Flexible structure 3D printing supporting method with variable rigidity adjustment function

Abstract

The invention discloses a flexible structure 3D printing supporting method with variable rigidity adjustment, relates to the technical field of additive manufacturing, and aims to solve the problem that an internal support of a complex structure is difficult to remove without damage. By constructing a multi-physical-field topological optimization and intelligent material response mechanism, accurate regulation and control of the stiffness characteristics of the supporting structure are achieved, a supporting area distribution diagram is generated based on geometric characteristics and stress analysis, and the non-uniform dot matrix supporting structure is generated by adopting a variable density method. A first rigidity state in the printing process is controlled and maintained through environmental parameters to guarantee supporting stability, and external stimulation is utilized to trigger conversion to a second rigidity state to achieve supporting softening; according to the method, part damage caused by traditional mechanical removal is avoided, and the removal efficiency and success rate of a complex internal structure support are remarkably improved while the printing precision is guaranteed.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of additive manufacturing, and more particularly, to a flexible structure 3D printing support method with variable rigidity adjustment. BACKGROUND

[0002] In the manufacturing of 3D printed parts with complex internal cavities and high surface quality requirements, the support structure causes a fundamental conflict between stability and removability due to the contradiction between the printing process and the post-processing requirements. Traditional support design is based on the assumption of static mechanical properties, simplifying the support structure as a rigid mechanical support with uniform material, and using empirical geometric configurations to describe the behavior of the support structure, without quantifying the dynamic adjustment effect of intelligent material response mechanism on the stability of the printing process and the removability of the post-processing.

[0003] In the prior art, due to the lack of dynamic matching relationship between the variable rigidity characteristics of intelligent materials and the mechanical requirements of the printing process and the removal requirements of the post-processing, the mechanical properties of the support structure in the printing process of high-value parts are insufficient or difficult to remove in the post-processing stage, resulting in the risk of printing failure or surface damage of precision parts with complex internal structures, and increasing production costs and quality risks. SUMMARY

[0004] In order to overcome the above-mentioned defects of the prior art, the embodiments of the present application provide a flexible structure 3D printing support method with variable rigidity adjustment and a system to solve the problems raised in the background art.

[0005] To achieve the above-mentioned purpose, the present application provides the following technical solutions: A flexible structure 3D printing support method with variable rigidity adjustment, comprising the following steps: S1, receiving three-dimensional model data of a part to be printed, identifying overhanging structures and critical stress regions including internal closed cavities based on geometric features, and generating a support region distribution map containing internal non-contact region support requirements; S2, generating a non-uniform lattice support structure suitable for internal closed cavities through a multi-physics field topology optimization algorithm according to the support region distribution map; S3, printing the internal support structure using a support material that responds to external stimuli; S4, controlling the environmental parameters during the printing process to keep the support material in a first rigidity state; S5, after the printing is completed, applying external stimuli to change the support material to a second rigidity state lower than the first rigidity state; S6, based on the flexibility of the support structure in the second rigidity state, removing the support structure from the internal part. In a preferred embodiment, three-dimensional model data of a part to be printed is received, overhanging structures including internal enclosed cavities and critical stress regions are identified based on geometric features, a support region distribution map containing internal non-contactable region support requirements is generated, and the specific steps include: three-dimensional model data of a part to be printed is received through a three-dimensional data interface; a geometric feature recognition algorithm is used to analyze the overhanging structure profile and internal enclosed cavity structure in the three-dimensional model; a preset overhanging angle threshold criterion is used to determine the boundary range of the overhanging region that needs support; a finite element stress contour analysis method is used to identify critical stress regions that occur during printing; the identified overhanging region boundary range and critical stress regions are spatially superimposed and fused, and a support region distribution map containing internal non-contactable region support requirements is generated based on the spatial superimposition and fusion results.

[0006] In a preferred embodiment, a finite element stress contour analysis method is used to identify critical stress regions that occur during printing, and the specific steps include: a finite element analysis model for finite element calculation is established, which contains material property parameters and printing process parameters; based on the established finite element analysis model, temperature load conditions and mechanical constraint conditions during printing are set; temperature load conditions refer to the temperature field distribution on the finite element analysis model and its variation with time; mechanical constraint conditions refer to the restriction conditions applied to the displacement freedom degrees of the finite element analysis model; thermal-mechanical coupled field finite element calculation is performed using the set temperature load conditions and mechanical constraint conditions to obtain stress distribution data during printing; stress distribution data refers to a series of numerical results obtained by thermal-mechanical coupled field finite element calculation for the stress state of each position inside the structure during printing; thermal-mechanical coupled field refers to a multi-physical field coupling analysis environment in finite element analysis that considers the interaction between temperature field and stress field, which simulates the influence of thermal expansion effect and material property change caused by temperature change on structural mechanical behavior by establishing the interaction relationship between temperature distribution and structural deformation; the calculated stress distribution data is color-mapped and contour-mapped to generate a finite element stress contour map; analyze the stress regions in the finite element stress contour map that exceed the material yield strength; material yield strength refers to the critical stress value at which plastic deformation occurs in the material during loading; Identify regions where the spacing between stress contour lines decreases in the stress finite element stress cloud map, locate locations where the rate of change of curvature of stress contour lines exceeds a set curvature change threshold, calculate the ratio of the stress difference between adjacent nodes to the average change level, screen out node clusters where the stress difference is greater than a specific multiple of the average change level, and determine the geometric abrupt regions where the node clusters are located and the adjacent regions of material discontinuities as critical stress regions. Stress contour lines are continuous curves that connect points with the same stress value in a finite element stress contour plot. A node is a connection point of mesh elements formed after discretizing a continuous structure in finite element analysis. A node cluster refers to a set of nodes that have consistent statistical distribution characteristics of stress values ​​and are spatially adjacent in a finite element stress cloud diagram.

[0007] In a preferred embodiment, based on the support region distribution map, a non-uniform lattice support structure suitable for an internal closed cavity is generated using a multiphysics topology optimization algorithm. Specific steps include: Based on the support demand intensity of different regions in the support area distribution map, an optimization function is established with the objectives of minimizing material usage and maximizing structural stiffness. Set the stress constraints and deformation constraints that the support structure must meet during the printing process; Stress constraints refer to the limitations imposed on the maximum stress value in structural optimization design to ensure safety. Deformation constraint conditions refer to the restrictions set on the maximum deformation in structural optimization design to meet functional requirements; A thermo-mechanical coupled multiphysics finite element analysis was performed on the support region to obtain the distribution data of the temperature field and stress field. The distribution data of the temperature field and stress field were used to simultaneously characterize a series of numerical results of the temperature state and mechanical state of the support region. In the implementation of the multiphysics topology optimization algorithm, the variable density method is adopted as the implementation means. Iterative calculation is carried out by establishing the correspondence between material density and physical properties. In each iteration, it is first checked whether the stress level and deformation under the current material layout meet the stress constraint condition and deformation constraint condition. Then, based on the temperature field and stress field distribution data obtained by thermo-mechanical coupled multiphysics finite element analysis, the material density distribution is updated. The optimal material layout is determined by convergence judgment. Finally, a non-uniform lattice support structure with spatial variable density characteristics is generated based on the optimized material density distribution result. A gradient transition zone with continuously varying stiffness is constructed at the interface between the support structure and the component body. The elastic modulus of the gradient transition zone decreases from the component body to the outer end of the support structure.

[0008] In a preferred embodiment, the internal support structure is printed using a support material that responds to external stimuli, and the specific steps include: Select a support material with external stimulus response characteristics as the printing material; External stimulus response characteristics refer to the properties of a supporting material that change its physical and mechanical properties when subjected to a specific type of external energy or chemical environment. Based on the distribution map of the support area and the non-uniform lattice support structure, plan the printing path of the support material.

