A polymorphic progressive three-dimensional forming method

Abstract

The present invention provides a polymorphic progressive three-dimensional forming method. First, a three-dimensional digital model is loaded for preprocessing, and then a prepolymer, a production compact, and a functional body are constructed respectively. The sliced data of each part are aligned and fused along the Z-axis. After that, through the controller, units such as the substrate, powder supply, and powder spreading are coordinated, and the laser scanning unit scans in different modes, spreading powder layer by layer on the powder bed and scanning for forming, and the cyclic operation is carried out until completion; this method has significant advantages. It adopts a three-state progressive forming strategy of prepolymer-compact-functional body, and acts on the metal powder layer with different laser parameters in stages. The energy gradient loading makes the metal phase change more controllable and reduces the generation of plasma. It not only avoids the waste of traditional high-energy scanning, improves the forming efficiency and powder utilization rate, but also can realize the integrated forming of complex structures, reduce the concentration of thermal stress, improve the performance of the formed parts, and the molten pool is stable, which is conducive to generating high-quality structures and is convenient for popularization.

Description

Technical Field

[0001] The present invention relates to the technical field of three-dimensional forming of metal entities, and particularly relates to a polymorphic progressive three-dimensional forming method. Background Art

[0002] Laser metal powder bed three-dimensional forming is an important additive manufacturing method. Based on laying metal powder on the surface layer of the powder bed, a high-power laser beam is used to scan and irradiate a selected area of the metal powder laying layer, so that free metal powder particles are melted and welded and deposited on the substrate. Then, through the step-by-step descent of the substrate and the cyclic execution of the powder laying and scanning irradiation steps, the welded deposits grow layer by layer on the substrate until complete forming. The micron-level control accuracy of the laser beam by existing microelectromechanical optical actuators, as well as their advantages of low inertia and high response speed, make laser metal powder bed three-dimensional forming equipment show significant advantages in the processing field of precision complex metal products, especially high-performance metal components with complex internal designs and three-dimensional surface microstructures.

[0003] The powder particle size that takes into account fluidity, loose bulk density, and powder layer thickness resolution is the core parameter for exerting the accuracy of laser metal powder bed three-dimensional forming. Currently, the powder particle size range for laser metal powder beds is defined as 15 - 53 μm, and the loose bulk density is about 50% of the solid. At the same time, to ensure the geometric resolution of laser beam scanning irradiation and selective area welding, it is necessary to mainly perform the welding deposition of the metal powder laying layer in a direct heating manner and suppress the parasitic welding deposition effect caused by heat conduction; increasing the shear gradient of the plane distribution of the laser beam spot energy field and shortening the single-point residence time of the laser beam scanning irradiation are the main methods to achieve this goal, that is, to complete the transformation of the metal powder laying layer from a free particle state to a dense state in a high-speed, continuous, and in-situ welding deposition manner. Furthermore, it can be seen that implementing high-energy density and high-speed laser scanning irradiation on the fine metal powder layer is the fundamental strategy of existing laser metal powder bed three-dimensional forming equipment.

[0004] On the other hand, there are significant differences between the welding process of fine metal powder under laser irradiation and the welding process of dense metal: the intensity of molten pool splashing, fume, and plasma flame in the former is much stronger than that in the latter. The strong dynamic effect of molten pool splashing will greatly change the flat shape of the powder laying layer around the molten pool, resulting in obvious powder thickness deviation and particle size segregation problems; furthermore, the fume and plasma flame will significantly attenuate the energy of the laser beam reaching the powder laying layer. Especially, splashing, fume, and plasma flame have characteristics such as multi-variables, strong non-linearity, and difficult to accurately measure, seriously damaging the welding stability of the metal powder laying layer, introducing process interference that cannot be ignored to laser metal powder bed three-dimensional forming, and severely degrading the actual three-dimensional forming performance.

[0005] By directly examining the standard particle size distribution range of 15 - 53 μm, it can be seen that the volume ratio of large powder particles to small powder particles exceeds 44 times at most. The laser beam heats these metal particles with huge volume differences within an extremely short residence time, resulting in a significant proportion of small particles being directly vaporized due to their low heat capacity and large conduction thermal resistance. These vaporized small metal particles act as multiple "micro - blasting points" within the laser beam irradiation range and are the main sources of molten pool splashing, flue gas, and plasma flames. There are public reports at home and abroad on weakening the central energy density of the laser beam through spot shaping, but it mainly aims at the overheating of the molten pool center and does not specifically expand new degrees of freedom for regulation to compensate for the thermokinetic differences caused by the powder particle size distribution. Currently, in the field of metal powder bed forming technology, the existing technology still has deficiencies in three - dimensional laser metal powder bed forming, lacking a method that can effectively control molten pool splashing, flue gas, and plasma flames and suppress their adverse effects on the forming process. Moreover, there are many problems such as large scanning thermal stress, poor forming accuracy, and low success rate. Summary of the Invention

[0006] The present invention proposes a multi - state progressive three - dimensional forming method and its method. This method is simple and feasible. By adding forming transition states and irradiating the surface layer of the powder bed multiple times with different scanning strategies, it can gradually avoid the severe splashing of the molten pool, flue gas, and plasma flames caused by high - energy irradiation of the metal powder layer at one time. At the same time, it can also prevent these situations from further deteriorating the forming accuracy and fineness, thereby effectively solving the problems of large scanning thermal stress, poor forming accuracy, and low success rate in the existing technology.

