3D printing method, printed product and printing apparatus

Abstract

A 3D printing method, comprising the following steps: preparing a raw-material powder, and loading a substrate into a selective laser melting device; performing slicing and layering processing on a three-dimensional model, and importing data into a 3D printer; selecting a multi-laser real-time heat treatment scanning policy, and selecting appropriate printing parameters; spreading the raw-material powder evenly on the substrate, a first laser system starting to scan and melt the raw-material powder, and at the same time, a subsequent laser system starting scanning following the first laser system, so as to form a melted layer, until the scanning of the layer is finished; controlling the substrate to descend to a set height, spreading the raw-material powder on the melted layer again, and rescanning the spread raw material powder; and repeating the previous step until printing is completed. By means of the method, the residual stress can be reduced more efficiently, the requirement for the preheating temperature of a substrate is low, and the problems of the surface roughness being high, the printing accuracy being low, etc. are avoided; and it is not necessary to adjust the chemical composition of a printing material in order to reduce its cracking susceptibility. The present invention further relates to a printed product and a printing apparatus.

Description

3D printing method, printing product and printing device Technical Field

[0001] The present invention relates to the field of laser melting additive manufacturing technology, and specifically to a 3D printing method, a printing product and a printing device, and in particular to a method for eliminating residual stress of materials in 3D printing. Background Art

[0002] During the 3D printing process, due to the rapid laser melting and cooling, huge residual stress will be generated inside the plastic material parts produced by additive manufacturing. Residual stress has many negative effects on additively manufactured parts. Extreme residual stress can cause parts to warp. In severe cases, residual stress can cause cracks in the parts during the printing process, causing the part printing to fail directly.

[0003] To reduce residual stress and cracking in plastic materials, such as alloys, during additive manufacturing, existing methods include laser remelting, increasing the substrate temperature, and adjusting the alloy composition.

[0004] (1) Laser remelting: In the existing laser remelting method, the laser will first scan the powder bed on which the raw material is laid to obtain a cladding layer. After the laser scans the layer, the cladding layer is scanned again at the set laser power and scanning rate to reduce the residual stress.

[0005] (2) Increasing the substrate temperature: This method is mainly used to reduce the temperature difference and gradient between the solidified molten pool and the substrate, thereby reducing the cooling rate and residual stress of the molten pool.

[0006] (3) Adjusting alloy composition: By adjusting the alloy composition, the crack sensitivity of the material during the additive manufacturing process can be reduced, and the alloy cracking can be reduced.

[0007] However, due to the limitations of their own technologies, the above three methods have the following disadvantages:

[0008] (1) Laser remelting: This technical method uses the laser to re-scan the cladding layer after the laser scans a certain layer of powder. This method has two major disadvantages. On the one hand, the two laser scans of each layer significantly increase the production time and reduce production efficiency. On the other hand, the existing laser remelting technology has solidified the molten pool before the second scan. After the second scan, the solidified solid is re-melted and re-solidified. During this re-solidification process, the temperature gradient between the molten pool and the substrate is still large, resulting in a large cooling rate, which makes the residual stress reduction effect limited.

[0009] (2) Substrate heating: Although substrate heating (≥300°C) can effectively reduce residual stress without reducing production efficiency, excessively high substrate temperature can cause significant damage to components in the machine's internal optical system, seals, and filtration systems. Currently, it is difficult to find these components that can withstand temperatures above 200°C. In addition, excessively high substrate temperature can result in excessively rough surfaces for printed parts.

[0010] (3) Adjusting alloy composition: For example, for high-temperature nickel-based alloys, one of the main ways to reduce the crack sensitivity of high-temperature alloys during the printing process is to reduce the composition of the main strengthening precipitation phase γ'. However, this method will sacrifice the mechanical properties that the material can achieve, such as high-temperature strength, and limit the service life of the alloy parts during service.

[0011] In order to address the shortcomings of the above-mentioned common methods and at the same time reduce the residual stress and cracking of 3D printed parts after production, a 3D printing method, printing product and printing device are provided.

[0012] Summary of the Invention

[0013] The purpose of the present invention is to provide a 3D printing method, printing product and printing device that can significantly reduce the residual stress of 3D printed parts while having the advantages of high production efficiency, low substrate preheating temperature requirements, and a wide range of material composition applications.

