Powder bed fusion 3D printing method of fully enclosed cavity structure

Abstract

The present application relates to the technical field of 3D printing, and discloses a powder bed fusion 3D printing method of a fully-closed cavity structure, which comprises the following steps: dividing a part to be printed into a main body model, a sheet model and a top cover model; in a pretreatment software, the main body model and the top cover model are assembled together and then sliced and imported into a printer; the printing of the main body model is completed by using the printer, and the excess powder in the cavity of the main body model; a sheet of the same material as the main body model is cut according to the shape of the sheet model and then overlapped on the upper surface of the main body model; the printer performs an empty scanning without powder spreading according to the contact assembly contour line of the main body model and the sheet model; and the printer prints the top cover model based on the main body model and the sheet model. The powder bed fusion 3D printing method of the fully-closed cavity structure solves the problems of cleaning the powder in the cavity and the problem that the upper surface of the cavity cannot be printed in suspension.

Description

Technical Field

[0001] This invention relates to the field of 3D printing technology, and more specifically to a powder bed fusion 3D printing method with a fully enclosed cavity structure. Background Technology

[0002] Powder bed fusion (PBF) 3D printing mainly uses powder as raw material and uses laser or electron beam as heat source to scan the powder layer by layer laid on the powder bed. The scanned powder melts and solidifies to form a solid. Layer by layer solids are added to finally form a part that is consistent with the input model.

[0003] Specifically, the steps of powder bed fusion 3D printing are as follows: 1. Determine the printing direction of the part and add supports according to the placement of the part; 2. Define the printing parameters and slice the processed model and support; 3. Import the slice data into the printer; 4. The printer lays powder layer by layer and prints layer by layer according to the slice data; 5. After printing, clean up the excess powder around the product; 6. Remove the excess support structure to obtain a three-dimensional solid product consistent with the design model.

[0004] Powder bed fusion (PBF) achieves three-dimensional forming primarily through the layer-by-layer deposition of powder raw materials and selective melting by a heat source. Currently, PPF can be categorized into two types based on the heat source: laser and electron beam. Compared to other 3D printing technologies, PPF offers higher printing precision and surface finish.

[0005] However, due to inherent limitations of the technology, it cannot perform suspended printing with a planar bottom structure. The difficulty of printing fully enclosed cavity structures using powder bed fusion technology lies in the inability to suspend the top surface of the cavity and the inability to remove unmelted powder from inside the cavity. Summary of the Invention

[0006] The purpose of this invention is to address the shortcomings of the above-mentioned technologies by providing a powder bed fusion 3D printing method with a fully enclosed cavity structure, which solves the problems of cleaning the powder inside the cavity and the inability to print while suspended on the upper surface of the cavity.

[0007] To achieve the above objectives, the powder bed fusion 3D printing method with a fully enclosed cavity structure designed in this invention includes the following steps:

[0008] A) Divide the parts to be printed into three models. The main model is the main part of the part, with a continuous cavity structure and an open top surface. The sheet model is a sheet-like solid structure, whose planar shape is consistent with the top surface of the cavity structure of the main model, and whose outline size is slightly larger than the outer outline of the cavity structure. The top cover model is a solid structure, which is the top cover of the part and completely covers the open structure of the main model.

[0009] B) In the preprocessing software, assemble the main body model and the top cover model together, slice them, and import them into the printer;

[0010] C) Use a printer to print the main model, and clean the excess powder inside the cavity of the main model after printing;

[0011] D) Use a thin sheet made of the same material as the main model, cut it according to the shape of the sheet model, and then attach it to the upper surface of the main model;

[0012] E) The printer performs a dry scan without spreading toner, following the contact assembly outline of the main model and the sheet model.

[0013] F) The printer uses the main body model and the sheet model as a base to print the top cover model.

[0014] Preferably, after the top cover model is printed, the cavity structure of the main body model is completely sealed.

[0015] Preferably, the upper surface of the main model has a pre-reserved overlapping structure for placing the sheet model, and when the sheet model is placed on the main model, its upper surface is flush with the upper surface of the main model.

[0016] Preferably, the thickness of the thin film model is adjusted according to the printing parameters to ensure that the heat source will not burn through the thin film model after a single layer of powder material is laid on the surface of the thin film model.

[0017] Preferably, in step D), the sheet model is processed using sheet profiles through cutting, laser cutting, or wire cutting.

[0018] Preferably, in step D), the sheet model is printed using a printer from the same furnace.

[0019] Preferably, in step D), after the main model and the thin sheet model are assembled, an external laser spot welding or resistance welding self-fusion welding method is introduced to weld the main model and the thin sheet model together. After welding, the weld is ground so that the weld is flush with the upper surface of the main model and the thin sheet model after assembly.

[0020] Preferably, when the part to be printed contains multiple discontinuous cavity structures along the powder layer stacking direction, for each additional cavity structure, a main body model and a thin sheet model are added. During printing, the parts are assembled in the order of main body model-thin sheet model-main body model-thin sheet model-…-thin sheet model-top cover model. After each main body model is printed, the excess powder inside the cavity of the main body model is cleaned.

