Partitioned additive manufacturing method for large complex-structure workpiece

Abstract

The invention discloses a partitioned additive manufacturing method for a large complex-structure workpiece, and belongs to the technical field of electric arc additive manufacturing. The method mainly comprises the steps that a three-dimensional model is optimized and decomposed based on additive manufacturing characteristics and a workpiece structure; taking the height of a single weld as the height of a slice to obtain a slice contour polygon; partitioning parameters are set, the slices are partitioned according to the size and the structure of the blank piece, and the distance between partitions is obtained through parameterized numerical simulation and data fitting; path filling modes of different partitions are determined, and partition additive paths are obtained; and in the material increasing process, monitoring and material increasing and decreasing are conducted on the partition connecting positions, and a blank piece is obtained. According to the method, the model is optimized, the model is reasonably partitioned, the partition connecting positions are monitored and subjected to additive and subtractive treatment in real time, the printing efficiency is guaranteed, meanwhile, the mechanical property of the partition connecting positions is improved, and the production cycle of large workpieces is shortened.

Description

Technical Field

[0001] The invention relates to a partitioned additive manufacturing method for a large-scale complex structure workpiece, and belongs to the technical field of arc additive manufacturing. Background Art

[0002] Wire Arc Additive Manufacture (WAAM) technology uses the principle of layer-by-layer cladding, adopts welding arc as heat source, and gradually forms metal parts from wire-surface-body according to the three-dimensional digital model under the control of software program by adding wire.

[0003] When producing large and complex structure workpieces, the workpiece cannot be formed by additive manufacturing in one go due to the accessibility, posture and structure of the welding robot. The workpiece can be produced by dividing the workpiece into multiple parts and assembling and welding them after the additive manufacturing is completed, but this will increase the production time of the workpiece and reduce the mechanical properties of the joints. In order to improve production efficiency and increase the mechanical properties of the partitioned joints, the present invention obtains the blank model and partition spacing through model processing, partitioning, numerical simulation and fitting, monitors the partitioned joints and adds and subtracts materials during the additive process, and proposes a partitioned additive manufacturing method for large and complex structure workpieces. Summary of the invention

[0004] In order to solve the problems existing in the prior art, the present invention provides a partitioned additive manufacturing method for a large-scale complex structure workpiece, which can solve the problems pointed out in the background technology.

[0005] In order to solve the above technical problems, the technical solution adopted by the present invention is:

[0006] A partitioned additive manufacturing method for a large complex structure workpiece comprises the following steps:

[0007] Step S1, optimizing the three-dimensional model based on the additive manufacturing characteristics and the workpiece structure to obtain a blank model;

[0008] Step S2, obtaining the weld reinforcement through a single-pass single-layer test, and slicing the blank model;

[0009] Step S3, partitioning the slices according to the size and structure of the blank model, and obtaining the spacing between the partitions through numerical simulation and data fitting;

[0010] Step S4, determining the filling path mode of different partitions to obtain the partitioned material adding path;

[0011] Step S5: During the material addition process, the partition connection is monitored and material is added or subtracted to obtain a blank.

[0012] According to one aspect of the present invention, step S1 further comprises:

[0013] Step S11, based on the characteristics of the arc additive process, the holes and windows in the original model are filled to form a regular geometric shape;

[0014] Step S12: Based on the workpiece structure, a 7mm margin is added to the inner wall area of ​​the workpiece structure area with a thickness of ≤10mm, and an 8mm margin is added to the outer wall to obtain a blank model.

[0015] According to one aspect of the present invention, step S2 further comprises:

[0016] Step S21, obtain multiple welds by single-pass single-layer welding, cut a cross section at every 10 mm interval at the weld forming stable position (the cross section is perpendicular to the welding direction), select 10 places in total, obtain the molten pool interface by grinding and corrosion, and measure the average weld width w and average excess height h of the weld, that is, the weld width w and weld excess height h;

[0017] Step S22: Slice the blank model using the weld excess height h as the single-layer slicing height, and the number of slicing layers M is:

[0018]

[0019] In the formula, Z max is the maximum value in the Z direction, Z min is the minimum value in the Z direction, and h is the weld excess height.