[0014] In order to solve the above technical problems, the technical solution adopted by the present invention is:

[0015] A 3D printing method comprises the following steps:

[0016] S1, prepare raw material powder, load it into the powder supply chamber of the selective laser melting equipment, load the substrate into the selective laser melting equipment, and introduce protective gas;

[0017] S2, slicing and layering the three-dimensional model of the part to be printed, and importing the layered data into the 3D printer;

[0018] S3, on the 3D printer operation page, select the pre-set multi-laser real-time heat treatment scanning strategy in the program, control two or more laser systems to scan simultaneously, and select appropriate printing parameters based on different raw materials;

[0019] S4: The 3D printer starts printing, spreading the raw material powder on the base of the print chamber. The first laser system starts scanning to melt the raw material powder. The subsequent laser systems follow the first laser system and start scanning to form a melted layer until the scanning is completed.

[0020] S5, after one layer of scanning is completed, the system controls the substrate to descend to a set height, and raw material powder is re-laid on the melted layer, and two or more sets of the laser systems scan the laid raw material powder again;

[0021] S6, repeat step S5 until printing is completed.

[0022] In a preferred embodiment, in step S1, the raw material powder is an alloy powder, including but not limited to one or more of nickel-based, titanium-based, iron-based and aluminum-based.

[0023] In a preferred embodiment, the alloy powder includes but is not limited to the following components in terms of mass percentage:

[0024] Fe: 0-95wt%; Co: 0-26wt%; Ni: 0-80wt%; Al: 0-10wt%; Ti: 0-95wt%; Cr: 0-30wt%; Mo: 0-30wt%; W: 0-20wt%; Nb: 0-7wt%; Ta : 0-11wt%; B: 0-0.1wt%; C: 0-2wt%; Zr: 0-8wt%; Hf: 0-5wt%; Si: 0-3wt%; V: 0-10wt%; O: 0-0.2wt%; Sn: 0-3wt%; Mn: 0-3wt%.

[0025] In a preferred solution, in step S1, the protective gas includes but is not limited to nitrogen or argon.

[0026] In a preferred embodiment, in step S3, the printing parameters include but are not limited to the first set of laser power, the first set of laser scanning rate, the first set of laser defocus, subsequent laser power, subsequent laser scanning rate, subsequent laser defocus, laser scanning interval time and melting layer thickness.

[0027] In a preferred solution, in step S4, before the raw material powder melted by the first laser system solidifies, the subsequent laser system performs a real-time annealing process before the molten pool solidifies.

[0028] In a preferred solution, in step S4, the time required for a single laser system scan of a certain layer is set to t, and the time required for multiple lasers to perform real-time heat treatment on a certain layer is set to t plus the laser scanning interval dt. Since the subsequent laser systems follow the first laser system for scanning, dt is much smaller than t, and the laser system scanning time is similar to the time required for a single scan of each layer, that is, t+dt≈t.

[0029] In order to better and more comprehensively protect the technology, this application also includes a 3D printed product manufactured using a 3D printing method.

[0030] In order to better and more comprehensively protect the technology, this application also includes a 3D printing device for performing a 3D printing method.

[0031] Due to the application of the above technical solution, the beneficial effects of this application compared with the prior art are:

[0032] The present application provides a 3D printing method, printing product, and printing device that can more efficiently reduce residual stress and have much higher production efficiency than existing laser remelting technology. The multi-laser real-time heat treatment technology has low requirements for substrate preheating temperature, thereby minimizing damage to equipment in the printing chamber during the printing process and avoiding problems such as high surface roughness and reduced printing accuracy caused by excessive substrate preheating temperature. The method also does not require the chemical composition of the printing material to be adjusted in order to reduce crack sensitivity, thereby eliminating the need to be forced to lower the original performance standards of the material. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the specific embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0034] FIG1 is a schematic flow chart of a 3D printing method according to the present invention;

[0035] FIG2 is a schematic diagram of multi-laser real-time heat treatment scanning of the present invention. DETAILED DESCRIPTION

[0036] In order to enable those skilled in the art to better understand the present invention, the following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts should fall within the scope of protection of this application.

[0037] It should be noted that the terms "first," "second," etc. in the specification and claims of the present application and the above-mentioned drawings are used to distinguish similar objects and are not necessarily used to describe a specific order or sequential sequence. It should be understood that the numbers used in this way can be interchanged where appropriate, so that the embodiments of the present application described herein. In addition, the terms "including" and "having," as well as any variations thereof, are intended to cover non-exclusive inclusions. For example, a process, method, system, product, or device comprising a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products, or devices.

[0038] In this application, terms such as "upper," "lower," "left," "right," "front," "back," "top," "bottom," "inner," "outer," "center," "vertical," "horizontal," "transverse," and "longitudinal" indicate positions or locations based on the positions or locations shown in the accompanying drawings. These terms are primarily intended to better describe the present invention and its embodiments and are not intended to limit the devices, elements, or components indicated to having a specific orientation, or to being constructed or operated in a specific orientation.