[0021] Preferably, when there are multiple non-interconnected cavity structures in the part to be printed, if the top surfaces of all cavity structures are at the same height, print according to steps A) to F). If the top surfaces of the cavity structures are at different heights, add multiple thin sheet models. For each cavity structure whose top surface is printed, assemble a thin sheet model to close the cavity structure.

[0022] Preferably, the cavity structure within the main model is a dome-shaped structure.

[0023] Compared with the prior art, the present invention has the following advantages: it solves the problem of cleaning powder inside the cavity and the problem of printing without suspension on the upper surface of the cavity. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the structure of the model in this invention;

[0025] Figure 2 A longitudinal sectional view of the main model.

[0026] The components in the diagram are labeled as follows:

[0027] Main body model 1, thin sheet model 2, top cover model 3, cavity structure 4. Detailed Implementation

[0028] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0029] A powder bed fusion 3D printing method with a fully enclosed cavity structure includes the following steps:

[0030] A) Divide the parts to be printed into three models, such as Figure 1 and Figure 2 As shown, the main body model 1 is the main body of the part, with a continuous cavity structure 4, and the top surface of the cavity structure 4 is an open structure. The sheet model 2 is a sheet-like solid structure, whose planar shape is consistent with the top surface of the cavity structure 4 of the main body model 1, and its outline size is slightly larger than the outer outline of the cavity structure 4. The top cover model 3 is a solid structure, which is the top cover of the part, and fully covers the open structure of the main body model 1.

[0031] B) In the preprocessing software, assemble the main body model 1 and the top cover model 3 together, slice them, and import them into the printer;

[0032] C) Use a printer to print the main model 1. After printing, clean the excess powder inside the cavity of the main model 1. You can use methods such as pouring, hammering the substrate with a rubber mallet, vacuuming, or nitrogen blowing to clean the powder inside the cavity structure.

[0033] D) Using a thin plate made of the same material as the main model 1, cut it according to the shape of the thin plate model 2 and attach it to the upper surface of the main model 1;

[0034] E) The printer performs a dry scan without spreading toner, following the contact assembly outline of the main body model 1 and the sheet model 2, to ensure that the main body model and the sheet model establish an effective connection, so that the sheet model does not fall into the cavity structure when printing the top cover model.

[0035] F) The printer uses the main body model 1 and the sheet model 2 as a base to print the top cover model 3.

[0036] After the top cover model 3 is printed, the cavity structure 4 of the main body model 1 is completely sealed.

[0037] In this embodiment, the upper surface of the main body model 1 is reserved with an overlapping structure for placing the thin sheet model 2. When the thin sheet model 2 is placed on the main body model 1, its upper surface is flush with the upper surface of the main body model 1.

[0038] In this embodiment, the thickness of the thin sheet model 2 is adjusted according to the printing parameters to ensure that the heat source will not burn through the thin sheet model 2 after a single layer of powder material is laid on the surface of the thin sheet model 2.

[0039] In addition, in step D), the sheet model 2 is processed using sheet profiles by cutting, laser cutting or wire cutting, or it can be printed using a printer in the same furnace.

[0040] Moreover, in step D), after the main body model 1 and the thin sheet model 2 are assembled, the main body model 1 and the thin sheet model 2 are welded together by external laser spot welding or resistance welding. After welding, the weld is ground so that the weld is flush with the upper surface of the main body model 1 and the thin sheet model 2 after assembly.

[0041] In other embodiments, when the part to be printed contains multiple discontinuous cavity structures 4 along the powder layer stacking direction, for each additional cavity structure 4, a main body model 1 and a thin sheet model 2 are added. During printing, the parts are assembled in the order of main body model 1-thin sheet model 2-main body model 1-thin sheet model 2-…-thin sheet model 2-top cover model 3. After each main body model 1 is printed, the excess powder inside the cavity of the main body model 1 is cleaned.

[0042] When there are multiple non-interconnected cavity structures 4 in the part to be printed, if the top surfaces of all cavity structures 4 are at the same height, print according to steps A to F. If the top surfaces of cavity structures 4 are at different heights, add multiple thin sheet models 2. For each top surface of a cavity structure 4 printed, assemble a thin sheet model 2 to close the cavity structure 4.

[0043] In some embodiments, the cavity structure 4 within the main body model 1 can be designed as a dome structure to reduce the effective area of ​​the sheet model.

[0044] If the cavity structure 4 of the main body model 1 is shallow, the powder inside the cavity can be cleaned directly without removing the parts. In this case, a vacuum cleaner can be used to clean the powder inside the cavity separately and maintain the remaining unmelted powder around the main body model 1, reducing the need for subsequent refilling of powder.

