A method for laser selective melting forming of a sandwiched cavity structure part

Abstract

This invention discloses a laser selective melting forming method for sandwich cavity structure parts. The method includes: acquiring a three-dimensional model of the part having at least two semi-enclosed cavities; adding wire-cut allowance structures at the ends to be removed after determining the forming direction; constructing powder-cleaning channels within the allowance structure that communicate with each cavity layer, wherein the channel communicating with the outermost cavity is a powder-cleaning hole, and the channel communicating with the inner cavities is a powder-cleaning tube, which extends through the outer cavity into the corresponding inner cavity without communicating with the outer cavity it passes through; performing laser selective melting forming; blowing air into the corresponding cavity through each powder-cleaning channel and discharging powder; and removing the wire-cut allowance structures. This invention designs differentiated powder-cleaning channels for different sandwich structures, achieving independent powder cleaning of multiple cavities, significantly reducing the difficulty of powder cleaning. The powder-cleaning channels are removed along with the wire-cut allowance without sealing, offering advantages such as high powder cleaning efficiency, no damage to the part, and low cost.

Description

Technical Field

[0001] This invention belongs to the field of additive manufacturing technology, and in particular relates to a laser selective melting forming method for sandwich cavity structure parts. Background Technology

[0002] Selective Laser Melting (SLM) is an additive manufacturing technology that uses a laser as an energy source to scan a bed of metal powder layer by layer according to a pre-planned path in a 3D CAD slicing model. The scanned metal powder melts and solidifies to achieve a metallurgical bond, ultimately producing the metal part designed in the model. SLM allows for precise control of energy input, forming method, scanning path, and layer thickness, enabling the manufacturing of metal parts with arbitrarily complex shapes. It boasts unique advantages such as high efficiency, low cost, high quality, and high performance. This technology has been widely used in aerospace, medical devices, automotive manufacturing, and mold making, and its application scope continues to expand with technological advancements.

[0003] Sandwich cavity structure parts refer to parts with a semi-enclosed inner cavity in their geometry, and the inner cavity is a multi-layered stacked structure. These types of parts are quite common in mechanical design and manufacturing. For sandwich cavity structure parts, when using laser selective melting forming, the part and the substrate form a closed cavity, and air blowing powder cannot directly reach the inner cavity, making powder cleaning difficult.

[0004] In the prior art, Chinese Patent Publication No. CN121988756A discloses an additive manufacturing method for a part and an additively formed part. This method is for cylindrical parts with an internal flow channel and a suspended structure. A powder cleaning vent pipe is set on the supporting structure body. One end of the powder cleaning vent pipe penetrates the outer surface of the supporting structure body, and the other end corresponds to but is not in contact with the end of the internal flow channel near the suspended structure, for venting into the internal flow channel. However, this method is for cylindrical parts with an internal flow channel structure that is open at both ends. The powder cleaning vent pipe only has a blowing function, and the powder flows out from the other end of the internal flow channel. Its structural characteristics determine that this method cannot be applied to multi-layer sandwich internal cavity structure parts with a semi-closed internal cavity structure that forms a fully closed cavity with the substrate.

[0005] Furthermore, Chinese Patent Publication No. CN111451499A discloses a laser selective melting forming method for parts with internal cavities. This method extends the internal cavity to the outside of the part by adding a 0.4mm thick pipe along the cavity outlet in 3D modeling software, facilitating powder removal. However, this method only addresses the extension of a single cavity. For sandwich cavity structures with multiple stacked cavities and no connecting channels between the cavities, the pipe structure of this method cannot achieve independent powder removal for each cavity layer.

[0006] For the aforementioned sandwich cavity structure parts, existing technologies typically employ two powder removal methods: First, a powder removal hole is opened in the part body and subsequently sealed by welding. However, welding easily causes deformation of the part, with varying degrees of deformation depending on size, making quantification difficult. Furthermore, welding quality is hard to guarantee, easily leading to metallurgical defects such as porosity and incomplete fusion, which can severely damage the part. Second, a low-temperature annealing process is added to the part, followed by wire cutting to remove the powder. However, the wire cutting fluid contaminates the powder, preventing its reuse and increasing powder and heat treatment costs. Both methods suffer from complex processes, long production cycles, and high production costs.