[0039] Furthermore, some of the above terms may be used to express other meanings besides indicating a position or location. For example, the term "on" may also be used to indicate a dependency or connection in certain circumstances. Those skilled in the art will understand the specific meanings of these terms in the present invention based on the specific circumstances.

[0040] Furthermore, the terms "installed," "disposed," "provided with," "connected," "connected," and "socketed" should be interpreted broadly. For example, they can refer to fixed connections, removable connections, or integral structures; mechanical connections or electrical connections; direct connections or indirect connections through an intermediary; or internal communication between two devices, elements, or components. Those skilled in the art will understand the specific meanings of these terms in the present invention based on specific circumstances.

[0041] It should be noted that, in the absence of conflict, the embodiments and features of the embodiments in this application can be combined with each other. The present application will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0042] Example 1

[0043] Referring to Figures 1 and 2 , this application provides a 3D printing method, comprising the following steps:

[0044] S1, preparing raw material powder, wherein the raw material powder is an alloy powder, and includes but is not limited to the following components in percentage by mass:

[0045] Co: 9.3wt%; Ni: balance; Al: 5.6wt%;

[0046] Ti: 0.7wt%; Cr: 8wt%; Mo: 0.5wt%;

[0047] W: 9.5wt%; Ta: 3.2wt%; B: 0.015wt%;

[0048] C:0.07wt%; Zr:0.01wt%; Hf:1.4wt%;

[0049] The substrate is loaded into the powder supply chamber of the selective laser melting equipment, and a protective gas is introduced, wherein the protective gas is nitrogen or argon;

[0050] S2, slicing and layering the three-dimensional model of the part to be printed, and importing the layered data into the 3D printer;

[0051] S3. On the 3D printer operation page, select the pre-set multi-laser real-time heat treatment scanning strategy in the program, control two or more laser systems to scan simultaneously, and select appropriate printing parameters according to different raw materials. The printing parameters include but are not limited to the first laser power, the first laser scanning rate, the first laser defocus amount, the subsequent laser power, the subsequent laser scanning rate, the subsequent laser defocus amount, the laser scanning interval time, and the thickness of the melt layer;

[0052] The specific parameters are as follows:

[0053] First laser power: 250W; First laser scanning rate: 1200mm / s; First laser defocus: 0.15mm; Subsequent laser power: 150W; Subsequent laser scanning rate: 1200mm / s; Subsequent laser defocus: 0.15mm; Laser scanning interval: 1ms; Melted layer thickness: 0.06mm;

[0054] S4, the 3D printer starts printing, spreading the raw material powder flat on the base plate of the print chamber. The first laser system starts scanning to melt the raw material powder. The subsequent laser systems follow the first laser system and start scanning to form a melt layer. Before the raw material powder melted by the first laser system solidifies, the subsequent laser systems perform a real-time annealing process before the molten pool of this layer solidifies until the scanning of this layer is completed;

[0055] S5, after one layer of scanning is completed, the system controls the substrate to descend to a set height, and raw material powder is re-laid on the melted layer, and two or more sets of the laser systems scan the laid raw material powder again;

[0056] S6, repeat step S5 until printing is completed.

[0057] Example 2

[0058] This application provides a 3D printing method, comprising the following steps:

[0059] S1, preparing raw material powder, wherein the raw material powder is an alloy powder, and includes but is not limited to the following components in percentage by mass:

[0060] Ti: balance; Al: 6.0wt%; V: 4wt%;

[0061] Fe: 0.2wt%; C: 0.1wt%; O: 0.1wt%;

[0062] The substrate is loaded into the powder supply chamber of the selective laser melting equipment, and a protective gas is introduced, wherein the protective gas is nitrogen or argon;

[0063] S2, slicing and layering the three-dimensional model of the part to be printed, and importing the layered data into the 3D printer;

[0064] S3. On the 3D printer operation page, select the pre-set multi-laser real-time heat treatment scanning strategy in the program, control two or more laser systems to scan simultaneously, and select appropriate printing parameters according to different raw materials. The printing parameters include but are not limited to the first laser power, the first laser scanning rate, the first laser defocus amount, the subsequent laser power, the subsequent laser scanning rate, the subsequent laser defocus amount, the laser scanning interval time, and the thickness of the melt layer;

[0065] The specific parameters are as follows:

[0066] First laser power: 200W; First laser scanning rate: 800mm / s; First laser defocus: 0.10mm; Subsequent laser power: 100W; Subsequent laser scanning rate: 800mm / s; Subsequent laser defocus: 0.1mm; Laser scanning interval: 5ms; Melted layer thickness: 0.04mm;