[0007] The technical solution of the present invention is as follows: A multi - state progressive three - dimensional forming method includes loading a three - dimensional digital model into a computer 3D working environment, duplicating the three - dimensional digital model twice to obtain a first copy for constructing a pre - polymer and a second copy for generating a dense body. The second copy is peeled off the cladding according to the thermal conduction avoidance distance parameter to obtain a dense body digital model. The dense body digital model is duplicated to obtain a third copy for preparing a functional body. The third copy designs the three - dimensional boundary of the functional body region according to the microstructure and micro - geometry, and obtains a functional body composed of a microstructure digital model and a micro - geometry digital model. The first copy, the dense body digital model, the microstructure digital model, and the micro - geometry digital model are respectively and independently sliced to generate their respective slice groups. Each slice assigns a value to the cross - sectional vector filling according to its matching laser parameters to generate vector blocks for each layer;

[0008] Each layer of pre - polymer slices searches for slices at the same height in the dense body, microstructure, and micro - geometry slice groups in the Z - axis direction, and adds the vector blocks to this layer of pre - polymer slices in the order of dense body - microstructure - micro - geometry, realizing the multi - state fusion of the slice data of each layer of the three - dimensional digital model;

[0009] The powder bed drives the substrate to descend to the powder spreading height. The powder supply unit supplies the powder required for a single powder spreading to the powder spreading unit. The powder spreading unit drives a doctor blade to push a strip-shaped powder pile to perform powder spreading, fill the depression on the upper surface of the powder bed generated by the descent of the substrate, and generate a metal powder layer. The laser scanning unit performs laser scanning in the order of pre-polymer, densified body, and functional body. After the laser scanning forming of the metal powder layer is completed, powder spreading and scanning are performed in a cycle, continuously depositing a metal powder welding layer until the slice data of the last layer is read and scanned completely.

[0010] The implementation steps of the above solution are specifically as follows:

[0011] S1. Model loading and preprocessing

[0012] Load the 3D digital model into the computer 3D working environment, and perform model integrity verification and characteristic dimension standardization processing;

[0013] S2. Pre-polymer construction

[0014] Copy the 3D digital model to obtain a first copy, perform slice processing on the first copy according to the powder spreading height parameter to obtain n layers of pre-polymer slices, and assign values to the cross-sectional pattern vectors of the pre-polymer slices according to the laser geometry and energy parameters of the pre-polymer to produce vector blocks of each layer of the pre-polymer.

[0015] S3. Densified body production

[0016] Copy the 3D digital model to obtain a second copy, strip the cladding of the second copy according to the heat conduction avoidance distance parameter to obtain a densified body digital model, perform slice processing on the densified body digital model according to the preset layer thickness parameter of the densified body to obtain m layers of densified body slices, and process the cross-section of the densified body slices according to the laser geometry and energy parameters of the densified body to generate vector blocks of each layer of the densified body.

[0017] S4. Functional body preparation

[0018] Copy the densified body digital model to obtain a third copy, set the 3D boundary of the functional body area according to the requirements of the microstructure and microgeometry design of 3D forming to obtain a microstructure digital model and a microgeometry digital model. Perform slice processing on the microstructure digital model according to the preset thickness parameter of the microstructure functional body to obtain b layers of microstructure slices, perform slice processing on the microgeometry digital model according to the preset thickness parameter of the microgeometry functional body to obtain d layers of microgeometry slices, and generate vector blocks of each layer of the microstructure functional body and the microgeometry functional body respectively according to their respective laser geometry and energy parameters.

[0019] S5. Data fusion

[0020] According to the principle of aligning objects in the Z-axis direction in three-dimensional space, the prepolymer slices of each layer are used as the base layer, and the corresponding layers in the dense body layer slices, microtissue slices and microgeometry slices are found at the same Z-direction height position, and the vector block data of the corresponding layer is added to the base layer in the order of dense body layer slices-microtissue slices-microgeometry slices. By adding and integrating layer by layer, the complete 1st to nth layer slice data of the three-dimensional digital model are finally obtained;

[0021] S6, Polymorphic Incremental Forming

[0022] Perform multi-state incremental forming printing, the powder bed drives the substrate to descend to the powder spreading height, the atmosphere unit adjusts the working gas in the forming chamber to an inert state, the powder supply unit supplies the powder required for a single powder spreading to the powder spreading unit, and the powder forms a strip-shaped powder pile on the right side of the scraper. The powder spreading unit drives the scraper to push the strip-shaped powder pile to perform the powder spreading action, fills the depression on the surface of the powder bed caused by the descending of the substrate and generates a metal powder layer, the laser scanning unit first performs a vector block scan of the prepolymer, then performs a vector block scan of the corresponding dense body, and finally performs a vector block scan of the corresponding micro-tissue functional body and micro-geometry functional body, the powder spreading unit returns to the zero point, and the metal powder bed laser scanning forming is completed;

[0023] S7, Cycle Forming

[0024] S6 is executed in a loop, and the prepolymer, dense body, and functional body composed of micro-structure functional body and micro-geometry functional body continue to deposit new metal powder welding layer until the n-th layer of polymorphic body slice data is read and sequentially scanned, the prepolymer, dense body and functional body grow to a complete form, and the polymorphic progressive laser metal powder bed three-dimensional forming process is completed.

[0025] Preferably, the prepolymer construction uses an adaptive grid partitioning algorithm to divide the cross section of each layer of the prepolymer slice into multiple sub-regions, and calculates the sub-region vector filling components region by region, accumulates the vector filling components of all sub-regions, and generates vector blocks of each layer of the prepolymer that characterize the laser energy distribution;

[0026] The laser geometry and energy parameters of the prepolymer include the laser scanning line spacing And the effective radius of the laser spot , used to measure the closeness of the sub-region and the laser geometric effect. The closer the sub-region is to the laser scanning path and the closer it is within the effective action range of the light spot, the closer the sub-region and the laser geometric effect are, and vice versa;

[0027] The vector filling value component of each sub-region is calculated as follows:

[0028] ;

[0029] in, For the area of the th sub-region, it can be accurately obtained by combining boundary contour tracing with geometric calculation. is the area of the cross-section of a prepolymer slice of a certain layer. is the perpendicular distance from the center of the sub-region to the nearest laser scanning line. is the distance from the center of the sub-region to the projection point of the center of the laser spot on the cross-section plane. represents the actual effective energy action situation after comprehensively considering the initial laser energy density and the energy absorption coefficient of the sub-region, where < ≤ , represents the comprehensive influence coefficient of the energy of the th sub-region.

