Additive manufacturing method based on micro selective laser melting technology

Abstract

The invention relates to a micro-selective laser melting technology additive manufacturing method, which comprises the following steps of: adopting superfine metal powder with a light spot size of less than 30 microns, a metal powder layer thickness of less than 10 microns and a D90 particle size of less than 30 microns, and combining scanning laser power, scanning rate, linear energy density and energy density control in a specific range; by means of the method, the complex-structure metal part with extremely high resolution and surface smoothness can be printed, a high-density component internal structure can be obtained even under the condition of low energy density or power, and an optical system is effectively protected. In addition, the printed component shows a defect-free microstructure and has excellent electrical property, thermal property and mechanical property, and particularly, the mechanical property better than that of a traditional manufacturing material is provided through ultra-fine grains and high dislocation density. An infrared laser can be used, and the cost is low.

Description

An additive manufacturing method based on micro-selective laser melting technology Technical Field

[0001] This invention relates to selective laser melting technology, and in particular to an additive manufacturing method based on micro-selective laser melting technology. Background Technology

[0002] Selective laser melting (SLM) is an emerging, high-efficiency additive manufacturing technology for producing metal parts. Its powder bed support allows it to fabricate complex geometries and high-resolution parts. Currently, common SLM equipment on the market typically has a resolution of 200-500 μm and a surface roughness of R = 10-30 μm. Resolution and roughness determine the equipment's manufacturing precision, which in turn limits further refinement of metal parts. The manufacturing precision of SLM technology mainly depends on the spot size, layer thickness, powder particle size, and corresponding process parameters of the manufacturing equipment. Traditional SLM equipment generally has a spot size of 50-100 μm, a powder layer thickness of 30-100 μm, a powder particle size of 15-53 μm, and process parameters involving volume energy density, etc. These equipment and process parameters are interconnected within the system. Therefore, achieving a high-precision printing process and microscale metal part fabrication requires a complete set of system parameters, including model generation, model slicing, path planning, parameter settings (laser power, scanning speed, laser spacing), and printing monitoring.

[0003] Furthermore, materials with high infrared reflectivity, such as copper, silver, gold, and aluminum, are crucial metals in industry. However, conventional selective laser melting (SLM) printing technology typically uses infrared wavelengths. This leads to insufficient energy input, making it difficult to process high-density, highly reflective material components, significantly limiting the development of highly reflective materials in 3D printing. Existing solutions include using ultra-high-power infrared lasers to process highly reflective materials, but the reflected laser light can damage laser optics components. Additionally, because highly reflective materials generally have high thermal conductivity, the large molten pool generated by ultra-high power input can transfer heat to the surrounding material, resulting in low-density printing. Another solution is to use short-wavelength lasers, which increase the energy absorption rate of highly reflective materials. However, these lasers are expensive, and the laser spot size cannot be reduced below 100μm, limiting printing accuracy. Therefore, high-precision selective laser melting equipment, with its high energy density process parameters, holds the potential for producing highly reflective materials.

[0004] It should be noted that the information disclosed in the background section above is only for understanding the background of this application, and therefore may include information that does not constitute prior art known to those skilled in the art.

[0005] Summary of the Invention

[0006] The main objective of this invention is to overcome the shortcomings of the aforementioned background technology and provide an additive manufacturing method based on micro-selective laser melting technology.

[0007] To achieve the above objectives, the present invention adopts the following technical solution:

[0008] An additive manufacturing method based on micro-selective laser melting technology includes:

[0009] During printing, the spot size used is less than 30 μm, the layer thickness of the metal powder is less than 10 μm, the D90 particle size of the metal powder is less than 30 μm, the power range of the scanning laser is 20-300W, the scanning rate is 100-3000 mm / s, the linear energy density η is 15 J / mm to 3000 J / mm, and the volume energy density λ is 15 J / mm. 3 Up to 30000J / mm 3 The scanning interval is 10-100μm.

[0010] Furthermore:

[0011] The metal powder has a particle size distribution of D10 below 7 μm, D50 below 14 μm, and D90 below 30 μm.

[0012] The scanning laser has a power range of 50-250W, a scanning rate of 200-1500mm / s, a linear energy density η of 33J / mm to 1250J / mm, and a volume energy density λ of 41J / mm. 3 Up to 4167J / mm 3 The scanning interval is 40-60μm.

[0013] During printing, the size of the incident laser spot is first enlarged by a collimating and beam expanding assembly, and then focused by an f-theta lens to reduce the laser spot to below 30μm.

