Multi-state progressive three-dimensional forming method

Abstract

The invention provides a multi-state progressive three-dimensional forming method. The method comprises the following steps: firstly, loading a three-dimensional mathematical model for preprocessing, then respectively constructing a prepolymer, producing a compact body and preparing a functional body, and aligning and fusing slice data of each part according to a Z axis; then, a controller cooperates with a base plate unit, a powder supply unit, a powder laying unit and the like, a laser scanning unit is used for scanning according to different modes, powder laying and scanning forming are conducted on the powder bed layer by layer, and operation is cycled till completion; the method has remarkable advantages, a prepolymer-compact body-functional body three-state incremental forming strategy is adopted, differential laser parameters act on a metal powder layer in stages, metal phase change is controllable through energy gradient loading, and plasma generation is reduced. Waste caused by traditional high-energy scanning is avoided, the forming efficiency and the powder utilization rate are improved, integrated forming of a complex structure can be achieved, thermal stress concentration is reduced, the performance of a formed part is improved, a molten pool is stable, a high-quality structure can be generated easily, and popularization is convenient.

Description

Technical Field

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

[0002] Laser metal powder bed 3D forming is an important additive manufacturing method. It is based on laying metal powder on the surface of the powder bed, and using a high-power laser beam to scan and irradiate the selected area of ​​the metal powder layer, so that the free metal powder particles are melted and deposited on the substrate, and then descend through the substrate layer by layer. The cyclic execution of the powder laying and scanning irradiation steps makes the molten deposit grow layer by layer on the substrate until it is fully formed. The existing micron-level control accuracy of the laser beam by the micron-level micro-electromechanical optical actuator, as well as its low inertia and high response speed advantages, make the laser metal powder bed 3D forming equipment show significant advantages in the field of precision and complex metal products, especially in the processing of high-performance metal parts with complex internal designs and three-dimensional surface microstructures.

[0003] The powder particle size that takes into account fluidity, bulk density, and resolution of the powder layer thickness is the core parameter for the three-dimensional forming accuracy of the laser metal powder bed. At present, the powder particle size range for the laser metal powder bed is defined as 15-53um, and the bulk density is about 50% of the entity. At the same time, in order to ensure the geometric resolution of laser beam scanning irradiation and selective fusion welding, it is necessary to mainly use direct heating to carry out the fusion welding deposition of the metal powder layer, and suppress the parasitic fusion welding deposition effect caused by heat conduction; improving 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 layer from the free particle state to the dense state by high-speed, continuous, in-situ fusion welding deposition. It can be further known that the implementation of high-energy density and high-speed laser scanning irradiation on the fine metal powder layer is the fundamental strategy of the existing laser metal powder bed three-dimensional forming equipment.

[0004] On the other hand, the fine metal powder fusion welding process under laser irradiation conditions is significantly different from the dense metal fusion welding process: the former has much stronger intensity of molten pool splashing, smoke, and plasma flame than the latter. The dynamic effect of strong molten pool splashing will greatly change the flat morphology of the powder layer around the molten pool, resulting in obvious powder thickness deviation and particle size segregation problems; further, the smoke and plasma flame will significantly attenuate the laser beam energy reaching the powder layer. In particular, splashing, smoke, and plasma flames have the characteristics of multivariate, strong nonlinearity, and difficulty in accurate measurement, which seriously undermine the stability of metal powder layer fusion welding, introduce non-negligible process interference to the laser metal powder bed three-dimensional forming, and seriously deteriorate the actual three-dimensional forming performance.