[0009] In a preferred embodiment, the printing path of the support material is planned based on the support area distribution map and the non-uniform lattice support structure. Specific steps include: Read the support demand intensity data of different levels marked on the support area distribution map; Analysis of the spatial distribution characteristics and density variation law of non-uniform lattice elements in a non-uniform lattice support structure; Non-uniform lattice elements refer to the basic building blocks in a lattice structure with spatial and density characteristics generated by the variable density method. The deposition rate and extrusion rate control parameters of the support material are determined based on the non-uniform lattice unit density distribution. When planning the printing path based on the geometric model of the non-uniform lattice support structure, the three-dimensional model is first sliced ​​to obtain the two-dimensional contour trajectory of each layer. Based on the comparison between the density distribution data of the non-uniform lattice unit and the preset density threshold, each layer is divided into different filling areas. For areas with density values ​​higher than a preset density threshold, a concentric circle path filling mode is used and a first spacing value is set to generate a dense material deposition path. Dense material deposition paths for areas with density values ​​higher than the preset density threshold are planned first. The generation of dense material deposition paths starts from the inside of the contour and expands outward in a spiral manner. For areas with density values ​​lower than the preset density threshold, a zigzag path filling mode is used and a second spacing value is set to generate a sparse material deposition path. The sparse material deposition path generates a reciprocating straight line along the contour direction, where the first spacing value is smaller than the second spacing value. The generation of sparse material deposition paths is performed after the generation of dense material deposition paths. Finally, all path data are integrated to generate a complete printhead movement trajectory that includes coordinate positioning and motion control. The determined deposition rate and extrusion amount control parameters and movement trajectory are mapped into action instructions for the print head on the travel path of the corresponding area, thereby generating a complete set of printing instructions including movement trajectory coordinate positioning instructions, material deposition rate control instructions, extrusion amount adjustment instructions, movement speed and temperature control. The planned printing path is verified through virtual printing simulation.

[0010] In a preferred embodiment, environmental parameters are controlled during the printing process to maintain the support material in a first stiffness state. Specific steps include: Establish environmental parameter control target values ​​corresponding to the first stiffness state of the supporting material. The environmental parameter control target values ​​include temperature control target values, humidity control target values, and atmosphere composition control target values. The first stiffness state refers to the specific physical state maintained by the support material through environmental parameter control during the 3D printing process. Under the first stiffness state, the elastic modulus of the support material reaches the upper limit of its performance range and its deformation resistance meets the requirements of the printing support. Atmosphere composition refers to the mixing ratio of various gas components in the printing environment space; Real-time acquisition of printing environment parameters, including temperature, humidity, and atmosphere composition parameters; The collected environmental parameters are compared and analyzed with the environmental parameter control target values; When environmental parameters are detected to deviate from the target values ​​for environmental parameter control, the environmental control device is activated to correct the parameters. Continuously monitor the changing trends of environmental parameters and dynamically adjust the operating parameters of the environmental control device based on the monitoring results.

[0011] In a preferred embodiment, after printing is completed, the supporting material is transformed into a second stiffness state lower than the first stiffness by applying an external stimulus. Specific steps include: Determine the type and parameters of external stimuli required to cause a change in the stiffness of the support material. External stimulus parameters refer to the physical quantities of the stimulus type that need to be controlled in order to achieve a change in the stiffness state of the support material. External stimulus types include thermal stimulation and solvent stimulation. Place the printed component into the stimulus application device; Apply external stimuli according to the preset external stimulus type and external stimulus parameters; Monitor changes in the physical state of the support material during stimulus application; When the supporting material is detected to have reached the preset second stiffness state characteristic, the stimulation application is stopped; The second stiffness state refers to the specific physical state that the support material changes to after printing by applying external stimuli. In the second stiffness state, the elastic modulus of the support material is reduced to the lower limit of its performance range and the flexibility meets the requirements for non-destructive removal.

[0012] In a preferred embodiment, based on the flexibility of the support structure under the second stiffness state, the support structure is removed from the interior of the part, specifically including the following steps: Check whether the supporting material has reached the preset second stiffness state; The removal operation is carried out using a special tool by utilizing the flexibility properties obtained by the support structure under the second stiffness state.

[0013] Compared with the prior art, the present invention has the following beneficial effects: 1. By combining multiphysics topology optimization algorithms with finite element stress cloud map analysis, precise design and intelligent control of the mechanical properties of the support structure are achieved. Based on temperature and stress field distribution data obtained from thermo-mechanical coupling field analysis, iterative optimization using a variable density method is driven to generate a non-uniform lattice support structure with spatial variable density characteristics. This effectively solves the contradiction between low material utilization and mismatch in mechanical properties of traditional uniform support structures. Compared with existing technologies, it can accurately predict the critical stress region during the printing process in the design stage. Through stiffness gradient transition zone design and lattice density distribution optimization, stress concentration is significantly reduced, and the load-bearing stability and reliability of the support structure during the printing process are improved.

[0014] 2. Through the innovative application of smart materials and external stimulus response mechanisms, the dynamic adjustment and non-destructive removal of the support structure stiffness are achieved. Based on precise control of environmental parameters, the first stiffness state during the printing process is maintained to ensure support stability. The transition to the second stiffness state triggered by external stimuli is used to achieve the soft removal of the support structure. Compared with existing technologies, this breakthrough overcomes the technical bottleneck of traditional support structures being difficult to remove from internal closed cavities. Through precise control of thermal or solvent stimulation, the support material acquires controllable flexibility after printing, which can ensure the mechanical support requirements during the printing process and achieve efficient and non-destructive removal of the support structure after printing. This significantly improves the printing success rate and surface quality of complex structural parts. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of a flexible structure 3D printing support method with adjustable variable stiffness according to the present invention. Detailed Implementation

[0016] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0017] Example 1: Figure 1 A schematic diagram of a flexible structure 3D printing support method with adjustable variable stiffness according to the present invention is provided, which includes the following steps: S1. Receive the 3D model data of the part to be printed, identify the overhang structure and critical stress area including the internal closed cavity based on geometric features, and generate a support area distribution map including the support requirements of the internal non-accessible area. S2. Based on the support area distribution map, a non-uniform lattice support structure suitable for the internal closed cavity is generated by a multiphysics topology optimization algorithm. S3. The internal support structure is printed using a support material that responds to external stimuli; S4. Control environmental parameters during the printing process to maintain the support material in a state of initial stiffness; S5. After printing, external stimuli are applied to transform the support material into a second stiffness state that is lower than the first stiffness. S6. Based on the flexibility of the support structure under the second stiffness state, remove the support structure from the inside of the part. The system receives the 3D model data of the part to be printed, identifies the overhanging structure and critical stress region, including the internal closed cavity, based on geometric features, and generates a support area distribution map that includes the support requirements for internal non-accessible areas. The specific implementation is as follows: Receiving the 3D model data of the part to be printed is the data input stage of the entire process. The system receives 3D model data generated by CAD software for a specific part to be printed through standardized 3D data interfaces (such as STL, STEP, 3MF and other industry standard formats). This data fully describes the geometry, topology and spatial dimensions of the part. After receiving the data, the model is preprocessed, including: model repair (repairing possible mesh errors, non-manifold edges, self-intersecting patches), coordinate system unification (converting the model to the construction coordinate system), and unit standardization (unifying to millimeters), providing standardized input data for subsequent analysis.

[0018] When using a geometric feature recognition algorithm based on normal vector analysis to process 3D models, the generation of the overhanging structure contour is a crucial step. The algorithm first traverses all triangular faces of the model and calculates the angle θ between the normal vector of each face and the normal vector of the construction platform (negative Z-axis direction). The overhanging structure is identified based on the size of the angle: when θ exceeds a preset critical value (usually 45°), it is marked as a potential overhanging area. At the same time, the internal structure of the model is analyzed using ray detection: detection rays are emitted from the model boundary inward. When the rays form a closed enclosure inside and cannot reach the outside, the area is determined to be an internal closed cavity. The inner surface of the top of the cavity is identified as a key support area, and its spatial coordinates and geometric features are recorded. Adjacent overhanging faces are clustered using a region growing algorithm, and continuous overhanging structure contours are extracted using a boundary tracing algorithm, ultimately generating accurate contour geometric data.

[0019] The recognition results are processed according to the preset overhang angle threshold judgment criteria. First, the preset overhang angle threshold value (such as 45°) is read. Then, the actual included angle of each recognition facet is calculated. The measured included angle is compared with the overhang angle threshold value. All facets that exceed the overhang angle threshold value are marked. The region growing algorithm is used to cluster spatially adjacent triangular facets with similar included angle features into continuous overhang regions. The precise contour boundary of each region is extracted by the boundary tracking algorithm to generate a set of data on the boundary range of the overhang region that needs to be supported. This set contains a list of vertex coordinates, area data and spatial orientation information of each overhang region.