[0020] According to one aspect of the present invention, step S3 further comprises:

[0021] Step S31, determining the length m, width n and robot working range c of the workpiece, if m>c or n>c, partitioning the slice contour according to the workpiece size so that the partition is within the robot working range;

[0022] Step S32, after partitioning by size, if there are special structures such as ring structures, circular structures and suspended structures in the partitions, the workpiece needs to be further partitioned according to the minimum area of ​​the special structure to reduce the impact of the special structure partition on the additive;

[0023] Step S33, determining the additive manufacturing order of each partition, if there is an internal partition, first add material to the internal partition, and then add material to the external partition;

[0024] Step S34: the filling paths between adjacent partitions are parallel straight line paths;

[0025] Step S35, constructing a three-dimensional multi-physics field coupled transient model at the partition connection to simulate the connection process of the parallel straight line paths between the partitions, and obtaining the connection height under different partition spacings;

[0026] Constructing a three-dimensional multi-physics coupled transient model including basic assumptions, control equations, geometric models, loading material properties and boundaries;

[0027] The basic assumptions include the following: the welding wire and arc are ignored to simplify the model, and only the solidification of the molten droplet and the molten pool is considered; the melting and solidification process of the molten pool is simulated by the change of the dynamic viscosity of the metal at different temperatures, so this model only considers the liquid phase and the gas phase; the liquid phase and the gas phase in the model are both incompressible laminar flows;

[0028] The governing equations of the three-dimensional multiphysics coupled transient model include the Navier-Stokes equations, the heat transfer equations, and the level set equations;

[0029] Navier-Stokes equations:

[0030]

[0031] Heat transfer equation:

[0032]

[0033] Level set equation:

[0034]

[0035] Where ρ is density, υ is velocity, p is pressure, T is temperature, F is momentum source term, μ is dynamic viscosity, I is unit matrix, C P is the specific heat capacity, k is the thermal conductivity, Q is the energy source term, ∈ ls is the interface thickness parameter, γ is the interface moving speed, Φ is the level set function, when Φ is 1, it is liquid phase, when Φ is 0, it is gas phase, and when 0<Φ<1, it is gas-liquid transition interface;

[0036] The differential equation to be solved is discretized and divided, and the flow area is divided into several subdomain units, and the vertex of each subdomain unit is called a node; the multiple unit finite element equations after discretization and division are combined into a continuum, and the matrices and vectors of the equilibrium equations of each unit are correspondingly combined to form an overall finite element matrix equation; the known boundary conditions are applied to the overall finite element matrix equation to limit the range of the solution; the numerical solutions of the velocity υ and pressure p in the Navier-Stokes equations are obtained by an iterative method, the numerical solutions of the temperature T in the heat transfer equations are obtained by an iterative method, and the numerical solutions of the level set function Φ in the level set equations are obtained by an iterative method;

[0037] The momentum source term F includes the buoyancy term and surface tension;

[0038] The buoyancy acts on the liquid phase, and the buoyancy term is:

[0039] F1=ρβg(TT m )

[0040] ρ is the density function with respect to temperature, β is the thermal expansion coefficient, T m is the solidus temperature;

[0041] Surface tension acts on the gas-liquid interface and is:

[0042] F2=γ0-σ(T-T0)

[0043] γ0 is the surface tension, σ is the surface tension coefficient, and T0 is the ambient temperature;

[0044] The energy source term Q is the arc heat input on the molten pool surface; the arc heat input q(r) is Gaussian distributed:

[0045]

[0046] η is the absorption rate, U is the voltage, I is the current, r0 is the effective radius of the arc, and r is the distance from any point in the horizontal direction to the center of the arc;

