3D printing method for controlling crystal specific orientation, control system and apparatus thereof

Abstract

The application provides a 3D printing method for controlling crystal specific orientation, a control system and equipment thereof, by setting a point exposure area in a laser scanning path to divide the laser scanning path into a pass scanning area and the point exposure area; controlling the laser beam to perform continuous pass scanning in the x-y plane on each layer of material corresponding to the pass scanning area to construct a part body; and controlling the laser beam to perform continuous exposure on each layer of material corresponding to the point exposure area to form a columnar crystal growing along the z axis in the point exposure area. By setting a separate exposure area, the orientation growth of the crystal grains in the x-y plane in the traditional pass scanning process is blocked, so that the growth mode of the crystal grains is changed, and the microstructure beneficial to the strength improvement of the part is arranged in a specific area in the part.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of 3D printing, in particular to a 3D printing method for controlling the specific orientation of crystal, a control system and a device thereof. BACKGROUND

[0002] When constructing a part by 3D printing, the part is often divided into several two-dimensional planar structures, and then printed layer by layer to finally form the part. Especially for powder laying and sintering / melting technology, a layer of powder is laid, and then a heat source (usually a laser) is used to selectively sinter / melt the laid layer of powder to construct the structure of the part in this layer. Through layer-by-layer powder laying and sintering / melting, the construction of the part is finally completed.

[0003] When constructing a part by 3D printing, due to the layer-by-layer processing method from point to line and then from line to plane, the performance of the part often has anisotropy. This anisotropy often does not conform to the actual demand for performance in each direction. Therefore, the prior art often controls the grain orientation through post-processing to optimize the mechanical properties in a specific direction. However, this processing method increases the post-processing procedure and makes it difficult to achieve the individualization and autonomy of the mechanical properties in a specific direction.

[0004] Therefore, how to effectively control the anisotropy of the part during 3D printing and use the anisotropy to improve the performance of the component is an important content of the development of 3D printing technology. SUMMARY

[0005] In order to achieve excellent performance of the part in a specific direction and meet the demand for mechanical properties of the part in a certain direction in actual use, one aspect of the present application provides a 3D printing method, comprising: setting a grain structure anisotropic region in a laser scanning path to divide the laser scanning path into a pass scanning region and the grain structure anisotropic region; controlling a laser beam to perform continuous pass scanning in the x-y plane on each layer of material corresponding to the pass scanning region using a first scanning parameter to construct a part body; and controlling the laser beam to perform exposure scanning on each layer of material corresponding to the grain structure anisotropic region using a second scanning parameter to form a crystal structure different from the grain orientation of the pass scanning region in the grain structure anisotropic region; wherein the combination of the part body and the crystal structure of the grain structure anisotropic region constitutes the finally formed part.

[0006] Preferably, the method of controlling the laser beam to perform continuous exposure on each layer of material corresponding to the grain structure heterotropic region comprises: grain formation: controlling the time parameter in the second scan parameter to perform scan exposure on any layer of material corresponding to the grain structure heterotropic region, so that the grain structure heterotropic region generates an exposure molten pool, and the solidification process of the static molten pool is controlled by controlling the exposure time of the laser beam, so as to form grains after solidification; and layer-by-layer grain formation to form crystal structure different from the grain orientation of the pass scan region.

[0007] Preferably, before the grain formation, the method comprises: path planning for the part, determining the pass scan path and the grain structure heterotropic region scan path according to the path planning, so that when the dynamic molten pool formed by the pass scan moves to the grain structure heterotropic region, the output of the laser beam is interrupted, and when the laser beam crosses the grain structure heterotropic region to re-enter the pass scan region, the output of the laser beam is restored; and when it is determined that the entire scan of the current layer corresponding to the pass scan region is completed, the grain formation is entered.

[0008] Preferably, the method of controlling the laser beam to perform scan exposure on each layer of material corresponding to the grain structure heterotropic region comprises: setting the offset and the overlap rate of the grain structure heterotropic region on each layer of material; controlling the laser beam to perform scan exposure after offset and overlap on each layer of material according to the offset and the overlap rate, so as to form crystal structure growing at a preset angle and position in the point exposure region.

[0009] Preferably, the calculation formula of the offset is: Offset = tan(0) * LayerThickness ; wherein θ is the angle of the crystal structure, and LayerThickness is the thickness of each layer of powder; and the calculation formula of the overlap rate is: Overlap = (Length - Offset) / Length * 100% ; wherein Length is the length of the crystal structure in each layer.

[0010] Preferably, the method comprises: identifying z-axis segments with continuity according to the three-dimensional model of the part; setting the target position of the corresponding crystal structure according to the identified z-axis segments with continuity; and setting the corresponding grain structure heterotropic region according to the set target position of the crystal structure.

[0011] Preferably, the first scan parameter and the second scan parameter are respectively performed by different laser beams, wherein one laser beam is used to perform continuous pass scan in the x-y plane on each layer of material corresponding to the pass scan region by using the first scan parameter, and the other laser beam is used to perform scan exposure on each layer of material corresponding to the point exposure region by using the second scan parameter.

[0012] In one aspect of the present application, a 3D printing control system is provided, which is configured to the method described above.

[0013] In one aspect of the present application, a 3D printing device is provided, which comprises a mechanical unit, a light path unit, and a control system as described above.

[0014] Preferably, the light path unit comprises a first laser for outputting a laser beam for continuous path scanning in the x-y plane on each layer of material corresponding to the path scanning area, and a second laser for outputting a laser beam for exposure scanning on each layer of material corresponding to the grain structure directional area.

