A laser selective melting method for forming a complex two-stage axial vortex generator.

Abstract

The application provides a laser selective melting forming method of a complex structure two-stage axial vortex device, and comprises the following steps: blank model formulation; part placement and support addition; the most end area of the outlet of the part convergence section is in a uniform annular expansion structure, at this time, the vortex device exists the case that the part printing growth direction is opposite to the scraper direction no matter the vortex device rotates by any angle along the central axis, that is, the scraper collision and the risk of powder rebound exist at this place; forming process; in the cavity and the blade height area of the vortex device part, a small layer thickness, low power and multiple outer contour scanning process is adopted; in the uniform annular expansion structure height area of the most end area of the outlet of the part convergence section, a lower powder scraping speed is adopted. The application has the following advantages: the surface roughness requirements of the blade and the cavity in the forming process are guaranteed, the powder cleaning after the printing is more thorough, the risk of the part scraper collision and the powder rebound is avoided, the support removal is facilitated, and the product qualified rate is effectively improved compared with the casting process.

Description

Technical Field

[0001] This invention relates to the field of metal additive manufacturing, and in particular to a laser selective melting forming method for a complex structured two-stage axial vortex generator. Background Technology

[0002] The vortex generator has a rotating structure with evenly distributed counter-rotating double-stage blades inside the cavity. The component is located at the head of the combustion chamber. The functions of the vortex generator in an aero-engine are: first, to create a low-pressure recirculation zone at the head of the combustion chamber to stabilize the flame; and second, to generate vortex air in the combustion chamber, thereby achieving complete combustion of the fuel by mixing it with the air.

[0003] Traditional eddy current generator manufacturing processes can only produce one product per mold, resulting in low production efficiency and long production cycles. Furthermore, due to abrupt changes in cross-sectional area and complex structures in eddy current generator parts, defects such as porosity and incomplete filling are prone to occur, leading to a low yield rate in the casting process.

[0004] Additive manufacturing technology, also known as 3D printing technology, is a digitally driven process that uses layer-by-layer deposition to achieve near-net-shape three-dimensional objects. There are many types of metal additive manufacturing technologies, among which laser selective melting (LSM) technology can fabricate complex structural parts and is widely used in the field of aero-engines.

[0005] This invention employs laser selective melting forming technology to fabricate eddy current generator parts. This method can overcome the shortcomings of traditional casting processes and has certain advantages in forming difficult-to-machine alloys and complex structural parts using casting processes. It can realize the fabrication of complex two-stage axial eddy current generators. This invention fully considers thorough powder removal inside the eddy current generator parts, scraper buffering during the forming process of the reverse scraper section of the rotating structure, and high surface finish printing of the part cavity and blades. Summary of the Invention

[0006] The purpose of this invention is to provide a laser selective melting forming method suitable for complex two-stage axial vortex generators, facilitating the transition from traditional processes to laser selective melting forming, and achieving high-quality manufacturing of nozzle-type parts through additive manufacturing. Furthermore, this invention considers scraper collision during the printing process, high-precision printing of cavities and blades, and powder cleaning after printing. Special supports and specific printing process parameters are designed according to the working conditions and structural characteristics of the parts.

[0007] This invention provides a laser selective melting forming method for a complex structured two-stage axial vortex generator, comprising the following steps: (1) blank model formulation

[0008] According to the design requirements, the upper and lower surfaces of the mounting edge need to be assembled with other parts, and the surface roughness requirement is Ra1.6. Normal printing using laser selective melting cannot guarantee this surface roughness. Therefore, a certain allowance is reserved on the upper and lower surfaces of the mounting edge, and the surface roughness will be improved later by machining the allowance of the mounting edge.

[0009] (2) Component placement and support addition

[0010] When the converging section outlet of the vortex generator part is placed vertically downwards, a large area of ​​unsupported surface exists inside the cavity, with a significant height difference. This necessitates the addition of numerous supports, which penetrate deeply into the part, making support removal and surface polishing relatively difficult. When the converging section outlet of the vortex generator part is placed vertically upwards, the internal blades form an angle of 45°-65° with the horizontal direction. An angle greater than 45° allows for self-forming. In this case, supports are needed at the edges of the inner and outer ring channels, the inner and outer ring blades, and the outer ring blades. However, the support height is small, and subsequent removal is simple, making this placement method feasible. A full-mesh support system is used, with a serrated contact surface between the mesh support and the part, inserting 0.1mm into the part. This facilitates removal while ensuring a secure connection. To effectively remove residual powder during printing, the side surfaces of the mesh support are designed with a hollow structure. Furthermore, self-supporting powder-cleaning holes are provided at regular intervals along the circumference of each annular surface formed by the lower supports. These two measures ensure thorough powder removal from the part. The self-supporting wall thickness of the conformal cavity structure in this invention is 1-2 mm.