[0020] Identifying critical stress regions during the printing process using finite element stress cloud diagram analysis is a systematic computational process. First, a finite element analysis model is established, incorporating material property parameters and printing process parameters. Material property parameters include constitutive relation data such as elastic modulus, Poisson's ratio, coefficient of thermal expansion, and yield strength. Printing process parameters include process control data such as printing temperature, printing speed, layer thickness, and cooling rate. Based on the established finite element analysis model, temperature load conditions and mechanical constraints are set during the printing process. The temperature load conditions need to simulate the dynamic temperature field changes caused by the movement of the printing heat source, including parameters such as heat source intensity, heat-affected zone range, and temperature variation over time. The mechanical constraints need to reflect the fixing effect of the printing platform on the part, including displacement freedom restriction methods such as fully fixed constraints and sliding constraints. Using the set temperature load conditions and mechanical constraints, a thermo-mechanical coupled field finite element calculation is performed. A sequential coupling analysis method is adopted. First, the transient temperature field distribution is solved to obtain temperature field data at each time step. Then, the temperature field results are used as the thermal load input. In stress field calculations, thermal expansion effects and temperature-related material property changes are considered. Stress distribution data is obtained through iterative solutions. The calculated stress distribution data is then used to generate finite element stress cloud maps using visualization technology. The generation process includes color mapping and contour plotting. Color mapping converts stress values ​​into color information, establishing a correspondence between stress values ​​and colors. Contour plotting connects spatial points with the same stress value to form a continuous curve. Regions in the stress cloud map that exceed the material's yield strength are analyzed, and the material's yield strength value is determined as a benchmark. All regions in the cloud map whose stress values ​​exceed this benchmark are identified, and their geometric locations and stress exceedance degrees are recorded. Critical stress regions are identified based on the characteristics of the stress cloud map. The distribution density and curvature changes of stress contour lines are analyzed, and locations with decreasing contour line spacing and abrupt curvature changes are identified. The stress difference between adjacent nodes is calculated, and regions with significant stress changes are selected. Nodes with similar stress characteristics and spatial proximity are clustered to form node clusters. Finally, the regions with abrupt geometric changes and the vicinity of the material interface where these clusters are located are determined as critical stress regions.

[0021] The boundary range of the overhanging region and the critical stress region are spatially superimposed and fused. First, the coordinate system and data format of the two are unified. The three-dimensional model space is divided into uniform voxel grids (usually with a grid size of 0.5-1.0 mm) using a spatial meshing method. The existence status of the overhanging region attributes and the critical stress region attributes are detected simultaneously for each grid cell. When a grid is covered by both types of regions at the same time, a weighted fusion algorithm is used to calculate the comprehensive support requirement strength of the region. The weights are dynamically adjusted according to the overhanging angle and the degree of stress concentration (for example, the weight of the overhanging angle factor is 0.6, and the weight of the stress concentration factor is 0.4).

[0022] Based on the fusion processing results, a digital support area distribution map is generated. The support requirement intensity of each grid unit is converted into color depth or numerical markers to generate a visual distribution map. In particular, for internal closed cavity areas, the cavity topology recognition algorithm is used to mark their "inaccessible" characteristics and distinguish them with special marks in the support area distribution map. Finally, a complete support area distribution map containing spatial location information, support strength level and regional characteristic markers is output, providing data support for the subsequent generation of support structures.

[0023] The critical stress region during the printing process is identified using the finite element stress cloud diagram analysis method. The specific implementation is as follows: A finite element analysis model is constructed for finite element calculations. This model must fully include material property parameters and printing process parameters. Material property parameters include constitutive parameters such as elastic modulus (describing the ratio of stress to strain during elastic deformation, typically exhibiting a negative correlation with temperature), Poisson's ratio (describing the ratio of transverse strain to axial strain, typically remaining relatively stable), coefficient of thermal expansion (describing the rate of dimensional change of a material under heat), and yield strength (the critical stress value for plastic deformation). Printing process parameters include process data such as printing temperature, printing speed, layer thickness, and cooling rate. These parameters are imported into the finite element analysis software through a material database interface to establish an accurate material constitutive model and a thermodynamic model of the printing process.

[0024] Based on the established finite element analysis model, temperature load conditions and mechanical constraint conditions are set during the printing process. The temperature load conditions need to simulate the temperature field distribution characteristics of the moving heat source of the print head, including parameters such as heat source intensity, heat-affected zone range, and temperature change over time. The mechanical constraint conditions need to reflect the fixing constraint effect of the printing platform on the part, including displacement freedom restriction methods such as complete fixed constraint and sliding constraint.

[0025] Temperature load conditions refer to the temperature field distribution and its variation with time on the finite element analysis model.

[0026] Mechanical constraints refer to the restrictions imposed on the displacement degrees of freedom of a finite element analysis model.

[0027] When identifying critical stress regions in the printing process using the finite element stress cloud diagram analysis method, based on the established finite element analysis model, temperature load conditions and mechanical constraint conditions are set for the printing process, and these conditions are used to perform finite element calculations of the thermo-mechanical coupled field. The calculation process adopts a sequential coupling analysis method: first, the transient temperature field distribution is solved based on the temperature load conditions to obtain temperature field data at each time step; then, the temperature field results are used as thermal loads and input into the stress field calculation, while considering the limiting effect of mechanical constraint conditions. The calculation fully considers the thermal expansion effect and the material property changes caused by temperature changes, and obtains the stress distribution data in the printing process through iterative solution.

[0028] Stress distribution data refers to a series of numerical results obtained through thermo-mechanical coupled field finite element calculations, used to measure the stress state at various locations inside the structure during the printing process.

[0029] Thermo-mechanical coupled field refers to a multi-physics coupled analysis environment in finite element analysis that simultaneously considers the interaction between temperature field and stress field. By establishing the interaction relationship between temperature distribution and structural deformation, it simulates the influence of thermal expansion effect and material property changes caused by temperature change on the mechanical behavior of structure under actual working conditions.

[0030] The calculated stress distribution data is used to generate a finite element stress cloud map using visualization technology. The generation process includes color mapping and contour plotting: color mapping converts stress values ​​into color information and establishes a correspondence between stress values ​​and colors; contour plotting connects spatial points with the same stress value to form a continuous curve, and the density of contour lines reflects the stress gradient change.

[0031] To analyze the stress regions in the stress cloud diagram that exceed the material's yield strength, first determine the material's yield strength value as the judgment benchmark, then identify all regions in the cloud diagram where the stress value exceeds the benchmark, and record the geometric location and degree of stress exceeding the limit of these regions.

[0032] The yield strength of a material refers to the critical stress value at which a material undergoes plastic deformation under stress.

[0033] The identification of critical stress regions is based on a comprehensive feature analysis of finite element stress contour maps. First, regions with significantly reduced spacing between stress contour lines are identified: by calculating the average distance between adjacent contour lines and comparing this distance to the overall average spacing, regions with a significantly reduced spacing ratio (e.g., 0.6) are marked as high-gradient regions, indicating drastic stress changes and potential stress concentration. Second, locations where the rate of curvature change of stress contour lines exceeds a set curvature change threshold are identified: using a curvature calculation algorithm, curvature values ​​are extracted along the contour line path, and the rate of curvature change (the amount of curvature change per unit arc length) is calculated. When the rate of change exceeds a set curvature change threshold (e.g., 0.6), the region is marked as a high-gradient region. When this occurs, the location is marked as a curvature abrupt change point, which typically corresponds to a sudden change in geometry, such as a sharp corner or groove. Next, the ratio of the stress difference between adjacent nodes to the average change level is calculated: all nodes are traversed, the stress difference between each node and its directly adjacent nodes is calculated, and the average stress change level of the entire model is statistically analyzed; then, the ratio of the stress difference to the average change level for each node is calculated, reflecting the significance of local stress changes. Subsequently, node clusters with stress differences greater than a specific multiple (e.g., 3 times) of the average change level are selected: spatially adjacent nodes with high stress difference ratios are grouped using a clustering algorithm to form node clusters. Each cluster must satisfy the conditions that the distance between internal nodes is less than a set threshold for node spacing within the cluster (e.g., 0.5 mm) and the stress values ​​are uniformly distributed. Finally, the regions where these node clusters are located—geometric abrupt change areas (e.g., acute angle transition areas, thin-thickness junctions) and adjacent areas of material discontinuities (e.g., material interfaces, pore edges)—are identified as critical stress regions. These regions are prone to stress concentration and potential failure during printing. Taking aero-engine turbine blades as an example, their material is a nickel-based superalloy with a yield strength of 1100 MPa (Megapascal is a unit of measurement for pressure or stress). In the finite element stress contour analysis, it was first identified that the average spacing of the stress contour lines in the transition area between the blade tenon and the blade body decreased from 2.0 mm to 0.9 mm, with a spacing ratio of 0.45 (lower than the set spacing ratio threshold of 0.6). This area was marked as a high gradient region; simultaneously, the rate of change of curvature of the contour lines in this area was detected to reach... (Exceeding the set threshold for rate of change of curvature) The results indicated a geometrical abrupt change. Nodal stress analysis revealed a stress difference of 420 MPa between adjacent nodes, while the overall model's average stress variation was 120 MPa, resulting in a ratio of 3.5 (exceeding the set threshold of 3 times). A clustering algorithm (cluster radius 0.3 mm) was used to identify a cluster containing 135 nodes. These nodes were concentrated at the sharp edges (corner radius < 0.5 mm) of the tenon transition zone and near the material interface. This area was ultimately identified as the critical stress region, with a maximum stress value of 1280 MPa, exceeding the material's yield strength by 16.3%. This region is highly susceptible to plastic deformation and interlayer delamination failure during printing.