[0015] The present application can effectively control the anisotropy of the part during 3D printing, and improve the mechanical properties of the part without increasing the post-processing procedure. Specifically, the method of the present application controls the laser beam to perform different processing operations on the materials corresponding to different areas based on different scanning parameters by setting the grain structure directional area and the path scanning area, thereby realizing the joint construction of the part body and the grain structure, and improving the mechanical properties of the part. The improvement of the mechanical properties is reflected in that the grain orientation growth in the x-y plane during the traditional path scanning process is blocked by setting the grain structure directional area, thereby changing the growth mode of the grain structure, and setting the microstructure in the specific area of the part that is beneficial to the improvement of the strength.

[0016] In addition, the solidification process of the static melt pool is adjusted by controlling the output time of the laser beam during the crystal growth process, further controlling the grain structure orientation, and thereby realizing the fine control of the component material.

[0017] Therefore, the present application can realize efficient, personalized and autonomous part construction during 3D printing, improve the mechanical properties of the part, and realize fine control of the construction material without increasing the post-processing procedure.

[0018] By setting the offset and overlap rate between adjacent layers, the present application can realize the thermal orientation of the grain structure at different angles in the z-axis direction, thereby realizing the growth of the grain structure along a specific direction, and controlling the mechanical properties of the component in a specific direction.

[0019] The present application can print the crystal structure growing along the z-axis direction in the part with irregular shape / hollow section, thereby enhancing the strength and stability of the part. BRIEF DESCRIPTION OF DRAWINGS

[0020] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed in the embodiments or prior art description. Obviously, the drawings in the following description only are the embodiments of the present application, and for those skilled in the art, other drawings can be obtained based on the provided drawings without any creative effort.

[0021] Figure 1 The figure shows the microscopic structure picture of the existing 3D printed part in the x-y plane;

[0022] Figure 2 The figure shows the flow chart of the 3D printing method provided by one of the embodiments of the present application;

[0023] Figure 3 、 4 , 5 respectively show the flow chart of the laser scanning provided by one of the embodiments of the present application;

[0024] Figure 6 The figure shows the model diagram of the cylindrical member provided by one of the embodiments of the present application;

[0025] Figure 7 The figure shows the cross section A-A of one of the slice layers in the cylindrical member under the existing scanning mode in the present application; Figure 6

[0026] Figure 8 The figure shows the cross section A-A of one of the slice layers in the cylindrical member under the scanning mode provided by one of the embodiments of the present application;

[0027] Figure 9 The figure shows the model diagram of the columnar crystal formed in the cylindrical member;

[0028] Figure 10 The figure shows the scanning diagram of the two lasers on one of the material layers provided by one of the embodiments of the present application;

[0029] Figure 11 The figure shows the flow chart of the crystal growth provided by one of the embodiments of the present application;

[0030] Figure 12 The figure shows the diagram of one of the cross section layers and the next cross section layer in the cylindrical member provided by one of the embodiments of the present application;

[0031] Figure 13 The figure shows the model diagram of the columnar crystal grown along the specific direction constructed in the cylindrical member provided by one of the embodiments of the present application;

[0032] Figure 14 ​The diagram shown is a schematic flowchart of constructing columnar crystals in an irregularly shaped / hollowed-out part according to one embodiment of the present invention;

[0033] Figure 15 The diagram shown is a schematic representation of a model for constructing columnar crystals in an irregularly shaped / hollowed-out part according to one embodiment of the present invention;

[0034] Figure 16 The diagram shown is a structural schematic of a 3D printing device provided in one embodiment of the present invention. Detailed Implementation

[0035] Embodiments of the present invention are described in detail below, examples of which are illustrated in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0036] One aspect of this invention provides a 3D printing device, preferably a 3D printing type that uses a laser beam / electron beam as an energy source. 3D printing technologies using laser beams / electron beams as energy sources include, but are not limited to, selective laser sintering (SLS), selective laser melting (SLM), and electron beam melting (EBM). These printing types all use laser beams / electron beams as energy sources, focusing energy on the surface of a material to melt it and build up layers to form 3D printed parts. They are suitable for manufacturing high-density, high-precision, and high-strength metal parts and are widely used in industries such as aerospace, medical devices, automotive, and shipbuilding. In summary, the basic principle of the 3D printing device involves using a computer to cut a 3D model of the part into a series of "slices" of varying thicknesses, manufacturing each slice from bottom to top using the device, and then bonding and stacking these layers to form a three-dimensional solid part.

[0037] refer to Figure 16 As shown, in some embodiments, the 3D printing equipment involved consists of at least a mechanical unit 10, an optical path unit 20, and a control system.

[0038] (Mechanical Unit 10)

[0039] The mechanical unit mainly consists of a powder spreading roller 11, powder supply bins 12 and 13, a forming bin 14 (with a forming platform 15), and auxiliary equipment. The powder supply bins 12 and 13 store and supply powder for 3D printing, and are driven to rise and fall by powder supply lifting devices 121 and 131. The powder spreading roller 11 is a rotating roller used to spread powder from the powder supply bins 12 and 13 onto the forming platform 15 of the forming bin 14. The powder spreading roller 11 is typically made of metal or plastic, and its surface usually has small grooves or toothed structures to uniformly compress and spread the powder material, thus evenly distributing the powder onto the forming platform 15. The forming bin 14 is used for part construction; that is, the part is finally constructed within the forming bin 14. The distance the forming bin 14 descends each time is the layer thickness. After the part is constructed, the forming bin 14 rises to facilitate the removal of the constructed part and preparation for the next construction. The rising and falling of the forming bin 14 is driven by the forming lifting device 141. During the part fabrication process, powder is laid layer by layer above the forming chamber 14, i.e., the forming platform 15, thereby forming a powder bed above the forming platform 15. Auxiliary equipment (not shown), such as a powder recovery system, powder handling equipment, and gas protection system, is used to recover and process the remaining metal powder and protect the metal powder during the printing process from external factors such as oxidation.

