DOE switching device and additive manufacturing equipment

Abstract

The utility model relates to a DOE switching device. The device is configured in an optical path of an additive manufacturing apparatus before a laser beam is incident on a deflection mirror (25) and includes a support portion (31), a separation portion (32), and a mounting portion (33). The supporting part (31) is respectively and fixedly connected with the deflecting mirror (25) and a component before a laser beam enters the deflecting mirror (25), the separating part (32) is detachably fixed on the supporting part (31), and the mounting part (33) is fixed on the separating part (32) and is provided with a diffractive optical element for shaping a Gaussian light spot of the laser beam into a flat-topped light spot. According to the invention, free switching among different light spot shapes can be realized, and repeated installation errors during DOE switching can be reduced, so that the light spot shape required by single crystal preparation can be better met.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of additive manufacturing, and more particularly to a DOE switching device and an additive manufacturing equipment with the same. BACKGROUND

[0002] Additive manufacturing (AM) technology based on powder bed, such as laser powder bed fusion (PBF-LB), melts and solidifies metal powder layer by layer by laser to achieve high-precision and complex-geometry component manufacturing. This technology has many advantages in metal component production, including reducing material waste, shortening production cycle and supporting lightweight design, and is widely used in the manufacturing of high-performance parts in aerospace, energy and medical industries.

[0003] The existing PBF-LB technology generally uses a Gaussian laser beam with a high-energy center and a low-energy edge during the manufacturing process, which is easy to cause high-temperature gradient in the molten pool, resulting in deep melting and strong convection and other solidification characteristics, which is not conducive to the preparation of single crystals. Beam shaping technology can achieve precise control of molten pool shape, size and heat flow vector by adjusting the energy distribution of the laser. Diffraction optical element (DOE) is an optical element based on diffraction optical theory with high diffraction efficiency, which changes the transmission characteristics and beam intensity by compensating the phase of the input beam. It has been widely used in beam shaping technology since the late 20th century. However, the existing beam shaping technology is difficult to achieve dynamic adjustment of different DOEs, lacks the ability to freely switch between different spot shapes, and especially lacks the technical means to switch DOEs without disassembling other original optical components to reduce repeated installation errors. This deficiency limits the realization of high-degree control of solidification heat flow vector, making it difficult to meet the needs of single crystal preparation. CONTENT OF THE UTILITY MODEL

[0004] The present application proposes a DOE switching device and an additive manufacturing equipment with the same, which can achieve free switching between different spot shapes and reduce the repeated installation error when switching DOEs, to better meet the required spot shape for single crystal preparation.

[0005] In a first aspect, the present application provides a DOE switching device, which is configured in the optical path of an additive manufacturing equipment before a laser beam enters a deflection mirror and includes: a support part fixedly connected with the deflection mirror and a component before the laser beam enters the deflection mirror, respectively; a separation part detachably fixed on the support part; and a mounting part fixed on the separation part and mounting a diffraction optical element for shaping a Gaussian spot of the laser beam into a flat-top spot.

[0006] According to a preferred embodiment of the present application, the component includes a laser or a collimating mirror or a beam expander.

[0007] According to a preferred embodiment of the present application, the mounting portion comprises at least one displacement adjuster for adjusting the displacement of the diffractive optical element in the X-axis and / or Y-axis direction.

[0008] According to a preferred embodiment of the present application, the mounting portion comprises a threaded snap ring arranged inside the mounting portion and used for detachably fixing the diffractive optical element.

[0009] According to a preferred embodiment of the present application, the separating portion is arranged inlaid with the supporting portion, so as to inlay the diffractive optical element in at least one groove of the supporting portion in the mounted state.

[0010] According to a preferred embodiment of the present application, the component is sleeved in the connecting plate, and the supporting portion is fixed with the component through the connecting plate.

[0011] According to a preferred embodiment of the present application, the supporting portion is fixed with the component and the deflection mirror through at least one first positioning pin and at least one first screw, respectively.

[0012] According to a preferred embodiment of the present application, the separating portion is fixed with the supporting portion through at least one second positioning pin and at least one second screw.

[0013] In a second aspect, the present application provides an additive manufacturing device comprising the apparatus of any one of the first aspect.