[0014] The size of the incident laser spot is increased to more than 16.9 mm by using the collimation and beam expanding assembly.

[0015] During printing, high-precision z-axis movement within ±5μm is achieved by using lead screw drive and sensor grating ruler positioning.

[0016] The powder is loaded into the lower powder supply cylinder. Before each layer is printed, the powder is supplied upwards and spread evenly on the top of the forming cylinder using a doctor blade that is horizontal and parallel to the powder bed.

[0017] The scraper blades used are single-bladed or double-bladed bladeless scrapers with spacing, or double-bladed bladed scrapers with spacing.

[0018] The blades used are V-shaped, trapezoidal, or semi-circular.

[0019] The scraper blades used are made of ceramic, metal, or rubber.

[0020] The laser is an infrared laser.

[0021] The present invention has the following beneficial effects:

[0022] Compared with the prior art, the present invention has the following advantages:

[0023] 1. High precision

[0024] The high-precision SLM equipment proposed in this invention can achieve printing resolution and surface roughness far exceeding those of existing equipment through the synergistic effect of a specific range of fine spot size, fine powder, thin layer thickness and laser printing process parameters, thereby enabling the printing of highly complex structures.

[0025] 2. High density

[0026] The high-precision SLM equipment proposed in this invention achieves high density within the component by synergistic effects of a specific range of fine laser spot, fine powder, thin layer thickness, and laser printing process parameters. Due to the small laser spot, the laser energy is more concentrated, allowing the material to form a smaller molten pool with lower overall heat dissipation. This enables high density to be achieved within the component at low energy density or low power without the need for ultra-high power laser parameters, thus protecting the laser optical system components.

[0027] 3. High performance

[0028] The products printed by this invention have a high-density internal structure, and the formed components are virtually defect-free, resulting in a near-defect-free microstructure and thus excellent electrical / thermal properties and other properties. Due to the formation of ultrafine grains and high dislocation density within the material, its mechanical properties are superior to those of conventionally manufactured materials.

[0029] 4. Low cost

[0030] Compared to short-wavelength laser printing equipment, this invention can achieve the aforementioned performance using infrared lasers, which are more cost-effective and technologically mature. While short-wavelength laser equipment has application limitations, infrared wavelengths are suitable for most metallic materials. This invention employs specific ranges of fine spot size, thin layer thickness, fine powder, and laser process parameters, making it applicable to both highly reflective and conventional materials, and it utilizes infrared lasers, significantly reducing equipment costs.

[0031] Other beneficial effects of the embodiments of the present invention will be further described below. Attached Figure Description

[0032] Figure 1 is a schematic diagram of the laser optical path according to an embodiment of the present invention;

[0033] Figures 2 to 4 are schematic diagrams of the three types of blades of the scraper strip according to an embodiment of the present invention;

[0034] Figure 5 is a schematic diagram of three shapes of the blade of the scraper strip according to an embodiment of the present invention;

[0035] Figure 6 is a micrograph of the component after laser processing according to an embodiment of the present invention.

[0036] Figure 7 is a schematic diagram of the printed components according to an embodiment of the present invention. Detailed Implementation

[0037] The embodiments of the present invention will be described in detail below. It should be emphasized that the following description is merely exemplary and not intended to limit the scope and application of the present invention.

[0038] It should be noted that when a component is referred to as "fixed to" or "set on" another component, it can be directly on or indirectly on that other component. When a component is referred to as "connected to" another component, it can be directly connected to or indirectly connected to that other component. Furthermore, a connection can be used for fixing, coupling, or communication.

[0039] It should be understood that the terms "length", "width", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", and "outer" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing the embodiments of the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the present invention.

[0040] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of embodiments of the present invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0041] This invention provides an additive manufacturing method based on micro-selective laser melting technology, comprising the following steps: during printing, the spot size used is less than 30 μm, the layer thickness of the metal powder is less than 10 μm, the D90 particle size of the metal powder is less than 30 μm, the power range of the scanning laser is 20-300W, the scanning rate is 100-3000 mm / s, the linear energy density η is 15 J / mm to 3000 J / mm, and the volume energy density λ is 15 J / mm. 3 Up to 30000J / mm 3 The scanning interval is 10-100μm.

[0042] In a preferred embodiment, the scanning laser has a power range of 50-250W, a scanning rate of 200-1500mm / s, a linear energy density η of 33J / mm to 1250J / mm, and a volume energy density λ of 41J / mm. 3 Up to 4167J / mm 3 The scanning interval is 40-60μm.