[0040] (Optical Path Unit 20)

[0041] The optical path unit 20 consists of a laser, a galvanometer, and a focusing lens. The laser is the core component of the optical path unit 20; it generates a laser beam, typically a high-power, high-energy-density light source. This beam is emitted towards the galvanometer assembly, activating the printing material and causing it to melt or sinter. For example, a CO2 laser or fiber laser is commonly used as the energy source. The galvanometer is a crucial component of the optical path unit 20, typically composed of two coplanar mirrors. The galvanometer can change the propagation direction and angle of the laser beam, ensuring it accurately illuminates the printing material and controlling the printing speed and shape. The focusing lens is an optical element, usually made of high-quality optical glass, possessing high transparency and optical performance. It minimizes optical loss and scattering as the laser beam passes through. It combines the functions of focusing and lensing. Unlike ordinary lenses, the main function of the focusing lens is to precisely focus the laser beam onto the printing material to control the laser's energy density and focal length, thereby enabling the printing material to melt or sinter within a specific area. In addition to the main components mentioned above, the optical path unit 20 may also include other optical elements, such as optical fibers, mirrors, and filters, to optimize parameters such as the quality, power, and color of the laser beam.

[0042] (Control system)

[0043] The control system is the core of the entire printing process, including printing parameter settings, laser scanning path planning, and motion control of the construction platform. The control system typically consists of two parts: an optical path control system and a mechanical control system. In other words, within the control logic, the control system controls both the mechanical unit 10 and the optical path unit 20.

[0044] In a specific spatial arrangement, the optical path unit 20 can be arranged above the mechanical unit 10, or it can be set up based on the core inventive points taught in this application, according to the actual structural design.

[0045] In current 3D printing scanning processes, the laser beam irradiates the material, forming the part from a point to a line, and then from a line to a surface. Due to the movement of the molten pool in the xy-plane, thermally affected components often cause the part to form columnar crystals composed of grains in the xy-plane. These columnar crystals are detrimental to the part's strength in the z-axis direction. If the part requires higher strength in the z-axis direction than in the xy-axis direction, further heat treatment is necessary to alter the microstructure of the material. For example... Figure 1 The images shown depict the microstructure of the 3D printed part in the xy plane, revealing that the microstructure on the part's surface tends to grow along the xy plane.

[0046] In other words, during the metal powder-layout 3D printing process, due to the point-to-line forming method, the microstructure of the component formed in the current layer, due to the regular thermal gradient, often exhibits a specific and consistent grain orientation. This consistent grain orientation often results in better mechanical properties in a certain direction, which is the anisotropy of the material. If the direction with better mechanical properties coincides with the actual needs, then the requirements can be met. However, if the direction with better mechanical properties does not coincide with the actual needs, it is difficult to fully utilize the material's properties. Therefore, in practice, especially in 3D printing parts, it is desirable to be able to manually control and adjust the orientation of the grains within the material to meet performance requirements.

[0047] Therefore, one aspect of this invention proposes a 3D printing method that uses point scanning to preferentially form crystal structures with specific orientations in the desired direction of the part, thereby improving the overall performance of the part.

[0048] Preferably, in actual implementation, the 3D printing method of the present invention is executed by the aforementioned control system. For example, the method can be designed into a language format that can be understood by a computer (e.g., a computer program) and stored in a memory, so that it can be invoked and executed by the control system during the 3D printing process.

[0049] The 3D printing method of this invention changes the scanning method of conventional laser forming by adding point exposure in the anisotropic grain region to achieve control of the microstructure within a tiny area of ​​the part. Specifically, the 3D printing method of this invention includes: setting anisotropic grain region in the laser scanning path to divide the laser scanning path into a pass scanning region and anisotropic grain region; controlling the laser beam to perform continuous pass scanning in the xy plane on each layer of material corresponding to the pass scanning region using a first scanning parameter to construct the main body of the part; and controlling the laser beam to perform exposure scanning on each layer of material corresponding to the anisotropic grain region using a second scanning parameter to form a crystal structure in the anisotropic grain region with a different grain orientation than that in the pass scanning region; the main body of the part and the crystal structure of the anisotropic grain region combine to form the final formed part.

[0050] In particular, spot exposure is preferred for scanning in the anisotropic grain structure region. Therefore, the anisotropic grain structure region can be used as a spot exposure region without limitation. The crystal structure in the anisotropic grain structure region is preferably displayed in a columnar shape, that is, columnar crystals are used as a form of the crystal structure formed.

[0051] In this application, the grain structure in the scanned region tends to grow along the xy plane, while the grain structure in the anisotropic region is controlled to, for example, tend to grow along the z-axis.