[0047] The inlet of the droplet level set is:

[0048]

[0049] By conditional judgment function if(r <r1,Φ i ,0) introduce the molten drop, r1 is the molten drop radius, f is the molten drop transition frequency, t is the time, and the molten drop temperature is T l +200K, T l is the liquidus temperature;

[0050] A geometric model is established, which includes a gas phase domain and a liquid phase domain. The gas phase domain is above the liquid phase domain. The width of the gas phase domain and the liquid phase domain is 4 times the weld width w. The length of the gas phase domain and the liquid phase domain is 50 mm. The height of the gas phase domain is the arc length, and the height of the liquid phase domain is 4 times the weld residual height h. A hexahedron is used to construct a structured grid.

[0051] Load material properties. The gas phase is argon and the liquid phase is 2219 aluminum alloy. The material properties include density ρ, thermal conductivity k (i.e. thermal conductivity k), dynamic viscosity μ, and specific heat capacity C. P ;

[0052] The dynamic viscosity of the liquid phase is:

[0053]

[0054] T m is the solidus temperature, T l is the liquidus temperature, and the melting and solidification of the molten pool are simulated by the change of dynamic viscosity at different temperatures; the other material properties are functions of temperature;

[0055] When the temperature is higher than T l When molten droplets and molten pool melt;

[0056] When the temperature is lower than T m When molten droplets and molten pool solidify;

[0057] When the temperature is T l and T m Between is the transition zone between the melting area and the solidification area;

[0058] When the temperature is higher than T l When the dynamic viscosity is 0.1N*s / m 2 , continuous molten droplets enter the molten pool;

[0059] When the temperature is lower than T m When the dynamic viscosity is 10000N*s / m 2 , the molten pool begins to cool, solidify and form two welds; the height of the joint is obtained by measuring the height between the two welds;

[0060] The liquid phase boundary conditions include thermal convection boundary and thermal radiation boundary; the thermal convection boundary is:

[0061] q c =h c (T-T0)

[0062] In the formula, h c is the convection coefficient, T0 is the ambient temperature;

[0063] The thermal radiation boundary is:

[0064] q r =εσ0(T 4 -T0 4 )

[0065] Where ε is the thermal emissivity and σ0 is the Stefan-Boltzmann constant;

[0066] The boundary conditions at the liquid phase boundary are:

[0067] q l =-q c -q r

[0068] When the partition spacing is less than 0.4×w, the spacing is too small;

[0069] When the partition spacing is greater than 0.8×w, the spacing is too large;

[0070] The partition spacing is set between 0.4×w and 0.8×w, denoted as z', and increases from 0.4×w to 0.8×w with a width of 0.05×w; the partition spacings are 0.4w, 0.45w, 0.5w, 0.55w, 0.6w, 0.65w, 0.7w, 0.75W, and 0.8w respectively;

[0071] Set up a transient solver and obtain the height h' of the connection at different partition spacings through parametric scanning;

[0072] Step S36, fitting the connection height h' and partition spacing z' obtained by parametric scanning to obtain a function of partition connection height and partition spacing; substituting the weld excess height h obtained by the test into the fitting equation to obtain the actual partition spacing z.

[0073] According to one aspect of the present invention, step S4 is further:

[0074] Step S41, determining different path parameters for each partition to obtain a partitioned additive path;

[0075] Step S42: Send the simulation path in the software to the robot program, control the robot to move on the substrate surface according to the path, and ensure that the additive path can be executed.

