system.

[0054] An embodiment of the present invention provides an additive manufacturing method, which uses the above-mentioned laser additive manufacturing system to perform additive manufacturing, and improves the red and blue laser composite processing optical path system to ultimately achieve improvements in multi-mode laser energy distribution, laser processing efficiency, and part molding quality.

[0055] Specifically, additive manufacturing methods include:

[0056] S1. Pretreatment of powder to be processed

[0057] The powder to be processed is placed in a vacuum drying oven for drying to remove impurities in the powder to meet the process requirements.

[0058] In some embodiments, the powder to be processed is selected from at least one of copper and aluminum, and can be any one or more of them, suitable for the above-mentioned high reflectivity material, and the powder purity is at least 99.0wt.%.

[0059] Furthermore, the powder to be processed is spherical particles. When used in a powder-spreading additive device, the particle size of the powder to be processed is 15-72μm (15μm, 20μm, 40μm, 60μm, 72μm, etc.); when used in a powder-feeding additive device, the particle size of the powder to be processed is 90-150μm (90μm, 120μm, 150μm, etc.).

[0060] In some embodiments, vacuum drying is used for drying, and the drying temperature is controlled to be 120-200°C, and the vacuum degree is -0.080 to -0.1 MPa. Specifically, the drying temperature can be 120°C, 150°C, 170°C, 200°C, etc., and the vacuum degree is -0.080 MPa, -0.090 MPa, -0.1 MPa, etc. The drying time is not limited, and is generally selected to be 0.5-3 hours according to the selected powder.

[0061] S2. Generate part scanning path

[0062] A 3D model is created using 3D modeling software according to the target part, and the virtual model is imported into the control system of additive manufacturing to generate a scanning path for the part. Specifically, the scanning path is manufactured by converting the information in the 3D model into multiple slices, and each slice is defined as a cross-sectional layer of the part using the above method.

[0063] In some embodiments, the 3D modeling software is selected from at least one of UG, Solidworks and CATIA, and may be any one of the above professional modeling software.

[0064] S3, Forming Manufacturing

[0065] Pour the powder to be processed into the powder storage bin and wait for the additive manufacturing of the high-energy laser beam. Under the protection of inert gas, use the laser additive manufacturing system to form the desired parts with high-reflectivity metal powder. The specific forming principle can refer to the existing technology.

[0066] In some embodiments, the powder storage bin is filled with inert gas for protection, and the high-purity inert gas may be but is not limited to nitrogen, argon, etc., with a purity of 99.999 vol.%. The inert gas used in the forming process may be but is not limited to nitrogen, argon, etc., with a purity of 99.999 vol.%.

[0067] It should be noted that the parts are processed by laser additive manufacturing technology. Since the naming methods of powder-laying and powder-feeding laser additive manufacturing systems are different at home and abroad, the optical path system and manufacturing method of the embodiment of the present invention can be used in the following laser additive manufacturing processes. The powder-laying laser additive manufacturing method is often named selective laser melting (Selective laser melting, SLM), selective laser sintering (Selective laser sintering, SLS), direct metal laser sintering forming technology (Direct Metal Laser-Sintering, DMLS), laser powder bed fusion (Laser Powder Bed Fusion, LPBF), etc.; the powder-feeding laser additive manufacturing method is often named laser metal cladding deposition technology (LMD, Laser Metal Deposition), laser near-net forming technology (LENS, Laser Engineered Net Shaping), laser solid forming technology (LSF, Laser Solid Forming), etc.

[0068] The inventors have optimized the parameters of the infrared laser generator 001 and the blue laser generator 005:

[0069] In some embodiments, the spot size of the infrared laser generator 001 is 1.2 to 2 times (such as 1.2 times, 1.5 times, 1.8 times, 2.0 times, etc.) the size of the four blue laser beams after combining, to ensure that the focus of the blue laser falls completely in the infrared laser, so that the formed molten pool can maintain a stable shape.