[0005] Directly examining the standard particle size distribution range of 15-53um, it can be seen that the volume ratio of large powder particles to small powder particles is as high as more than 44 times. The laser beam heats these metal particles with huge volume differences at the same time in a very 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-explosion points" within the laser beam irradiation range, and are the main source of molten pool splashing, smoke, and plasma flames. There are public reports at home and abroad that the energy density of the laser beam center is weakened by spot shaping, but it is mainly aimed at overheating in the center of the molten pool, and has not specifically expanded new control freedom to compensate for the thermodynamic differences caused by the powder particle size distribution. At present, in the field of metal powder bed forming technology, the existing technology is still insufficient in the three-dimensional forming of laser metal powder beds. There is a lack of a method that can effectively control the molten pool splashing, smoke, and plasma flames, and inhibit their adverse effects on the forming process. There are also 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 polymorphic progressive three-dimensional forming method and method thereof. The method scheme is simple and feasible. By increasing the forming transition state and irradiating the powder bed surface multiple times with different scanning strategies, the violent splashing of the molten pool, smoke and plasma flames caused by one-time high-energy irradiation of the metal powder layer are avoided in a progressive manner. At the same time, these situations can also be prevented from further causing the degradation of forming accuracy and fineness, thereby effectively solving the problems of large scanning thermal stress, poor forming accuracy and low success rate in the prior art.

[0007] The technical solution of the present invention is as follows: a polymorphic progressive three-dimensional forming method, comprising loading a three-dimensional digital model into a computer 3D operating environment, duplicating the three-dimensional digital model twice to obtain a first copy of a prepolymer and a second copy of a dense body, peeling off the shell of the second copy according to a heat conduction avoidance distance parameter to obtain a dense body digital model, duplicating the dense body digital model to obtain a third copy of a functional body, designing a three-dimensional boundary of a functional body region according to microstructure and microgeometry on the third copy to obtain a functional body composed of a microstructure digital model and a microgeometry digital model, independently slicing the first copy, the dense body digital model, the microstructure digital model and the microgeometry digital model to generate respective slice groups, and filling and assigning values ​​to the cross-sectional vector of each slice 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 to achieve polymorphic fusion of slice data of each layer of the three-dimensional digital model; The powder bed drives the substrate to descend to the powder spreading height, and the powder supply unit supplies the powder required for a single powder spreading to the powder spreading unit. The powder spreading unit drives the scraper to push the strip powder pile to perform powder spreading, 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 performs laser scanning in the order of prepolymer, dense body and functional body. After the laser scanning and forming of the metal powder layer is completed, the powder spreading scanning is performed in a loop to continuously deposit the metal powder fusion welding layer until the slice data of the last layer is read and scanned.

[0008] The implementation steps of the scheme are as follows: S1. Model loading and preprocessing Load the 3D digital model into the computer 3D working environment to perform model integrity verification and feature size standardization; S2. Prepolymer Construction The three-dimensional digital model is copied to obtain a first copy, and the first copy is sliced ​​according to the powder laying height parameter to obtain n layers of prepolymer slices. According to the laser geometry and energy parameters of the prepolymer, the cross-sectional pattern vector of the prepolymer slice is filled and assigned to produce the vector blocks of each layer of the prepolymer; S3. Dense body production Copy the three-dimensional digital model to obtain a second copy, and peel off the cladding of the second copy according to the heat conduction avoidance distance parameter to obtain a dense body digital model, slice the dense body digital model according to the preset layer thickness parameter of the dense body to obtain m layers of dense body slices, and process the cross section of the dense body slice according to the laser geometry and energy parameters of the dense body to generate vector blocks of each layer of the dense body; S4. Functional preparation The dense body digital model is copied to obtain a third copy, and the three-dimensional boundary of the functional body region is set according to the micro-tissue and micro-geometry design requirements of the three-dimensional forming to obtain the micro-tissue digital model and the micro-geometry digital model. The micro-tissue digital model is sliced ​​according to the preset thickness parameter of the micro-tissue functional body to obtain the b-layer micro-tissue slice, and the micro-geometry digital model is sliced ​​according to the preset thickness parameter of the micro-geometry functional body to obtain the d-layer micro-geometry slice. According to the respective laser geometry and energy parameters, the vector blocks of each layer of the micro-tissue functional body and the micro-geometry functional body are respectively generated; S5. Data Fusion 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; S6, Polymorphic Incremental Forming 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; S7, Cycle Forming 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.