[0052] More specifically, see reference Figure 2 As shown, the 3D printing method of the present invention comprises the following steps: S101. Setting a point exposure area in the laser scanning path to divide the laser scanning path into a pass scanning area and a point exposure area; S102. Controlling the laser beam to perform continuous pass scanning in the xy plane on each layer of material corresponding to the pass scanning area using a first scanning parameter to construct the main body of the part; and S103. Controlling the laser beam to perform continuous exposure on each layer of material corresponding to the point exposure area using a second scanning parameter to form columnar crystals growing along the z-axis in the point exposure area; wherein, the combination of the main body of the part and the columnar crystals constitutes the final formed part.

[0053] It should be understood that the step numbers provided here are for identifying the corresponding steps and do not restrict the order of the steps in the specific implementation process. For example, the execution order of S102 can be before or after S103, or it can be combined with S103 synchronously or semi-synchronously.

[0054] Before 3D printing, the preparation work begins with selecting a suitable material based on the requirements of the desired part, such as NiTi alloy or stainless steel powder. Next, a part model is designed and converted into a printable file, such as an STL file. Then, the STL file is imported into the 3D printing software, and printing parameters are set according to the desired part size, layer thickness, and printing speed. Finally, appropriate laser scanning parameters are selected based on the geometry and material properties of the part to be manufactured, such as laser power, scanning speed, laser focal length, and preset scanning path.

[0055] In some embodiments, the present invention sets the size and shape of the dot exposure area in the laser scanning path. Typically, the size and shape of the dot exposure area need to be determined based on the characteristics of the printing material and the required performance of the part. For example, the shape of the dot exposure area can be set to circular or square, and the size and shape can be set by controlling the scanning range and scanning speed of the laser beam. In some 3D printing equipment, the shape of the dot exposure area can also be adjusted by adjusting the focus and offset of the laser beam. It is important to note that the size and shape of the dot exposure area have a significant impact on both printing quality and printing speed. A smaller dot exposure area can improve printing accuracy but reduce printing speed. Conversely, a larger dot exposure area can improve printing speed but reduce printing accuracy. Therefore, adjustments need to be made according to specific requirements in actual operation. Typically, the diameter / length of the dot exposure area is set to 30μm-3mm, and the present invention preferably sets it to 45-100μm.

[0056] In some embodiments, the present invention sets the positions of the dot exposure areas within the laser scanning path. The positions of the dot exposure areas can be automatically generated by slicing software or set manually. For example, in cases where multiple dot exposure areas may be distributed across the cross-section of a part, the slicing software can automatically calculate the appropriate positions of the dot exposure areas based on the geometry and / or support structure of each layer and add them to the laser scanning path to ensure that each dot exposure area is fully exposed. This automatic calculation method simplifies the printing process and improves printing efficiency and accuracy. Alternatively, the slicing software can provide a user-defined function to manually set the dot exposure areas within its visual interface to meet the needs of manual dot exposure area setting.

[0057] It should be understood that after removing the designated spot exposure area from the cross-section of the part, the remaining area can all be designated as the pass scan area. Since the laser beam scans along a preset laser scanning path, the laser scanning path after removing the spot exposure area is designated as the pass scan area. In other words, only the spot exposure area needs to be set within the laser scanning path, and the rest is automatically assigned to the pass scan area. This can be understood as dividing the laser scanning path into pass scan areas and spot exposure areas by setting spot exposure areas within it.

[0058] After setting the point exposure area, the part can be constructed, which includes performing S102 and S103 as described above.

[0059] More specifically, S103 is: crystal formation: controlling the time parameter in the second scanning parameters to scan and expose any layer of material corresponding to the point exposure area, so that the point exposure area generates an exposure molten pool, and controlling the solidification process of the exposure molten pool by controlling the exposure time of the laser beam, so as to form grains after solidification; and forming columnar crystals layer by layer.

[0060] After entering the crystallization stage, the laser scanning path needs to be adjusted to ensure continuous laser output on any layer of material corresponding to the point exposure area, creating a static molten pool in that area. This static molten pool is relative to the pass scan; that is, during point exposure scanning, the molten pool's relative movement speed is much slower than the pass scan speed, resulting in a microstructure with a different grain orientation in the point exposure area compared to the pass scan area. Specifically, the corresponding laser scanning path needs to be calculated based on the position and shape of the point exposure area and input into the 3D printing equipment's control system. The laser beam spot needs to be aligned with the point exposure area of ​​the current layer, and the laser beam's output power and scanning speed need to be controlled to ensure continuous laser output on the point exposure area, thus creating a static molten pool. After the static molten pool is created in the point exposure area, the laser beam exposure time needs to be controlled to control the solidification process of the static molten pool. For example, by controlling the laser beam's output power and scanning speed, the solidification rate of the static molten pool can be controlled to form grains after solidification. The above crystallization process is repeated on each layer of material. In controlling the laser beam exposure time, it is also necessary to determine the optimal exposure time for each exposure area based on the material properties and printing parameters to ensure the quality and precision of grain formation. Typically, adjusting the exposure time requires multiple trials and optimizations to find the best combination of parameters.

[0061] Ultimately, during the layer-by-layer crystallization process, the grains grow along a direction perpendicular to the manufacturing direction (xy-axis) (z-axis), forming columnar crystals. That is, after all layers of crystallization are completed, a series of columnar crystals extending along the z-axis will be formed within the part.

[0062] Both continuous scanning of the scanned area and continuous exposure of the point exposure area are controlled by laser beams, but they differ in that:

[0063] Continuous pass scanning is the process of a laser beam scanning and moving on a powder bed. During this process, the laser beam scans along a preset path and moves the spot to the required position to construct the main body of the part and control the quality and precision of the surface of the main body of the part.