[0070] In order to ensure the full melting and high-quality forming of high-reflectivity materials, the infrared laser generator 001 will maintain a continuous light-emitting state during the laser processing process, and the blue-light laser generator 005 can selectively have 2 beams or 4 beams for compounding. In order to reduce energy consumption and improve the quality and life of the blue-light laser generator, the blue-light laser generator 005 is preferably a pulsed laser with a low off / on frequency. According to the scanning speed and the single-pass forming length, the off / on frequency is preferably 1-10HZ, that is, blue light will be emitted before each processing of unmelted materials to ensure that the high-reflectivity materials can fully absorb the blue light and melt completely. In the blue light off process, the high-energy infrared laser expands and maintains the shape and depth of the molten pool, ensuring that it can achieve effective melting and rapid forming while reducing the high energy consumption caused by the continuous output of blue light.

[0071] In some embodiments, when the laser additive manufacturing system is used in a powder feeding additive device, the power of the infrared laser generator 001 is 3000-6000W (such as 3000W, 4000W, 5000W, 6000W, etc.), and the power of the blue light laser generator 005 is 300-1000W (such as 300W, 500W, 700W, 1000W, etc.); the power of the infrared laser generator 001 is relatively high to ensure that there is enough energy to fully melt the high reflectivity material; the blue light laser generator 005 is low power to ensure that there is enough energy to fully melt the high reflectivity material without causing the size of the blue light laser to be too large due to the required energy density being too high. The laser spot diameter of the blue laser generator 005 is 1-2mm (such as 1.0mm, 1.5mm, 2.0mm, etc.), so that the blue laser generator 005 has a good beam quality and focal spot at the set power, to prevent the blue light from being unable to fully melt the high reflectivity material due to energy loss during the optical fiber propagation process. The spot size of the infrared laser generator 001 is 1.2 to 2 times the size of the four blue laser beams after the beam is combined, and is adjusted according to the laser spot diameter of the blue laser generator 005.

[0072] In another embodiment, when the laser additive manufacturing system is used in a powder-spreading additive device, the power of the infrared laser generator 001 is 500-1000W (such as 500W, 700W, 1000W, etc.), the power of the blue laser generator 005 is 50-100W (such as 50W, 80W, 100W, etc.), and the laser spot diameter of the blue laser generator 005 is 30-50μm (such as 30μm, 40μm, 50μm, etc.). The power of the generator and the laser spot diameter are matched to ensure good beam quality and focal spot at the set power, so as to prevent the high reflectivity material from being unable to be fully melted due to the energy loss of the blue light in the process of optical fiber propagation.

[0073] It should be added that both powder feeding and powder spreading additive equipment use high-power and large-size infrared lasers to expand the molten pool and stabilize the molten pool morphology after the blue laser fully melts the high-reflectivity material. This not only solves the extremely high energy density required for processing high-reflectivity materials with a pure infrared laser, but also solves the dilemma of low output energy of the blue laser, which cannot melt the material and the molten pool well, and expands the scope of use of laser additive manufacturing systems.

[0074] The features and performance of the present invention are further described in detail below in conjunction with the embodiments.

[0075] Example 1

[0076] This embodiment provides an additive manufacturing method using Figure 1 Laser additive manufacturing systems in additive manufacturing are used for additive manufacturing as follows:

[0077] like Figure 1 As shown, a laser additive manufacturing system provided by this embodiment includes an infrared laser generator 001, an infrared light collimating lens 0031, a blue light laser generator 005, a blue light collimating lens 0032, a dichroic mirror 004, and a focusing lens 006. The infrared laser generator 001, the infrared light collimating lens 0031, the dichroic mirror 004, and the focusing lens 006 are optically connected in sequence through an optical fiber 002 (double-clad active optical fiber), and the blue light laser generator 005, the blue light collimating lens 0032, the dichroic mirror 004, and the focusing lens 006 are optically connected in sequence through an optical fiber (double-clad active optical fiber).