[0009] 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; 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; The vector filling value component of each sub-region is calculated as follows: ; in, For the The area of ​​each sub-region can be accurately obtained by combining boundary contour tracking with geometric calculation. is the cross-sectional area of ​​a 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 laser spot center on the cross-sectional plane, It represents the actual effective energy effect after comprehensively considering the initial laser energy density and the sub-region energy absorption coefficient, where < ≤ , Indicates The comprehensive energy impact coefficient of each sub-region.

[0010] Preferably, the n prepolymer slices are sequentially numbered as 3011, ……, 301n, where n is a natural number greater than or equal to 1, the m compact body slices are sequentially numbered as 3031, ……, 303m, 1 < m ≤ n, the b microtissue slices are sequentially numbered as 3051, ……, 305b, 1 < b ≤ n, and the d microgeometry slices are sequentially numbered as 3061, ……, 306d, 1 < d ≤ n; Separate Z-axis height index tables are established for the multiple prepolymer slices, compact body slices, microtissue slices, and microgeometry slices respectively, 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.

[0011] Preferably, the index table of the prepolymer slices starts from the Z value of the 3011 slice. Each prepolymer slice matches zero or one or more of the compact body slices, microtissue slices, and microgeometry functional bodies. The prepolymer region contains the compact body region, and the compact body region contains the functional body region.

[0012] Preferably, in the polymorphic 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 first to the nth layers of the complete three-dimensional digital model.

[0013] Preferably, during the polymorphic incremental forming printing of the nth layer of the three-dimensional 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 for 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 of 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 prepolymerization scanning, so that the small particles in the metal powder spreading layer in the scanned area are melted and bonded to the remaining particles to form the prepolymer of this layer; If there is a dense body vector block in the prepolymer of the layer, the controller reads and generates a scanning instruction sequence and sends it to the laser scanning unit, and controls the laser scanning unit to perform laser dense scanning, so that the scanned prepolymer is completely melted, cooled and solidified to form a dense metal deposit; If there is a functional body vector block in the dense body, the controller reads and generates a scanning instruction sequence and sends it to the laser scanning unit, and controls the laser scanning unit to perform laser functional scanning; After all the vector blocks of the nth layer of three-dimensional digital model are scanned, the controller controls the powder spreading unit to return to the zero position and the forming is completed.

[0014] Preferably, the laser scanning unit includes three modes: laser pre-focusing scanning, laser density scanning and laser functional scanning. The laser pre-focusing scanning is a laser energy input that matches the small particle melting requirement of the metal powder layer. The laser energy input value and the scanning single point dwell time do not meet the large particle metal powder melting requirement. The prepolymer is produced by scanning in a high line speed, small spacing and low energy input mode. The forming area of ​​the prepolymer is the scanning direct irradiation area. The laser dense scanning is to match the laser energy input with the requirement of sufficient melting of the porous metal sintered body, and the scanning is performed in a manner of low linear speed, large spacing, and high energy input. The laser scanning single point dwell time is long, and the forming area of ​​the dense body includes the scanning direct irradiation area and the heat conduction area; The laser functional scanning includes laser micro-tissue functional body scanning and laser micro-geometry functional body scanning.

[0015] Preferably, the laser scanning of micro-geometric functional bodies matches the laser energy input with the melting requirements of micro-section dense bodies, and adopts high linear speed, small pitch, small spot, and high energy input. The direct irradiation range of a single scanning point is small, the dwell time is short, the lateral heat conduction range is small, and the vertical heat conduction depth is large, so that dense bodies with deep micro-sections can be melted and cooled in a short time to form fine grains and glassy structures, further increasing the energy input, removing trace metals by evaporation, and generating micro-geometric functional bodies.

[0016] Preferably, the laser microstructure functional body scanning is to match the laser energy input with the melting requirements of large-section dense bodies, using low speed, large spacing, large defocused spot, and high energy input. The scanning single-point irradiation range is large and the dwell time is long. The depth of the molten pool is suppressed by the large-section thermal diffusion, and a large-section shallow molten pool is generated on the dense metal surface, which is then self-leveled, cooled and solidified to generate a smooth surface with low roughness functionality.