[0014] It should be understood that the general description above and the detailed description below are only exemplary and are not limiting of the present application. BRIEF DESCRIPTION OF DRAWINGS

[0015] The accompanying drawings, which are incorporated herein and form part of the specification, illustrate one or more embodiments of the present disclosure and, together with the description, explain the principles of the present disclosure and serve to make and use the present disclosure.

[0016] Figure 1 A schematic diagram of a conventional additive manufacturing device is shown;

[0017] Figure 2 An exploded structure schematic diagram of the DOE switching apparatus in the optical path according to an embodiment of the present application is shown;

[0018] Figure 3 A use state structure schematic diagram of the DOE switching apparatus in the optical path according to an embodiment of the present application is shown;

[0019] Figure 4 A partial use state structure schematic diagram of the DOE switching apparatus in the optical path according to an embodiment of the present application is shown. DETAILED DESCRIPTION

[0020] Example implementations will now be described more fully with reference to the accompanying drawings. Example implementations may, however, be implemented in many different forms and should not be construed as limited to the examples set forth herein; rather, these example implementations are provided so that this disclosure will be thorough and complete, and will fully convey the inventive aspects of the example implementations to those skilled in the art. The described features, structures, or characteristics can be combined in one or more implementations in any suitable manner. In the following description, numerous specific details are provided to give a thorough understanding of implementations of the present application.

[0021] The "additive manufacturing (AM)" described in this application is a three-dimensional printing technology that manufactures components by adding powder material layer by layer and melting and solidifying the powder material layer by layer with a laser beam. This technology is based on a digital model generated by computer-aided design (CAD) software, precisely controls the melting and solidification process of each layer of material, and gradually manufactures a complete component.

[0022] Figure 1 A schematic diagram of a conventional additive manufacturing device is shown. For ease of understanding, the overall structure of the additive manufacturing device is described first. Referring to Figure 1 , the additive manufacturing device 10 mainly includes a printing cabin 11, a powder reservoir 12, a forming cylinder 13, a base plate 14, a powder spreading device 16, an optical path composed of multiple optical components, and a control system (such as a computer control system), etc.

[0023] The printing cabin 11 provides a working space for the manufacture of the component 17, and the working state is in a closed state to prevent interference from the external environment, ensuring that the printing process is carried out in a controlled atmosphere. For example, during the manufacturing process, the cabin needs to be filled with a protective gas such as argon or nitrogen to prevent the metal powder from reacting with oxygen in the air during high-temperature melting. The powder reservoir 12 is used to store metal powder, and the powder material consumption in the additive manufacturing process is carried out layer by layer, and the powder reservoir 12 is used to quantitatively deliver metal powder to the working plane 19. The forming cylinder 13 is arranged below the printing cabin 11, and the inside is arranged with the base plate 14 and the lifting device for controlling the lifting of the base plate 14, and as the printing layers increase, the forming cylinder 13 will gradually descend to provide printing space for subsequent layers. The powder spreading device 16 (scraper / roller) is used to uniformly spread the metal powder on the working plane 19 on the base plate 14 to form a powder layer / powder bed 15. The thickness of the powder spread on each layer is usually between tens of microns and hundreds of microns. The control system 18 is used to control various aspects of the manufacturing process, by setting parameters such as printing path, laser power, scanning speed, powder spreading thickness, etc., to ensure printing accuracy and component quality, and is used to monitor the running state of the device, such as temperature, gas pressure, laser output, etc., to ensure the stability of the printing process.

[0024] It should be understood that the additive manufacturing process is carried out by using the additive manufacturing device 10 of the present application. Figure 1 The general additive manufacturing process (3D printing method) mainly involves driving the powder in the powder reservoir 12 to be supplied onto the working plane 19 of the printing cabin 11 or to be released onto the substrate 14 by using the powder falling container arranged in the printing cabin 11 in other embodiments by using the control system 18, then driving the powder spreading device 16 to move along the working plane to uniformly cover the powder on the substrate 14 in a powder layer with a specific layer thickness, then driving the laser beam to selectively melt the powder layer spread on the substrate 14 according to the preset scanning path and process parameters (configured in the 3D model) to form a solidified layer, then driving the forming cylinder 13 to descend by a distance of one layer thickness and continue the operations of powder supply, powder spreading and melting of the powder layer, layer by layer accumulation, until the forming preparation of the component 17 matching the structure of the designed 3D model is completed on the substrate 14 (i.e. in the powder bed 15). In addition, some other operations are also involved, such as the supply and control of protective gas, wind field, monitoring of the printing process, etc., which are not expanded one by one here.