[0043] The improved selective laser melting method of this invention uses a spot diameter of less than 30 μm, a powder layer thickness of less than 10 μm, and a powder diameter of less than 30 μm. Combined with the above-mentioned laser printing process parameters, including multiple optimization designs such as using volume energy density to optimize the process window, it can prepare high-precision metal material structures and can prepare high-density, highly reflective metal components.

[0044] The microselective laser melting additive manufacturing method proposed in this invention achieves significant technical advantages by employing a spot size of less than 30 μm, a metal powder layer thickness of less than 10 μm, and ultrafine metal powder with a D90 particle size of less than 30 μm, combined with specific ranges of scanning laser power, scanning rate, and linear and volume energy density control. This method can print complex metal parts with extremely high resolution and smooth surfaces, while forming smaller molten pools and lower heat dissipation. This allows for the acquisition of highly dense internal structures even under lower energy density or power conditions, while also effectively protecting the optical system. Furthermore, the printed components exhibit defect-free microstructures and possess excellent electrical, thermal, and mechanical properties. In particular, the ultrafine grains and high dislocation density provide superior mechanical properties compared to traditional manufacturing materials. In terms of cost-effectiveness, this invention can use mature infrared lasers, significantly reducing costs compared to short-wavelength laser printing equipment, while maintaining applicability to high reflectivity and conventional materials. This makes the technology widely applicable and competitive in the additive manufacturing field.

[0045] In some preferred embodiments, the present invention also proposes an optimized scraper structure design, particularly a double-edged, bladeless, spaced scraper (see Figure 3) or a double-edged, bladed, spaced scraper (see Figure 4), so that fine powder can be evenly spread on the powder bed.

[0046] The following describes specific embodiments of the present invention.

[0047] Upgrading of high-precision selective laser melting equipment

[0048] Optical system: The laser spot size is reduced to 20-30 μm. The laser is a Gaussian beam, and its spot size can be obtained by the following formula:

[0049] Where D is the spot size, M² is determined by the product of the beam parameters of the actual beam and the corresponding basic Gaussian beam, and the divergence of the laser (1.05 in this case), λ is the laser wavelength (1064-1080 nm), f is the focal length of the f-theta lens (255 mm), and d is the incident spot size (16.9 mm). A schematic diagram of the optical path of the incident laser through the f-theta lens is shown in Figure 1. As can be seen from the equation, the larger the incident spot size d, the smaller the beam size D. This invention proposes using an improved collimating and beam expanding assembly to increase the incident light to 16.9 mm+, thereby achieving spot refinement.

[0050] The powder supply and molding system was modified by reducing the printing layer thickness to 10μm to match the fine light spot. High-precision z-axis movement (±5μm) was achieved by using lead screw drive and sensor grating ruler positioning. This resulted in higher process energy density, which is beneficial for processing highly reflective materials, higher model slicing accuracy, and easier reproduction of complex part designs.

[0051] Powder spreading system: The powder is loaded into the lower powder supply cylinder. A certain amount of powder is supplied upwards before each layer is printed. The supplied powder is evenly spread above the forming cylinder using a doctor blade that is horizontal and parallel to the powder bed. The doctor blade is made of ceramic, metal, or rubber, and its shape is a single-edged (Figure 2), a double-edged blade without a blade spacing (Figure 3), or a double-edged blade with a blade spacing (Figure 4). The blade can be V-shaped, trapezoidal, or semi-circular (Figure 5). The doctor blade drive mechanism can move at a constant speed of 5mm / s-500mm / s.

[0052] Preparation of micro-metal powder: Using a 25μm sieve, spherical metal powder is sieved to separate particles smaller than 30μm. Then, using a 5μm sieve, metal powder smaller than 5μm is separated to obtain spherical metal powder with a particle size distribution of 5-25μm. The D10 (the 10% cumulative percentage of powder diameter sorted by diameter) is below 7μm, the D50 is below 14μm, and the D90 is below 30μm. After sieving, the powder is placed in a vacuum drying oven and dried at 120℃ for 12 hours.

[0053] Preparation before 3D printing components

[0054] Generation of scanning model: A geometric model of the component to be formed is created on the computer. The geometric model is discretized into several two-dimensional slices using slicing software. The layer thickness is set to 10μm. A scanning model is generated based on the geometric contour of each two-dimensional slice. The scanning laser path is set to 40-60μm. Preparation of forming substrate: The material of the forming substrate should be consistent with the composition of the printing material and should be treated with 100-mesh sandblasting.