[0017] An apparatus using a polymorphic progressive three-dimensional forming method comprises a frame, a forming chamber is arranged on the frame, a powder bed is arranged in the frame, and an upper end of the powder bed is engaged and connected with a bottom plate of the forming chamber; The powder bed is provided with a substrate, and the powder bed can drive the substrate to move up and down and position. When the substrate is at zero position, it is flush with the upper edge of the powder bed and the bottom plate of the forming chamber; The forming chamber is provided with a powder supply unit and a powder spreading unit, and the frame is provided with a powder return unit, the opening of the powder return 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, and the powder spreading unit can horizontally move back and forth on the bottom plate of the forming chamber to spread powder on the top of the powder bed and push excess powder into the opening of the powder return unit; An atmosphere unit is provided in the frame, and an air inlet and an exhaust port of the atmosphere unit are connected to two side plates of the forming chamber. The atmosphere unit inhales gas in the forming chamber through the air inlet, and sends the gas back to the forming chamber through the exhaust port after filtering and purification; A laser scanning unit is provided on the top of the forming chamber. The scanning range of the laser scanning unit covers the top of the powder bed. The laser scanning unit can scan and irradiate a selected area on the surface of the powder bed according to the set laser power, linear speed and spot diameter parameters. Beneficial Effects

[0018] The polymorphic progressive three-dimensional forming method of the present invention is a process of laser scanning to process free powder particles of the powdered metal layer and generate the required three-dimensional metal structure, which goes through three forming transition states of metal prepolymerization state, metal densification state and metal functional state. Through the three-state progressive forming strategy of prepolymer-densified body-functional body, differentiated laser parameters are used to act on the metal powder layer in stages. In the prepolymerization stage, high-line speed and low-energy scanning are adopted to melt only small particles on the surface to form a porous skeleton, which significantly reduces the disturbance of the molten pool and the generation of splashing. In the densification stage, the energy input is increased on the basis of the prepolymer, and the molten pool range is constrained by heat conduction avoidance design to avoid energy leakage causing free powder splashing. In the functional stage, customized parameters are used to achieve micro-area refinement and accurately control the molten pool morphology. This energy gradient loading mode makes the metal phase change process more controllable, greatly reduces the amount of plasma generated, and significantly improves the forming stability.

[0019] The present invention avoids the energy waste caused by traditional high-energy one-time scanning through staged forming of prepolymer, dense body and functional body, and significantly improves the forming efficiency and powder utilization rate: low-energy scanning of prepolymer reduces powder splashing and smoke generation, and fine scanning of functional body directly realizes the requirements of surface finish and geometric accuracy, reducing subsequent machining and polishing processes.

[0020] The present invention can realize integrated forming of complex internal structure and high-precision external features through layered data fusion of prepolymer, dense body and functional body. The prepolymer provides a stable support structure as a transition state. The problem of thermal stress concentration caused by high energy concentrated input in traditional processes is avoided by staged energy loading of prepolymer, dense body and functional body. The rapid melting-cooling strategy of the functional body forms fine grains or glassy structure, further improving the mechanical properties and corrosion resistance of the formed parts.

[0021] According to the particle size distribution characteristics of metal powder and the difference in hot melting behavior under laser scanning energy input, the present invention adopts multiple differentiated energy and geometric strategies to implement laser selective scanning and gradually complete the three-dimensional forming of metal powder bed. It has the advantages of less smoke splashing and slight plasma sparks. Its stable molten pool state is conducive to the generation of high-resolution, high-strength metal organizational structure and complex and fine geometric structure, and it is easy to promote and apply in laser metal powder bed three-dimensional forming equipment of various sizes. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments.