[0025] It should be understood that in the additive manufacturing device 10, the laser beam is precisely melted and scanned on the powder layer after being processed by various optical elements arranged in the optical path. The optical elements arranged in the optical path, for example, include a laser 21, a collimating mirror 22, a beam expander 23, a deflection mirror 25 (e.g. a galvanometer) and a focusing mirror 26 (an F-Theta lens) in sequence along the propagation path of the laser beam. After the laser beam is emitted from the laser 21, it is collimated by the collimating mirror 22, expanded in diameter by the beam expander 23, controlled in deflection by the deflection mirror 25 and precisely focused by the focusing mirror 26 to irradiate the powder layer.

[0026] According to the embodiments of the present application, a diffractive optical element 24 (DOE) is arranged in the optical path. The diffractive optical element 24 may, for example, be arranged in the optical path between the beam expander 23 and the deflection mirror 25 for shaping the laser beam emitted from the beam expander 23 from a Gaussian laser beam with Gaussian distribution of the light spot into a flat-top laser beam (e.g. a circular flat-top laser beam) with flat-top distribution of the light spot, and the shaped laser beam then passes through the deflection mirror 25 and the focusing mirror 26 in sequence to irradiate the powder layer.

[0027] In order to realize free switching between different light spot shapes (e.g. circular Gaussian light spot / circular / triangular / rectangular flat-top light spot) and reduce the repeated installation error when switching the DOE, and to better meet the required light spot shape for single crystal preparation, the embodiments of the present application provide a DOE switching device.

[0028] Figure 2 An exploded structural schematic diagram of the DOE switching device in the optical path according to the embodiments of the present application is shown, Figure 3Fig. 2 shows a schematic diagram of the DOE switching device in use in the optical path according to an embodiment of the present application, Figure 4 Fig. 3 shows a schematic diagram of the DOE switching device in use in the optical path according to an embodiment of the present application.

[0029] With reference to Figures 2-4 The DOE switching device according to an embodiment of the present application is arranged in the optical path before the laser beam enters the deflection mirror 25 in the additive manufacturing equipment, more specifically, between the beam expander 23 and the deflection mirror 25. The device comprises a support part 31, a separation part 32 and a mounting part 33. The support part 31 is fixedly connected to the beam expander 23 at one end and to the deflection mirror 25 at the other end in the optical path; the separation part 32 is detachably fixed to the support part 31; the mounting part 33 is fixed to the separation part 32 and mounts a diffractive optical element (DOE) for shaping the Gaussian beam spot of the laser beam into a flat-top beam spot.

[0030] Specifically, the support part 31 is fixed to the beam expander 23 and the deflection mirror 25 by two first positioning pins 34a, 34b for positioning and two first screws 35a, 35b for fixing, wherein the beam expander 23 is sleeved in the connecting plate 30, and the first positioning pins 34a, 34b and the first screws 35a, 35b are arranged through the connecting plate 30 to fix the support part 31 and the deflection mirror 25. The separation part 32 is fixed to the support part 31 by two second positioning pins 36a, 36b for positioning and two second screws 37a, 37b for fixing.

[0031] The length of the first positioning pins 34a, 34b is greater than that of the second positioning pins 36a, 36b, and the length of the first screws 35a, 35b is greater than that of the second screws 37a, 37b. The design of the separation part 32 makes the switching of the DOE in the optical path more convenient. The separation part 32 is firmly mounted on the support part 31 by the two second positioning pins 36a, 36b and the two second screws 37a, 37b. Compared with the first positioning pins 34a, 34b and the first screws 35a, 35b, the second positioning pins 36a, 36b and the second screws 37a, 37b are shorter in length, because the fixing between the separation part 32 and the support part 31 does not need to bear excessive mechanical stress, but requires to be easily and quickly detached. This design makes it easy for the operator to remove the separation part 32 from the support part 31 by detaching the second screws 37a, 37b when switching the DOE, without having to disassemble the entire support structure or other optical path elements, thereby reducing the repeated installation errors when switching the DOE.