[0055] 3D printed material components

[0056] Based on the scanning model, a modified high-precision selective laser melting device is used to laminate material powder to manufacture shaped components. Specifically, the process includes the following steps:

[0057] Control the oxygen content in the molding cavity to be below 500 ppm, and turn on the substrate preheating to 200°C;

[0058] The powder feeding device is controlled to supply highly reactive material powder to the forming cylinder, and the automatic powder spreading device spreads the aforementioned highly reactive material powder evenly on the forming substrate.

[0059] The laser emitted by the laser printing molding equipment scans the highly reflective material powder on the molding substrate according to the scanning model until it is completely melted, forming a single-layer cross-section of the component; the laser line energy density η used is between 33J / mm and 1250J / mm, and the laser line energy density η is the ratio of laser power P to scanning speed V, that is, the power range is 50-250W, and the scanning speed is 200-1500mm / s.

[0060] After each layer is processed, the forming cylinder descends 10μm. Due to the powder bulk density of approximately 60%, there will be some settling on the surface of the component after printing and sintering. The gap between the component and the powder spreading device can reach more than 20μm, so most of the powder can be evenly spread on the component after the previous layer has been printed. According to the scanning path, steps b and c are repeated to melt and stack the 3D printing metal powder layer by layer, finally obtaining the target component. The energy density λ of the laser used is between 41J / mm². 3 Up to 4167J / mm 3 Between these, the laser energy density λ is the ratio of the product of laser power P, scanning speed V, powder layer thickness t, and laser scanning distance, i.e., power range 50-250W, scanning speed 200-1500mm / s, and scanning distance 30-80μm;

[0061] Example 1:

[0062] Pure copper components were prepared using the aforementioned infrared wavelength laser 3D printing technology.

[0063] Step 1: Build a component model on the computer, use slicing software to discretize the geometric model into layers with a thickness of 10μm, generate a scanning model from the two-dimensional geometric contour, and use laser scanning spacing of 50μm.

[0064] Step 2: Prepare pure copper powder, near-spherical powder, D10 = 3.43 μm, D50 = 12.55, D90 = 26.41 μm.

[0065] Step 3: Fix the substrate on the forming cylinder, adjust the substrate level and the height of the powder spreading device to the appropriate position to ensure that the scraper can feed the metal powder into the forming cylinder.

[0066] Step 4: First, turn on the protective gas (argon) to fill the cavity. When the oxygen content inside the cavity reaches a certain value, turn on the fan to circulate the gas inside the cavity and control the oxygen content inside the cavity to be below 500ppm.

[0067] Step 4: Control the powder feeding device to supply pure copper powder to the forming cylinder, and then spread the pure copper powder evenly.

[0068] Step 5: The laser beam enters the forming chamber through the laser emission system and reaches the substrate with a spot diameter of 25 μm. It scans along the previously determined scanning path using a "zigzag" pattern to form a single-layer cross-section of the component. The laser scanning speed is 600 mm / s, the laser air jump speed is 3500 mm / s, and the laser power is 200 W. At this point, the laser linear energy density η is 333 J / mm², and the volume energy density is 667 J / mm². 3 .

[0069] Step 6: After each layer is processed, the forming cylinder descends by 10μm. Based on the scanning path in step 1, steps 5 and 6 are repeated to melt the pure copper powder layer by layer, accumulate and bond it, and finally obtain the target component molded part.

[0070] Step 7: Wire electrical discharge machining separates the component from the substrate to obtain the component.

[0071] Figure 6 shows a microstructure photograph of the component after laser processing in this example. It can be seen that the structure has high density and no defects such as cracks or pores.

[0072] Example 2:

[0073] Multi-scale TPMS structure printing using high-precision selective laser melting

[0074] The SS316L powder, with a particle size range of 5-25 μm, was provided by Beijing AMC Powder Metallurgy Technology Co., Ltd. The oxygen concentration was controlled below 500 ppm by injecting nitrogen as a protective gas. The optimal process parameters for this system were 50 W laser power, 50 μm overlap distance, 10 μm slice thickness, and 1000 mm / s scanning speed, achieving a solid density of 99.7% for the printed cubes. The final printed assembly, after piece-by-piece printing, is shown in Figure 7.

[0075] Compared with the prior art, the embodiments of the present invention have the following advantages:

[0076] 1. High precision

[0077] The high-precision SLM equipment proposed in this invention can achieve printing resolution and surface roughness far exceeding those of existing equipment through the synergistic effect of a specific range of fine spot size, fine powder, thin layer thickness and laser printing process parameters, thereby enabling the printing of highly complex structures.