[0023] Figure 1 It is a schematic diagram of three-dimensional area planning and slicing of the present invention; Figure 2 It is a schematic diagram of the layer-by-layer multi-state incremental forming of the present invention; Figure 3 This is a control signal connection diagram of the present invention; Figure 4 It is a structural schematic diagram of the device of the present invention; Reference numerals: 1. Frame; 2. Forming chamber; 3. Powder bed; 31. Base plate; 4. Powder supply unit; 41. Strip powder pile; 5. Powder spreading unit; 51. Scraper; 6. Powder return unit; 7. Atmosphere unit; 71. Air inlet; 72. Exhaust port; 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-tissue digital model; 306. Micro-geometry digital model; 500. Three-dimensional metal formed body; 501. Metal powder layer; 5001. Prepolymer; 5002. Dense body; 5003. Functional body; 3011-301n. Prepolymer slice; 3031-303m. Dense body slice; 3051-305b. Micro-tissue slice; 3061-306d. Micro-geometry slice. DETAILED DESCRIPTION

[0024] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0025] A polymorphic progressive three-dimensional forming method comprises the following steps: S1, model loading and preprocessing, loading the three-dimensional digital model 300 into the computer 3D operating environment, performing model integrity verification and feature size standardization processing; S2, prepolymer construction, copy the three-dimensional digital model 300 to obtain the first copy 301, slice the first copy 301 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, wherein 3011 is the first layer and 301n is the last layer, and vector filling is performed on the cross-sectional pattern of 3011-301n according to the vector direction, width, spacing and spot compensation of the laser geometric parameters of the prepolymer 5001, and the shape, position and accuracy of the filling are determined, and according to the energy deposition and curing effect of the prepolymer laser energy parameters power, spot and linear speed, the vector blocks of each layer of the prepolymer 5001 are produced; Adaptive meshing algorithm is used to divide the cross section of each layer of prepolymer slice into multiple sub-regions, and the vector filling components of the sub-regions are calculated region by region, and the vector filling components of all sub-regions are accumulated to generate vector blocks of each layer of prepolymer 5001 representing the laser energy distribution, laser geometry of prepolymer 5001 and laser scanning line spacing in energy parameters And the effective radius of the laser spot , which is used to measure the closeness of the sub-region and the laser geometry. The closer the sub-region is to the laser scanning path and the closer it is within the effective action range of the spot, the closer the sub-region and the laser geometry are, and vice versa. The specific steps are as follows: a. Determine the length of the minimum circumscribed rectangle of the prepolymer slice cross section on the X-axis and Y-axis, and use the adaptive meshing algorithm to divide the prepolymer slice cross section into Sub-regions, determine the average scale of each sub-region on the X-axis and Y-axis, and calculate the comprehensive energy impact coefficient of each sub-region ; b. The initial energy density of the laser to obtain the prepolymer is , the energy absorption coefficient of each sub-region based on its laser action characteristics is ,in < ≤ ; Determine the vector filling component of each sub-region, and then determine the vector filling value of the cross-sectional pattern of the prepolymer slice. The calculation method of the vector filling value component of each said 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 and geometric calculation. is the area of the cross-section of a certain layer of prepolymer slice. 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-sectional 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. Laser scanning line spacing and the effective action radius of the laser spot are used to measure the tightness of the geometric action of the laser on this sub-region. The closer the sub-region is to the laser scanning path and the more within the effective action range of the spot, the larger this value is.

[0026] C. Sum the of each sub-region to obtain the vector block filling data of this layer of prepolymer slice; S3. Dense body production Copy the 3D digital model 300 to obtain the second copy 302, and 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. 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 of vector blocks of the dense body 5002; S4. Functional body preparation Copy the dense body digital model 303 to obtain the third copy 304. According to the requirements of the microstructure and microgeometry design 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. 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. 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 of vector blocks of the microstructure functional body and the microgeometry functional body respectively; S5. Data fusion 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; S6, Polymorphic Incremental Forming 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; 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: 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; 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; If the dense body 5002 has a vector block of the functional body 5003, 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 functional scanning; After all the vector blocks of the n-th layer 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.