[0007] Therefore, how to design a reasonable forming method for sandwich cavity structure parts so that they can be smoothly formed in one piece through laser selective melting forming process, reduce the difficulty of powder cleaning, shorten the manufacturing cycle, reduce production costs, and improve production efficiency is a technical problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0008] To address the problems existing in the prior art, this invention provides a laser selective melting forming method for sandwich cavity structure parts. This method constructs differentiated powder cleaning channels for different cavity layers within the wire cutting allowance of the part—the outer layer uses powder cleaning holes, and the inner layer uses powder cleaning tubes extending into the corresponding cavity. This ensures that each cavity layer has independent air blowing and powder discharge channels, allowing it to be smoothly formed in one piece through the laser selective melting forming process. This achieves efficient powder cleaning of the closed cavity during the printing process, reduces the difficulty of powder cleaning, shortens the manufacturing cycle, reduces production costs, and improves production efficiency. Furthermore, this method features high powder cleaning efficiency, no damage to the part body, simplified process, and low cost.

[0009] This invention is implemented as follows: a laser selective melting forming method for sandwich cavity structure parts, comprising the following steps: Obtain a three-dimensional model of the sandwich cavity structure part, which has at least two cavities, each of which is a semi-closed structure. Determine the forming direction of the sandwich cavity structure parts; In the three-dimensional model, a wire cutting allowance structure is added to the end of the sandwich cavity structure part to be cut off; Within the range of the wire cutting allowance structure, a powder cleaning channel is constructed that communicates with the inner cavity of each layer respectively; wherein, the powder cleaning channel communicating with the outermost inner cavity is a powder cleaning hole structure, and the powder cleaning channel communicating with at least one inner cavity is a powder cleaning tube structure. The powder cleaning tube structure passes through the outer inner cavity and extends into the corresponding inner cavity, and is not connected to the outer inner cavity it passes through. Based on the three-dimensional model with the added wire cutting allowance structure and powder cleaning channel, laser selective melting is performed to form an additively molded part. The additively molded part is subjected to a powder removal process by blowing air into the corresponding inner cavity through each of the powder removal channels and discharging the powder. Remove the wire-cut allowance structure to obtain the sandwich cavity structure part.

[0010] In the above technical solution, preferably, the wall thickness D of the powder cleaning pipe structure satisfies: 0.5mm≤D≤1mm.

[0011] In the above technical solution, preferably, the dimension L of the wire cutting allowance structure along the forming direction of the part satisfies: 3mm≤L≤15mm.

[0012] In the above technical solution, preferably, the cross-sectional shape of the powder cleaning hole structure and / or the powder cleaning tube structure is any one of circular, arched, or elliptical.

[0013] In the above technical solution, preferably, when the number of inner cavity layers N of the sandwich inner cavity structure part is ≥3, the powder cleaning pipe structure corresponding to each inner cavity is arranged alternately along the circumference of the part, and each powder cleaning pipe structure is independently connected to the corresponding inner cavity.

[0014] In the above technical solution, preferably, the forming direction of the sandwich cavity structure part is determined by the principle of good forming stability, small number of supports and short forming time.

[0015] In the above technical solution, preferably, the additively molded part is subjected to a powder removal process, including: A vibration platform combined with compressed air is used to clean the powder from the surface and interior of the additively molded part. Compressed air is blown into the corresponding inner cavity through each of the powder cleaning channels to discharge the residual powder in each inner cavity from the corresponding powder cleaning channel.

[0016] In the above technical solution, preferably, removing the wire cutting allowance structure specifically involves: cutting the wire cutting allowance structure from the additively molded part using a wire cutting method.

[0017] In the above technical solution, preferably, before removing the wire cutting allowance structure, the additive molded part with the wire cutting allowance structure is further subjected to heat treatment.

[0018] In the above technical solution, preferably, after removing the wire cutting allowance structure, the method further includes: grinding, polishing and sandblasting the outer surface of the sandwich cavity structure part.