[0076] According to one aspect of the present invention, step S5 is further:

[0077] Step S51, real-time monitoring of the forming condition, molten pool temperature, welding current and voltage of the partition connection by means of an infrared thermal imager, a three-dimensional scanner and a teaching pendant;

[0078] Step S52: During each layer of material addition, if it is observed that the height of the partition connection is greater than 1.1 times the weld excess height h, the partition spacing z is increased by 5% to reduce the height of the partition connection;

[0079] Step S53: After each layer of material addition is completed, if the height of the partition connection is greater than 1.1 times the weld excess height h, use a subtractive device to remove the portion higher than the weld excess height h;

[0080] Step S54: During each layer of material addition, if it is observed that there is unfused at the partition connection, the partition spacing z is reduced by 5% to eliminate the unfused in the partition;

[0081] Step S55: After each layer of material addition is completed, if there is unfused area at the partition connection, the unfused area is filled with additive equipment, and then the part higher than the weld excess height h is removed with subtractive equipment;

[0082] Step S56, repeat steps S51 to S55 until a blank is obtained.

[0083] Compared with the prior art, the present invention has the following beneficial effects:

[0084] The present invention optimizes the geometric model and partitions the geometric model by means of partitioned arc additive. The height of the connection under different partition spacings is quickly obtained by parametric scanning through numerical simulation, and then the function of the partition spacing and the connection height is obtained by fitting, and the actual weld residual height h is substituted into the fitting function to obtain a reasonable partition spacing. Real-time monitoring and the use of additive and subtractive processes at the partition connection enable large and complex structure workpieces to be quickly formed at one time without the need to disassemble the workpiece and then assemble and weld it, thereby improving the performance of the partition connection, reducing the production cycle, and realizing the partitioned additive manufacturing of large and complex structures.

[0085] The present invention discloses a partitioned additive manufacturing method for a large complex structure workpiece, which mainly includes: optimizing and decomposing a three-dimensional model based on the additive manufacturing characteristics and the workpiece structure; using the height of a single weld as the slice height to obtain a slice contour polygon; setting partition parameters, partitioning the slice according to the size and structure of the blank, and obtaining the spacing between the partitions through parameterized numerical simulation and data fitting; determining the filling path mode of different partitions to obtain a partitioned additive path; monitoring and adding and subtracting materials at the partition connection during the additive process to obtain a blank. By optimizing the model, the model is partitioned reasonably, and the partition connection is monitored and added and subtracted in real time, while ensuring the printing efficiency, the mechanical properties of the partition connection are increased, and the production cycle of large workpieces is reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0086] Figure 1 This is a flow chart of the partitioned additive manufacturing process of the present invention;

[0087] Figure 2 It is a schematic diagram of the original workpiece model;

[0088] Figure 3 This is a schematic diagram of the blank model;

[0089] Figure 4 Schematic diagram of the multi-physics geometry model for simulating the height of the connection;

[0090] Figure 5 A schematic diagram of the partitioning is provided;

[0091] Figure 6 Schematic diagram of the partitioned additive path. DETAILED DESCRIPTION

[0092] In order to enable those skilled in the art to better understand the scheme of the present invention, the technical scheme in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0093] like Figure 1 As shown, a partitioned additive manufacturing method for a large complex structure workpiece includes the following steps:

[0094] Step S1, optimizing the three-dimensional model based on the additive manufacturing characteristics and the workpiece structure to obtain a blank model;

[0095] Step S2, obtaining the weld reinforcement h through a single-pass single-layer test, and slicing the model;

[0096] Step S3, partitioning the slices according to the size and structure of the blank, and obtaining the spacing between the partitions through numerical simulation and data fitting;

[0097] Step S4, determining the filling path mode of different partitions to obtain the partitioned material adding path;

[0098] Step S5: During the material addition process, the partition connection is monitored and material is added or subtracted to obtain a blank.

[0099] Step S1 is further as follows:

[0100] Step S11: Import the original digital model of the large 2219 aluminum alloy frame into Solidworks. The original model of the frame is as follows: Figure 2 As shown; the windows and threaded holes on the side frames of the frame are filled into a flat surface, and the complex structure is simplified into a simple structure;

[0101] Step S12: Since the frame is large and the thickness of some walls is less than 10 mm, the thin wall will deform during the material addition process. Therefore, the inner wall is increased by 7 mm and the outer wall is increased by 8 mm to obtain the blank model as shown in FIG. Figure 3 shown.