[0027] It should be noted that the three-dimensional digital model of the part to be formed is first planned in a computer 3D operating environment to determine the pre-polymerized, dense and functional areas, and the spatial relationship between them is that the pre-polymerized area can contain the dense area, and the dense area can contain the functional area; S7, Cycle Forming S6 is executed in a loop, and the prepolymer 5001, the dense body 5002, and the functional body 5003 composed of the microstructure functional body and the microgeometric functional body continue to deposit new metal powder welding layers until the polymorphic body slice data of the nth layer is read and sequentially scanned, the prepolymer 5001, the dense body 5002, and the functional body 5003 grow to a complete form, and the polymorphic progressive laser metal powder bed 3D forming process is completed.

[0028] Furthermore, Z-axis height index tables are independently established for multiple pre-polymer slices, dense body slices, micro-tissue slices and micro-geometry slices to record the Z value of each slice. Based on the index table of the pre-polymer slice, the index tables of the dense body slice, micro-tissue slice and micro-geometry slice are traversed to find matches of pre-polymer slices, dense body slices, micro-tissue slices and micro-geometry slices with the same Z value, and the vector block data are fused in the order of the pre-polymer slice, dense body slice, micro-tissue slice and micro-geometry slice to achieve accurate fusion of polymorphic data.

[0029] Furthermore, the index table of the prepolymer slice takes the Z value of slice No. 3011 as the starting point, and each prepolymer slice matches zero or one or more of dense body slices, microtissue slices and microgeometric functional bodies. The prepolymer 5001 region contains the dense body 5002 region, and the dense body 5002 region contains the functional body 5003 region.

[0030] Furthermore, in the polymorphic incremental forming step S6, the substrate 31, the powder supply unit 4, the powder spreading unit 5, the powder bed 3, the laser scanning unit 8 and the atmosphere unit 7 are all electrically connected to the 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 sends an operation command 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 circulating purification. The controller 100 sends a return to zero command 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 1st to nth layer slicing data of the three-dimensional digital model 300.

[0031] Furthermore, the laser scanning unit 8 includes three modes: laser pre-focusing scanning, laser density scanning and laser functional scanning. The laser pre-focusing scanning is a laser energy input that matches the small particle melting requirement of the metal powder layer. The laser energy input value and the scanning single point residence time do not meet the melting requirement of large particle metal powder. The prepolymer 5001 is produced by scanning at a high linear speed, a small pitch and a low energy input. The forming area of ​​the prepolymer 5001 is the direct irradiation area of ​​the scanning. The smoke, splash and plasma flame generated by sintering are slight, and the force disturbance to the powder bed in the adjacent area is slight. It can be sintered by scanning without support.

[0032] Laser dense scanning matches the laser energy input with the requirement of fully melting the porous metal sintered body. Its heat conduction ability and specific heat capacity per unit volume far exceed those of free metal powder. Scanning is performed in a manner of low linear speed, large spacing, and high energy input. The heat conduction effect is significant, and the laser scanning single point residence time is long. The forming area of ​​the dense body 5002 includes the scanning direct irradiation area and the heat conduction area. Since there are no small particles of free metal powder in the dense scanning area, the smoke, splash, and plasma flame generated by the molten pool are slight. Through the heat conduction avoidance distance, the heat of the molten pool of laser dense scanning can be prevented from leaking to the free powder area outside the prepolymer 5001; Laser functional scanning includes laser microstructure functional body scanning and laser microgeometry functional body scanning. Laser microgeometry functional body scanning matches the laser energy input to the melting demand of micro-section dense body 5002. It adopts high linear speed, small pitch, small spot, and high energy input. The direct irradiation range of a single scanning point is small, the dwell time is short, the lateral heat conduction range is small, and the vertical heat conduction depth is large. The dense body 5002 with a deep micro-section is melted and cooled in a short time to form fine grains and glassy structure, and further increase the energy input to remove trace metal by evaporation to generate a microgeometry functional body. Laser microstructure functional body scanning matches the laser energy input to the melting demand of large-section dense body 5002. It adopts low speed, large pitch, large defocus spot, and high energy input. The single scanning point irradiation range is large, the dwell time is long, and the depth of the molten pool is suppressed by the large-section heat diffusion. A large-section shallow molten pool is generated on the surface of the dense metal, which then self-levels, cools and solidifies to generate a smooth surface with low roughness functionality.