[0078] 2. High density

[0079] The high-precision SLM equipment proposed in this invention achieves high density within the component by synergistic effects of a specific range of fine laser spot, fine powder, thin layer thickness, and laser printing process parameters. Due to the small laser spot, the laser energy is more concentrated, allowing the material to form a smaller molten pool with lower overall heat dissipation. This enables high density to be achieved within the component at low energy density or low power without the need for ultra-high power laser parameters, thus protecting the laser optical system components.

[0080] 3. High performance

[0081] The products printed by this invention have a high-density internal structure, and the formed components are virtually defect-free, resulting in a near-defect-free microstructure and thus excellent electrical / thermal properties and other properties. Due to the formation of ultrafine grains and high dislocation density within the material, its mechanical properties are superior to those of conventionally manufactured materials.

[0082] 4. Low cost

[0083] Compared to short-wavelength laser printing equipment, this invention can achieve the aforementioned performance using infrared lasers, which are more cost-effective and technologically mature. While short-wavelength laser equipment has application limitations, infrared wavelengths are suitable for most metallic materials. This invention employs specific ranges of fine spot size, thin layer thickness, fine powder, and laser process parameters, making it applicable to both highly reflective and conventional materials, and it utilizes infrared lasers, significantly reducing equipment costs.

[0084] The above description provides a further detailed explanation of the present invention in conjunction with specific / preferred embodiments, and it should not be construed that the specific implementation of the present invention is limited to these descriptions. For those skilled in the art, various substitutions or modifications can be made to these described embodiments without departing from the concept of the present invention, and all such substitutions or modifications should be considered within the scope of protection of the present invention. In the description of this specification, the reference to terms such as "an embodiment," "some embodiments," "preferred embodiment," "example," "specific example," or "some examples," etc., indicates that the specific features, structures, materials, or characteristics described in connection with that embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described can be combined in any suitable manner in one or more embodiments or examples. Without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification and the features of different embodiments or examples. Although the embodiments of the present invention and their advantages have been described in detail, it should be understood that various changes, substitutions, and modifications can be made herein without departing from the scope of protection of the patent application.

Claims

1. An additive manufacturing method based on micro-selective laser melting technology, characterized in that, include: During printing, the spot size used is less than 30 μm, the layer thickness of the metal powder is less than 10 μm, the D90 particle size of the metal powder is less than 30 μm, the power range of the scanning laser is 20-300W, the scanning rate is 100-3000 mm / s, the linear energy density η is 15 J / mm to 3000 J / mm, and the volume energy density λ is 15 J / mm. 3 Up to 30000J / mm 3 The scanning interval is 10-100μm.

2. The method as described in claim 1, characterized in that, The metal powder has a particle size distribution of D10 below 7 μm, D50 below 14 μm, and D90 below 30 μm.

3. The method as described in claim 1, characterized in that, The scanning laser has a power range of 50-250W, a scanning rate of 200-1500mm / s, a linear energy density η of 33J / mm to 1250J / mm, and a volume energy density λ of 41J / mm. 3 Up to 4167J / mm 3 The scanning interval is 40-60μm.

4. The method as described in claim 1, characterized in that, During printing, the size of the incident laser spot is first enlarged by a collimating and beam expanding assembly, and then focused by an f-theta lens to reduce the laser spot to below 30μm.

5. The method as described in claim 4, characterized in that, The size of the incident laser spot is increased to more than 16.9 mm by using the collimation and beam expanding assembly.

6. The method according to any one of claims 1 to 5, characterized in that, During printing, high-precision z-axis movement within ±5μm is achieved by using lead screw drive and sensor grating ruler positioning.

7. The method according to any one of claims 1 to 6, characterized in that, The powder is loaded into the lower powder supply cylinder. Before each layer is printed, the powder is supplied upwards and spread evenly on the top of the forming cylinder using a doctor blade that is horizontal and parallel to the powder bed.

8. The method according to any one of claims 1 to 7, characterized in that, The scraper blades used are single-bladed or double-bladed bladeless scrapers with spacing, or double-bladed bladed scrapers with spacing.

9. The method according to any one of claims 1 to 8, characterized in that, The blades used are V-shaped, trapezoidal, or semi-circular.

10. The method according to any one of claims 1 to 9, characterized in that, The scraper blades used are made of ceramic, metal, or rubber.

11. The method according to any one of claims 1 to 10, characterized in that, The laser is an infrared laser.

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