[0045] If the sheet model 2 is a part printed in the same furnace as the main model 1, it can be printed at the height of the last few layers of the main model 1. A support structure is used below the main model 1. When cleaning the powder from the inner cavity of the main model 1, the sheet model 2 is removed, ensuring the parallelism between the upper and lower planes of the sheet model 2 as much as possible during removal. If deformation occurs during the removal of the sheet model 2, it can be flattened using rolling or heavy pressing before being assembled back into the main model 1.

[0046] If the main body model 1 is not a completely empty structure, but is filled with a topological structure, then after the sheet model 2 is assembled with the main body model 1, since the topological structure supports the sheet model 2, step E) can be skipped, and step F) can be executed directly to spread powder and print the top cover model 3.

[0047] Finally, to prevent edge warping caused by deformation of the thin sheet model 2 after assembly from preventing the main body model 1 and the thin sheet model 2 from being ineffectively connected during the air scan, an auxiliary fixture can be introduced to press the thin sheet model 2 firmly before performing the air scan. After the scan is completed, the auxiliary fixture can be removed before proceeding to step F.

[0048] To reduce the structural strength risks caused by the overlap between the main model 1 and the thin sheet model 2, the scanning area can be increased during the empty scan to fully scan the effective overlap area of ​​the main model 1 and the thin sheet model 2, ensuring that there are no assembly gaps between the main model 1 and the thin sheet model 2 after the scan is completed.

Claims

1. A powder bed fusion 3D printing method with a fully enclosed cavity structure, characterized in that: Includes the following steps: A) The parts to be printed are divided into three models. The main body model (1) is the main body of the part, with a continuous cavity structure (4) and the top surface of the cavity structure (4) is an open structure. The sheet model (2) is a sheet-like solid structure, and its planar shape is consistent with the top surface of the cavity structure (4) of the main body model (1), and its outline size is slightly larger than the outer outline of the cavity structure (4). The top cover model (3) is a solid structure, which is the top cover of the part, and fully covers the open structure of the main body model (1). The upper surface of the main body model (1) has a reserved overlapping structure for placing the sheet model (2). When the sheet model (2) is placed on the main body model (1), its upper surface is flush with the upper surface of the main body model (1). B) In the preprocessing software, assemble the main body model (1) and the top cover model (3) together, slice them, and import them into the printer; C) Use a printer to print the main model (1), and clean up any excess powder inside the cavity of the main model (1) after printing; D) Use a thin plate made of the same material as the main model (1), cut it according to the shape of the thin plate model (2), and attach it to the upper surface of the main model (1); E) The printer performs a dry scan without spreading toner, following the contact assembly outline of the main body model (1) and the sheet model (2). F) The printer uses the main body model (1) and the sheet model (2) as a base to print the top cover model (3). After the top cover model (3) is printed, the cavity structure (4) of the main body model (1) is completely sealed.

2. The powder bed fusion 3D printing method for a fully enclosed cavity structure as described in claim 1, characterized in that: The thickness of the thin sheet model (2) is adjusted according to the printing parameters to ensure that the heat source will not burn through the thin sheet model (2) after a single layer of powder material is laid on the surface of the thin sheet model (2).

3. The powder bed fusion 3D printing method for a fully enclosed cavity structure as described in claim 1, characterized in that: In step D), the sheet model (2) is processed using sheet profiles by cutting, laser cutting or wire cutting.

4. The powder bed fusion 3D printing method with a fully enclosed cavity structure as described in claim 1, characterized in that: In step D), the sheet model (2) is printed using a printer from the same furnace.

5. The powder bed fusion 3D printing method for a fully enclosed cavity structure as described in claim 1, characterized in that: In step D), after the main body model (1) and the thin sheet model (2) are assembled, the main body model (1) and the thin sheet model (2) are welded together by external laser spot welding or resistance welding. After welding, the weld is ground so that the weld is flush with the upper surface of the main body model (1) and the thin sheet model (2) after assembly.

6. The powder bed fusion 3D printing method for a fully enclosed cavity structure as described in claim 1, characterized in that: When the part to be printed contains multiple discontinuous cavity structures (4) along the powder layer stacking direction, for each cavity structure (4) added, a main body model (1) and a thin sheet model (2) are added. During printing, the parts are assembled in the order of main body model (1) - thin sheet model (2) - main body model (1) - thin sheet model (2) - ... - thin sheet model (2) - top cover model (3). For each main body model (1) printed, the excess powder in the cavity of the main body model (1) is cleaned.

7. The powder bed fusion 3D printing method for a fully enclosed cavity structure as described in claim 1, characterized in that: When there are multiple non-interconnected cavity structures (4) in the part to be printed, if the top surfaces of all cavity structures (4) are at the same height, print according to steps A) to F). If the top surfaces of cavity structures (4) are at different heights, add multiple sheet models (2). For each top surface of a cavity structure (4) printed, assemble a sheet model (2) to close the cavity structure (4).

8. The powder bed fusion 3D printing method for a fully enclosed cavity structure as described in claim 1, characterized in that: The cavity structure (4) inside the main model (1) is a dome structure.

Images