[0034] Stress contour lines are continuous curves connecting points with the same stress value in a finite element stress contour plot. Nodes are the connection points of mesh elements formed after discretizing a continuous structure in finite element analysis.

[0035] A node cluster refers to a set of nodes that have consistent statistical distribution characteristics of stress values ​​and are spatially adjacent in a finite element stress cloud diagram.

[0036] Based on the support region distribution map, a non-uniform lattice support structure suitable for an internal closed cavity is generated using a multiphysics topology optimization algorithm. The specific implementation is as follows: Based on the support demand intensity data of different regions in the support area distribution map, an optimization function is established. The optimization function takes minimizing material usage as the primary objective and maximizing structural stiffness as a parallel objective. By introducing a weighted coordination coefficient, the relative importance of the two objectives is balanced. The weight allocation is adjusted according to the actual engineering requirements. Regions with high-strength support demand receive a higher weight for maximizing stiffness, while regions with low-strength demand are assigned a higher weight for minimizing material usage.

[0037] The mechanical performance constraints that the support structure must meet during the printing process are set. The stress constraint requires that the maximum equivalent stress of the support structure in the working state must not exceed the allowable stress value of the material. This value is determined based on the yield strength of the material and taking into account the safety factor. The deformation constraint requires that the maximum deformation of the support structure when subjected to printing load must be less than the allowable deformation threshold. This deformation threshold is determined according to the printing accuracy requirements and the functional requirements of the part.

[0038] Stress constraints refer to the restrictions on the maximum stress value set in structural optimization design to ensure safety.

[0039] Deformation constraint conditions refer to the restrictions set on the maximum deformation in structural optimization design to meet functional requirements.

[0040] A thermo-mechanical coupled multiphysics finite element analysis was performed on the support region. An analytical model incorporating material thermophysical parameters and mechanical properties was established. Temperature boundary conditions (including heat source model, thermal convection coefficient, and radiation coefficient) and mechanical constraints (including fixed constraints, sliding constraints, and symmetric constraints) were set during the printing process. The transient heat conduction control equation was used to solve for the temperature field distribution, which considers the combined effects of material density, specific heat capacity, thermal conductivity, and heat source terms. After obtaining the temperature field distribution data, it was used as the thermal load input for stress field calculation. Thermal stress was calculated through a thermo-mechanical coupled constitutive relation, which considers the interaction between the elastic matrix, total strain, and thermal strain. An iterative method was used for coupled solution, alternately solving the temperature field and stress field within each time step until the residuals met the convergence condition. The final output temperature field step-by-step data includes the temperature values ​​and gradient distribution of each node, and the stress field distribution data includes the equivalent stress, principal stress, and stress components of each node. These data collectively characterize a series of numerical results representing the temperature and mechanical states of the support region.

[0041] The heat source model is a mathematical model used to accurately simulate the heating process of materials by the print head (such as a laser or nozzle) in additive manufacturing. This model defines the energy distribution form and temporal variation law of the heat source in space. A Gaussian distribution model is usually used to describe the non-uniform distribution characteristics of laser energy in the action area. The thermal convection coefficient is a key parameter characterizing the intensity of convective heat transfer between the flowing gas in the printing chamber and the surface of the part. It is defined as the convective heat transfer per unit area under a unit temperature difference. The thermal convection coefficient comprehensively reflects the combined effect of forced convection (driven by a circulating fan) and natural convection (caused by a temperature gradient). Its value depends on the airflow velocity, gas properties (density, viscosity, thermal conductivity), surface geometry of the part, and the size of the temperature difference. The emissivity is a dimensionless physical parameter characterizing the ability of a material surface to dissipate heat through thermal radiation. Its value is between 0 (ideal reflector) and 1 (ideal blackbody). The emissivity defines the ratio of the radiation capacity of an actual surface to that of an ideal blackbody surface at the same temperature. It depends on the material type, surface roughness, degree of oxidation, and temperature range.

[0042] In the implementation of the multiphysics topology optimization algorithm, the variable density method is used as the core implementation method. This method iteratively calculates by establishing a mathematical correspondence between the relative density of materials and their physical properties. Physical parameters such as the elastic modulus of the materials are expressed as functions of the relative density. At the beginning of each iteration, a finite element analysis is first performed on the current material layout to check whether its stress level and deformation meet the preset stress constraint and deformation constraint conditions. The stress constraint condition requires that the maximum equivalent stress of the structure does not exceed the allowable stress value of the material, and the deformation constraint condition requires that the maximum deformation of the structure is less than the allowable deformation threshold. Subsequently, based on the temperature field distribution data and stress field distribution data obtained from the thermo-mechanical coupled multiphysics finite element analysis, the derivatives of the objective function and constraints with respect to the design variables are calculated through sensitivity analysis. Based on these derivative information, the material density distribution is updated using the optimization criterion method or the moving asymptote method, so that the material density in high-stress areas increases and the material density in low-stress areas decreases. The convergence judgment criteria (including indicators such as the change in the objective function, the degree of constraint violation, and the change in design variables) determine whether the optimal material layout has been reached.

[0043] Finally, based on the optimized material density distribution, the threshold method is used to discretize the continuous density field into a solid material distribution, generating a non-uniform lattice support structure with spatially variable density characteristics. High-density regions form dense rods, while low-density regions form porous structures. Taking the optimized design of an aero-engine turbine blade support structure as an example, the implementation process of this method is explained in detail. The blade uses a nickel-based superalloy material (Inconel 718) with an elastic modulus of 205 GPa, a Poisson's ratio of 0.31, and a yield strength of 1100 MPa. During the optimization process, the allowable stress value is set to 1000 MPa (safety factor 1.1), and the allowable deformation threshold is 0.2 mm. The correlation between the material's relative density and elastic modulus is established using the variable density method. The elastic modulus of a completely dense material (relative density 1.0) is 205 GPa, while the elastic modulus of a material with a relative density of 0.3 is only 25 GPa. In each iteration calculation, a finite element analysis is first performed on the current material layout. It is found that in a certain iteration, the maximum equivalent stress reaches 1250 MPa (exceeding...). The maximum deformation was 0.25 mm (exceeding the allowable threshold of 25%). Subsequently, based on thermo-mechanical coupling analysis data, the temperature field distribution showed that the temperature gradient in the leading edge region of the blade reached 150°C / mm. Stress field analysis showed that the stress concentration factor in this region was 3.5. The derivative distribution of the objective function with respect to the design variables was calculated through sensitivity analysis. The moving asymptote method was used to update the material density: the relative density of the material was increased from 0.6 to 0.85 in the high-stress region of the leading edge, and the relative density was decreased from 0.7 to 0.45 in the low-stress region. After 68 iterations, the optimization results met all constraints: the maximum equivalent stress was reduced to 980 MPa, and the maximum deformation was reduced to 0.18 mm. Finally, a non-uniform lattice support structure with spatially variable density characteristics was generated.

[0044] A gradient transition zone with continuously varying stiffness is constructed at the interface between the support structure and the part body. The range of variation of the elastic modulus is determined based on the elastic modulus value of the part body material and the target modulus value of the outer end of the support structure. A variable density optimization method is used to generate a density gradient distribution in the contact area, so that the material density gradually decreases along the direction away from the part, and finally the continuous change of stiffness at the interface is achieved.

[0045] The internal support structure is printed using a support material that responds to external stimuli, specifically as follows: When selecting a support material with external stimulus response characteristics, it is first necessary to screen suitable smart material types based on printing process parameters and post-stimulation processing requirements. Material selection is based on the following criteria: the material must undergo controllable changes in mechanical properties under external stimuli (such as heat, light, and solvents); the material and the part's main material must have good compatibility at the printing temperature to avoid excessively strong or weak interfacial bonding; the material must maintain a stable physical state during printing and achieve a significant stiffness change after stimulus response. Typically, thermally responsive shape memory polymers (such as polyurethane-based materials) or solvent-responsive water-soluble polymers are preferred materials. During the selection process, candidate materials that meet the requirements are searched through material databases, and their stimulus response sensitivity, printability, and adhesion performance with the main material are verified through experimental testing to ultimately determine the optimal support material.

[0046] External stimulus response characteristics refer to the properties of a supporting material that change its physical and mechanical properties when subjected to a specific type of external energy or chemical environment.