[0011] At the very end of the part convergence section outlet, there is a uniform annular expansion structure. At this point, regardless of the angle the vortex generator rotates along its central axis, the part's printing growth direction may be opposite to the squeegee direction, posing a risk of squeegee collision and powder ejection. To mitigate this risk, multiple inclined plate-like supports are installed in the risk area. The inclination direction of these supports is the same as the squeegee's powder-spreading direction, effectively reducing the impact force of the squeegee on the powder and part, ensuring no printing risk in this area.

[0012] (3) Molding process

[0013] The specific part setting parameters are shown in Table 1.

[0014] Table 1. Main process parameters for eddy current laser selective melting

[0015]

[0016] During the part forming process, the scanning path first scans the core, then the outer contour; plate-shaped solid supports only scan the core; and mesh supports are scanned only in a single pass with alternating layers. This scanning method ensures the forming accuracy and efficiency of the parts, while also making support removal easier and improving manufacturing efficiency. In the cavity and blade height areas of the eddy current generator parts, a small layer thickness, low power, and multiple outer contour scanning processes are employed. At the very end of the convergence section exit region, which exhibits a uniform annular expansion structure, a lower powder scraping speed is used.

[0017] This invention provides a laser selective melting forming scheme for complex structured two-stage axial vortex generators. With appropriate placement, support settings, and process parameter control, it can ensure the surface roughness requirements of the blades and cavity during the forming process. At the same time, it can achieve more thorough powder cleaning after printing, avoid the risk of part scraper collision and powder ejection, and facilitate the removal of supports.

[0018] Compared with the prior art, the advantages of this invention are:

[0019] It ensures the surface roughness requirements of the blades and cavity during the forming process, and the powder cleaning is more thorough after printing, avoiding the risk of part scraper collision and powder ejection. It also facilitates the removal of supports, effectively improving the product qualification rate compared with the casting process. Attached Figure Description

[0020] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments:

[0021] Figure 1 Schematic diagram of eddy current generator components;

[0022] Figure 2 Side view of vortex generator component;

[0023] Figure 3 Schematic diagram of the internal cavity and blades of the vortex generator;

[0024] Figure 4 : Schematic diagram of adding margin for eddy current generator parts;

[0025] Figure 5 : Schematic diagram of adding support for eddy current generator components;

[0026] Figure 6 Schematic diagram of the self-supporting conformal cavity structure of eddy current generator parts. Detailed Implementation

[0027] The present invention will be further explained below with reference to specific implementation schemes, but it is not limited to the present invention. The structures, proportions, sizes, etc. shown in the accompanying drawings are only used to complement the content disclosed in the specification, so as to enable those skilled in the art to understand and read, and are not intended to limit the conditions under which the present invention can be implemented. Therefore, they have no substantial technical significance. Any modification of the structure, change of the proportion relationship or adjustment of the size, without affecting the effect and purpose that the present invention can produce, should still fall within the scope of the technical content disclosed in the present invention.

[0028] like Figure 1-3 As shown, the vortex generator has a rotating structure. The parts have an inner ring channel and an outer ring channel. The inside of the channel is an inner ring blade and an outer ring blade. The middle of the part is the mounting edge, and the bottom of the part is the converging section outlet.

[0029] Step 1: Use modeling software to create a 3D model of the eddy current generator. Extrude the upper and lower surfaces of the mounting edge by 1mm each, resulting in a 2mm thicker mounting edge. Figure 4 As shown.

[0030] Step 2: Import the part's digital model into the model processing software and add support.

[0031] The part is manufactured using laser selective melting forming technology. The part placement method and overall support addition scheme are as follows: Figure 5 As shown, the converging section outlet end of the vortex generator component is placed vertically upwards. Supports are added to the edges of the inner and outer annular channels, the inner and outer annular blades, and the outer annular blades of the vortex generator. These supports are full-mesh supports, with a serrated contact surface between the mesh supports and the component, and the mesh supports are inserted 0.1mm into the component. The side surfaces of the mesh supports are designed with a hollow structure. In addition, self-supporting powder-cleaning holes are provided on each annular surface formed by the lower supports, averaging every 30°-60° around the circumference of the ring. Figure 6 As shown, the above two measures ensure thorough cleaning of the parts, and the self-supporting structure has a thickness of 2mm.

[0032] Multiple inclined plate-shaped supports are installed at the very end of the part convergence section exit area. The inclination direction of these supports is the same as the powder spreading direction of the doctor blade, which can effectively reduce the impact force of the doctor blade on the powder and parts, ensuring no printing risk at this point. The thickness of the inclined plate-shaped supports is 3-7mm.

[0033] Step 3: Use software to slice and fill the eddy current model after adding supports, set specific process parameters, and generate a .cli format processing file.

[0034] See Table 2 for specific printing parameters.

[0035] Table 2. Main process parameters for eddy current laser selective melting.