[0030] Preferably, the n prepolymer slices are sequentially numbered 3011,..., 301n, where n is a natural number greater than 1, the m compact body slices are sequentially numbered 3031,..., 303m, 1 < m ≤ n, the b microtissue slices are sequentially numbered 3051,..., 305b, 1 < b ≤ n, and the d microgeometry slices are sequentially numbered 3061,..., 306d, 1 < d ≤ n;

[0031] Separate Z-axis height index tables are established for the multiple prepolymer slices, compact body slices, microtissue slices, and microgeometry slices respectively, used to record the Z values of each slice. Based on the index table of the prepolymer slices, traverse the index tables of the compact body slices, microtissue slices, and microgeometry slices to find the matching prepolymer slices, compact body slices, microtissue slices, and microgeometry slices with the same Z value, and fuse the vector block data in the order of prepolymer slices, compact body slices, microtissue slices, and microgeometry slices to achieve precise fusion of polymorphic data.

[0032] Preferably, the index table of the prepolymer slices starts with the Z value of the 3011st slice, and each prepolymer slice matches zero or one or more of the compact body slice, microtissue slice, and microgeometry functional body. The prepolymer region contains the compact body region, and the compact body region contains the functional body region.

[0033] Preferably, in the multi-state incremental forming step S6, the substrate, powder supply unit, powder spreading unit, powder bed, laser scanning unit, and atmosphere unit are all electrically connected to a controller. Before forming, the powder supply unit injects a sufficient amount of metal powder and closes the forming chamber. The controller issues an operation instruction to the atmosphere unit to control the atmosphere unit to adjust the working gas in the forming chamber to an inert state and maintain cyclic purification. The controller issues a zeroing instruction to the powder bed and the powder spreading unit to control the powder bed to drive the substrate to the zero position and control the powder spreading unit to run to the zero position. The controller loads the slice data of the 1st to the nth layers of the complete 3D digital model.

[0034] Preferably, when performing multi-state incremental forming printing on the nth layer of the 3D digital model, the controller first issues a lowering instruction to the powder bed and a powder supply instruction to the powder supply unit, respectively driving the substrate to lower the powder spreading height and driving the powder supply unit to output the metal powder of a single powder spreading amount to the powder spreading unit. The controller issues a powder spreading instruction to the powder spreading unit to control the powder spreading unit to push the metal powder to fill the depression in the powder bed generated by the lowering of the substrate and push the excess powder into the powder return unit. The controller reads the prepolymer vector block data of the nth layer, generates a scanning instruction sequence, and sends it to the laser scanning unit to control the laser scanning unit to perform laser prepolymer scanning, so that the small particles in the metal powder spreading layer in the scanned area are melted and adhered to the remaining particles to form the prepolymer of this layer;

[0035] If there is a densified body vector block in the prepolymer of this layer, the controller reads and generates a scanning instruction sequence and sends it to the laser scanning unit to control the laser scanning unit to perform laser densification scanning, so that the scanned prepolymer is completely melted and cooled and solidified to form a dense metal deposit;

[0036] If there is a functional body vector block in the densified body, the controller reads and generates a scanning instruction sequence and sends it to the laser scanning unit to control the laser scanning unit to perform laser functional scanning;

[0037] After all the vector blocks of the nth layer of the 3D digital model are scanned, the controller controls the powder spreading unit to return to the zero position, and the forming is completed.

[0038] Preferably, the laser scanning unit includes three scanning methods: laser prepolymer scanning, laser densification scanning, and laser functional scanning. The laser prepolymer scanning is that the laser energy input matches the melting requirement of the small particles in the metal powder spreading layer. The laser energy input value and the single-point dwell time of scanning do not meet the melting requirement of the large-particle metal powder. A high linear velocity, small pitch, and low energy input method is used for scanning to produce a prepolymer. The forming area of the prepolymer is the directly irradiated area of the scanning;

[0039] The laser densification scanning is such that the laser energy input matches the full melting requirement of the porous metal sintered body, and it is scanned in a manner of low linear velocity, large spacing, and high energy input. The single-point residence time of the laser scanning is long. The forming area of the compact includes the directly irradiated area by scanning and the heat conduction area.

[0040] The laser functional scanning includes laser microstructural functional body scanning and laser microgeometric functional body scanning.

[0041] Preferably, the laser microgeometric functional body scanning is such that the laser energy input matches the melting requirement of the microsection compact. It adopts high linear velocity, small spacing, small spot, and high energy input. The single-point direct irradiation range of the scanning is small, the residence time is short, the lateral heat conduction range is small, and the vertical heat conduction depth is large. It realizes the melting and cooling of the deep microsection compact in a short time, forms fine grains and vitreous tissues, and further increases the energy input to remove trace metals by evaporation to generate a microgeometric functional body.

[0042] Preferably, the laser microstructural functional body scanning is such that the laser energy input matches the melting requirement of the large-section compact. It adopts low speed, large spacing, large defocused spot, and high energy input. The single-point irradiation range of the scanning is large, the residence time is long, the depth of the molten pool is suppressed by the large-section heat diffusion, and a large-section shallow molten pool is generated on the surface of the dense metal. Then it self-levels and cools and solidifies to generate a smooth surface with low roughness functionality.

[0043] An apparatus applying the multi-state progressive three-dimensional forming method includes a frame. A forming chamber is provided on the frame, and a powder bed is provided in the frame. The upper opening of the powder bed is fitted and connected to the bottom plate of the forming chamber.