[0047] When planning the printing path based on the support area distribution map and the non-uniform lattice support structure, the first step is to read the support strength requirements data of different levels marked on the support area distribution map. These data represent the support strength level of each area in the form of color depth or numerical markers. Next, the digital model of the non-uniform lattice support structure is analyzed to extract the spatial coordinates, density values, and geometric dimension parameters of the non-uniform lattice units. Then, a mapping relationship between the density of the non-uniform lattice units and the printing parameters is established: for high-density areas (density values ​​higher than the preset density threshold), a lower printing deposition rate and a larger material extrusion amount are set to ensure material packing density and structural strength; for low-density areas (density values ​​lower than the preset density threshold), a higher printing deposition rate and a smaller material extrusion amount are set to improve printing efficiency and save material. Finally, the movement trajectory of the print head is generated based on the geometric features of the lattice structure, including path sequence optimization, empty travel reduction, and interlayer connection processing, to ensure that the printing path completely covers the support area and avoids interference with the part.

[0048] For example, taking the printing path planning of the internal support structure of an aero-engine turbine blade as an example, the implementation process of this method is specifically explained. The blade is made of nickel-based high-temperature alloy material, and its support area distribution map adopts a color coding system: the dark red area (RGB:255, 0, 0) represents high-strength support requirements, corresponding to support strength level 5; the orange area (RGB:255, 165, 0) represents medium-strength support, level 3; and the light yellow area (RGB:255, 255, 0) represents low-strength support, level 1. By analyzing the digital model (STL format) of the non-uniform lattice support structure, spatial coordinate data of 285,000 lattice units are extracted. Among them, high-density units (relative density > 0.8) account for 35%, mainly distributed at the connection between the blade tenon and the blade body; low-density units (relative density < 0.4) account for 40%, distributed in the middle area of ​​the blade body. When establishing the printing parameter mapping relationship, the density threshold is set to 0. 6. For high-density areas (such as tenon joints, with an average density of 0.92), the printing deposition rate is set to 25 mm / s, the material extrusion rate is 0.15 cubic millimeters per second, and the nozzle temperature is 210°C to ensure sufficient material melting and dense deposition. For low-density areas (such as the middle of the blade, with an average density of 0.35), the printing deposition rate is set to 60 mm / s, the material extrusion rate is 0.06 cubic millimeters per second, and the nozzle temperature is adjusted to 205°C to improve printing efficiency. When generating printing paths based on the geometric features of the dot matrix structure, concentric circle path filling mode is used in high-density areas, with a path spacing of 0.2 mm and a layer thickness of 0.04 mm; sawtooth path filling is used in low-density areas, with a path spacing of 0.5 mm and a layer thickness of 0.06 mm. The path optimization algorithm reduces idle travel time by 35% and ensures the continuity of interlayer connection paths. In particular, a 50% path overlap rate is added in the 83° acute angle transition area to prevent material shortage.

[0049] Based on the support area distribution map and the non-uniform lattice support structure, the printing path of the support material is planned, and the specific implementation is as follows: The data interface reads the support demand intensity data of different levels marked on the support area distribution map. This data is stored in digital form and usually uses gradient color coding or numerical marking to represent the support demand intensity. High intensity areas correspond to dark colors or high values, and low intensity areas correspond to light colors or low values. The reading process includes parsing the data file format, extracting the coordinate range and intensity value of each area, and converting it into an internal data structure for subsequent processing. The intensity data is associated with spatial location to form the support area distribution map.

[0050] Analyzing the spatial distribution characteristics and density variation patterns of non-uniform lattice elements in a non-uniform lattice support structure is a key step in printing path planning. This process involves reading the digital model file of the non-uniform lattice structure (such as AMF or 3MF format) and extracting the spatial coordinates, geometric dimensions, and relative density values ​​of each non-uniform lattice element.

[0051] First, a spatial index structure for non-uniform lattice units is established. An octree or KD tree algorithm is used to manage the spatial partitioning of the units. The center coordinates and boundary range of each unit are calculated. Then, the spatial distribution characteristics of the units are analyzed, including calculating the distribution density of units in the X, Y, and Z directions, identifying the spatial positional relationship between high-density unit clusters and low-density unit clusters, and analyzing the directional and periodic characteristics of the unit arrangement.

[0052] To analyze the density variation patterns, the distribution range of density values ​​throughout the entire structure is first statistically analyzed, and the probability density function of the density distribution is calculated to identify regions with drastic density gradient changes. Then, the correlation between density values ​​and spatial location is analyzed, and a mathematical model of density values ​​varying with coordinates is established. Finally, abrupt density transition interfaces and gradual transition regions are identified, and the spatial distribution patterns and geometric characteristics of these regions are analyzed. Principal component analysis (PCA) is used to determine the main direction of density distribution change, and Fourier transform is used to analyze the periodicity of the density distribution. The entire process is accelerated using parallel computing technology, and statistical analysis is performed on massive amounts of non-uniform lattice unit data. Finally, a complete descriptive report containing spatial distribution characteristics and density variation patterns is generated.

[0053] Non-uniform lattice elements refer to the basic building blocks of lattice structures with spatial and density characteristics generated by the variable density method.

[0054] When planning the printing path based on the geometric model of a non-uniform lattice support structure, the 3D model is first sliced. This process employs an adaptive layer thickness algorithm, dynamically adjusting the layer thickness according to the model's geometric complexity. Smaller layer thicknesses are used in areas with large curvature variations to ensure accuracy, while larger layer thicknesses are used in flat areas to improve efficiency. The slicing process discretizes the 3D model into a series of 2D cross-sections parallel to the construction platform. The 2D contour trajectory of each layer is obtained by calculating the intersection lines between the model and each slicing plane. These contour trajectories consist of a series of continuous line segments, accurately describing the boundary of the area to be filled in that layer. After obtaining the 2D contour trajectories, the printing path is then calculated based on the comparison between the non-uniform lattice element density distribution data and a preset density threshold. The layer region is divided into different filling regions. This process first meshes the internal region of each layer contour into pixel units, with each pixel unit corresponding to a spatial location. Then, the density value of that location in the non-uniform dot matrix is ​​read and compared with a preset density threshold (usually 0.6). Pixels with density values ​​higher than the preset density threshold are classified as high-density filling regions, which require denser material deposition to ensure structural strength. Pixels with density values ​​lower than the preset density threshold are classified as low-density filling regions, which can use sparser material deposition to improve efficiency. After the region division is completed, the system assigns different filling parameters and path strategies to different regions to ensure that the printing path is precisely matched with the structural mechanical performance requirements.

[0055] When planning printing paths based on non-uniform lattice density distribution, the model area is first divided into high-density and low-density regions according to a preset density threshold. For regions with density values ​​higher than the preset threshold (usually 0.6), a concentric circle path filling mode is used to generate a dense material deposition path. This dense material deposition path generation process starts from the inner starting point of the contour and expands outward along a spiral trajectory. The path spacing is set to a small first spacing value (usually 0.2-0.4mm) to ensure the compactness of the material deposition and structural strength. The path generation sequence of these high-density regions is prioritized to ensure the structural stability of critical load-bearing areas during printing. For regions with density values ​​lower than the preset density threshold, a zigzag path filling mode is used to generate a sparse material deposition path. This path generates reciprocating straight lines along the contour direction, and the path spacing is set to a small first spacing value (usually 0.2-0.4mm) to ensure the compactness of the material deposition and structural strength. A larger second spacing value (typically 0.6-1.0 mm) is set to improve printing efficiency and save material. The generation of sparse material deposition paths is performed after the high-density area paths are completed. This sequential arrangement ensures that structural stability takes precedence over printing efficiency. During path generation, motion optimization is performed on both paths, including acceleration planning, corner smoothing, and minimization of idle travel. Finally, the concentric circle paths in the high-density area and the zigzag paths in the low-density area are integrated to generate a printhead movement trajectory containing complete coordinate positioning information (X, Y, Z coordinate sequence), motion control parameters (moving speed, acceleration, jerk), and material deposition instructions (extrusion amount, deposition rate). This trajectory data also includes special processing instructions for interlayer connection paths and transition areas to ensure the continuity of the printing process and the consistency of material deposition.