[0078] The angle between the dichroic mirror 004 and the horizontal plane is 40°. The blue laser generator 005 is a low-power blue laser with four gallium nitride as pump sources. The blue laser generator 005 and the focusing lens 006 are configured to excite a Gaussian beam (TEM) from the blue laser generator 005. 00 ) and the two beams overlap at the half-peak height of the Gaussian beam. The dichroic mirror 004 is coated with an infrared light-transmitting film on the side facing the infrared laser generator 001, and is coated with a blue light total reflection film on the side facing the blue laser generator 005, ensuring that both the infrared laser and the blue laser can be output by the cladding gun head after effective focusing.

[0079] The infrared laser generator 001 uses a rated power of 6000W, a wavelength of 1064nm, and an energy form of Gaussian beam (TEM 00 ), the energy density distribution is as follows Figure 2 As shown in (a), an infrared laser generator with a focusing diameter of 4 mm.

[0080] The blue laser generator 005 uses 4 laser beams with a rated power of 1000W, of which the single focal diameter is 1.8mm and the energy form is Gaussian beam (TEM 00 ) of the blue laser generator, the spot diameter of the four laser beams after beam combination is about 2.3mm, the wavelength is 450nm, and the energy density distribution is as follows Figure 2 As shown in (b).

[0081] The infrared laser generator 001 is connected to an Nd:YAG (neodymium-doped yttrium aluminum garnet laser) pump source, and the blue laser generator 005 is connected to a GaN (gallium nitride) pump source. Then, the infrared laser generator 001 and the blue laser generator 005 are connected to an external motor control system, and the final optical path output part, i.e., the focusing lens 006, is connected to the cladding gun head. The operation steps not mentioned in this embodiment can refer to the contents of the above description.

[0082] Table 1 shows the absorption of light of different wavelengths by different types of high reflectivity powder materials.

[0083] Table 1. Absorption of various high reflectivity materials under different wavelengths

[0084]

[0085] It can be seen that the absorption rate of the powder material to the infrared / blue light laser composite is the highest, which exceeds the absorption of the powder material to a single band of light. Afterwards, the infrared / blue light laser composite processing system proposed in this embodiment is used to perform additive manufacturing of pure copper parts.

[0086] The pure copper additive manufacturing process performed on the surface of the copper substrate in Example 1 is as follows: the single blue laser power used is 650W, the on / off light frequency is 5HZ, the red laser power is 2000W, the scanning speed is 10mm / s, and the powder feeding speed is 1.5g / min.

[0087] Figure 3 The processed laser additive layer is shown, with good surface quality and only a small number of holes in the cross section, indicating that the red and blue light composite processing proposed in this embodiment has good application prospects.

[0088] Example 2

[0089] The same optical path system as in Example 1 is used, except that the following parameters are controlled:

[0090] The additive manufacturing process of 7075 aluminum alloy on the surface of the aluminum alloy substrate is as follows: the single blue laser power used is 850W, the on / off frequency of the light is 4HZ, the red laser power is 1500W, the scanning speed is 10mm / s, and the powder feeding speed is 1.5g / min.

[0091] Figure 4 The processed 7075 aluminum alloy laser additive layer is displayed. The surface quality of the single-pass deposited layer is good, with only a small number of holes in the cross section. Under the influence of the infrared laser Gaussian beam, the deposited layer is deeper, ensuring good bonding with the substrate interface, and solving the current problems of difficult welding, poor fusion, and difficult additive manufacturing of aluminum alloys.

[0092] Example 3

[0093] The same optical path system as in Example 1 is used, except that the following parameters are controlled:

[0094] The pure copper additive manufacturing process on the surface of the copper substrate is as follows: the power of a single blue laser is 700W, the on / off frequency of the light is 4HZ, the spot diameter after the four beams are focused is 2.88mm, the power of the red laser is 1200W, the scanning speed is 8mm / s, and the powder feeding speed is 2.5g / min.