[0032] In switching the DOE, the support part 31 remains fixed in the optical path between the beam expander 23 and the deflection mirror 25 without disassembly, and the DOE is separated from the optical path by disassembling the separation part 32 from the support part 31. Specifically, in switching the DOE, the support part 31 is fixed in the optical path without disassembly, the mounting part 33 is fixed on the separation part 32 without disassembly, and the separation part 32 is separated from the support part 31, i.e., the DOE is separated from the optical path, by disassembling the second positioning pins 36a, 36b and the second screws 37a, 37b between the support part 31 and the separation part 32. After separation, the operator can replace the DOE, and the support part 31 and its connection with the beam expander 23 and the deflection mirror 25 are not affected at all. Through this separation mechanism, not only the complexity of repeated installation is greatly reduced, but also the optical path after each DOE switching is accurately aligned, thereby avoiding the influence of error accumulation on the shaping effect of the laser.

[0033] In some embodiments, the separation part 32 is fitted with the support part 31 to embed the DOE in at least part of the groove of the support part 31 in the mounted state, so as to effectively utilize the space and meet the demand of realizing DOE switching in a smaller design space. Each tiny displacement or deviation in the optical path can have a significant impact on the quality and characteristics of the final laser beam, and the fitted structure can minimize the possibility of such displacement. Since the separation part 32 and the support part 31 have a fitted structure, it means that in the fixed state, the separation part can be tightly combined with the support part to ensure that the position or posture of the DOE will not change during the transmission of the laser beam due to external vibration or improper operation. Not only does it ensure that the propagation path of the laser beam will not deviate, but it also greatly improves the quality and stability of the beam shaping, which is particularly important in high-precision machining or single-crystal manufacturing processes.

[0034] In some embodiments, the mounting part 33 further comprises a displacement adjuster 33a and / or a displacement adjuster 33b to realize high-precision fine adjustment of the position of the DOE in the X-axis and / or Y-axis direction. Among them, the displacement adjuster 33a is configured to adjust the displacement of the DOE in the Y-axis direction, and the displacement adjuster 33b is configured to adjust the displacement of the DOE in the X-axis direction. Through this bidirectional adjustment function, the propagation path of the laser beam can be accurately controlled after switching the DOE, ensuring the stability of the spot shape and improving the accuracy of the optical system.

[0035] In some embodiments, the mounting portion 33 further comprises an internally threaded snap ring 33c designed to secure the DOE and prevent it from being displaced due to external vibrations or other factors during operation. The use of the threaded snap ring not only simplifies the process of mounting and dismounting the DOE, but also provides additional structural stability. Specifically, the threaded snap ring 33c is integrated inside the mounting portion 33, and when the DOE is placed in the mounting portion 33, the threaded snap ring can securely fix it. Since the threaded snap ring uses a threaded fastening method, it can largely resist the effects of vibrations and external forces, so that the DOE will not be displaced during laser processing, and the operator can quickly complete the switching operation without worrying about optical system errors caused by insecure mounting during switching.

[0036] In some embodiments, the beam expander 23 is removed from the optical path before the laser beam enters the deflection mirror 25, and the support portion 31 can be arranged in the optical path between the collimator lens 22 and the deflection mirror 25, i.e., the support portion 31 is fixedly connected to the collimator lens 22 at one end of the optical path and fixedly connected to the deflection mirror 25 at the other end. Removing the beam expander 23 can be suitable for scenarios where the diameter of the laser beam is not critical, because the beam expander is usually used to expand the diameter of the laser beam to make subsequent focusing operations more accurate. If the beam expander is removed, the collimator lens 22 in the optical path will be relied on to maintain the collimation of the laser beam to ensure that it can be stably directed to the deflection mirror 25.

[0037] In some embodiments, the collimator lens 22 and the beam expander 23 are removed from the optical path before the laser beam enters the deflection mirror 25, and the support portion 31 can be arranged in the optical path between the laser 21 and the deflection mirror 25, i.e., the support portion 31 is fixedly connected to the laser 21 at one end of the optical path and fixedly connected to the deflection mirror 25 at the other end.

