A method for suppressing sputtering laser selective melting

Abstract

This invention discloses a method for suppressing spatter in laser selective melting, comprising the following steps: Powder material is laid layer by layer from bottom to top according to the layer thickness of the three-dimensional model of the part, and laser scanning and melting are performed; when the thickness of the processed layer is above a preset thickness, the laser scanning and melting process employs a two-stage scanning method: controlling the laser energy input for an initial scan, causing the surface powder material to melt or sinter and form a surface sintered layer; adjusting the laser scanning parameters for a second scan, completely melting the surface sintered layer and the powder material below it; when the thickness of the processed layer is less than the preset thickness, the laser scanning and melting process employs a single-stage scanning method: controlling the laser energy input for scanning, causing the powder material of the processed layer thickness to completely melt. This invention can suppress spatter during the printing process, improve printing efficiency, ensure printing quality, and reduce the impact of spatter particles on unscanned powder.

Description

Technical Field

[0001] This invention relates to the field of additive manufacturing technology, and in particular to a method for suppressing sputtering laser selective melting. Background Technology

[0002] Additive manufacturing (AM), commonly known as 3D printing, differs from traditional machining technologies such as cutting. Additive manufacturing creates parts by layering materials and has broad application prospects in aerospace, automotive, biomedicine, and industrial production.

[0003] Selective Laser Melting (SLM) / Laser Powder Bed Laser Fusion (LPBF) is a commonly used additive manufacturing technology. Its principle is as follows: a 3D CAD model of the part is divided into two-dimensional planes of predetermined thickness. Powder is laid flat on a substrate, and a laser selectively melts the corresponding areas on the powder bed, forming a dense cross-section of the part. After one layer is processed, the forming cylinder is lowered by one layer thickness, and another layer of powder is laid on top and scanned by the laser. This process of laying powder layer by layer and processing the two-dimensional cross-section layer by layer is continued until the 3D part is completed. Since theoretically any complex spatial geometry can be transformed into cross-sectional information that can be scanned layer by layer by the laser after slicing, SLM technology is theoretically almost unrestricted by the complexity of the part, enabling high-precision and rapid processing of complex parts.

[0004] However, during the SLM / LPBF process, the high-energy laser beam scanning the powder heats the powder / molten pool surface above the material's boiling point, leading to intense evaporation. Because the contact area of ​​the accumulated powder particles is limited, their heat dissipation capacity is far lower than that of solid materials. Therefore, heat accumulates more easily when the laser irradiates the powder, resulting in a faster temperature rise. Thus, the thicker the powder layer during printing, the more pronounced the heat accumulation effect of the powder material, and the higher the required laser energy density, leading to more intense material evaporation. Due to the loose accumulation of powder particles, under the combined action of vapor and protective gas, a large amount of powder outside the molten pool, and even molten metal droplets within the molten pool, are blown out of the laser scanning area by the vapor, forming splashes. Figure 1(As shown). Since splatter particles cannot be completely removed by the protective airflow, some inevitably fall into unscanned areas, causing powder contamination. This affects subsequent powder applications, consequently impacting the stability of the SLM process, material loss, post-processing costs, and the performance of printed parts, thus affecting printing efficiency. Simultaneously, splatter particles may fly into the scanning area, blocking the laser beam, reducing local heat input and potentially causing defects in the corresponding area; or they may fall onto the material surface, forming localized protrusions, which may affect subsequent powder spreading, damage the powder spreading blade, or even lead to printing failure. Furthermore, splatter represents material loss in the laser scanning area, causing poor uniformity of local powder thickness, thus affecting additive manufacturing quality. Summary of the Invention

[0005] The purpose of this invention is to provide a method for suppressing spatter in laser selective melting to solve the problems existing in the prior art. This method can suppress spatter during the printing process, improve printing efficiency, ensure printing quality, reduce the impact of spatter particles on unscanned powder, and improve the reusability of powder.

[0006] To achieve the above objectives, the present invention provides the following solution:

[0007] This invention provides a method for suppressing sputtering laser selective melting, comprising the following steps:

[0008] The 3D model of the part is sliced ​​into several processing layers. Based on the thickness of each layer of the 3D model, powder material is laid layer by layer from bottom to top and then laser scanning is used to melt and shape it.