[0044] A substrate is provided in the powder bed. The powder bed can drive the substrate to move up and down and be positioned. When the substrate is at the zero position, it is flush with the edge of the upper opening of the powder bed and the bottom plate of the forming chamber.

[0045] A powder supply unit and a powder spreading unit are provided in the forming chamber. A powder recycling unit is provided in the frame. The opening of the powder recycling unit is connected to the bottom plate of the forming chamber. The powder supply unit can quantitatively output metal powder to the powder spreading unit. The powder spreading unit can move horizontally back and forth on the bottom plate of the forming chamber to spread powder on the upper opening of the powder bed and push the excess powder into the opening of the powder recycling unit.

[0046] An atmosphere unit is provided in the frame. The air inlet and outlet of the atmosphere unit are connected to the two side plates of the forming chamber. The atmosphere unit inhales the gas in the forming chamber through the air inlet, filters and purifies it, and then sends it back to the forming chamber through the air outlet.

[0047] A laser scanning unit is provided at the top of the forming chamber. The scanning range of the laser scanning unit covers the upper opening of the powder bed, and the laser scanning unit can scan and irradiate a selected area on the surface layer of the powder bed according to the set laser power, linear velocity, and spot diameter parameters. Beneficial effects

[0048] In the polymorphic progressive three-dimensional forming method of the present invention, the process of laser scanning to process the free powder particles on the powder-laying metal layer and generate the required three-dimensional metal structure experiences three forming transition states, namely, the metal prepolymer state, the metal dense state, and the metal functional state. Through the three-state progressive forming strategy of prepolymer-dense body-functional body, different laser parameters are used in stages to act on the metal powder layer. In the prepolymerization stage, high linear velocity and low energy scanning are adopted, and only the small particles on the surface layer are melted to form a porous skeleton, significantly reducing the melt pool disturbance and splash generation. In the densification stage, the energy input is increased on the basis of the prepolymer, and the melt pool range is restricted through the heat conduction avoidance design to avoid the free powder splashing caused by energy leakage. In the functional stage, customized parameters are used to achieve micro-region refinement and accurately control the melt pool morphology. This energy gradient loading mode makes the metal phase change process more controllable, greatly reduces the generation of plasma, and significantly improves the forming stability.

[0049] Through the staged forming of the prepolymer, dense body, and functional body, the present invention avoids the energy waste caused by the traditional high-energy one-time scanning, improves the forming efficiency and significantly improves the powder utilization rate: the low-energy scanning of the prepolymer reduces the powder splash and soot generation, and the fine scanning of the functional body directly meets the requirements of surface finish and geometric accuracy, reducing the subsequent machining and polishing processes.

[0050] Through the hierarchical data fusion of the prepolymer, dense body, and functional body, the present invention can achieve the integrated forming of complex internal structures and high-precision external features. The prepolymer provides a stable support structure as a transition state. Through the staged energy loading of the prepolymer, dense body, and functional body, the problem of thermal stress concentration caused by the high-energy concentrated input in the traditional process is avoided. The rapid melting-cooling strategy of the functional body forms fine-grained or glassy structures, further improving the mechanical properties and corrosion resistance of the formed parts.

[0051] According to the particle size distribution characteristics of the metal powder and the difference in the hot melting behavior under the laser scanning energy input, the present invention adopts multiple differential energy and geometric strategies to implement laser selective area scanning and gradually complete the three-dimensional forming of the metal powder bed. It has the advantages of less flue gas splash and slight plasma sparks. Its stable melt pool state helps to generate high-resolution, high-strength metal tissue structures and complex, fine geometric structures, and is easy to be popularized and applied in three-dimensional forming equipment of laser metal powder beds of various sizes. Description of the drawings

[0052] The present invention will be further described in detail below in conjunction with the drawings and specific embodiments.

[0053] Figure 1 Schematic diagram of three - dimensional area planning and slicing for the present invention;

[0054] Figure 2 Schematic diagram of layer - by - layer polymorphic incremental forming for the present invention;

[0055] Figure 3 Connection diagram of control signals for the present invention;

[0056] Figure 4 Schematic structural diagram of the device of the present invention;

[0057] Reference numerals in the drawings:

[0058] 1. Frame; 2. Forming chamber; 3. Powder bed; 31. Substrate; 4. Powder supply unit; 41. Ribbon powder pile; 5. Powder spreading unit; 51. Doctor blade; 6. Powder recycling unit; 7. Atmosphere unit; 71. Air inlet; 72. Exhaust outlet; 8. Laser scanning unit; 100. Controller; 300. Three - dimensional digital model; 301. First copy; 302. Second copy; 303. Dense body digital model; 304. Third copy; 305. Micro - structure digital model; 306. Micro - geometry digital model; 500. Three - dimensional metal formed body; 501. Metal powder layer; 5001. Pre - polymer; 5002. Dense body; 5003. Functional body; 3011 - 301n. Pre - polymer slices; 3031 - 303m. Dense body slices; 3051 - 305b. Micro - structure slices; 3061 - 306d. Micro - geometry slices. Detailed implementation manners

[0059] Next, in combination with the embodiments of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts fall within the scope of protection of the present invention.