[0019] The advantages and positive effects of this invention are: 1) This invention utilizes the wire EDM allowance structure of the part as the carrier space for the powder cleaning channel. Different powder cleaning structures are designed for different layers—the outermost layer uses powder cleaning holes and the inner layer uses powder cleaning tubes, so that each layer's inner cavity has an independent air blowing and powder discharge channel, which greatly reduces the difficulty of powder cleaning. The powder cleaning channel can be removed as a whole during the wire EDM process, eliminating the need to open powder cleaning holes in the part body, saving the subsequent welding and sealing process, shortening the manufacturing cycle, and reducing manufacturing costs. The effect is especially obvious for mass-produced parts.

[0020] 2) This invention features a powder-cleaning tube structure designed for the inner cavity. This tube extends into the inner cavity through the outer cavity and is not connected to other cavities it passes through, forming a one-to-one independent powder-cleaning channel for the inner cavity. Compared to structures that only have powder-cleaning holes on multiple inner cavities, the powder-cleaning tube structure allows compressed air to reach the depths of the inner cavity for purging, overcoming the problem of gas dispersion and attenuation after entering the outer cavity and its inability to effectively enter the inner cavity. It also prevents powder from the inner cavity from being blown into the outer cavity, causing secondary contamination. The powder cleaning of each inner cavity is independent, making it easy for operators to accurately determine whether the powder in each inner cavity has been completely removed.

[0021] 3) This invention utilizes the wire-cut allowance area to set up a powder cleaning channel. The powder cleaning channel does not occupy the space of the part body and does not cause any damage to the part body. After the allowance structure is removed by wire cutting, the powder cleaning channel is also removed, leaving no additional structure on the part body. No additional sealing treatment is required, avoiding the deformation and metallurgical defects caused by welding sealing, and ensuring the integrity and dimensional accuracy of the part.

[0022] 4) The powder cleaning channel design of this invention can be flexibly adjusted according to the part structure within the allowance range of the online cutting process. The cross-sectional shape of the powder cleaning hole and the powder cleaning tube can be selected as circular, arched, or elliptical as needed. The number and arrangement of the powder cleaning tubes can be flexibly set according to the spatial distribution of the inner cavity. In addition, this invention can also be used in other situations that require regional powder cleaning. For example, when the internal support area of ​​the part is large, this invention can be used to design a powder cleaning channel inside the support structure to enhance gas flow, making it highly versatile.

[0023] 5) The process design of this invention, which involves cleaning the powder before heat treatment, avoids the problem of metal powder in the inner cavity sintering and sticking together during heat treatment, making it difficult to remove. This further reduces the difficulty of cleaning the powder and improves the cleaning efficiency. At the same time, the wire-cutting allowance is not removed during heat treatment, which provides support and fixation for the part, effectively reducing deformation during the heat treatment process.

[0024] 6) In this invention, the wall thickness D of the powder cleaning tube is limited to 0.5mm to 1mm, which ensures that the powder cleaning tube can self-form and not collapse during the printing process, and also ensures that the tube cavity has sufficient cross-sectional area for gas and powder to pass through; the size L of the wire cutting allowance structure is limited to 3mm to 15mm, which ensures that the allowance structure has enough space to open the powder cleaning channel, and avoids material waste and printing time extension, thus balancing forming quality and manufacturing cost. Attached Figure Description

[0025] Figure 1 A schematic diagram of the inner cavity of a sandwich cavity structure component provided in an embodiment of the present invention; Figure 2 A schematic diagram of the forming direction of a sandwich cavity structure part provided in an embodiment of the present invention; Figure 3 This is a schematic diagram of the structure for adding wire cutting allowance provided in an embodiment of the present invention; Figure 4 A schematic diagram of the outermost inner cavity powder cleaning channel (powder cleaning hole) provided in an embodiment of the present invention. Figure 1 ; Figure 5 A schematic diagram of the outermost inner cavity powder cleaning channel (powder cleaning hole) provided in an embodiment of the present invention. Figure 2 ; Figure 6 Schematic diagram of the inner cavity powder cleaning channel (powder cleaning tube) provided in the embodiment of the present invention. Figure 1 ; Figure 7 Schematic diagram of the inner cavity powder cleaning channel (powder cleaning tube) provided in the embodiment of the present invention. Figure 2 ; Figure 8 This is an enlarged schematic diagram of the powder cleaning tube structure provided in an embodiment of the present invention.