[0009] When the thickness of the processed layer is above the preset thickness, the laser scanning melting forming adopts a two-stage scanning forming method: controlling the laser energy input, performing an initial scan on the scanned layer, so that the surface powder material melts or sinters and forms a surface sintered layer; adjusting the laser scanning parameters, performing a second scan on the cross-sectional area of ​​the part, completely melting the surface sintered layer and the powder material below it, and then cooling and solidifying to form the shape.

[0010] When the thickness of the processed layer is less than the preset thickness, the laser scanning melting forming adopts a one-time scanning forming method: controlling the laser energy input, scanning the cross-sectional area of ​​the part, so that the powder material of the processed layer thickness is completely melted, and then cooled and solidified to form the shape.

[0011] Preferably, when slicing the three-dimensional model of the part, the thickness of each processing layer is above the preset thickness, and each processing layer is processed using a two-stage scanning forming method.

[0012] Preferably, when slicing the 3D model of the part, a variable layer thickness printing strategy is used. Different layer thicknesses are set at different positions according to the different requirements of the printing process for manufacturing speed and local accuracy. During the printing process, some processing layers are processed by a two-stage scanning forming method, while other processing layers are processed by a one-stage scanning forming method.

[0013] Preferably, in the secondary scanning forming method, during the initial scanning, any one, two, or three of the following methods are used to control the laser scanning process: increasing the scanning speed, increasing the spot area, and reducing the laser power.

[0014] Preferably, in the secondary scanning forming method, the initial scanning area is the complete area of ​​the layer that needs to be printed, or it is an area generated by enlarging the cross-sectional contour of the part, so that the surface sintering layer completely covers the processing area.

[0015] The present invention achieves the following technical effects compared to the prior art:

[0016] This invention provides a method for suppressing sputtering laser selective melting. When the thickness of the scanned layer is greater than a preset thickness, the laser energy input is controlled to perform an initial scan of the scanned layer with a low energy density, causing the surface powder material to melt or sinter and form a surface sintered layer. Then, the laser scanning parameters are adjusted to perform a second scan of the cross-sectional area of ​​the part, completely melting the surface sintered layer and the underlying powder material. The material is then cooled and solidified. By combining the initial and second scans, the low laser energy density used in the initial scan only melts or sintersulates the surface powder material to form a surface sintered layer. This allows the surface powder material to be sintered into a thin film. After sintering, there is tension between the powder particles, making it difficult for individual particles to be further evaporated. Instead of splashing away from their original positions, the protective gas flow is constrained by surrounding particles and cannot move easily. Powder below the surface sintering layer is also prevented from flying above the surface sintering layer because it is covered by the surface sintering layer. Therefore, pre-sintering can suppress powder splashing and ensure print quality. When the thickness of the processed layer is less than the preset thickness, a one-time scanning forming method is used to scan and control the laser energy input so that the powder material of the processed layer thickness is completely melted and then cooled and solidified to ensure printing efficiency. This invention uses different laser scanning melting forming methods according to the different thicknesses of the scanned layers, taking into account both printing efficiency and printing quality, reducing the impact on powder that is not scanned by the laser, and increasing the number of times the powder can be reused. Attached Figure Description

[0017] Figure 1 This is a schematic diagram illustrating the spatter generated during laser scanning in existing technology.

[0018] Figure 2This is a schematic diagram illustrating the suppression of spatter during laser scanning using the secondary scanning forming method of the present invention;

[0019] Figure 3 The images show a comparison of the spattering conditions during laser scanning forming using the secondary scanning forming method of this invention and the conventional scanning forming method.

[0020] In the figure: 1-laser beam, 2-substrate, 3-formed part, 4-unscanned powder area, 5-melt channel cross section of scanned area, 6-splatter particles, 7-surface sintering layer. Detailed Implementation

[0021] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0022] like Figure 2 As shown, this embodiment provides a method for suppressing sputtering laser selective melting, including the following steps:

[0023] The 3D model of the part is sliced ​​into several processing layers. Based on the thickness of each layer of the 3D model, powder material is laid layer by layer from bottom to top and then laser scanning is used to melt and shape it.

[0024] When the thickness of the processed layer is above the preset thickness, the laser scanning melting forming adopts a secondary scanning forming method: control the laser energy input, perform an initial scan on the scanned layer, so that the surface powder material melts or sinters and forms a surface sintered layer 7; adjust the laser scanning parameters, perform a secondary scan on the cross-sectional area of ​​the part, completely melt the surface sintered layer 7 and the powder material below it, and then cool and solidify to form the shape.