[0064] Laser exposure refers to the process of directly irradiating a material with a laser beam. In this process, the laser beam irradiates the material surface, causing a physical or chemical reaction. For example, a laser beam directly irradiating powder can melt or sinter it into a solid component. The shape and properties of the component are controlled by adjusting parameters such as laser power, irradiation time, and irradiation position.

[0065] refer to Figure 3 As shown, in one example executed in a work sequence, the 3D printing method of the present invention comprises the following steps:

[0066] S201. Set the laser scanning path;

[0067] S202. Set a point exposure area in the laser scanning path;

[0068] S203. Control the laser beam to perform continuous scans in the xy plane on the corresponding layer material in the scan area;

[0069] A control system is used to control a laser beam to perform continuous xy-plane scans on the corresponding layer of material in the scanned area for material processing. Simultaneously, the position information of the laser beam at each time point is recorded to facilitate subsequent determination of the dynamic molten pool position.

[0070] During this process, the laser beam is focused into a spot to irradiate the corresponding material in the scan area of ​​the pass. After the laser beam irradiates the material surface, it will cause the material surface to melt and form a molten pool. Then, it moves along the xy axis on the forming platform (current powder layer) to form a dynamic molten pool, which melts and solidifies the material of the current layer corresponding to the scan area of ​​the pass in sequence.

[0071] S204. Obtain the real-time position of the dynamic molten pool formed on the material corresponding to the spot in the scan area of ​​each pass;

[0072] The control system is used to obtain the real-time position of the dynamic molten pool formed on the material corresponding to the laser beam spot in the scan area of ​​each pass, so as to determine whether it has moved to the point exposure area.

[0073] The diameter of the laser spot typically depends on factors such as the optical design of the laser system, the wavelength of the laser, and the parameters of the focusing lens. Generally, the diameter of the laser spot can vary from a few micrometers to tens of millimeters. This diameter can, to some extent, control the melting and solidification process of the printing material, thus affecting the printing quality. In this invention, the diameter of the laser spot is preferably set at 30 μm.

[0074] S205. Determine if the dynamic melt pool has moved to the point exposure area; if so, proceed to S206.

[0075] The control system analyzes and compares the position information of the dynamic melt pool to determine whether the dynamic melt pool has moved to the set point exposure area. If so, S206 is executed.

[0076] S206. Interrupt laser output;

[0077] S207. Control the laser beam to cross the point exposure area to re-enter the pass scan area, return to execute S203, and simultaneously execute S208;

[0078] The laser beam output is interrupted by the control system, causing it to stop irradiating. During 3D printing, the movement of the laser beam is controlled by the control system. When it is necessary to interrupt the laser beam output in a certain area, the control system sends a command to the laser to stop outputting and simultaneously moves the laser beam to the new target position. It's important to note that even if the laser stops outputting, the control system can still control the position movement of the laser beam. This is because the laser beam's position control and the laser's output are controlled separately. Typically, 3D printers use gas lasers or semiconductor lasers, whose output is controlled by a controller and circuitry, while the laser beam's position is constrained by the optical path unit.

[0079] The control system controls the laser beam to cross the point exposure area and re-enter the pass scanning area, returning to execute S203 to continue material processing, while simultaneously executing S208.

[0080] S208. Determine whether the scanning of the current layer corresponding to the scan area of ​​the trace has been completed; if so, proceed to S209.

[0081] S209. Crystal preparation.

[0082] During the 3D printing process, the control system will determine whether the scanning of the current layer corresponding to the scan area of ​​the pass has been completed, in order to determine whether laser exposure needs to continue, that is, return to the exposure area of ​​each point to perform continuous exposure (crystallization) on the exposure area of ​​the point.

[0083] If the scanning of the current layer (including consecutive passes and continuous exposure of the point exposure area) is complete, the following steps are required: determine whether the scanning of the entire model is complete. If it is, the entire 3D printing process ends; if the scanning of the entire model is not yet complete, the scanning of the next layer needs to be performed. Repeat steps S201-S209 until the scanning of the entire model is complete. During step S208, the control system needs to monitor various parameters in real time during the laser scanning process to ensure that the scanning quality and speed of each layer are controlled and optimized. Furthermore, the control system needs to record and process data for subsequent process analysis and optimization.

[0084] refer to Figure 4 As shown, in one example executed in a work sequence, the 3D printing method of the present invention comprises the following steps:

[0085] S301. Set the laser scanning path;

[0086] S302. Set a point exposure area in the laser scanning path;

[0087] S303. Control the laser beam to perform continuous scans in the xy plane on the corresponding layer material in the scan area;

[0088] S304. Obtain the real-time position of the dynamic molten pool formed on the material corresponding to the spot in the scan area of ​​each pass;

[0089] S305. Determine if the dynamic melt pool has moved to the point exposure area; if so, proceed to S306.

[0090] S306. Crystal fabrication;

[0091] S307. Control the laser beam to cross the point exposure area to re-enter the pass scan area, return to execute S203, and simultaneously execute S308;

[0092] S308. Determine whether the scanning of the current layer corresponding to the scan area of ​​the track has been completed; if so, end the current process.

[0093] The difference between this example and S201-S209 is that in S201-S209, when the laser beam encounters the dot exposure area, it interrupts the laser output and controls the laser beam to continue scanning beyond the dot exposure area until the continuous scanning of the entire layer's scan area is completed. Then the laser beam returns to the dot exposure area and begins dot exposure to form a crystal. This means that dot exposure is performed after all scans are completed. In this example, when the laser beam encounters the dot exposure area, it first performs dot exposure to form a crystal in the dot exposure area, and then moves to the next scan area for continuous scanning. This process is repeated until the entire layer is scanned. This means that dot exposure and continuous scanning are performed alternately. This scanning method can reduce the laser jump distance and improve printing efficiency.