[0095] Figure 5 The processed pure copper laser additive layer is shown. The surface quality after multi-layer cladding is good, with no obvious cracks or poor welding.

[0096] Example 4

[0097] The same optical path system as in Example 1 is used, except that the following parameters are controlled:

[0098] The additive manufacturing process of 7075 aluminum alloy on the surface of the aluminum alloy substrate is as follows: the single blue laser power used is 750W, the on / off frequency of the light is 3HZ, the red laser power is 1800W, the scanning speed is 6mm / s, and the powder feeding speed is 2.1g / min.

[0099] Figure 6 The processed 7075 aluminum alloy laser additive layer is displayed. The single-layer deposition thickness can reach 0.3 to 0.5 mm. There are no cracks or holes on the macroscopic surface, and the molding quality is good.

[0100] Comparative Example 1

[0101] The only difference from Example 1 is that the blue laser generator 005 is turned off and only the infrared laser generator 001 is used. The specific parameters used are: infrared laser power 2000W, scanning speed 5mm / s, and powder feeding speed 1.5g / min.

[0102] Figure 7 The laser additive manufacturing Ni625 / Ni60A layer on the pure copper surface is shown. Large cracks and holes appear on the entire coating, and some cracks even extend from the top of the coating to the substrate, indicating that it is not appropriate to use only infrared laser for laser additive manufacturing on the pure copper substrate surface.

[0103] Comparative Example 2

[0104] The only difference from Example 2 is that the infrared laser generator 001 is turned off, and only the blue light laser generator 005 is used to perform laser additive manufacturing of 7075 aluminum alloy coating. The specific parameters used are: blue light laser power 750W, scanning speed 20mm / s, and powder feeding speed 1.5g / min.

[0105] Figure 8 The surface quality of 7075 aluminum alloy and internal defects of coating after using only blue light additive manufacturing were demonstrated. Although the visual inspection results of the surface quality of the aluminum alloy coating after processing were acceptable, metallographic inspection revealed that the coating was full of holes, indicating that it is inappropriate to use only blue light laser for laser additive manufacturing on the surface of aluminum alloy substrate.

[0106] Comparative Example 3

[0107] The only difference from Example 1 is that the additive manufacturing process of 7075 aluminum alloy on the surface of the aluminum alloy substrate is: the single blue light laser power used is 350W, the on / off light frequency is 4HZ, the red light laser power is 1000W, the scanning speed is 10mm / s, and the powder feeding speed is 2.5g / min.

[0108] Fig. 9 The processed 7075 aluminum alloy laser additive layer is shown. Due to the low input energy and fast scanning speed, obvious cracking occurred after the deposition of a single layer of 7075 aluminum alloy.

[0109] Comparative Example 4

[0110] The only difference from Example 1 is that the pure copper alloy additive manufacturing process performed on the surface of the copper alloy substrate is: the single blue light laser power used is 11000W, the on / off light frequency is 4HZ, the red light laser power is 5100W, the scanning speed is 6mm / s, and the powder feeding speed is 2.5g / min.

[0111] Fig.10 The processed pure copper laser additive layer is shown. Due to the high input energy and low scanning speed, a large number of pores appeared after the deposition of the pure copper layer, indicating that reasonable process selection based on the material is very important for the additive manufacturing results.