[0025] When the thickness of the processed layer is less than the preset thickness, the laser scanning melting forming adopts a one-time scanning forming method: controlling the laser energy input, scanning the cross-sectional area of ​​the part, so that the powder material of the processed layer thickness is completely melted, and then cooled and solidified to form the shape.

[0026] When slicing the 3D model of a part, the thickness of each processing layer can be above the preset thickness, and each processing layer can be processed using a two-stage scanning forming method. Alternatively, a variable layer thickness printing strategy can be used, setting different layer thicknesses at different locations according to the different requirements of the printing process for manufacturing speed and local accuracy. During the printing process, some processing layers are processed using a two-stage scanning forming method, while other processing layers are processed using a one-stage scanning forming method.

[0027] In the secondary scanning forming method, during the initial scan, one, two, or three of the following methods are used to control the laser scanning process to improve processing efficiency: increasing the scanning speed, increasing the spot area, and reducing the laser power. The laser energy input is controlled to ensure that no violent evaporation occurs, but to bring the surface of the powder material to the sintering temperature, thereby creating a surface sintered layer 7 on the powder material surface without causing violent evaporation.

[0028] In the two-stage scanning forming method, the initial scanning area is the complete area to be printed in the layer, or an area enlarged based on the cross-sectional contour of the part. That is, the surface sintering layer 7 can be the shape to be formed in this layer, or it can be appropriately extended based on the target shape so that the surface sintering layer 7 completely covers the processing area. The complete area to be printed refers to the part that needs to remain in the printed result after printing, including the cross-sectional portion of the part and the cross-sectional portion of the support structure added for printing. Any portion of the surface sintering layer 7 larger than the part's cross-section can be removed subsequently.

[0029] like Figure 3 As shown, TC4 titanium alloy powder was used as the material for laser scanning melting and forming. The top three images show the effect of using the secondary scanning forming method of the present invention to suppress spatter, while the bottom three images show the powder spatter situation when scanning using the conventional scanning forming method. The comparison shows that using the secondary scanning forming method of the present invention to scan effectively suppresses the generation of spatter.

[0030] Specific examples have been used to illustrate the principles and implementation methods of this invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of this invention. Furthermore, those skilled in the art will recognize that, based on the ideas of this invention, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of this invention.

Claims

1. A method for suppressing sputtering laser selective melting, characterized in that, Includes the following steps: The 3D model of the part is sliced ​​into several processing layers. Based on the thickness of each layer of the 3D model, powder material is laid layer by layer from bottom to top and then laser scanning is used to melt and shape it. When slicing the 3D model of the part, a variable layer thickness printing strategy is used. Different layer thicknesses are set at different positions according to the different requirements of the printing process for manufacturing speed and local accuracy. During the printing process, some processing layers are processed by a two-stage scanning forming method, while other processing layers are processed by a one-stage scanning forming method. When the thickness of the processed layer is above the preset thickness, the laser scanning melting forming adopts a two-stage scanning forming method: controlling the laser energy input, performing an initial scan on the scanned layer, so that the surface powder material melts or sinters and forms a surface sintered layer; adjusting the laser scanning parameters, performing a second scan on the cross-sectional area of ​​the part, completely melting the surface sintered layer and the powder material below it, and then cooling and solidifying to form the shape. When the thickness of the processed layer is less than the preset thickness, the laser scanning melting forming adopts a one-time scanning forming method: controlling the laser energy input, scanning the cross-sectional area of ​​the part, so that the powder material of the processed layer thickness is completely melted, and then cooled and solidified to form the shape.

2. The method for suppressing sputtering laser selective melting according to claim 1, characterized in that: In the secondary scanning forming method, during the initial scan, any one, two, or three of the following methods are used to control the laser scanning process: increasing the scanning speed, increasing the spot area, and reducing the laser power.

3. The method for suppressing sputtering laser selective melting according to claim 1, characterized in that: In the secondary scanning forming method, the initial scanning area is the complete area of ​​the layer that needs to be printed, or it is an area generated by enlarging the cross-sectional contour of the part, so that the surface sintering layer completely covers the processing area.

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