[0026] In the figure: 100, sandwich inner cavity structure part; 110, first inner cavity; 120, second inner cavity; 200, wire cutting allowance structure; 210, powder cleaning hole; 220, powder cleaning tube. Detailed Implementation

[0027] 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 a part of the embodiments of the present invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0028] To facilitate a clear description of the technical solutions in the embodiments of the present invention, it should be noted that in the embodiments of the present invention, the terms "first" and "second" are used to distinguish identical or similar items with essentially the same function and effect. For example, the first threshold and the second threshold are merely used to distinguish different thresholds and do not limit their order. Those skilled in the art will understand that the terms "first" and "second" do not limit the quantity or execution order, and the terms "first" and "second" are not necessarily different.

[0029] It should be noted that in this invention, the terms "exemplary" or "for example" are used to indicate examples, illustrations, or descriptions. Any embodiment or design described as "exemplary" or "for example" in this invention should not be construed as being more preferred or advantageous than other embodiments or designs. Specifically, the use of terms such as "exemplary" or "for example" is intended to present the relevant concepts in a concrete manner.

[0030] In this invention, "at least one" refers to one or more, and "more than one" refers to two or more. "And / or" describes the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A alone, A and B simultaneously, or B alone, where A and B can be singular or plural. The character " / " generally indicates that the preceding and following related objects are in an "or" relationship. "At least one of the following" or similar expressions refer to any combination of these items, including any combination of single or plural items. For example, at least one of a, b, or c can represent: a, b, c, a combination of a and b, a combination of a and c, a combination of b and c, or a, b, and c, where a, b, and c can be single or multiple.

[0031] Example This invention provides a laser selective melting forming method for sandwich cavity structure parts, as detailed below: First, a three-dimensional model of the sandwich cavity structure part 100 is obtained. The three-dimensional model of the sandwich cavity structure part 100 is created using 3D modeling software such as UG or Pro / engineer. The sandwich cavity structure part 100 has at least two cavities, with the number of cavity layers N≥2 (N can be 3, 4, 5, etc.). Each cavity layer is a semi-closed structure, and the cavities can be evenly distributed along the part body or randomly distributed along the part body, without specific limitations. In this embodiment, an example with two cavity layers and each cavity layer evenly distributed along the part body is used for illustration. The bottom of the sandwich cavity structure part 100 has a cut-off end, which is opposite to the substrate during subsequent forming processes.

[0032] For double-layered sandwich cavity structures, such as Figure 1 As shown, the sandwich cavity structure part 100 has a first inner cavity 110 (i.e., the outermost inner cavity) and a second inner cavity 120 (i.e., the inner cavity). The first inner cavity 110 is located near the outer wall of the part, and the second inner cavity 120 is located inside the first inner cavity 110. The first inner cavity 110 and the second inner cavity 120 are separated by the part body, and there is no connecting channel between them. Each inner cavity is a semi-closed structure, that is, each inner cavity has an opening at the bottom of the part (the end face to be cut), while the top and other directions of each inner cavity are closed by the part body.

[0033] By using 3D modeling software to accurately construct the 3D model of the sandwich cavity structure parts, a digital foundation is provided for the subsequent addition of wire cutting allowance structures and powder cleaning channels, ensuring that the geometric dimensions and spatial relationships of each layer of the cavity are accurate, thereby ensuring that the final printed parts are consistent with the design model.

[0034] After obtaining the 3D model of the part, such as Figure 2 As shown, the forming direction of the part is determined based on its structure. The selection of the forming direction is based on the principles of good forming stability, fewer supports, and shorter forming time. In this embodiment, the forming direction is determined by... Figure 1 Taking the double-layer sandwich cavity structure part 100 as an example, the forming direction of this part is selected to be vertically placed along the axial direction of the part, so that the end of the part to be cut faces the substrate. Under this forming direction, the structure of the part is the most stable and the number of supports required is the least. It should be noted that for sandwich cavity structure parts of different shapes, their forming direction can be adjusted accordingly according to the above basic principles, and is not limited to this embodiment.