[0060] A polymorphic incremental three - dimensional forming method includes the following steps:

[0061] S1. Model loading and pre - processing: Load the three - dimensional digital model 300 into the computer 3D working environment, and perform model integrity verification and characteristic dimension standardization processing;

[0062] S2. Prepolymer construction: Copy the 3D digital model 300 to obtain the first copy 301. Slice the first copy 301 according to the powder spreading height parameter to obtain n prepolymer slices. The n prepolymer slices are sequentially numbered as 3011, ……, 301n, where n is a natural number greater than or equal to 1. Among them, 3011 is the first layer and 301n is the last layer. Vector filling is performed on the cross-sectional patterns of 3011 - 301n according to the vector direction, width, spacing, and spot compensation of the prepolymer 5001 laser geometry parameters, which determines the shape, position, and accuracy of the filling, and according to the prepolymer laser energy parameters of power, spot, and linear velocity, the energy deposition and curing effect on the prepolymer are affected, and each layer of vector blocks of the prepolymer 5001 are produced;

[0063] Use the adaptive mesh generation algorithm to divide the cross-section of each layer of prepolymer slice into multiple sub-regions, and calculate the vector filling components of the sub-regions one by one. Accumulate the vector filling components of all sub-regions to generate each layer of vector blocks of the prepolymer 5001 representing the laser energy distribution. The laser scan line spacing in the laser geometry and energy parameters of the prepolymer 5001 and the effective action radius of the laser spot are used to measure the degree of closeness of the sub-regions to the laser geometry action. The closer the sub-region is to the laser scan path and within the effective action range of the spot, the closer the sub-region is to the laser geometry action, and vice versa. The specific steps are as follows:

[0064] a. Determine the lengths of the minimum circumscribed rectangle of the prepolymer slice cross-section on the X-axis and Y-axis. Use the adaptive mesh generation algorithm to divide the cross-section of the prepolymer slice into sub-regions, determine the average scales of each sub-region on the X-axis and Y-axis, and calculate the comprehensive energy influence coefficient of each sub-region ;

[0065] b. Obtain the initial energy density of the prepolymer laser as , and the energy absorption coefficient of each sub-region based on its characteristics related to the laser action is , where < ≤ ;

[0066] Determine the vector filling component of each sub-region, and then determine the vector filling value of the prepolymer slice cross-section pattern. The calculation method of the vector filling value component of each said sub-region is as follows:

[0067] ;

[0068] Among them, is the area of the th sub-region, which can be accurately obtained by combining boundary contour tracing and geometric calculation, is the cross-sectional area of a prepolymer slice of a certain layer. is the perpendicular distance from the center of the sub-region to the nearest laser scan line. is the distance from the center of the sub-region to the projection point of the center of the laser spot on the cross-sectional plane. represents the actual effective energy action situation after comprehensively considering the initial laser energy density and the energy absorption coefficient of the sub-region. Laser scan line spacing and the effective action radius of the laser spot are used to measure the closeness of the sub-region to the laser geometric action. The closer the sub-region is to the laser scan path and within the effective action range of the spot, the larger this value is.

[0069] C. Sum the of each sub-region to obtain the vector block filling data of the prepolymer slice of this layer.

[0070] S3. Dense body production

[0071] Copy the three-dimensional digital model 300 to obtain the second copy 302, strip the cladding of the second copy 302 according to the heat conduction avoidance distance parameter to obtain the dense body digital model 303, slice the dense body digital model 303 according to the preset layer thickness parameter of the dense body 5002 to obtain m layers of dense body slices, and the m dense body slices are sequentially numbered as 3031, ……, 303m, 1 < m ≤ n. According to the laser geometry and energy parameters of the dense body 5002, process the cross-section of the dense body slice to generate each layer vector block of the dense body 5002.

[0072] S4. Functional body preparation

[0073] Copy the dense body digital model 303 to obtain the third copy 304. According to the three-dimensional microstructure and microgeometry design requirements of three-dimensional forming, set the three-dimensional boundary of the functional body 5003 region to obtain the microstructure digital model 305 and the microgeometry digital model 306. Slice the microstructure digital model 305 according to the preset thickness parameter of the microstructure functional body to obtain b layers of microstructure slices, and slice the microgeometry digital model 306 according to the preset thickness parameter of the microgeometry functional body to obtain d layers of microgeometry slices. The b microstructure slices are sequentially numbered as 3051, ……, 305b, 1 < b ≤ n, and the d microgeometry slices are sequentially numbered as 3061, ……, 306d, 1 < d ≤ n. According to their respective laser geometry and energy parameters, generate each layer vector block of the microstructure functional body and the microgeometry functional body respectively.

[0074] S5. Data fusion

[0075] According to the principle of aligning objects in the Z-axis direction in three-dimensional space, each layer of prepolymer slices is used as the base layer, and the corresponding layers in the dense body slices, microtissue slices and microgeometry slices are found at the same Z-direction height position, and the vector block data of the corresponding layer is added to the base layer in the order of dense body slices-microtissue slices-microgeometry slices. By adding and integrating layer by layer, the complete 1st to nth layer slice data of the three-dimensional digital model 300 are finally obtained;

[0076] S6, Polymorphic Incremental Forming

[0077] Perform polymorphic incremental forming printing, the powder bed 3 drives the substrate 31 to descend to the powder spreading height, the atmosphere unit 7 adjusts the working gas of the forming chamber 2 to an inert state, the powder supply unit 4 supplies the powder required for a single powder spreading to the powder spreading unit 5, and the powder forms a strip-shaped powder pile 41 on the right side of the scraper 51. The powder spreading unit 5 drives the scraper 51 to push the strip-shaped powder pile 41 to perform the powder spreading action, fills the depression on the surface of the powder bed 3 caused by the descending substrate 31 and generates a metal powder layer 501, the laser scanning unit 8 first performs a vector block scan of the prepolymer 5001, then performs a vector block scan of the corresponding dense body 5002, and finally performs a vector block scan of the corresponding micro-tissue functional body and micro-geometry functional body, the powder spreading unit 5 returns to the zero point, and the laser scanning forming of the metal powder bed 3 is completed;

[0078] When a total of n-1 layers of metal powder forming have been completed in the powder bed 3, the generated three-dimensional metal formed body 500 is located on the substrate 31, which includes an incomplete prepolymer 5001, a dense body 5002 and a functional body 5003, then the steps of the n-th layer polymorphic incremental forming are as follows:

[0079] When the n-th layer of the three-dimensional digital model 300 is printed by polymorphic incremental forming, the controller 100 first sends a descending command to the powder bed 3 and a powder supply command to the powder supply unit 4, respectively driving the substrate 31 to descend the powder spreading height and driving the powder supply unit 4 to output a single powder spreading amount of metal powder to the powder spreading unit 5. The controller 100 sends a powder spreading command to the powder spreading unit 5, controls the powder spreading unit 5 to push the metal powder to fill the depression of the powder bed 3 caused by the descent of the substrate 31, and pushes the excess powder into the powder return unit 6. The controller 100 reads the vector block data of the prepolymer 5001 of the n-th layer, generates a scanning command sequence and sends it to the laser scanning unit 8, controls the laser scanning unit 8 to perform laser prepolymer scanning, so that the small particles in the metal powder spreading layer in the scanned area are melted and bonded with the remaining particles to form the prepolymer 5001 of this layer;

[0080] If there is a dense body 5002 vector block in the prepolymer 5001 of the layer, the controller 100 reads and generates a scanning instruction sequence and sends it to the laser scanning unit 8, and controls the laser scanning unit 8 to perform laser dense scanning, so that the scanned prepolymer is completely melted, cooled and solidified to form a dense metal deposit;

[0081] If the compact body 5002 has a functional body 5003 vector block, the controller 100 reads and generates a scanning instruction sequence and sends it to the laser scanning unit 8 to control the laser scanning unit 8 to perform laser functional scanning;

[0082] After all the vector blocks of the nth layer of the three-dimensional digital model 300 are scanned, the controller 100 controls the powder spreading unit 5 to return to the zero position, and the forming is completed.

[0083] It should be particularly noted that first, in the computer 3D working environment, the three-dimensional digital model of the component to be formed is planned to determine the pre-polymerized state, dense state, and functional state regions therein. The spatial relationship is that the pre-polymerized state region can contain the dense state region, and the dense state region can contain the functional state region;

[0084] S7. Cyclic forming

[0085] Execute S6 in a loop. The prepolymer 5001, the compact body 5002, and the functional body 5003 composed of the microstructural functional body and the micro-geometric functional body continuously deposit a new metal powder welding layer until the multi-state body slice data of the nth layer is read and sequentially scanned. The prepolymer 5001, the compact body 5002, and the functional body 5003 grow to a complete form, and the three-dimensional forming process of the multi-state progressive laser metal powder bed 3 is completed.

[0086] Furthermore, multiple prepolymer slices, compact body slices, microstructural slices, and micro-geometric slices independently establish Z-axis height index tables for recording the Z values of each slice. Based on the index table of the prepolymer slices, traverse the index tables of the compact body slices, microstructural slices, and micro-geometric slices to find the matching prepolymer slices, compact body slices, microstructural slices, and micro-geometric slices with the same Z value, and fuse the vector block data in the order of the prepolymer slices, compact body slices, microstructural slices, and micro-geometric slices to achieve precise fusion of multi-state data.

[0087] Furthermore, the index table of the prepolymer slices starts from the Z value of the 3011st slice. Each prepolymer slice matches zero or one or more of the compact body slices, microstructural slices, and micro-geometric functional bodies. The prepolymer 5001 region contains the compact body 5002 region, and the compact body 5002 region contains the functional body 5003 region.

[0088] Furthermore, in the multi-state incremental forming step S6, the substrate 31, powder supply unit 4, powder spreading unit 5, powder bed 3, laser scanning unit 8, and atmosphere unit 7 are all electrically connected to a controller 100. Before forming, the powder supply unit 4 injects a sufficient amount of metal powder and closes the forming chamber 2. The controller 100 issues an operation instruction to the atmosphere unit 7 to control the atmosphere unit 7 to adjust the working gas in the forming chamber 2 to an inert state and maintain cyclic purification. The controller 100 issues a zeroing instruction to the powder bed 3 and the powder spreading unit 5 to control the powder bed 3 to drive the substrate 31 to run to the zero position and control the powder spreading unit 5 to run to the zero position. The controller 100 loads the complete slice data of the 1st to the nth layers of the three-dimensional digital model 300.

[0089] Furthermore, the laser scanning unit 8 includes three scanning methods: laser pre-consolidation scanning, laser densification scanning, and laser functional scanning. Laser pre-consolidation scanning is to match the laser energy input to the melting requirement of small particles in the metal powder spreading layer. The laser energy input value and the single-point dwell time of the scan do not meet the melting requirement of large-particle metal powder. The pre-consolidation body 5001 is produced by scanning in a manner of high linear velocity, small pitch, and low energy input. The forming area of the pre-consolidation body 5001 is the directly irradiated area of the scan. The smoke, spatter, and plasma flame generated during sintering are slight, and the force disturbance to the powder bed in the adjacent area is slight, enabling scan sintering without support.

[0090] Laser densification scanning is to match the laser energy input to the sufficient melting requirement of the porous metal sintered body. Its heat conduction ability and specific heat capacity per unit volume are much higher than those of free metal powder. Scanning is carried out in a manner of low linear velocity, large pitch, and high energy input. The heat conduction effect is significant, and the single-point dwell time of the laser scan is long. The forming area of the densified body 5002 includes the directly irradiated area of the scan and the heat conduction area. Since there is no small-particle free metal powder in the densification scan area, the smoke, spatter, and plasma flame generated by the molten pool are slight. Through the heat conduction avoidance distance, the heat leakage of the molten pool in the laser densification scan can be prevented from leaking to the free powder area outside the pre-consolidation body 5001;

[0091] Laser functional scanning includes laser micro-tissue functional body scanning and laser micro-geometry functional body scanning. Laser micro-geometry functional body scanning matches the melting requirements of the laser energy input to the micro-section dense body 5002. It adopts a high linear velocity, small pitch, small spot, and high energy input. The direct irradiation range of a single scanned point is small, the residence time is short, the lateral heat conduction range is small, and the vertical heat conduction depth is large. It realizes the melting and cooling of the deep dense body 5002 with a micro-section in a short time, forms fine grains and vitreous tissues, and further increases the energy input to remove trace metals by evaporation to generate a micro-geometry functional body. Laser micro-tissue functional body scanning matches the melting requirements of the laser energy input to the large-section dense body 5002. It adopts a low velocity, large pitch, large defocused spot, and high energy input. The irradiation range of a single scanned point is large, the residence time is long, the depth of the molten pool is inhibited by the thermal diffusion of the large section, a large-section shallow molten pool is generated on the surface of the dense metal, and then it self-levels and cools and solidifies to generate a smooth surface with low roughness functionality.