[0056] Taking the printing of the support structure for an aero-engine turbine blade (material: Inconel 718) as an example, the blade support area is first divided into high-density and low-density areas based on a preset density threshold of 0.6. In the high-density area (average density 0.85) at the connection between the blade tenon and the blade body, a concentric circle path filling mode is adopted. Starting from the inner starting point of the contour (X=25.3mm, Y=18.7mm, Z=42.0mm), a dense material deposition path is generated by expanding outward along a spiral trajectory with a path spacing of 0.25mm. The system prioritizes planning paths for these areas. For the generation process, the deposition rate is set to 25 mm / s and the extrusion amount is 0.15 mm³ / mm to ensure the structural stability of this critical load-bearing area. In the low-density area (average density 0.35) in the middle of the blade, a 45° zigzag path filling mode is used to generate reciprocating straight paths along the contour direction. The path spacing is set to 0.75 mm, the deposition rate is increased to 55 mm / s, and the extrusion amount is reduced to 0.06 mm³ / mm to improve printing efficiency. The path generation in the low-density area is performed after the high-density area is completed. This sequential arrangement ensures that the tenon area forms a stable support first.

[0057] During path optimization, corner smoothing is performed on high-density paths (minimum radius of curvature 0.3mm), and idle travel optimization is implemented on low-density paths (reducing idle travel distance by 35%). The final integrated printhead movement trajectory contains 285,000 coordinate points, with a total path length of 120m in the high-density area and 85m in the low-density area. Motion parameters include: maximum printing speed of 100mm / s, acceleration limit of 1200mm / s², and includes interlayer connection instructions to ensure precise connection of interlayer paths from Z=42.0mm to Z=42.06mm.

[0058] The process of mapping the determined deposition rate, extrusion rate control parameters, and movement trajectory into printhead action commands is a multi-layered parameter conversion and command generation process. First, the movement trajectory data obtained through path planning is read. This data includes the printhead's coordinate sequence in three-dimensional space (X, Y, Z coordinate points) and corresponding motion parameters. Then, based on the density characteristics of the area where each path segment is located, a preset parameter mapping rule is invoked to convert the relative density value into specific deposition rate and extrusion rate values. The deposition rate mapping uses a linear interpolation algorithm, calculating specific values ​​based on the density value within a preset minimum and maximum deposition rate range. The extrusion rate mapping uses an exponential relationship model to ensure that the material bulk density in high-density areas meets the requirements. Next, these parameters are converted into specific machine commands. The coordinate trajectory is converted into G0 (rapid traverse) and G1 (linear interpolation traverse) commands in G-code, each command containing the target coordinate point and feed rate. The deposition rate is converted into extruder motor speed control parameters, reflected in the linear traverse commands through the E value (extrusion rate parameter). Extrusion rate adjustment is achieved by controlling the stepping pulse frequency and duty cycle of the feed motor, specifically manifested as an increment of the E value in the G-code. The travel speed is controlled via the F parameter (feed rate), with different feed rates set for different areas based on path curvature and accuracy requirements. Temperature control is converted into M104 (set extruder temperature) and M109 (wait for the extruder to reach temperature) commands to ensure temperature stability during printing. Finally, the system sorts and optimizes all commands according to time and spatial order, adding necessary start / stop, retraction, and layer switching commands to generate a complete printing command set. This command set also includes error detection and printing progress monitoring commands to ensure the reliability and monitorability of the printing process.

[0059] The planned printing path is verified through virtual printing simulation. Using simulation software (such as Simplify3D or a custom simulation tool), the printing instruction set is loaded to simulate the print head's movement trajectory and material deposition process. During the simulation, the presence of path interference (e.g., print head collision with already printed structures), uniform material deposition (e.g., matching of extrusion volume and speed), and reasonable printing time are detected. Based on the simulation results, printing parameters are optimized, such as adjusting the speed curve or correcting the path sequence, to ensure the reliability of actual printing.

[0060] During the printing process, environmental parameters are controlled to maintain the support material in a state of initial stiffness. Specifically, this is implemented as follows: First, a correspondence between the physicochemical properties of the support material and the target values ​​of environmental parameters is established. The target values ​​of environmental parameters include temperature control, humidity control, and atmosphere composition control. The temperature control target value is determined based on the glass transition temperature or melting point of the support material and is usually set within a safe range of 10-15°C lower than the critical temperature at which the material undergoes a stiffness transition to prevent accidental softening. The humidity control target value is set according to the hygroscopic characteristics of the material and is usually controlled below the material's critical hygroscopic value to avoid moisture affecting the material's performance. The atmosphere composition control target value is configured according to the material's requirements for oxidation resistance and anti-deterioration. Usually, a mixture of inert gas (such as nitrogen or argon) and air is used, and the oxygen content is controlled below 1% to prevent oxidation. All environmental parameter control target values ​​are verified and optimized through material property testing and process experiments to form a complete set of control parameters.

[0061] The first stiffness state refers to the specific physical state maintained by the support material during the 3D printing process through environmental parameter control. In this state, the elastic modulus of the support material reaches the upper limit of its performance range (for example, for thermoplastic polyurethane materials, the elastic modulus is maintained at 1.2-1.5 GPa), and the deformation resistance meets the requirements of the printed support (for example, the compression deformation is less than 5%). The maintenance of the first stiffness state depends on the precise control of environmental parameters, especially the temperature must be strictly kept below the material softening point, while the humidity and atmosphere composition must be stable within the target range.

[0062] Atmosphere composition refers to the mixing ratio of various gas components in the printing environment, typically including... The mixture with a small amount of other gases is prepared by first determining the target proportions of each gas based on material requirements (e.g., Then, the gas is precisely proportioned using a gas mixing device. Gas mixing is achieved using a mass flow controller, and the flow rate of each gas is calculated based on the target ratio: when the total flow rate is set to 10 L / min, The mixed gas is fed into the printing chamber through a circulation system to ensure a uniform atmosphere distribution.

[0063] Real-time acquisition of printing environment parameters, including temperature, humidity, and atmosphere composition parameters. Temperature parameters are acquired using PT100 (100 ohms resistance at 0°C) temperature sensors distributed at multiple locations within the printing chamber, with a sampling frequency of 10Hz and an accuracy of ±0.1°C. Humidity parameters are acquired using capacitive humidity sensors, with a sampling frequency of 5Hz and an accuracy of ±2%RH. Atmosphere composition parameters are acquired using an infrared gas analyzer or electrochemical sensor, with a sampling frequency of 1Hz and an accuracy of [missing information]. All sensor data is converted into digital signals through a data acquisition card and transmitted to the central control system to form a real-time environmental data stream.

[0064] During the environmental parameter comparison and analysis process, the system compares the real-time collected environmental parameters with the environmental parameter control target values ​​in detail. For each monitoring parameter, the system calculates the deviation between the measured value and the target value, which is obtained by subtracting the target value from the measured value. At the same time, it calculates the relative deviation rate, which is obtained by dividing the absolute value of the deviation by the target value and then multiplying by 100%. The system further analyzes the changing trend of parameter deviations, uses the moving average algorithm to calculate the short-term rate of change of the parameters, and predicts the future direction of parameter changes. All comparison and analysis results are stored in the system database and generate real-time updated monitoring charts for visualization. When the absolute deviation of any environmental parameter exceeds its allowable fluctuation range, the system immediately triggers an early warning mechanism. For example, the allowable fluctuation range for temperature is ±2 degrees Celsius, the allowable fluctuation range for humidity is ±5% relative humidity, and the allowable fluctuation range for oxygen concentration is ±0.2%.

[0065] When environmental parameters deviate from their control targets, the system immediately activates the environmental control device to perform parameter correction. For temperature parameters deviating from their control targets, the system activates the corresponding temperature control equipment based on the direction of deviation: when the monitored temperature is below the control target, the heating device is automatically activated, and the required heating power is calculated using proportional and integral control algorithms based on the current temperature deviation and its cumulative deviation; when the monitored temperature is above the control target, the cooling circulation system is activated to remove excess heat through refrigerant circulation. For humidity parameters deviating from their control targets, the system activates the humidity control equipment based on the direction of humidity deviation: when the ambient humidity is below the control target, the humidification device is activated, and the required humidification amount is calculated based on the humidity deviation and the space area; when the ambient humidity is above the control target, the dehumidification device is activated, and the operating time of the dehumidification device is determined based on the humidity deviation and the time coefficient. For atmosphere composition parameters deviating from their control targets, the system adjusts the gas mixing device: when the oxygen concentration is too high, the flow rate of inert nitrogen is increased; when the carbon dioxide concentration is too low, the supply flow rate of carbon dioxide is increased accordingly. The entire calibration process adopts a closed-loop feedback control mechanism. The system monitors parameter changes in real time and dynamically adjusts the operating parameters of each regulating device to ensure that environmental parameters are stably maintained within the target range.

[0066] Continuous monitoring of environmental parameter trends and dynamic adjustment of environmental control device operating parameters based on monitoring results. The monitoring process includes recording historical data, establishing time series models (such as ARIMA models), predicting future parameter changes, and preemptively adjusting the control device based on the predictions: for example, increasing cooling power in advance if temperature is predicted to rise, and starting the humidifier in advance if humidity is predicted to fall. Dynamically adjusted parameters include the proportional, integral, and derivative coefficients of PID control, as well as the device's operating cycle and intensity. Through this proactive control, environmental parameters are kept stable within the target range.