[0035] After determining the forming direction, such as Figure 3 As shown, in the 3D model, a wire cutting allowance structure 200 is added to the end of the part to be cut (i.e., the end facing the substrate). The dimension L of the wire cutting allowance structure 200 along the forming direction of the part 100 satisfies: 3mm ≤ L ≤ 15mm, facilitating subsequent separation from the substrate. In this embodiment, the wire cutting allowance L is illustrated as 5mm, but is not specifically limited. The bottom surface of the wire cutting allowance structure 200 is attached to the substrate, and the part 100 is placed on the substrate through the wire cutting allowance structure 200. The presence of the wire cutting allowance structure 200 provides cutting allowance for subsequent wire cutting processes, avoiding damage to the part body during cutting; on the other hand, it provides space for the construction of the powder cleaning channel.

[0036] The rational selection of the forming direction ensures the stability of the part structure and the forming quality during the printing process, while reducing the number of support structures, shortening the forming time, and reducing material consumption and post-processing workload. The size range of the wire EDM allowance structure is limited to 3mm to 15mm, which ensures that the wire EDM allowance structure has sufficient structural strength to open the powder cleaning channel, while avoiding material waste and prolonged printing time caused by excessive allowance, thus balancing forming quality and manufacturing cost.

[0037] After adding the wire cutting allowance structure 200, within the range of the wire cutting allowance structure 200, a powder cleaning channel is constructed that is connected to the inner cavity of each layer.

[0038] like Figure 4 and Figure 5 As shown, a powder-cleaning hole 210 is constructed within the area of ​​the wire-cut allowance structure 200 for the outermost inner cavity (i.e., the first inner cavity 110). One end of the powder-cleaning hole 210 communicates with the first inner cavity 110, and the other end of the powder-cleaning hole 210 penetrates the outer peripheral surface of the wire-cut allowance structure 200. The cross-sectional shape of the powder-cleaning hole 210 can be any one of circular, arched, or elliptical shapes, and must meet the self-forming requirements of the laser selective melting forming process. In this embodiment, a circular hole with a diameter of 3 mm is used as an example for illustrating the powder-cleaning hole 210, but no specific limitation is made.

[0039] The cross-sectional shape of the powder cleaning hole 210 should meet the requirements of the SLM self-forming process. Specifically, circular holes are easier to process and have less airflow resistance; arched structures have better self-support in SLM unsupported printing, and the top is less prone to collapse, making them suitable for larger hole diameters; elliptical structures are suitable for space-constrained situations, allowing for a larger channel cross-sectional area within a limited wire cutting allowance. The number of powder cleaning holes 210 can be set according to the circumferential length of the first inner cavity 110 to ensure that the airflow can cover all areas of the first inner cavity 110 during powder cleaning. The connection between the powder cleaning hole 210 and the first inner cavity 110 should be unobstructed.

[0040] The powder cleaning hole structure directly connects the outermost inner cavity with the external environment. Since the outermost inner cavity is close to the outer wall of the part, the air blowing path is short, and efficient powder cleaning can be achieved by using the powder cleaning hole. The powder cleaning hole is set within the wire cutting allowance structure and does not occupy the space of the part body. After the powder cleaning is completed, it is removed along with the wire cutting allowance structure, without causing any damage to the part body.

[0041] like Figures 6-8As shown, a powder cleaning tube 220 is constructed within the area of ​​the wire-cut allowance structure 200 for the inner cavity (i.e., the second inner cavity 120). One end of the powder cleaning tube 220 penetrates the outer peripheral surface of the wire-cut allowance structure 200, and the other end of the powder cleaning tube 220 extends into the second inner cavity 120 through the first inner cavity 110. The powder cleaning tube 220 is not connected to the outer first inner cavity 110; that is, when the powder cleaning tube 220 passes through the first inner cavity 110, the tube wall of the powder cleaning tube 220 separates the internal channel of the powder cleaning tube 220 from the first inner cavity 110, and the powder cleaning tube 220 is only connected to its corresponding second inner cavity 120.