[0092] The device applying the polymorphic progressive three-dimensional forming method includes a frame 1. A forming chamber 2 is provided on the frame 1. A powder bed 3 is provided in the frame 1. The upper opening of the powder bed 3 is fitted and connected to the bottom plate of the forming chamber 2. A substrate 31 is provided in the powder bed 3. The powder bed 3 can drive the substrate 31 to move up and down and be positioned. When the substrate 31 is at the zero position, it is flush with the edge of the upper opening of the powder bed 3 and the bottom plate of the forming chamber 2. A powder supply unit 4 and a powder spreading unit 5 are provided in the forming chamber 2. A powder recycling unit 6 is provided in the frame 1. The opening of the powder recycling unit 6 is connected to the bottom plate of the forming chamber 2. The powder supply unit 4 can quantitatively output metal powder to the powder spreading unit 5. The powder spreading unit 5 can move horizontally back and forth on the bottom plate of the forming chamber 2 to spread powder on the upper opening of the powder bed 3 and push the excess powder into the opening of the powder recycling unit 6. An atmosphere unit 7 is provided in the frame 1. The air inlet 71 and the air outlet 72 of the atmosphere unit 7 are connected to the two side plates of the forming chamber 2. The atmosphere unit 7 inhales the gas in the forming chamber 2 through the air inlet 71, and after filtration and purification, it is sent back to the forming chamber 2 through the air outlet 72. A laser scanning unit 8 is provided at the top of the forming chamber 2. The scanning range of the laser scanning unit 8 covers the upper opening of the powder bed 3, and the laser scanning unit 8 can scan and irradiate the selected area on the surface layer of the powder bed 3 according to the set laser power, linear velocity, and spot diameter parameters.

[0093] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims

1. A polymorphic progressive three-dimensional forming method, characterized in that, The method comprises: The three-dimensional digital model (300) is loaded into a computer 3D operating environment, and the three-dimensional digital model (300) is duplicated twice to obtain a first copy (301) of the prepolymer (5001) and a second copy (302) of the dense body (5002). The second copy (302) peels off the shell according to the heat conduction avoidance distance parameter to obtain a dense body digital model (303). The dense body digital model (303) is duplicated to obtain a third copy (304) of the functional body (5003). The third copy (304) designs the three-dimensional boundary of the functional body (5003) region according to the microstructure and microgeometry to obtain a functional body (5003) composed of a microstructure digital model (305) and a microgeometry digital model (306). The first copy (301), the dense body digital model (303), the microstructure digital model (305) and the microgeometry digital model (306) are sliced ​​independently to generate respective slice groups. Each slice is filled and assigned a value to a cross-sectional vector according to its matching laser parameters to generate vector blocks of each layer. Each layer of prepolymer slices searches for slices of the same height in the dense body, microtissue and microgeometry slice groups in the Z-axis direction, and adds vector blocks to the layer of prepolymer slices in the order of dense body-microtissue-microgeometry, thereby realizing polymorphic fusion of slice data of each layer of the three-dimensional digital model (300); The powder bed (3) drives the substrate (31) to descend to a powder spreading height, the powder supply unit (4) supplies the powder required for a single powder spreading to the powder spreading unit (5), the powder spreading unit (5) drives the scraper (51) to push the strip-shaped powder pile (41) to perform powder spreading, fills the depression on the surface of the powder bed (3) generated by the descent of the substrate (31) and generates a metal powder layer (501), the laser scanning unit (8) performs laser scanning in the order of the prepolymer (5001), the dense body (5002) and the functional body (5003), and after the metal powder layer (501) is formed by laser scanning, the powder spreading scanning is performed cyclically to continuously deposit the metal powder fusion welding layer until the slice data of the last layer is read and scanned; The first copy (301) is sliced ​​according to the powder laying height parameter to obtain n layers of prepolymer slices, the n prepolymer slices are numbered 3011, ..., 301n in sequence, n is a natural number greater than 1, and the prepolymer slice cross-section pattern vector is filled and assigned according to the laser geometry and energy parameters of the prepolymer (5001) to produce the vector blocks of each layer of the prepolymer (5001); The dense body digital model (303) is sliced ​​according to the preset layer thickness parameters of the dense body (5002) to obtain m layers of dense body slices, and the m dense body slices are numbered 3031, ..., 303m, 1 <m≤n,依致密体(5002)激光几何与能量参数,处理致密体切片横截面,生成致密体(5002)的各层向量块; The micro - tissue digital model (305) is sliced into b layers of micro - tissue slices according to the preset thickness parameter of the micro - tissue functional body. The b micro - tissue slices are sequentially numbered as 3051, ……, 305b, where 1 < b ≤ n. The micro - geometry digital model (306) is sliced into d layers of micro - geometry slices according to the preset thickness parameter of the micro - geometry functional body. The multiple micro - geometry slices are sequentially numbered as 3061, ……, 306d, where 1 < d ≤ n. According to their respective laser geometry and energy parameters, vector blocks of each layer of the micro - tissue functional body and the micro - geometry functional body are generated respectively.