[0038] According to the embodiments of the present application, the described PBF-LB process (3D printing method) generally involves controlling the laser beam shaped in a flat-top spot form by a diffractive optical element (DOE) at least during the additive manufacturing process according to a predetermined scanning path and process parameters, to selectively melt the metal powder laid layer by layer on the substrate 14 to form a layer-by-layer consolidated layer until the manufacture of a single crystal component is completed.

[0039] According to the embodiments of the PBF-LB process of the present application, the diffractive optical element 24 can be configured in the optical path between the beam expander 23 and the deflection mirror 25, for example, to shape the laser beam emitted from the beam expander 23 from a Gaussian laser beam with a Gaussian distribution of spots into a flat-top laser beam (e.g., a circular flat-top laser beam) with a flat-top distribution of spots. The shaped laser beam then passes through the deflection mirror 25 and the focusing lens 26 in turn to irradiate the powder layer.

[0040] By introducing beam shaping techniques into the PBF-LB process to fabricate single-crystal components (e.g., nickel-based superalloy components), the control ability of the melt pool morphology and the adjustment flexibility of the solidification front heat flux vector can be enhanced. It should be understood that a traditional Gaussian laser beam generates a high temperature gradient during melting, which easily leads to deep melting and strong convection phenomena, which are very detrimental to single-crystal growth. By shaping the laser beam into a flat-top distribution using a diffractive optical element 24, the laser energy can be more uniformly distributed in the melt pool, reducing the temperature gradient of the melt pool and reducing the Marangoni convection. In addition, the flat-top laser beam not only improves the dynamic behavior of the melt pool, but the heat conduction type melt pool it causes also promotes a stable and controllable melting and solidification process. Because the melt pool profile and the solidification direction are more stable, and the melt pool aspect ratio is larger, the material can grow better along the build direction when solidifying, which is crucial for the formation of strong texture along the build direction. At the same time, the precise matching of the optimized flat-top spot size and other PBF-LB process parameters causes the solidification heat flux vector to periodically deflect towards at least two <100> crystal directions configured for the target single crystal orientation, which in turn triggers the single crystal dynamic selection effect, which is crucial for the formation of single crystal / near-single crystal microstructure.

[0041] It should be understood that the configuration of the DOE switching device described above can be used as Figure 1 The structure of the additive manufacturing apparatus 10 shown forms an improved additive manufacturing apparatus 10 according to embodiments of the present application.

[0042] Other embodiments of the application will be apparent to those skilled in the art from consideration of the specification and practice of the application disclosed herein. It is intended that the specification and examples be considered as exemplary only, with the true scope of the application being indicated by the following claims.

Claims

1. A DOE switching device, configured in the light path of an additive manufacturing equipment before a laser beam enters a deflection mirror (25) and comprising: a support part (31) fixedly connected with the deflection mirror (25) and a component before the laser beam enters the deflection mirror (25) respectively; a separation part (32) detachably fixed on the support part (31); and a mounting part (33) fixed on the separation part (32) and mounting a diffractive optical element for reshaping a Gaussian spot of the laser beam into a flat-top spot.

2. The device according to claim 1, wherein the component comprises a laser (21) or a collimating mirror (22) or a beam expander (23).

3. The device according to claim 1, wherein the mounting part (33) comprises at least one displacement adjuster (33a, 33b) for adjusting the displacement of the diffractive optical element in the X-axis and / or Y-axis direction.

4. The device according to claim 1, wherein the mounting part (33) comprises a threaded snap ring (33c) arranged inside the mounting part (33) and used for detachably fixing the diffractive optical element.

5. The device according to claim 1, wherein the separation part (32) is arranged in a fit-in manner with the support part (31) to fit the diffractive optical element in at least one groove of the support part (31) in the mounted state.

6. The device according to claim 1, wherein the component is sleeved in a connecting plate (30), and the support part (31) is fixed with the component through the connecting plate (30).

7. The device according to claim 1, wherein the support part (31) is fixed with the component and the deflection mirror (25) respectively through at least one first positioning pin (34a, 34b) and at least one first screw (35a, 35b).

8. The device according to claim 1, wherein the separation part (32) is fixed with the support part (31) through at least one second positioning pin (36a, 36b) and at least one second screw (37a, 37b).

9. An additive manufacturing equipment (10) comprising the device according to any one of claims 1 to 8.

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