[0042] The wall thickness D of the powder cleaning tube 220 satisfies: 0.5mm ≤ D ≤ 1mm. The cross-sectional shape of the powder cleaning tube 220 can be any one of circular, arched, or elliptical shapes, and must meet the self-forming requirements of the laser selective melting forming process. In this embodiment, an arched shape is used as an example for illustration, but no specific limitation is made. The powder cleaning tube 220 is as follows... Figure 8 As shown, a powder cleaning tube channel is formed on the outer body of the wire-cutting allowance structure 200, outside the powder cleaning hole 210, in the solid area. The powder cleaning tube 220 forms a channel through which gas and powder can pass. The powder cleaning tube 220 needs to pass through the first inner cavity 110 and extend into the second inner cavity 120, connecting the second inner cavity 120 with the external environment, for independent powder cleaning of the second inner cavity 120.

[0043] The powder cleaning tube 220 features an arched cross-section design, with an arched top structure that allows it to self-form during SLM layer-by-layer printing without the need for additional support, avoiding the problem of large unsupported area and easy collapse of circular holes. The wall thickness D of the powder cleaning tube 220 is limited to 0.5mm to 1mm. When D is less than 0.5mm, the wall is too thin, making it prone to deformation or collapse due to thermal stress during printing, potentially blocking the tube channel. When D is greater than 1mm, the wall is too thick, occupying too much wire cutting allowance space and increasing the consumption of printing material and time. The number of powder cleaning tubes 220 can be set according to the circumferential length and spatial distribution of the second inner cavity 120. Each powder cleaning tube 220 is arranged at intervals along the circumferential spacing of the wire cutting allowance structure 200, ensuring that each second inner cavity 120 corresponds to at least one powder cleaning tube 220.

[0044] The cleaning tube structure extends directly from the outer inner cavity into the inner inner cavity, forming a one-to-one independent cleaning channel. When compressed air is blown into the inner cavity through the cleaning tube, the airflow reaches every corner of the inner cavity, expelling the powder from the same channel or the other side, achieving independent cleaning of the inner cavity. Because the cleaning tube is not connected to other cavities it passes through, it avoids the problem of powder from the inner cavity being blown into the outer cavity, causing secondary contamination, and also facilitates the determination of whether each inner cavity has been thoroughly cleaned.

[0045] When the number of inner cavity layers N of the sandwich cavity structure component 100 is greater than or equal to 3, the cleaning pipes 220 corresponding to each inner cavity can be arranged alternately along the circumference of the component. Each cleaning pipe 220 is independently connected to its corresponding inner cavity and does not communicate with other layers, forming a one-to-one cleaning effect. The alternate arrangement of the cleaning pipes avoids interference between multiple pipes in a limited space, ensuring that each inner cavity has an independent cleaning channel and that the inner cavities do not interfere with each other, further improving the cleaning efficiency of the multi-layer sandwich structure.

[0046] After constructing the powder cleaning channel, export the 3D model as an STL file, setting both the trigonometric tolerance and adjacent tolerance to 0.0025. Then, open the STL part model with Magics software and use the repair wizard to repair the part model, ensuring the model data is complete and error-free.

[0047] The STL format triangular tolerance and adjacent tolerance are both set to 0.0025, ensuring that the model data accuracy matches the printing accuracy of the laser selective melting forming equipment, avoiding printing size deviations due to insufficient data accuracy. The Magics software's repair function can automatically detect and repair problems such as incorrect triangular faces, overlapping surfaces, and gaps in the model, ensuring the integrity and reliability of the printing data and avoiding printing failures due to model issues.

[0048] Laser selective melting forming is performed on a 3D model with added wire cutting allowance structure 200 and powder cleaning channels (powder cleaning holes 210 and powder cleaning tubes 220). Specifically, the repaired 3D model is sliced ​​to generate scanning path data for each layer cross-section; the sliced ​​data is imported into the laser selective melting forming equipment, sufficient metal powder is added to the equipment, the substrate is leveled, and printing conditions are set. After the conditions are met, the equipment is started to print, completing the manufacturing of the part and obtaining an additively molded part. This additively molded part includes the part, the wire cutting allowance structure 200, and the powder cleaning channels (powder cleaning holes 210 and powder cleaning tubes 220).