[0102] The step S2 is further as follows:

[0103] Step S21, 5 welds are obtained by single-pass single-layer welding, and a cross section is cut at every 10 mm interval at each weld forming stable position (the cross section is perpendicular to the welding direction), and a total of 10 locations are selected, and the molten pool interface is obtained by grinding and etching, and the average weld width and average excess height of the weld are measured to be 6 mm and 2 mm;

[0104] Step S22, the height of the blank is 530 mm, the weld excess height is 2 mm as the single-layer slicing height, and the number of layered slicing layers is 265.

[0105] The step S3 is further as follows:

[0106] Step S31, the blank has a length of 3000 mm, a width of 2000 mm, and a reachable range of the robot of 2500 mm. Since the size of the blank exceeds the reachable range of the robot, the model slices are manually divided into two partitions;

[0107] Step S32: In the two divided partitions, due to the different welding gun postures in the near-end and far-end additive processes, the model slices are further divided into four partitions, such as Figure 4 As shown;

[0108] Step S33: Since there is no internal partition in the four partitions, there is no mandatory requirement for the order of the partitions; the four partitions are set as partition 1, partition 2, partition 3, and partition 4, and material addition is performed in sequence according to the order of the partition numbers;

[0109] Step S34: the filling paths between adjacent partitions are parallel straight line paths;

[0110] Step S35, constructing a three-dimensional multi-physics field coupled transient model at the partition connection to simulate the connection process of the parallel straight line paths between the partitions, and obtaining the connection height under different partition spacings;

[0111] Building multi-physics coupling models includes basic assumptions, governing equations, geometric models, loading material properties and boundaries;

[0112] Basic assumptions: Ignore the welding wire and arc to simplify the model, and only consider the solidification of the molten droplet and the molten pool; simulate the melting and solidification process of the molten pool by changing the dynamic viscosity of the metal at different temperatures. Therefore, this model only considers the liquid phase and the gas phase; the liquid phase and the gas phase in the model are both incompressible laminar flows;

[0113] The governing equations of the multiphysics coupling model include the Navier-Stokes equations, the heat transfer equations, and the level set equations;

[0114] Navier-Stokes equations:

[0115]

[0116] Heat transfer equation:

[0117]

[0118] Level set equation:

[0119]

[0120] Where ρ is density, υ is velocity, p is pressure, T is temperature, F is momentum source term, μ is dynamic viscosity, I is unit matrix, C P is the specific heat capacity, k is the thermal conductivity, Q is the energy source term, ∈ ls is the interface thickness parameter, γ is the interface moving speed, Φ is the level set function, when Φ is 1, it is liquid phase, when Φ is 0, it is gas phase, and when 0<Φ<1, it is gas-liquid transition interface;

[0121] The differential equation to be solved is discretized and divided, and the flow area is divided into several subdomain units, and the vertex of each subdomain unit is called a node; the multiple unit finite element equations after discretization and division are combined into a continuum, and the matrices and vectors of the equilibrium equations of each unit are correspondingly combined to form an overall finite element matrix equation; the known boundary conditions are applied to the overall finite element matrix equation to limit the range of the solution; the numerical solutions of the velocity v and pressure p in the Navier-Stokes equations are obtained by an iterative method, the numerical solutions of the temperature T in the heat transfer equations are obtained by an iterative method, and the numerical solutions of the level set function φ in the level set equations are obtained by an iterative method;

[0122] The momentum source term F includes the buoyancy term and surface tension;

[0123] The buoyancy acts on the liquid phase, and the buoyancy term is:

[0124] F1=ρβg(TT m )

[0125] ρ is 2380kg*m -3 , β is 1.5*10 -4 , T m 847K;