[0094] Therefore, the main difference between the two examples lies in the different execution order of spot exposure and pass scanning, resulting in a different printing order for the entire layer. In S201-S209, pass scanning is performed first, followed by spot exposure; while in this example, spot exposure and pass scanning are performed alternately.

[0095] refer to Figure 5 As shown, in one example executed in a work sequence, the 3D printing method of the present invention comprises the following steps:

[0096] S401. Set the laser scanning path;

[0097] S402. Set the point exposure area in the laser scanning path;

[0098] S403. Control the first laser beam to perform continuous pass scanning in the xy plane on the corresponding layer material in the pass scanning area; S413. Control the second laser beam to perform continuous exposure (crystallization) on the corresponding layer material in the point exposure area; wherein, S403 and S413 are performed synchronously;

[0099] After S403, S404 is entered to obtain the real-time position of the dynamic molten pool formed on the material corresponding to the spot in the scan area of ​​each pass;

[0100] S405. Determine if the dynamic melt pool has moved to the point exposure area; if so, proceed to S406.

[0101] S406. Interrupt laser output;

[0102] S407. Control the laser beam to cross the point exposure area to re-enter the pass scan area, return to execute S403, and simultaneously execute S408;

[0103] S408. Determine whether the scanning of the current layer corresponding to the scan area of ​​the current pass has been completed; if yes, end the process.

[0104] After S413, proceed to S414. Determine whether the exposure of the current layer corresponding to the point exposure area has been completed; if so, end the process.

[0105] The difference from S201-S209 is that this example uses different laser beams to control continuous scans and continuous exposures. Specifically, the first scan parameters and the second scan parameters are executed by different laser beams. One laser beam (the first laser beam) is used to perform continuous scans in the xy plane on each layer of material corresponding to the scan area using the first scan parameters, while the other laser beam (the second laser beam) is used to perform exposure scans on each layer of material corresponding to the point exposure area using the second scan parameters. This simultaneous use of dual laser beams further improves scanning efficiency.

[0106] In some embodiments, reference Figure 10 As shown, the aforementioned optical path unit 20 has two lasers, namely a first laser 21 and a second laser 22. The first laser 21 is used to output a laser beam for continuous scanning in the xy plane on each layer of material corresponding to the pass scanning area; the second laser 22 is used to output a laser beam for continuous exposure on each layer of material corresponding to the point exposure area.

[0107] To facilitate a clearer understanding of the present invention, the 3D printing method of the present invention will be described in detail below using a cylindrical part as a printing example.

[0108] like Figure 6 As shown, the printing objective is set as follows: to process a cylindrical component, and it is desired that the component has high mechanical properties in the z-axis direction perpendicular to the radial direction.

[0109] like Figure 7 As shown, for Figure 6 Consider a cylindrical component with cross-section AA of all its layers, assuming a laser scanning path of a1-a26. Traditional 3D printing methods, due to their continuous pass-through scanning in the xy-plane, result in a strong grain orientation in this cylindrical component within the xy-plane. This grain orientation is detrimental to strength in the z-axis direction, reducing interlayer bonding strength and leading to lower tensile and yield strength in this direction.

[0110] like Figure 8 As shown, for Figure 6In a cylindrical component, the cross-section AA of each layer is defined. The laser scanning path is a1-a26. This invention divides the laser scanning path into two parts: the point exposure areas b1-b7 within a1-a26, and the pass scanning area. The remaining path after deducting the point exposure areas b1-b7 is the pass scanning area. Based on this configuration, the 3D printing method of this invention changes the traditional pass scanning method for component forming. By setting point exposure areas at preset positions on the scanning path and controlling the scanning method of these point exposure areas, the directional growth of the microstructure in the z-axis direction can be achieved, forming a structure like... Figure 9 The columnar crystals c1-c7 shown are used to improve the z-axis strength.

[0111] In one scanning method, a control system controls the laser beam to start from position a1 and perform continuous scans of the scanned area in the xy plane along a scan path from a1 to a26, directly completing the scan of the current layer in the scanned area. During the scanning process, the position of the dynamic molten pool formed by the laser beam spot on the material corresponding to the scanned area is determined in real time. When the dynamic molten pool moves to the point exposure areas b1-b7, the laser output is interrupted, and the laser beam is controlled to cross the point exposure areas b1-b7 to scan the scanned area along a preset scan path. After completing the scan of the current layer corresponding to the scanned area, the laser beam is then controlled to continuously expose the material corresponding to the point exposure areas b1-b7 to form a crystal.

[0112] In one scanning method, the control system controls the laser beam to start from position a1 and perform continuous pass scanning in the xy plane along the scanning path a1-a26, directly completing the scanning of the entire current layer in the pass scanning area. During the scanning process, the position of the dynamic molten pool formed by the laser beam spot on the corresponding material in the pass scanning area is determined in real time. When the dynamic molten pool moves to the point exposure area b1-b7, the laser beam is first controlled to continuously expose the point exposure area b1-b7 to form a crystal. After crystal formation, the laser beam is controlled to continue scanning along the preset scanning path. That is, the entire scanning of the current layer is completed by alternating between point exposure and pass scanning.