[0067] After printing, external stimuli are applied to cause the supporting material to change to a second stiffness state lower than the first stiffness. Specifically, the process is as follows: When determining the type and parameters of external stimulus required to induce a stiffness change in the support material, the chemical composition and physical properties of the support material are first analyzed. For thermally responsive materials (such as shape memory polymers), thermal stimulation is selected as the primary mode of action. Key parameters include stimulation temperature, heating rate, holding time, and temperature uniformity. The stimulation temperature should be set within 10-20°C above the material's glass transition temperature (Tg), and the heating rate should be controlled at 2-5°C / min to ensure uniform heating of the material. The holding time is calculated and determined based on the material thickness and thermal conductivity. For solvent-responsive materials (such as water-soluble polymers), solvent stimulation is selected as the primary mode of action. Key parameters include solvent concentration, application temperature, stimulation time, and penetration depth. The solvent concentration is usually set as a 60-80% aqueous solution, and the application temperature is set at 40-60°C based on the material's solubility characteristics. The stimulation time is determined through experimental testing. All parameters are optimized through material performance testing and process experiments to establish a correlation curve between the stimulation parameters and the degree of stiffness change.

[0068] The printed components are placed in a dedicated stimulation application device. For thermal stimulation, a precision constant temperature chamber with forced convection is used to ensure uniform temperature distribution (fluctuation ≤ ±1°C). The components are fixed in the center of the working area by special clamps to ensure that all surfaces are exposed to the thermal environment without obstruction. For solvent stimulation, an immersion tank with stirring function is used to maintain uniform solvent concentration (concentration deviation ≤ ±2%). The components are fixed by a mesh support to ensure complete immersion and full contact between each surface and the solvent. The device is equipped with multi-point sensors to monitor the spatial distribution of stimulation parameters in real time.

[0069] Stimulation is applied according to the preset external stimulus type and parameters. For thermal stimulation, a programmed temperature control method is used: the temperature is increased from room temperature to the target temperature (e.g., 75°C) at a rate of 3°C / min. After reaching the target temperature, the holding time is started. The temperature stability is maintained by PID (intelligent control algorithm). For solvent stimulation, the solvent concentration is controlled to be maintained at the set value (e.g., 70%). The temperature is maintained constant by a water bath. The stirring speed is controlled at 200-300 rpm (rpm is a physical unit used to set the rotation speed of the stirrer to ensure the uniformity of the solvent concentration) to ensure uniform concentration. Throughout the stimulation process, all parameters are recorded in real time and fed back to the control system.

[0070] During the application of stimuli, the physical state changes of the supporting material are monitored in real time. Monitoring indicators include: changes in elastic modulus (measured in real time using a dynamic mechanical analyzer), deformation (measured using a laser displacement sensor), and surface morphology changes (observed using an optical microscope). For thermal stimuli, the temperature-modulus change curve is monitored, and the sampling frequency is increased when the modulus value enters a rapid decline phase. For solvent stimuli, the swelling ratio and dissolution rate are monitored. High-speed video recording is initiated when significant swelling occurs on the surface. All monitoring data are correlated with time to establish a database of material state changes.

[0071] When the support material is detected to have reached the preset second stiffness state characteristics, the stimulation application is immediately stopped. The stopping determination is based on multiple indicators: the primary indicator is that the elastic modulus drops to the lower limit of the performance range (e.g., from 1.2 GPa to 15 MPa), and the secondary indicator is that the deformation reaches a predetermined threshold (e.g., elongation ≥ 100%) or the surface condition meets the requirements (e.g., complete swelling). The stopping process includes: for thermal stimulation, the heating power is immediately cut off and the cooling fan is started; for solvent stimulation, the solvent is immediately discharged and the rinsing and drying procedures are started. After stopping, the condition of the component is confirmed to ensure that the support material has completed the stiffness transformation.

[0072] The second stiffness state refers to the specific physical state that the supporting material reaches after being stimulated and transformed. In this state, the material's elastic modulus is reduced to the lower limit of the performance range (usually 1-5% of the original modulus), and its flexibility is significantly improved (elongation at break ≥150%), which can meet the mechanical requirements for non-destructive removal. The verification methods include: modulus testing (using a portable hardness tester), flexibility testing (using a bending test), and peel force testing (using a tensile test). All verification indicators must meet the predetermined standards before subsequent removal operations can be carried out.

[0073] Based on the flexibility of the support structure under the second stiffness state, the support structure is removed from the interior of the part, specifically as follows: Before proceeding with the removal operation, it is essential to first detect and verify whether the support material has reached the preset second stiffness state. The detection process employs a multi-index comprehensive verification method: the real-time elastic modulus of the support material is measured using a portable dynamic mechanical analyzer to confirm that it has decreased to the lower limit of the performance range (e.g., from 1.2 GPa at the time of printing to 15 MPa); the deformation recovery characteristics of the material are evaluated using a flexibility testing device, measuring its elongation at break (≥150%) and compression rebound rate (≥80%); a trial peeling operation is performed, using a standard force gauge to measure the peeling resistance, confirming that its value is below the preset resistance threshold (e.g., <2 N / cm); all test data are compared with the characteristic parameters of the second stiffness state; when the elastic modulus, flexibility, and peeling resistance all meet the requirements, the system generates a status confirmation signal, allowing subsequent removal operations to proceed.

[0074] Select specialized removal tools based on the location and shape of the support structure. For externally visible and accessible support structures, choose soft clamping tools (such as silicone clamps) and flexible scrapers; for support structures in internal enclosed cavities, insert specialized tools through pre-designed process channels in the part, including endoscopic visual clamps, flexible suction devices, and micro rotary cutting tools.

[0075] The removal operation is carried out by utilizing the high flexibility of the support structure under the second stiffness state.

[0076] After the removal operation is completed, the parts are thoroughly inspected. An industrial endoscope is used to scan the internal cavity from all angles to check for any residual support material. The surface quality of the parts is measured with a surface roughness meter to confirm that the Ra (surface roughness evaluation index) value does not change by more than 0.2 μm. Dimensional accuracy is verified to ensure that the deviation of key dimensions is within the allowable range (±0.1 mm). If any residue or damage is found, it is immediately addressed until it fully meets the requirements.

[0077] The above embodiments can be implemented, in whole or in part, by software, hardware, firmware, or any other combination thereof. When implemented using software, the above embodiments can be implemented, in whole or in part, in the form of a computer program product.

[0078] Those skilled in the art will recognize that the modules and algorithm steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of this application.

[0079] In addition, the functional modules in the various embodiments of this application can be integrated into one processing module, or each module can exist physically separately, or two or more modules can be integrated into one module.

[0080] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

[0081] In conclusion, the above description is only a preferred embodiment of the present invention and is 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 within the protection scope of the present invention.

Claims

1. A method for 3D printing a flexible structure support with adjustable variable stiffness, characterized in that... ； S1. Receive the 3D model data of the part to be printed, identify the overhang structure and critical stress area including the internal closed cavity based on geometric features, and generate a support area distribution map including the support requirements of the internal non-accessible area. S2. Based on the support area distribution map, a non-uniform lattice support structure suitable for the internal closed cavity is generated by a multiphysics topology optimization algorithm. S3. The internal support structure is printed using a support material that responds to external stimuli; S4. Control environmental parameters during the printing process to maintain the support material in a state of initial stiffness; S5. After printing, external stimuli are applied to transform the support material into a second stiffness state that is lower than the first stiffness. S6. Based on the flexibility of the support structure under the second stiffness state, remove the support structure from the inside of the part.

2. The method for 3D printing support of a flexible structure with adjustable variable stiffness according to claim 1, characterized in that: The process involves receiving the 3D model data of the part to be printed, identifying the overhanging structure and critical stress region, including internal enclosed cavities, based on geometric features, and generating a support area distribution map that includes the support requirements for internal non-accessible areas. Specific steps include: Receive the 3D model data of the part to be printed through a 3D data interface; Geometric feature recognition algorithms were used to analyze the outline of the overhanging structure and the internal closed cavity structure in the 3D model. The boundary range of the suspended area that needs to be supported is determined based on the preset suspension angle threshold judgment criteria. The critical stress region that occurs during the printing process is identified using the finite element stress cloud diagram analysis method. The identified overhanging area boundary range and critical stress area are spatially superimposed and fused. Based on the spatial superimposition and fusion processing results, a support area distribution map including the support requirements of the internal inaccessible areas is generated.