[0126] Surface tension acts on the gas-liquid interface and is:

[0127] F2=γ0-σ(T-T0)

[0128] γ0 is 0.871N*m -1 ,σ is -1.55*10 -4 N / m*k, T0 is 293K;

[0129] The energy source term Q is the arc heat input on the molten pool surface; the arc heat input q(r) is Gaussian distributed:

[0130]

[0131] η is 0.3, U is 22.9V, I is 214A, r0 is 3.4mm, and r is the distance from any point in the horizontal direction to the arc center;

[0132] The inlet of the droplet level set is:

[0133]

[0134] Through the conditional judgment function if(r<r1,φ i , 0) introduce the molten drop, r1 is 2.9mm, f is 5, t is the time, and the molten drop temperature is 200K higher than the liquidus temperature, that is, 1133K;

[0135] A geometric model is established, which includes a gas domain and a liquid domain. The gas domain is above the liquid domain. The width of the gas domain and the liquid domain is 4 times the weld width w, that is, 24 mm. The length of the gas domain and the liquid domain is 50 mm. The height of the gas domain is the arc length, that is, 3 mm. The height of the liquid domain is 4 times the weld height h, that is, 8 mm. A hexahedron is used to construct a structured grid. The geometric model is as follows: Figure 5 As shown, the oblique line stripe area represents the liquid phase area of ​​the molten pool, the blank area above represents the gas phase area, and the middle gray area is the gas-liquid interface;

[0136] Load the material properties, as shown in Table 1. The gas phase is argon, the liquid phase is 2219 aluminum alloy,

[0137] Table 1. Thermophysical properties of 2219 aluminum alloy

[0138]

[0139]

[0140] The dynamic viscosity of the liquid phase is:

[0141]

[0142] T m 847K, T l The melting and solidification of the molten pool are simulated by the change of dynamic viscosity at different temperatures; the other material properties are functions of temperature; when the temperature is higher than 933K, the molten droplet and the molten pool melt; when the temperature is lower than 847K, the molten droplet and the molten pool solidify; when the temperature is between 847K and 933K, it is the transition zone between the melting area and the solidification area; when the temperature is higher than T l When the dynamic viscosity is 0.1N*s / m 2 , continuous molten droplets enter the molten pool; when the temperature is lower than T m When the dynamic viscosity is 10000N*s / m 2 , the molten pool begins to cool, solidify and form two welds; the height of the joint is obtained by measuring the height between the two welds;

[0143] The liquid phase boundary conditions include thermal convection boundary and thermal radiation boundary; the thermal convection boundary is:

[0144] q c =h c (T-T0)

[0145] In the formula, h c is the convection coefficient, T0 is the ambient temperature; h c 20W / m 2 *K, T0 is 293K;

[0146] The thermal radiation boundary is:

[0147] q r =εσ0(T 4 -T0 4 )

[0148] Where ε is the thermal emissivity, σ0 is the Stefan-Boltzmann constant; ε is 0.4;

[0149] The boundary conditions at the liquid phase boundary are:

[0150] q l =-q c -q r

[0151] The initial temperatures of the liquid phase and the gas phase were set to 500K. Through parametric scanning, the partition spacings were 2.4mm, 2.7mm, 3mm, 3.3mm, 3.6mm, 3.9mm, 4.2mm, 4.5mm, and 4.8mm, and the connection heights were 4.1mm, 3.5mm, 3.1mm, 2.8mm, 2.4mm, 2.1mm, 1.5mm, 1.2mm, and 0.8mm, respectively.

[0152] Step S35: The fitting function of the partition spacing with respect to the connection height is obtained by linear fitting:

[0153] y=-0.74*x+5.38

[0154] Substituting the weld excess height of 2mm into x can obtain the spacing between the partitions, which is 3.9mm.