[0113] In one scanning method, the control system controls the laser beam to start from position a1 and perform continuous scans in the xy plane along the scanning path a1-a26, directly completing the scanning of the entire current layer of the scanned area. During the scanning process, the controller controls the first laser beam to perform continuous scans in the xy plane on the corresponding layer material of the scanned area, while simultaneously controlling the second laser beam to continuously expose the corresponding layer material of the point exposure area.

[0114] Regardless of the scanning method used, after completing the full scan of the current layer (spot exposure + pass scanning), the forming platform is lowered by one layer thickness, and the powder spreading roller is used to spread a new layer of powder on the already processed current layer. The equipment then switches to the next layer for processing. This process of scanning layer by layer continues until the entire cylindrical component is manufactured, thereby forming columnar crystals along the z-axis in the spot exposure area, as shown in the image. Figure 9 The columnar crystals shown are c1-c7.

[0115] This invention enables effective control of anisotropy in 3D printing and improves part construction performance without additional post-processing. Specifically, the method uses point exposure areas and pass scanning areas to control the laser beam to perform different processing operations on the material in different areas, thereby achieving the joint construction of the part body and columnar crystals, thus improving the part's mechanical properties. This improvement in mechanical properties is achieved by using separate exposure areas to block the oriented growth of grains in the xy-plane during traditional pass scanning, thereby altering the grain growth pattern and creating microstructures within specific regions of the part that enhance its strength.

[0116] Furthermore, during the crystallization process, the solidification process of the static molten pool is adjusted by controlling the output time of the laser beam, thereby further controlling the grain orientation and achieving precise control over the construction material.

[0117] Therefore, this invention can achieve efficient, personalized, and autonomous part construction during the 3D printing process, improve the mechanical properties of the parts, and achieve precise control over the construction materials without adding post-processing procedures.

[0118] refer to Figure 11 As shown, in some embodiments, the aforementioned S103 may also be composed of the following steps: S501. Setting the offset and overlap rate of the spot exposure area on each layer of material; and S502. Controlling the laser beam to continuously expose the spot exposure area after offset and overlap on each layer of material according to the offset and overlap rate, so as to form a columnar crystal grown at a predetermined angle and position in the spot exposure area.

[0119] In one specific embodiment, a 3D model containing columnar crystals is designed using graphics software. This model should include the shape of the part and information such as the position, shape, and angle of the internal columnar crystals. Then, corresponding G-code is generated based on the designed 3D model. This code contains the commands and instructions that the 3D printer needs to execute to control parameters such as the laser scanning path and the height of the printed layers. When writing the G-code, information such as the position and angle of the columnar crystals needs to be considered, and parameters such as the offset and overlap rate of the point exposure area during each layer printing need to be set. During continuous exposure of the point exposure area, the laser beam is controlled to offset and overlap between different layers according to preset parameters, so that the columnar crystals gradually grow at predetermined angles and positions.

[0120] Each layer of printing requires consideration of parameters such as the offset and overlap rate of the dot exposure area to ensure that the grains gradually grow into columnar crystals at predetermined angles and positions. Specifically, the angle and position of the columnar crystals within the component need to be determined to allocate parameters such as offset and overlap rate. These parameters should be selected based on the required structural strength and mechanical properties to ensure that the printed columnar crystals possess the necessary characteristics.

[0121] Specifically, the offset should be selected based on the position and angle of the columnar crystals and adjusted during each layer's printing. If the offset is set incorrectly, the columnar crystals may break or deviate from their intended position. Simultaneously, the overlap rate of the exposure areas for each layer must be set to ensure proper alignment of the columnar crystals between adjacent layers. The overlap rate should also be selected based on the position and angle of the columnar crystals and adjusted during each layer's printing. Incorrect overlap rate settings may result in defects or gaps in the columnar crystals. During the printing process, parameters need to be continuously adjusted to ensure the columnar crystals gradually grow according to the expected position and angle.

[0122] In one embodiment, the offset is calculated as follows:

[0123] Offset = tan(0) * LayerThickness ;

[0124] Where θ is the angle of the columnar crystal, and LayerThickness is the thickness of each powder layer;

[0125] Offset can be understood as displacement along the z-axis. This offset is used to ensure that the columnar crystals grow in the component along the intended direction. During the printing process, the exposed area of ​​the laser beam at each layer is composed of a series of continuous contour lines from the laser irradiation points. These contour lines accumulate in the longitudinal direction, introducing errors that may cause the columnar crystals to deviate from the intended direction along the z-axis. To address this issue, the columnar crystals can be fine-tuned along the intended direction in each layer, achieving a more accurate strengthening effect.

[0126] In one embodiment, the overlap rate is calculated as follows:

[0127] Overlap = (Length - Offset) / Length * 100% ;

[0128] Where Length is the length of the columnar crystal in each layer.

[0129] S501 and S502 mainly explain how to form a scanning method along the z-axis at a specific angle in a component. Figure 12 This diagram illustrates a cross-sectional layer n and the next cross-sectional layer n+1 within a cylindrical component. When scanning the next cross-sectional layer n+1 after completing the scan of the current cross-sectional layer n (spot exposure + pass scan), it is necessary to obtain the offset and overlap rate of the set spot exposure area. This information is used to control the scanning of cross-sectional layer n+1. For example... Figure 13 As shown, d1-d3 represent columnar crystals grown along a specific direction within a cylindrical component. By setting the offset and overlap ratio between adjacent layers, thermal orientation of grains at different angles along the z-axis can be achieved, thereby enabling grain growth along a specific direction and controlling the mechanical properties of the component in that specific direction.