[0036]

[0037] The first layer of powder formed by laser selective melting is exposed and sintered twice to ensure that the solid part and the substrate are fully bonded after laser sintering. The powder ratio of the first 5 layers is set to 300%, and the powder ratio of the subsequent layers is set to 150%. At the beginning of each layer of powder laying, the scanning direction is rotated 67° clockwise to minimize the number of overlaps, prevent internal stress and cracks in the part, and ensure the accuracy of the part forming.

[0038] During the part forming process, the scanning path first scans the core, then the outer contour; plate-shaped solid supports only scan the core; and mesh supports are scanned only in a single pass. This scanning method ensures the forming accuracy and efficiency of the parts, while also making support removal easier and improving manufacturing efficiency. In the cavity and blade height regions of the eddy current generator parts, a low layer thickness of 30μm, low power of 110W, and a three-pass outer contour scanning process are used. At the very end of the convergence section exit region, which exhibits a uniform annular expansion structure, a powder scraping speed of 60mm / s is employed.

[0039] Step 4: Import the processing file described in Step 3 into the laser selective melting forming equipment to form the part.

[0040] Step 5: Clean the powder from the surface of the formed parts and inside the support. Use a rubber hammer to tap the substrate, and then use an air gun to clean the powder through the cleaning holes. Repeat the tapping and air blowing process until the powder is completely cleaned.

[0041] Step 6: Perform stress-relief annealing on the formed whole. The heat treatment regime is: 600-700℃, hold for 1-3 hours, and cool to room temperature with Ar2 gas.

[0042] Step 7: Use wire cutting to separate the support from the substrate and separate the parts from the support.

[0043] Step 8: Manually remove the supports from the parts. During the removal process, prevent the parts from deforming and avoid any damage, bumps, or dents.

[0044] Step 9: Perform solution treatment on the eddy current generator parts. The heat treatment regime is: 1150~1250℃, hold for 1~3h, and cool to room temperature with Ar2 gas.

[0045] Step 10: Grind and polish the entire surface of the part. There should be no defects visible to the naked eye on the surface of the part.

[0046] Step 11: Sandblast the surface of the parts. The sandblasting should be uniform, and the surface of the parts should not have any stains, bumps, or scratches.

[0047] Step 12: Machin the mounting edges of the parts to allow for additional material.

[0048] Step 13: Perform ultrasonic cleaning on the surface of the parts.

[0049] Matters not covered in this invention are common knowledge.

[0050] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method of laser engineered net shaping of a complex structure two-stage axial flow inducer, comprising: The method comprises the following steps: (1) blank model making The upper and lower surfaces of the installation edge need to be assembled with other parts, and a certain amount of allowance is reserved on the upper and lower surfaces of the installation edge, and the surface roughness is improved by machining the allowance of the installation edge in the later stage; (2) part placement and support addition When the vortex part convergent section outlet end is placed vertically downward, there is a large area of suspended surface inside the cavity, and the height distance is large, a large amount of support needs to be added, and the support penetrates into the part interior with a deep distance, and the support removal and support surface polishing are relatively difficult; when the vortex part convergent section outlet end is placed vertically upward, the blades inside the part form an angle of 45°-65° with the horizontal direction, and the angle greater than 45° can realize self-forming; the support adopts full grid support, the contact surface of the grid support and the part is sawtooth-shaped, and is inserted into the part by 0.1mm, which is convenient for removal while ensuring firm connection; the side surface of the grid support is provided with a hollow structure, and each ring surface formed by the lower support is provided with a self-supporting powder removal hole structure at intervals along the circumference of the ring; The most end part of the part convergent section outlet is in a uniform annular expansion structure, at this time, the vortex exists the situation that the part printing growth direction is opposite to the scraper direction no matter how much the vortex rotates along the central axis, that is, the most end part of the part convergent section outlet exists the risk of scraper collision and powder bouncing; in order to alleviate this risk, a plurality of inclined plate-shaped supports are arranged at the risk area, the inclination direction of the support is the same as the direction of the scraper powder laying, which can effectively alleviate the impact force of the scraper on the powder and the part, and ensure that the most end part of the part convergent section outlet has no printing risk; (3) forming process In the part forming process, the part scanning path is to scan the core first and then scan the outer contour; the plate-shaped solid support only scans the core; the grid support is only single-layer scanning; In the cavity and blade height area of the vortex part, a small layer thickness, low power and multiple outer contour scanning process is adopted; the most end part of the part convergent section outlet is in a uniform annular expansion structure, and a lower scraping speed is adopted.

2. The method of claim 1, wherein the method is a laser engineered net shaping method. The part placement and support addition, the self-supporting wall thickness of the random cavity structure is 1-2mm.

3. The method of claim 1, wherein the method is a laser engineered net shaping method. In the forming process, the most end part of the part convergent section outlet is in a uniform annular expansion structure, and a scraping speed of 50-70mm / s is adopted.

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