[0155] The step S4 is further as follows:

[0156] Step S41: The filling paths of the four partitions are all set to reciprocating straight line paths, with a filling width of 3.9 mm. The partition path diagram is shown in FIG. Figure 6 As shown;

[0157] Step S42: Send the simulation path in the software to the robot program, control the robot to move on the substrate surface according to the path, and ensure that the additive path can be executed.

[0158] The step S5 is further as follows:

[0159] Step S51, real-time monitoring of the forming condition, welding current, voltage and molten pool temperature of the partition connection by means of an infrared thermal imager, a three-dimensional scanner and a teaching pendant;

[0160] Step S52: During the material addition process, when the height of the partition connection is found to be greater than 2.2 mm through the three-dimensional scanner, the spacing between the partitions is increased by 5% to reduce the height of the partition connection;

[0161] Step S53: After each layer of material addition is completed, if the height of the partition connection is greater than 2.2 mm, a subtractive device is used to remove the excess height of the connection;

[0162] Step S54: During the material addition process, if the three-dimensional scanner finds that there is unfused joints at the partition connections, the spacing between the partitions is reduced by 5% to eliminate the unfused joints in the partitions;

[0163] Step S55: After each layer of additive material is completed, if there is still unfused area at the partition connection, first use additive equipment to fill the unfused area, and then use subtractive equipment to process and remove the part higher than 2 mm;

[0164] Step S56, repeat steps S51 to S55 to obtain a blank.

[0165] The average tensile strength of the partitioned connection is 454.1MPa, the average yield strength is 391.8MPa, the average elongation is 6.5%, and the grains at the connection are fine equiaxed crystals; the average tensile strength of the parent material is 451.8MPa, the average yield strength is 397.3MPa, the average elongation is 6.1%, and the grains of the parent material are fine equiaxed crystals; the mechanical properties of the partitioned connection are similar to those of the parent material; the average tensile strength of the connection obtained by butt welding is 412.5MPa, the average yield strength is 356.3MPa, and the average elongation is 5.4%, and the grains of the connection obtained by butt welding are coarse columnar dendrites; the strength of the partitioned connection obtained by additive manufacturing is 10% higher than that of the connection obtained by butt welding.

[0166] It should be understood that in order to streamline the present disclosure and aid in understanding one or more of the various inventive aspects, in the above description of exemplary embodiments of the present invention, various features of the present invention are sometimes grouped together into a single embodiment, figure, or description thereof. However, this disclosed method should not be interpreted as reflecting the intention that the claimed invention requires more features than those expressly recited in each claim. Rather, as reflected in the claims, inventive aspects lie in less than all of the features of the previously disclosed embodiments. Therefore, the claims that follow the detailed description are hereby expressly incorporated into the detailed description, with each claim itself serving as a separate embodiment of the present invention.

[0167] Although the present invention has been described according to a limited number of embodiments, it will be apparent to those skilled in the art, with the benefit of the above description, that other embodiments may be envisioned within the scope of the invention thus described. In addition, it should be noted that the language used in this specification is selected primarily for readability and teaching purposes, rather than for explaining or defining the subject matter of the present invention. Therefore, many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the appended claims. The disclosure of the present invention is illustrative, not restrictive, with respect to the scope of the present invention, which is defined by the appended claims.

[0168] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A partitioned additive manufacturing method for a large complex structure workpiece, characterized in that: The following steps are involved: Step S1, optimizing the three-dimensional model of the workpiece to obtain a blank model; Step S2, obtaining the weld reinforcement h through a single-pass single-layer test, and slicing the blank model; Step S3, partitioning the slices according to the size and structure of the blank model, and obtaining the spacing between the partitions through numerical simulation and data fitting; Step S4, determining the filling path mode of different partitions to obtain the partitioned material adding path; Step S5: During the material addition process, the partition connection is monitored and material is added or subtracted to obtain a blank.