[0049] After printing, the additively molded part undergoes a powder removal process. This includes the following steps: First, a vibration platform combined with compressed air is used to perform preliminary powder cleaning on the surface and interior of the additively molded part. The additively molded part is placed on the vibration platform, and the vibration loosens the metal powder adhering to the surface of the part and remaining in the internal cavity. At the same time, compressed air at 0.6MPa to 0.8MPa is used to blow away the surface powder of the molded part.

[0050] Then, compressed air is blown into the corresponding inner cavity through each cleaning channel to expel the residual powder from each inner cavity through the corresponding cleaning channel. Specifically, for the first inner cavity 110, a high-pressure air gun is aimed at the outer opening of the cleaning hole 210, and compressed air is blown into the first inner cavity 110. The residual metal powder in the first inner cavity 110 is discharged in the reverse direction from the cleaning hole 210 under the influence of the airflow. For the second inner cavity 120, a high-pressure air gun is aimed at the outer opening of the cleaning tube 220, and the cleaning tube 220 directly introduces compressed air into the second inner cavity 120. The residual metal powder in the second inner cavity 120 is discharged in the reverse direction from the cleaning tube 220 under the influence of the airflow. The entire cleaning process is repeated multiple times until it is confirmed that the powder in each inner cavity has been completely removed. Personnel protection measures should be taken during the operation.

[0051] During the aforementioned powder cleaning process, the powder cleaning of the first inner cavity 110 and the second inner cavity 120 is independent of each other. The first inner cavity 110 receives air and discharges powder through the powder cleaning hole 210, while the second inner cavity 120 receives air and discharges powder through the powder cleaning pipe 220. Since the powder cleaning pipe 220 is not connected to the first inner cavity 110, the powder in the second inner cavity 120 will not enter the interior of the first inner cavity 110.

[0052] The vibration platform, used in conjunction with compressed air, causes the metal powder in the inner cavity to change from a static, accumulated state to a loose state, increasing its fluidity and making it easier for the compressed air to carry the powder out. A high-pressure air gun delivers air directly into the inner cavity through a cleaning pipe, reaching deep into the inner cavity and overcoming the problem of airflow dispersion and attenuation when passing through the outer cavity, resulting in more thorough powder removal from the inner cavity. The independent powder removal process design for each inner cavity allows operators to judge the completion of powder removal for each cavity by observing whether the discharged airflow contains powder, improving the reliability and efficiency of the powder removal process.

[0053] The second inner cavity 120 uses the wire cutting allowance of the parts to open the powder cleaning channel. If the powder cleaning hole structure is still used, the current powder cleaning method is to use a vibrating platform and air gun to blow away the powder. After the gas enters the first inner cavity 110, it will form a dispersion effect, and the effect of reaching the second inner cavity 120 is weak. Moreover, after the powder flows out of the second inner cavity 120, it will remain inside the first inner cavity 110, which increases the difficulty of powder cleaning. At the same time, it is difficult to determine whether the powder inside the second inner cavity 120 has been completely removed.

[0054] After powder removal, the additively formed part with wire cutting allowance 200 is subjected to heat treatment. The purpose of heat treatment is to eliminate the thermal stress generated during laser selective melting forming and improve the microstructure and mechanical properties of the part.

[0055] After heat treatment, the wire-cutting allowance structure 200 is removed from the additively formed part using wire EDM. Specifically, the heat-treated additively formed part is fixed on a wire EDM fixture, the cutting position is adjusted, and the wire EDM equipment is started to cut the wire-cutting allowance structure 200 from the additively formed part, obtaining the part. Since the powder cleaning hole 210 and the powder cleaning tube 220 are both located within the range of the wire-cutting allowance structure 200, after the wire EDM removes the wire-cutting allowance structure 200, the powder cleaning hole 210 and the powder cleaning tube 220 are removed along with the wire-cutting allowance structure 200, leaving no trace of powder cleaning channels on the part body.

[0056] After wire cutting, the outer surface of the part is ground, polished, and sandblasted to obtain the surface quality and dimensional accuracy that meet the design requirements.