[0067] S4, the 3D printer starts printing, spreading the raw material powder flat on the base plate of the print chamber. The first laser system starts scanning to melt the raw material powder. The subsequent laser systems follow the first laser system and start scanning to form a melt layer. Before the raw material powder melted by the first laser system solidifies, the subsequent laser systems perform a real-time annealing process before the molten pool of this layer solidifies until the scanning of this layer is completed;

[0068] S5, after one layer of scanning is completed, the system controls the substrate to descend to a set height, and raw material powder is re-laid on the melted layer, and two or more sets of the laser systems scan the laid raw material powder again;

[0069] S6, repeat step S5 until printing is completed.

[0070] Example 3

[0071] This application provides a 3D printing method, comprising the following steps:

[0072] S1, preparing raw material powder, wherein the raw material powder is an alloy powder, and includes but is not limited to the following components in percentage by mass:

[0073] Fe: balance; Cr: 19wt%; Ni: 9wt%; C: 0.05wt%;

[0074] The substrate is loaded into the powder supply chamber of the selective laser melting equipment, and a protective gas is introduced, wherein the protective gas is nitrogen or argon;

[0075] S2, slicing and layering the three-dimensional model of the part to be printed, and importing the layered data into the 3D printer;

[0076] S3. On the 3D printer operation page, select the pre-set multi-laser real-time heat treatment scanning strategy in the program, control two or more laser systems to scan simultaneously, and select appropriate printing parameters according to different raw materials. The printing parameters include but are not limited to the first laser power, the first laser scanning rate, the first laser defocus amount, the subsequent laser power, the subsequent laser scanning rate, the subsequent laser defocus amount, the laser scanning interval time, and the thickness of the melt layer;

[0077] The specific parameters are as follows:

[0078] First laser power: 120W; First laser scanning rate: 500mm / s; First laser defocus: 0.06mm; Subsequent laser power: 50W; Subsequent laser scanning rate: 500mm / s; Subsequent laser defocus: 0.06mm; Laser scanning interval: 10ms; Melted layer thickness: 0.03mm;

[0079] S4, the 3D printer starts printing, spreading the raw material powder flat on the base plate of the print chamber. The first laser system starts scanning to melt the raw material powder. The subsequent laser systems follow the first laser system and start scanning to form a melt layer. Before the raw material powder melted by the first laser system solidifies, the subsequent laser systems perform a real-time annealing process before the molten pool of this layer solidifies until the scanning of this layer is completed;

[0080] S5, after one layer of scanning is completed, the system controls the substrate to descend to a set height, and raw material powder is re-laid on the melted layer, and two or more sets of the laser systems scan the laid raw material powder again;

[0081] S6, repeat step S5 until printing is completed.

[0082] The above embodiment illustrates that the 3D printer involved in this method will control two or more laser systems to scan simultaneously, and the subsequent lasers will follow the scanning trajectory of the first laser. Before the raw material powder melted by the first laser is solidified, the subsequent laser system reaches the molten pool and performs a real-time annealing treatment to reduce the cooling rate of the molten pool, thereby achieving the effect of reducing residual stress.

[0083] Assuming the time required for a single laser scan of a layer is t, the time required for multiple lasers to scan a layer in real-time heat treatment is simply t plus the laser scan interval dt. Since subsequent laser systems scan immediately after the initial laser system, dt is significantly less than t. Therefore, the laser system scan time and the time required for a single scan of each layer are almost equal: t + dt ≈ t. In contrast, with existing laser remelting technology, the laser scans a complete layer and then repeats it one or more times. The laser scan time is n * t, where n is the number of repeated scans. Therefore, the production efficiency of the method proposed in this invention is far superior to that of existing laser remelting technology.

[0084] In addition to the difference in production efficiency, the method proposed in the present invention and the existing laser remelting technology also have obvious differences in the effect of reducing residual stress. The existing laser remelting technology has solidified the molten pool before the second scan. After the second scan, the solidified solid is re-melted and re-solidified. During this re-solidification process, the temperature gradient between the molten pool and the substrate is still large, resulting in a large cooling rate, which limits the effect of reducing residual stress. In the method proposed in the present invention, the subsequent laser system performs an "in-situ annealing" before the solidification of this layer of molten pool. Therefore, the cooling rate of the molten pool is greatly reduced, and the residual stress elimination effect is significant.