2. The method according to claim 1, characterized in that Step S1 includes the following contents: Step S11, the optimization method of the three-dimensional model is: filling holes and windows in the three-dimensional model to form a regular geometric shape; Step S12: Based on the workpiece structure, at least 7 mm of margin is added to the inner wall area of ​​the workpiece structure area with a thickness of ≤10 mm, and at least 8 mm of margin is added to the outer wall area to obtain a blank model.

3. The method according to claim 2, characterized in that Step S2 includes the following contents: Step S21, obtain multiple welds by single-pass single-layer welding, cut a cross section at a stable position of the weld formation at every 10 mm interval, the cross section is perpendicular to the welding direction, and a total of 10 locations are selected, and the molten pool interface is obtained by grinding and etching, and the average weld width w and average excess height h of the weld are measured, that is, the weld width w and the weld excess height h; Step S22: Slice the blank model using the weld excess height h as the single-layer slicing height, and the number of slicing layers M is: In the formula, Z max is the maximum value in the Z direction, Z min is the minimum value in the Z direction, and h is the weld excess height.

4. The method according to claim 3, characterized in that Step S3 includes the following contents: Step S31, determining the length m, width n and robot working range c of the workpiece, if m>c or n>c, partitioning the slice contour according to the workpiece size so that the partition is within the robot working range; Step S32: After partitioning by size, if there is a special structure in the partition, the workpiece needs to be further partitioned according to the minimum area of ​​the special structure to reduce the impact of the special structure partition on the additive; Step S33, determining the additive manufacturing order of each partition, if there is an internal partition, first add material to the internal partition, and then add material to the external partition; Step S34: the filling paths between adjacent partitions are parallel straight line paths; Step S35, constructing a three-dimensional multi-physics field coupled transient model at the partition connection to simulate the connection process of the parallel straight line paths between the partitions, and obtaining the connection height h' under different partition spacings; the partition spacing is set to be between 0.4w and 0.8w, denoted as z'; Step S36, fitting the connection height h' and the partition spacing z' to obtain the fitting equation y=-0.74x+5.38 of the partition connection height h' and the partition spacing z'; substituting the weld excess height h obtained in step S21 into the fitting equation to obtain the actual partition spacing z.

5. The method according to claim 4, characterized in that In step S32, the special structures include a ring structure, a circular structure and a suspended structure.

6. The method according to claim 4, characterized in that Step S4 includes the following contents: Step S41, determining different path parameters for each partition to obtain a partitioned additive path; Step S42: Send the simulation path to the robot program, control the robot to move on the substrate surface according to the path, and ensure that the additive path can be executed.

7. The method according to claim 6, characterized in that Step S5 includes the following contents: Step S51, real-time monitoring of the forming condition, molten pool temperature, welding current and voltage of the partition connection by means of an infrared thermal imager, a three-dimensional scanner and a teaching pendant; Step S52: During each layer of material addition, if it is observed that the height of the partition connection is greater than 1.1 times the weld excess height h, the partition spacing z is increased by 5% to reduce the height of the partition connection; Step S53: After each layer of material addition is completed, if the height of the partition connection is greater than 1.1 times the weld excess height h, use a subtractive device to remove the portion higher than the weld excess height h; Step S54: During each layer of material addition, if it is observed that there is unfused at the partition connection, the partition spacing z is reduced by 5% to eliminate the unfused in the partition; Step S55: After each layer of material addition is completed, if there is unfused area at the partition connection, the unfused area is filled with additive equipment, and then the part higher than the weld excess height h is removed with subtractive equipment; Step S56, repeat steps S51 to S55 until a blank is obtained.

8. A large-scale complex structure workpiece obtained by the method according to any one of claims 1 to 7, characterized in that: The mechanical properties of partitioned joints of large and complex structure workpieces are comparable to those of the parent material.

9. The large complex structure workpiece according to claim 8, characterized in that: It includes a large 2219 aluminum alloy frame with a height of 530mm, a length of 3000mm and a width of 2000mm.

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