2. The polymorphic progressive three-dimensional forming method according to claim 1, wherein For the construction of the prepolymer (5001), an adaptive mesh - generation algorithm is used to divide the cross - section of each layer of the prepolymer slice into multiple sub - regions, and the vector filling component of each sub - region is calculated zone by zone. The vector filling value components of all sub - regions are accumulated to generate vector blocks of each layer of the prepolymer (5001) representing the laser energy distribution. The laser geometric and energy parameters of the prepolymer (5001) include the laser scanning line spacing and the effective action radius of the laser spot , which are used to measure the tightness of the interaction between the sub-region and the laser geometry. The closer the sub-region is to the laser scanning path and the more it is within the effective action range of the spot, the tighter the interaction between the sub-region and the laser geometry, and vice versa; The calculation method of the vector filling value component of each sub - region is as follows: ； Among them, is the area of the th sub-region, which can be accurately obtained by combining boundary contour tracing with geometric calculations. is the area of the cross-section of a certain layer of prepolymer slice. is the vertical distance from the center of the sub-region to the nearest laser scanning line. is the distance from the center of the sub-region to the projection point of the center of the laser spot on the cross-section plane. represents the actual effective energy action situation after comprehensively considering the initial energy density of the laser and the energy absorption coefficient of the sub-region, where < ≤ , represents the comprehensive influence coefficient of the energy of the th sub-region.

3. A polymorphic progressive three-dimensional forming method according to claim 1, characterized in that Multiple prepolymer slices, dense body slices, micro - tissue slices and micro - geometry slices respectively establish Z - axis height index tables to record the Z values of each slice. Taking the index table of the prepolymer slice as the reference and the Z value of slice 3011 as the starting point, the index tables of the dense body slices, micro - tissue slices and micro - geometry slices are traversed to find the matching prepolymer slices, dense body slices, micro - tissue slices and micro - geometry slices with the same Z value, and the vector block data is fused in the order of prepolymer slices, dense body slices, micro - tissue slices and micro - geometry slices to achieve the precise fusion of polymorphic data.

4. A polymorphic progressive three-dimensional forming method according to claim 1, characterized in that The substrate (31), powder supply unit (4), powder spreading unit (5), powder bed (3), laser scanning unit (8) and atmosphere unit (7) are all electrically connected to a controller (100). Before forming, the powder supply unit (4) injects a sufficient amount of metal powder and closes the forming chamber (2). The controller (100) issues an operation instruction to the atmosphere unit (7) to control the atmosphere unit (7) to adjust the working gas in the forming chamber (2) to an inert state and maintain cyclic purification. The controller (100) loads the complete slice data of the 1st to the nth layers of the three - dimensional digital model (300).

5. A polymorphic progressive three-dimensional forming method according to claim 4, characterized in that When printing the nth layer of the three - dimensional digital model (300) by multi - state progressive forming, the controller (100) first issues a lowering instruction to the powder bed (3) and a powder supply instruction to the powder supply unit (4), driving the substrate (31) to lower by the powder spreading height and driving the powder supply unit (4) to output the metal powder with a single - time powder spreading amount to the powder spreading unit (5). The controller (100) issues a powder spreading instruction to the powder spreading unit (5) to control the powder spreading unit (5) to push the metal powder to fill the depression of the powder bed (3) caused by the lowering of the substrate (31), and push the excess powder into the powder recycling unit (6). The controller (100) reads the vector block data of the prepolymer (5001) of the nth layer, generates a scanning instruction sequence and sends it to the laser scanning unit (8) to control the laser scanning unit (8) to perform laser prepolymer scanning, so that the small particles in the metal powder spreading layer in the scanned area are melted and adhered to the remaining particles to form the prepolymer (5001) of this layer. If there is a vector block of the densified body (5002) in the prepolymer (5001) of this layer, the controller (100) reads and generates a sequence of scanning instructions and sends them to the laser scanning unit (8), controlling the laser scanning unit (8) to perform laser densification scanning, so that the scanned prepolymer is completely melted and cooled and solidified to form a densified metal deposit; If there is a vector block of the functional body (5003) in the densified body (5002), the controller (100) reads and generates a sequence of scanning instructions and sends them to the laser scanning unit (8), controlling the laser scanning unit (8) to perform laser functional scanning; After all the vector blocks of the three-dimensional digital model (300) of the nth layer are scanned, the controller (100) controls the powder spreading unit (5) to return to the zero position, and the forming is completed.

6. A polymorphic progressive three-dimensional forming method according to any one of claims 1-4, characterized in that, The area of the prepolymer (5001) may include the area of the densified body (5002), the area of the densified body (5002) may include the area of the functional body (5003), the laser scanning unit (8) includes three scanning methods: laser prepolymer scanning, laser densification scanning and laser functional scanning. The laser prepolymer scanning is that the laser energy input matches the melting requirement of the small particles in the metal powder spreading layer. The forming area of the prepolymer (5001) is the directly irradiated area by scanning. The laser densification scanning is that the laser energy input matches the sufficient melting requirement of the porous metal sintered body. The forming area of the densified body (5002) includes the directly irradiated area by scanning and the heat conduction area. The laser functional scanning includes laser microstructure functional body scanning and laser microgeometry functional body scanning.

7. A polymorphic progressive three-dimensional forming method according to claim 6, characterized in that The laser microgeometry functional body scanning is that the laser energy input matches the melting requirement of the microsection densified body (5002), realizing the melting and cooling of the microsection deep densified body (5002) in a short time, forming fine grains and glassy tissues, and further increasing the energy input to remove trace metals by evaporation to generate a microgeometry functional body.

8. A polymorphic progressive three-dimensional forming method according to claim 6, characterized in that, The laser microstructure functional body scanning is that the laser energy input matches the melting requirement of the large-section densified body (5002), generating a large-section shallow molten pool on the surface of the densified metal, and then self-leveling, cooling and solidifying to generate a smooth surface with low roughness functionality.

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