[0057] The sequential process of powder removal followed by heat treatment avoids powder sintering and adhesion during heat treatment, reducing the difficulty of powder removal. Heat treatment is performed with the substrate attached, and the wire-cut allowance structure provides support and fixation for the part, reducing the risk of deformation during heat treatment. The wire-cut allowance structure's size range of 3mm to 15mm ensures sufficient operating space during wire cutting, allowing for precise and controllable cutting positions and preventing damage to the part itself. The powder removal channel is removed along with the wire-cut allowance structure, eliminating the need for additional sealing processes and simplifying the manufacturing process. Subsequent grinding, polishing, and sandblasting further improve the surface quality of the part, meeting usage requirements.

[0058] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Any simple modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of the present invention shall fall within the scope of the technical solution of the present invention.

Claims

1. A laser selective melting forming method for sandwich cavity structure parts, characterized in that, Includes the following steps: Obtain a three-dimensional model of the sandwich cavity structure part, which has at least two cavities, each of which is a semi-closed structure. Determine the forming direction of the sandwich cavity structure parts; In the three-dimensional model, a wire cutting allowance structure is added to the end of the sandwich cavity structure part to be cut off; Within the range of the wire cutting allowance structure, a powder cleaning channel is constructed that communicates with the inner cavity of each layer respectively; wherein, the powder cleaning channel communicating with the outermost inner cavity is a powder cleaning hole structure, and the powder cleaning channel communicating with at least one inner cavity is a powder cleaning tube structure. The powder cleaning tube structure passes through the outer inner cavity and extends into the corresponding inner cavity, and is not connected to the outer inner cavity it passes through. Based on the three-dimensional model with the added wire cutting allowance structure and powder cleaning channel, laser selective melting is performed to form an additively molded part. The additively molded part is subjected to a powder removal process by blowing air into the corresponding inner cavity through each of the powder removal channels and discharging the powder. Remove the wire-cut allowance structure to obtain the sandwich cavity structure part.

2. The laser selective melting forming method for sandwich cavity structure parts according to claim 1, characterized in that, The wall thickness D of the powder cleaning pipe structure satisfies: 0.5mm≤D≤1mm.

3. The laser selective melting forming method for sandwich cavity structure parts according to claim 1, characterized in that, The dimension L of the wire cutting allowance structure along the forming direction of the part satisfies: 3mm≤L≤15mm.

4. The laser selective melting forming method for sandwich cavity structure parts according to claim 1, characterized in that, The cross-sectional shape of the powder cleaning hole structure and / or the powder cleaning tube structure is any one of circular, arched, or elliptical.

5. The laser selective melting forming method for sandwich cavity structure parts according to claim 1, characterized in that, When the number of inner cavity layers N of the sandwich inner cavity structure part is greater than or equal to 3, the powder cleaning pipe structure corresponding to each inner cavity is arranged alternately along the circumference of the part, and each powder cleaning pipe structure is independently connected to the corresponding inner cavity.

6. The laser selective melting forming method for sandwich cavity structure parts according to claim 1, characterized in that, The forming direction of the sandwich cavity structure parts is determined based on the principles of good forming stability, fewer supports, and shorter forming time.

7. The laser selective melting forming method for sandwich cavity structure parts according to claim 1, characterized in that, The additively molded part is subjected to a powder removal process, including: A vibration platform combined with compressed air is used to clean the powder from the surface and interior of the additively molded part. Compressed air is blown into the corresponding inner cavity through each of the powder cleaning channels to discharge the residual powder in each inner cavity from the corresponding powder cleaning channel.

8. The laser selective melting forming method for sandwich cavity structure parts according to claim 1, characterized in that, Removing the wire-cut allowance structure specifically involves cutting the wire-cut allowance structure from the additively molded part using wire cutting.

9. The laser selective melting forming method for sandwich cavity structure parts according to claim 1, characterized in that, Before removing the wire cutting allowance structure, the process further includes: heat-treating the additively formed part with the wire cutting allowance structure.

10. The laser selective melting forming method for sandwich cavity structure parts according to claim 1, characterized in that, After removing the wire-cut allowance structure, the process further includes grinding, polishing, and sandblasting the outer surface of the sandwich cavity structure part.

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