[0033] The equipment using the polymorphic progressive three-dimensional forming method comprises a frame 1, a forming chamber 2 is arranged on the frame 1, a powder bed 3 is arranged in the frame 1, the upper opening of the powder bed 3 is engaged with the bottom plate of the forming chamber 2, a base plate 31 is arranged in the powder bed 3, the powder bed 3 can drive the base plate 31 to move up and down and position, when the base plate 31 is at zero position, it is flush with the upper edge 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 arranged in the forming chamber 2, a powder return unit 6 is arranged in the frame 1, the opening of the powder return unit 6 is connected with the bottom plate of the forming chamber 2, the powder supply unit 4 can quantitatively output metal powder to the powder spreading unit 5, and the powder spreading unit 5 can be in the forming chamber 2. The frame 1 is provided with an atmosphere unit 7, and the air inlet 71 and the exhaust port 72 of the atmosphere unit 7 are connected with 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 sends it back to the forming chamber 2 through the exhaust port 72 after filtering and purification. A laser scanning unit 8 is provided on the top of the forming chamber 2. The scanning range of the laser scanning unit 8 covers the upper mouth of the powder bed 3, and the laser scanning unit 8 can scan and irradiate the selected area on the surface of the powder bed 3 according to the set laser power, linear velocity and spot diameter parameters.

[0034] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in 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.

2. A polymorphic progressive three-dimensional forming method according to claim 1, characterized in that: The prepolymer (5001) is constructed by using an adaptive meshing algorithm to divide each layer of the prepolymer slice cross section into a plurality of sub-regions, and calculates the sub-region vector filling components region by region, and accumulates the vector filling value components of all sub-regions to generate vector blocks of each layer of the prepolymer (5001) that characterize the laser energy distribution; The laser geometry and energy parameters of the prepolymer (5001) include the laser scanning line spacing And the effective radius of the laser spot , used to measure the closeness of the sub-region to 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 is to the laser geometric effect, and vice versa; The vector filling value component of each sub-region is calculated as follows: ； in, For the The area of ​​each sub-region can be accurately obtained by combining boundary contour tracking with geometric calculation. is the cross-sectional area of ​​a 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 laser spot center on the cross-sectional plane, It represents the actual effective energy effect after comprehensively considering the initial laser energy density and the sub-region energy absorption coefficient, where < ≤ , Indicates The comprehensive energy impact coefficient of each sub-region.

3. A polymorphic progressive three-dimensional forming method according to claim 1, characterized in that: 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 digital model (303) of the compact body is sliced into m slices of the compact body according to the preset layer thickness parameter of the compact body (5002), and the m slices of the compact body are sequentially numbered as 3031, ……, 303m, where 1 < m ≤ n. According to the laser geometry and energy parameters of the compact body (5002), the cross-section of the compact body slice is processed to generate vector blocks of each layer of the compact body (5002). The digital model (305) of the micro-tissue is sliced into b slices of the micro-tissue according to the preset thickness parameter of the micro-tissue functional body. The b slices of the micro-tissue are sequentially numbered as 3051, ……, 305b, where 1 < b ≤ n. The digital model (306) of the micro-geometry is sliced into d slices of the micro-geometry according to the preset thickness parameter of the micro-geometry functional body. The multiple slices of the micro-geometry 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.

4. A polymorphic progressive three-dimensional forming method according to claim 3, characterized in that: Multiple index tables of the Z-axis height are independently established for the pre-polymer slices, the compact body slices, the micro-tissue slices, and the micro-geometry slices to record the Z values of each slice. Taking the index table of the pre-polymer slices as the reference and starting from the Z value of the 3011th slice, traverse the index tables of the compact body slices, the micro-tissue slices, and the micro-geometry slices to find the pre-polymer slices, the compact body slices, the micro-tissue slices, and the micro-geometry slices with the same Z value for matching, and fuse the vector block data in the order of the pre-polymer slices, the compact body slices, the micro-tissue slices, and the micro-geometry slices to achieve precise fusion of polymorphic data.