[0130] By setting the offset and overlap rate of each columnar crystal layer in the printing software, columnar crystals can be grown in a specific direction within a cylindrical component.

[0131] It should be noted that these parameter examples are only used to illustrate how the offset formula and overlap rate formula are calculated. The specific parameter settings should be adjusted and optimized according to the actual situation.

[0132] refer to Figure 14 As shown, in some embodiments, the 3D printing method provided by the present invention may further consist of the following steps:

[0133] S601. Identify a continuous z-axis segment based on the 3D model of the part; S602. Set the target position of the corresponding columnar crystal based on the identified continuous z-axis segment; and S603. Set the corresponding point exposure area based on the set target position of the columnar crystal.

[0134] First, based on the 3D model of the part, the z-axis segments of the part need to be determined through calculation and analysis. A continuous z-axis segment refers to a part without interruption or missing sections in the z-axis direction. Continuous z-axis segments can be determined by calculating features such as the volume, surface area, and shape of the model. Alternatively, graphics processing algorithms, such as tracing contour lines, can be used to extract the contour of each z-axis segment. By comparing the distances between adjacent contours, it can be determined which contour lines are continuous, thus identifying the continuous z-axis segments.

[0135] Secondly, after identifying the continuous z-axis segment, the target position of the corresponding columnar crystal needs to be set according to the preset design requirements of the columnar crystal. For example, if a columnar crystal growing along the z-axis is set inside a cylindrical component, the offset and overlap rate of the columnar crystal in each layer can be calculated, and the target position of the columnar crystal in each layer can be calculated accordingly.

[0136] Finally, based on the target location of the columnar crystal, a corresponding spot exposure area needs to be set at that location. A spot exposure area refers to the exposure process performed at a specific location within each layer to achieve a specific shape and structure. During this process, parameters such as the size, shape, and location of the spot exposure area can be adjusted as needed to ensure that the shape and structure of the columnar crystal are well controlled and achieved.

[0137] like Figure 15 As shown, e1-e11 represent columnar crystals constructed within parts with irregular shapes / hollowed-out sections. It should be noted that the columnar crystals e1-e11 shown in the figure only represent the z-axis distribution within the part and do not represent their actual placement. In reality, the columnar crystals are located inside the part and are micrometer-sized, making them imperceptible from the outside. This allows for the printing of columnar crystals growing along the z-axis in parts with irregular shapes / hollowed-out sections, thereby enhancing the part's strength and stability.

[0138] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0139] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature through an intermediate medium. Furthermore, "above," "over," and "on top" of the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0140] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A 3D printing method, characterized in that, include: A point exposure area is set in the laser scanning path to divide the laser scanning path into a pass scanning area and the point exposure area; The laser beam is controlled to perform continuous scans in the xy plane on each layer of material corresponding to the scan area using the first scanning parameters to construct the main body of the part. During the scan, the real-time position of the dynamic molten pool formed by the light spot on the material corresponding to the scan area is acquired. When it is determined that the dynamic molten pool has moved to the point exposure area, the laser output is interrupted. When the laser beam is controlled to cross the point exposure area and re-enter the scan area, the output of the laser beam is restored. And when it is determined that all scans of the current layer corresponding to the said scan area have been completed, the crystal fabrication process begins; Crystal formation: The time parameter in the second scanning parameter is controlled to scan and expose any layer of material corresponding to the point exposure area, so that a static molten pool is generated in the point exposure area, and the solidification process of the static molten pool is controlled by controlling the exposure time of the laser beam, so as to form grains after solidification. And layer-by-layer crystallization to form columnar crystals with grain orientations different from those in the scanned regions; The main body of the part is combined with the columnar crystal in the dot exposure area to form the final shaped part.

2. The 3D printing method according to claim 1, characterized in that, The crystal preparation process also includes: Set the offset and overlap rate of the point exposure area on each layer of material; The laser beam is controlled to perform offset and overlap scanning exposure on each layer of material according to the offset and overlap rate, so as to form a crystal structure grown at a preset angle and position in the point exposure area.

3. The 3D printing method according to claim 2, characterized in that, The offset is calculated as follows: Offset = tan(θ) * LayerThickness; Where θ is the angle of the crystal structure, and LayerThickness is the thickness of each powder layer; The formula for calculating the overlap rate is: Overlap = (Length - Offset) / Length * 100%; Where Length is the length of the crystal structure in each layer.

4. The 3D printing method according to claim 1, characterized in that, Also includes: Identify continuous z-axis segments based on the 3D model of the part; Set the target position of the corresponding crystal structure based on the identified continuous z-axis segment; as well as Set the corresponding point exposure area according to the target location of the crystal structure.

5. The 3D printing method according to claim 1, characterized in that, The first scanning parameters and the second scanning parameters are executed by different laser beams. One laser beam is used to perform continuous scans in the xy plane on each layer of material corresponding to the scan area using the first scanning parameters, and the other laser beam is used to perform scanning exposure on each layer of material corresponding to the point exposure area using the second scanning parameters.

6. A 3D printing control system, characterized in that, The control system is configured to perform the method according to any one of claims 1-5.

7. A 3D printing device, characterized in that, include: Mechanical unit; Optical path unit; as well as Includes the control system described in claim 6.

8. The 3D printing equipment according to claim 7, characterized in that, The optical path unit includes: A first laser is used to output a laser beam for continuous scanning in the xy plane on each layer of material corresponding to the scanned area; and The second laser is used to output a laser beam for exposure scanning on each layer of material corresponding to the point exposure area.

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