[0112] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A laser additive manufacturing system for forming a red and blue laser composite processing optical path, characterized in that: It comprises an infrared laser generator, an infrared light collimating lens, a blue light laser generator, a blue light collimating lens, a dichroic mirror and a focusing lens, wherein the infrared laser generator, the infrared light collimating lens, the dichroic mirror and the focusing lens are optically connected in sequence through an optical fiber, and the blue light laser generator, the blue light collimating lens, the dichroic mirror and the focusing lens are optically connected in sequence through an optical fiber; The side of the dichroic mirror facing the infrared laser generator is coated with an infrared light-transmitting film layer, and the side facing the blue light laser generator is coated with a blue light total reflection film; The optical path output portion of the focusing lens is used for connecting to an external galvanometer system or a cladding gun head; The dichroic mirror is tilted, and the angle between the dichroic mirror and the horizontal plane is 30-45 degrees; The infrared laser generator is located above the dichroic mirror, and the blue laser generator is located on one side of the dichroic mirror; The blue laser generator is a low-power blue laser with four gallium nitride as pump sources, and the blue laser generator and the focusing lens are configured to excite parallel light beams with energy of Gaussian beams from the blue laser generator, and the two light beams overlap at the half-peak height of the Gaussian beam; The output multiple blue parallel laser beams converge at a focusing lens at an angle of 10 to 45 degrees to the incident axis. As a result, 1 / 3 to 2 / 3 of the beam diameter will undergo energy superposition, so that the incident center axis converges into a nearly circular or rectangular spot with a diameter 1 to 1.5 times that of the original single blue light beam, and the converged blue light beam falls completely inside the infrared laser.

2. The laser additive manufacturing system according to claim 1, characterized in that: The infrared laser generator is a YAG fiber laser.

3. The laser additive manufacturing system according to claim 2, characterized in that: The optical fiber is a double-clad active optical fiber.

4. The laser additive manufacturing system according to claim 2, characterized in that: It also includes a control system, which is connected to the infrared laser generator and the blue laser generator.

5. An additive manufacturing method, characterized in that: Additive manufacturing is performed using the laser additive manufacturing system according to any one of claims 1 to 4.

6. The additive manufacturing method according to claim 5, characterized in that: The spot size of the infrared laser generator is 1.2 to 2 times the size of the four blue laser beams after the beam is combined. The infrared laser generator maintains a continuous light emitting state during the laser processing process, and the on / off frequency of the blue laser generator is 1-10HZ.

7. The additive manufacturing method according to claim 6, characterized in that: When the laser additive manufacturing system is used in a powder feeding additive device, the power of the infrared laser generator is 3000-6000W, the power of the blue laser generator is 300-1000W; and the laser spot diameter of the blue laser generator is 1-2mm.

8. The additive manufacturing method according to claim 7, characterized in that: When the laser additive manufacturing system is used in a powder-spreading additive device, the power of the infrared laser generator is 500-1000W, the power of the blue laser generator is 50-100W, and the laser spot diameter of the blue laser generator is 30-50μm.

9. The additive manufacturing method according to claim 7, characterized in that: include: Use 3D modeling software to build a 3D model based on the target part, and import the virtual model into the additive manufacturing control system to generate the part scanning path; Pour the powder to be processed into the powder storage bin and wait for the high-energy laser beam to form the additive manufacturing; Under the protection of an inert gas, the laser additive manufacturing system is used to form and manufacture desired parts from high-reflectivity metal powder.

10. The additive manufacturing method according to claim 9, characterized in that: The three-dimensional modeling software is selected from at least one of UG, Solidworks and CATIA.

11. The additive manufacturing method according to claim 9, characterized in that: The powder to be processed is selected from at least one of copper and aluminum.

12. The additive manufacturing method according to claim 11, characterized in that: The powder to be processed is spherical particles. When used in a powder-spreading additive device, the particle size of the powder to be processed is 15-72µm; when used in a powder-feeding additive device, the particle size of the powder to be processed is 90-150µm.

13. The additive manufacturing method according to claim 9, characterized in that: The powder to be processed is dried before being poured into the powder storage silo.

14. The additive manufacturing method according to claim 13, characterized in that: The drying is carried out by vacuum drying, the drying temperature is controlled at 120-200°C, and the vacuum degree is -0.080~-0.1MPa.

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