5. The polymorphic progressive three-dimensional forming method according to claim 3, characterized in that: The substrate (31), the powder supply unit (4), the powder spreading unit (5), the powder bed (3), the laser scanning unit (8), and the 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).

6. A polymorphic progressive three-dimensional forming method according to claim 5, 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 descending instruction to the powder bed (3) and a powder supply instruction to the powder supply unit (4), driving the substrate (31) to descend by the powder spreading height and driving the powder supply unit (4) to output the metal powder with a single 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) generated by the descent 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 pre-polymer (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 pre-polymerization 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 pre-polymer (5001) of this layer. If the prepolymer (5001) of the layer has a dense body (5002) vector block, 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; If the dense 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), and controls the laser scanning unit (8) to perform laser functional scanning; After all 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.

7. A polymorphic progressive three-dimensional forming method according to any one of claims 1 to 5, characterized in that: The prepolymer (5001) region may include a dense body (5002) region, and the dense body (5002) region may include a functional body (5003) region. The laser scanning unit (8) includes three modes: laser prepolymer scanning, laser dense scanning, and laser functional scanning. The laser prepolymer scanning is a laser energy input that matches the small particle melting requirement of the metal powder layer. The forming area of ​​the prepolymer (5001) is a scanning direct irradiation area. The laser dense scanning is a laser energy input that matches the sufficient melting requirement of the porous metal sintered body. The forming area of ​​the dense body (5002) includes a scanning direct irradiation area and a heat conduction area. The laser functional scanning includes laser microstructure functional body scanning and laser microgeometry functional body scanning.

8. A polymorphic progressive three-dimensional forming method according to claim 7, characterized in that: The laser scanning of the micro-geometric functional body matches the laser energy input with the melting requirements of the micro-section dense body (5002), so as to achieve the melting and cooling of the micro-section deep dense body (5002) in a short time, form fine grains and glassy structure, further increase the energy input, remove trace metal by evaporation, and generate a micro-geometric functional body.

9. A polymorphic progressive three-dimensional forming method according to claim 7, characterized in that: The laser microstructure functional body scanning matches the laser energy input with the melting requirements of the large-section dense body (5002), generates a large-section shallow molten pool on the dense metal surface, and then self-levels, cools and solidifies to generate a smooth surface with low roughness functionality.

10. A device using the polymorphic progressive three-dimensional forming method according to claim 1, characterized in that: The invention comprises a frame (1), wherein a forming chamber (2) is provided on the frame (1), a powder bed (3) is provided in the frame (1), and the upper opening of the powder bed (3) is engaged with the bottom plate of the forming chamber (2); a base plate (31) is provided in the powder bed (3), and the powder bed (3) can drive the base plate (31) to move up and down and position, and when the base plate (31) is in zero position, it is flush with the upper edge of the powder bed (3) and the bottom plate of the forming chamber (2); The forming chamber (2) is provided with a powder supply unit (4) and a powder spreading unit (5), and the frame (1) is provided with a powder return unit (6). The opening of the powder return 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 back and forth horizontally on the bottom plate of the forming chamber (2) to spread powder on the upper opening of the powder bed (3) and push excess powder into the opening of the powder return unit (6); An atmosphere unit (7) is provided in the frame (1); an air inlet (71) and an air outlet (72) of the atmosphere unit (7) are connected to two side plates of the forming chamber (2); the atmosphere unit (7) inhales gas in the forming chamber (2) through the air inlet (71), and returns the gas to the forming chamber (2) through the air outlet (72) after filtering and purification; A laser scanning unit (8) is provided on 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 a selected area on the surface of the powder bed (3) according to set laser power, linear speed, and spot diameter parameters.

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