[0085] In addition, the multi-laser real-time heat treatment technology in the present invention has low requirements for the substrate preheating temperature, so the damage to the equipment in the printing chamber during the printing process is low, and problems such as high surface roughness caused by excessively high substrate preheating temperature are avoided; this method also does not require the chemical composition of the printed material to be adjusted in order to reduce crack sensitivity, thereby eliminating the need to be forced to lower the original performance standards of the material.

[0086] In summary, the 3D printing method proposed in the present invention can significantly reduce the residual stress of 3D printed parts, while also having the advantages of high production efficiency, low substrate preheating temperature requirements, and a wide range of material composition applications.

[0087] In order to better and more comprehensively protect the technology, this application also includes technical solutions for 3D printing products and 3D printing devices, specifically including a 3D printing product manufactured using a 3D printing method; and a 3D printing device for executing the 3D printing method.

[0088] The method of the present invention can be applied to different multi-laser 3D printing systems (lasers ≥ 2). The specific multi-laser scanning interval duration, the specific scanning parameters of the first laser and subsequent lasers, and the laser spatial distribution (flat-top distribution or Gaussian distribution) involved in the present invention are merely illustrative and are not intended to limit their specific parameter data. Applicable material systems include but are not limited to nickel-based, titanium-based, iron-based, aluminum-based alloy systems. For those skilled in the art, other different forms of changes or modifications can be made based on the above description, and it is not necessary and impossible to list all implementation methods here.

[0089] Finally, it should be noted that the above are only preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art can still modify the technical solutions described in the aforementioned embodiments or make equivalent replacements for some of the technical features therein. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A 3D printing method, characterized in that: The steps include: S1, prepare raw material powder, load it into the powder supply chamber of the selective laser melting equipment, load the substrate into the selective laser melting equipment, and introduce protective gas; S2, slicing and layering the three-dimensional model of the required printed part, and importing the layered data into the 3D printer; S3, in the 3D printer operation page, select the multi-laser real-time heat treatment scanning strategy preset in the program, adjust more than two laser systems to scan simultaneously, and select appropriate printing parameters according to different raw materials; S4, the 3D printer starts printing, and the raw material powder is spread flat on the substrate of the printing chamber. The first laser system starts scanning and melting the raw material powder, and the subsequent laser systems follow the first laser system to start scanning to form a melted layer until the scanning is completed; S5, after one layer of scanning is completed, the system controls the substrate to descend to a set height, and the raw material powder is re-laid on the molten layer, and the two or more sets of the laser systems scan the laid raw material powder again; S6, repeat step S5 until printing is completed.

2. The 3D printing method according to claim 1, characterized in that: In step S1 , the raw material powder is an alloy powder, including but not limited to one or more of nickel-based, titanium-based, iron-based and aluminum-based.

3. The 3D printing method according to claim 2, characterized in that: The alloy powder includes, but is not limited to, the following components by mass percentage: Fe: 0-95wt%; Co: 0-26wt%; Ni: 0-80wt%; Al: 0-10wt%; Ti: 0-95wt%; Cr: 0-30wt%; Mo: 0-30wt%; W: 0-20wt%; Nb: 0-7wt%; Ta: 0-11wt%; B: 0-0.1wt%; C: 0-2wt%; Zr: 0-8wt%; Hf: 0-5wt%; Si: 0-3wt%; V: 0-10wt%; O: 0-0.2wt%; Sn: 0-3wt%; Mn: 0-3wt%.

4. The 3D printing method according to claim 1, characterized in that: In step S1, the protective gas includes but is not limited to nitrogen or argon.

5. The 3D printing method according to claim 1, wherein: In step S3, the printing parameters include but are not limited to the first set of laser power, the first set of laser scanning rate, the first set of laser defocus, subsequent laser power, subsequent laser scanning rate, subsequent laser defocus, laser scanning interval time and melting layer thickness.

6. The 3D printing method according to claim 1, characterized in that: In step S4, before the raw material powder melted by the first laser system solidifies, the subsequent laser system performs a real-time annealing process before the molten pool solidifies.

7. The 3D printing method according to claim 6, characterized in that: In step S4, the time required for a single laser scan of a layer is set to t, and the time required for multiple laser real-time heat treatment scanning of a layer is set to t plus the laser scanning interval dt. Since the subsequent laser systems follow the first laser system for scanning, dt is much smaller than t, and the scanning time of the laser system is similar to the time required for a single scan of each layer, that is, t+dt≈t.

8. A 3D printed product, characterized in that: The 3D printing method according to any one of claims 1 to 7 is used for manufacturing.

9. A 3D printing device, characterized in that: Used to perform the 3D printing method according to any one of claims 1 to 7.

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