3. The method for 3D printing support of a flexible structure with adjustable variable stiffness according to claim 2, characterized in that: The critical stress region during the printing process is identified using the finite element stress cloud diagram analysis method. Specific steps include: A finite element analysis model is established for finite element calculations. The finite element analysis model includes material property parameters and printing process parameters. Based on the established finite element analysis model, temperature load conditions and mechanical constraint conditions are set during the printing process; Temperature load conditions refer to the temperature field distribution and its variation with time on the finite element analysis model. Mechanical constraints refer to the restrictions imposed on the displacement degrees of freedom of a finite element analysis model; By using the set temperature load conditions and mechanical constraint conditions, finite element calculations of the thermo-mechanical coupled field are performed to obtain stress distribution data during the printing process; Stress distribution data refers to a series of numerical results obtained through thermo-mechanical coupled field finite element calculations, which are used to measure the stress state at various locations inside the structure during the printing process. Thermo-mechanical coupled field refers to a multi-physics field coupled analysis environment in finite element analysis that simultaneously considers the interaction between temperature field and stress field. By establishing the interaction relationship between temperature distribution and structural deformation, it simulates the influence of thermal expansion effect and material property changes caused by temperature change on the mechanical behavior of structure under actual working conditions. The calculated stress distribution data is used to generate a finite element stress cloud map through color mapping and contour lines. Analyze the stress regions exceeding the material's yield strength in the finite element stress contour plot; The yield strength of a material refers to the critical stress value at which a material undergoes plastic deformation under stress. Identify regions where the spacing between stress contour lines decreases in the stress finite element stress cloud map, locate locations where the rate of change of curvature of stress contour lines exceeds a set curvature change threshold, calculate the ratio of the stress difference between adjacent nodes to the average change level, screen out node clusters where the stress difference is greater than a specific multiple of the average change level, and determine the geometric abrupt regions where the node clusters are located and the adjacent regions of material discontinuities as critical stress regions. Stress contour lines are continuous curves that connect points with the same stress value in a finite element stress contour plot. A node is a connection point of mesh elements formed after discretizing a continuous structure in finite element analysis. A node cluster refers to a set of nodes that have consistent statistical distribution characteristics of stress values ​​and are spatially adjacent in a finite element stress cloud diagram.

4. The method for 3D printing support of a flexible structure with adjustable variable stiffness according to claim 3, characterized in that: Based on the support region distribution map, a non-uniform lattice support structure suitable for an internal closed cavity is generated using a multiphysics topology optimization algorithm. Specific steps include: Based on the support demand intensity of different regions in the support area distribution map, an optimization function is established with the objectives of minimizing material usage and maximizing structural stiffness. Set the stress constraints and deformation constraints that the support structure must meet during the printing process; Stress constraints refer to the limitations imposed on the maximum stress value in structural optimization design to ensure safety. Deformation constraint conditions refer to the restrictions set on the maximum deformation in structural optimization design to meet functional requirements; A thermo-mechanical coupled multiphysics finite element analysis was performed on the support region to obtain the distribution data of the temperature field and stress field. The distribution data of the temperature field and stress field were used to simultaneously characterize a series of numerical results of the temperature state and mechanical state of the support region. The variable density method is used as a multiphysics topology optimization algorithm. The correspondence between material density and physical properties is established for iterative calculation. In each iteration, it is checked whether the stress level and deformation under the current material layout meet the stress constraint and deformation constraint conditions. Based on the temperature field and stress field distribution data obtained from the thermo-mechanical coupled multiphysics finite element analysis, the material density distribution is updated. The optimal material layout is determined by convergence judgment. A non-uniform lattice support structure is generated based on the optimized material density distribution results. A gradient transition zone with continuously varying stiffness is constructed at the interface between the support structure and the component body. The elastic modulus of the gradient transition zone decreases from the component body to the outer end of the support structure.

5. The method for 3D printing support of a flexible structure with adjustable variable stiffness according to claim 4, characterized in that: The internal support structure is printed using a support material that responds to external stimuli. Specific steps include: Select a support material with external stimulus response characteristics as the printing material; External stimulus response characteristics refer to the properties of a supporting material that change its physical and mechanical properties when subjected to a specific type of external energy or chemical environment. Based on the distribution map of the support area and the non-uniform lattice support structure, plan the printing path of the support material.

6. The method for 3D printing support of a flexible structure with adjustable variable stiffness according to claim 5, characterized in that: Based on the support area distribution map and the non-uniform lattice support structure, the printing path of the support material is planned. The specific steps include: Read the support demand intensity data of different levels marked on the support area distribution map; Analysis of the spatial distribution characteristics and density variation law of non-uniform lattice elements in a non-uniform lattice support structure; Non-uniform lattice elements refer to the basic building blocks in a lattice structure with spatial and density characteristics generated by the variable density method. The deposition rate and extrusion rate control parameters of the support material are determined based on the non-uniform lattice unit density distribution. When planning the printing path based on the geometric model of the non-uniform lattice support structure, the three-dimensional model is first sliced ​​to obtain the two-dimensional contour trajectory of each layer. Based on the comparison between the density distribution data of the non-uniform lattice unit and the preset density threshold, each layer is divided into different filling areas. For areas with density values ​​higher than the preset density threshold, a concentric circle path filling mode is used and a first spacing value is set to generate a dense material deposition path. Dense material deposition paths for areas with density values ​​higher than the preset density threshold are planned first. The generation of dense material deposition paths starts from the inside of the contour and expands outward in a spiral manner. For areas with density values ​​lower than the preset density threshold, a zigzag path filling mode is used and a second spacing value is set to generate a sparse material deposition path. The sparse material deposition path generates a reciprocating straight line along the contour direction, where the first spacing value is smaller than the second spacing value. The generation of sparse material deposition paths is performed after the generation of dense material deposition paths. All path data are integrated to generate a complete printhead movement trajectory that includes coordinate positioning and motion control. The determined deposition rate and extrusion amount control parameters and movement trajectory are mapped into action instructions for the print head on the travel path of the corresponding area, thereby generating a complete set of printing instructions including movement trajectory coordinate positioning instructions, material deposition rate control instructions, extrusion amount adjustment instructions, movement speed and temperature control. The planned printing path is verified through virtual printing simulation.

7. A method for 3D printing support of a flexible structure with adjustable variable stiffness according to claim 6, characterized in that: During the printing process, environmental parameters are controlled to maintain the support material at its initial stiffness. Specific steps include: Establish environmental parameter control target values ​​corresponding to the first stiffness state of the supporting material. The environmental parameter control target values ​​include temperature control target values, humidity control target values, and atmosphere composition control target values. The first stiffness state refers to the specific physical state maintained by the support material through environmental parameter control during the 3D printing process. Under the first stiffness state, the elastic modulus of the support material reaches the upper limit of its performance range and its deformation resistance meets the requirements of the printing support. Atmosphere composition refers to the mixing ratio of various gas components in the printing environment space; Real-time acquisition of printing environment parameters, including temperature, humidity, and atmosphere composition parameters; The collected environmental parameters are compared and analyzed with the environmental parameter control target values; When environmental parameters are detected to deviate from the target values ​​for environmental parameter control, the environmental control device is activated to correct the parameters. Continuously monitor the changing trends of environmental parameters and dynamically adjust the operating parameters of the environmental control device based on the monitoring results.

8. A method for 3D printing support of a flexible structure with adjustable variable stiffness according to claim 7, characterized in that: After printing, external stimuli are applied to transform the support material into a second stiffness state lower than the first stiffness. The specific steps include: Determine the type and parameters of external stimuli required to cause a change in the stiffness of the support material. External stimulus parameters refer to the physical quantities of the stimulus type that need to be controlled in order to achieve a change in the stiffness state of the support material. External stimulus types include thermal stimulation and solvent stimulation. Place the printed component into the stimulus application device; Apply external stimuli according to the preset external stimulus type and external stimulus parameters; Monitor changes in the physical state of the support material during stimulus application; When the supporting material is detected to have reached the preset second stiffness state characteristic, the stimulation application is stopped; The second stiffness state refers to the specific physical state that the support material changes to after printing by applying external stimuli. In the second stiffness state, the elastic modulus of the support material is reduced to the lower limit of its performance range and the flexibility meets the requirements for non-destructive removal.

9. A method for 3D printing a flexible structure with adjustable variable stiffness according to claim 8, characterized in that: Based on the flexibility of the support structure under the second stiffness state, the support structure is removed from the interior of the part. The specific steps include: Check whether the supporting material has reached the preset second stiffness state; The removal operation is carried out using a special tool by utilizing the flexibility properties obtained by the support structure under the second stiffness state.

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