3D printing tree support automatic generation method and system based on SLA light curing process and 3D printing equipment

Abstract

The embodiment of the invention relates to the technical field of additive manufacturing, and discloses a 3D printing tree support automatic generation method and system based on an SLA photocuring process, and the method comprises the steps: obtaining a to-be-printed three-dimensional grid model and placement azimuth information; identifying all overhanging areas needing to be supported in the three-dimensional grid model, and calculating the normal direction and the required supporting force of each overhanging point of the overhanging areas; simulating the fluid static pressure of the resin liquid on the supporting structure and the equivalent shrinkage force corresponding to curing shrinkage in the printing process through a pre-constructed mechanical model to obtain the corrected supporting force; performing tree-supported growth simulation by adopting an improved space colonization algorithm to obtain a growth skeleton; and optimizing and verifying the growth skeleton through a multi-objective optimization algorithm, and iteratively optimizing to generate a final tree support structure. According to the embodiment of the invention, an automatic, efficient and reliable tree support generation method is realized.

Description

TECHNICAL FIELD

[0001] The embodiment of the present application relates to the field of additive manufacturing technology, in particular to a 3D printing tree support automatic generation method, system and 3D printing equipment based on SLA light curing process. BACKGROUND

[0002] At present, in the SLA 3D printing process, since the resin material is in a liquid state, support structures must be added to the suspended part of the printed part to prevent the model from collapsing and deforming. The traditional support (such as straight grid support) has the following disadvantages: the support has a large contact surface with the model, which wastes resin material and increases the amount of consumables. Since the support is firmly connected with the model, the model surface is easily damaged when the support is removed, affecting the appearance and precision, and making the post-processing difficult.

[0003] The automatic support generation function of the existing software (such as some commercial slicing software) is mostly based on simple geometric rules, and cannot adaptively optimize the number and position of the support, so a large amount of manual intervention and addition is often required, and therefore the degree of intelligence is low.

[0004] Tree support (Tree Support) is a kind of bionic support structure, which has the characteristics of taking the trunk as the base point and supporting the model through the branch-like fractal structure, and has the advantages of small contact point, easy stripping and less consumables. However, the existing tree support generation algorithm faces challenges: first, the mechanical stability is insufficient: when printing large or heavy models, the traditional tree support may collapse due to insufficient strength. Second, the contradiction between generation efficiency and reliability: it is difficult to find the optimal solution between "sufficient support" and "not excessive support" in automatic generation. Third, lack of SLA process pertinence: the existing method does not fully consider the influence of resin viscosity, light curing shrinkage and other specific factors in SLA process on the stability of the support.

[0005] Therefore, an intelligent system capable of automatically, efficiently and reliably generating tree-shaped supports suitable for SLA process is urgently needed. SUMMARY

[0006] In view of the above problems, the embodiment of the present application provides a 3D printing tree support automatic generation method, system and 3D printing equipment based on SLA light curing process, which is used to solve the problems of low automation, low efficiency and poor reliability of the bionic support structure in the prior art.

[0007] According to one aspect of the embodiment of the present application, a 3D printing tree support automatic generation method based on SLA light curing process is provided, which comprises:

[0008] obtaining a three-dimensional grid model to be printed and placement orientation information of the three-dimensional grid model;

[0009] By analyzing the grid data of the three-dimensional mesh model, all overhanging areas needing support in the three-dimensional mesh model are identified, and the normal and required support force of each overhanging point of the overhanging area are calculated;

[0010] By simulating the hydrostatic pressure of the resin liquid on the support structure and the equivalent shrinkage force corresponding to the solidification shrinkage in the printing process through the pre-constructed mechanical model, the required support force is corrected according to the hydrostatic pressure and the equivalent shrinkage force, and a corrected support force is obtained;

[0011] According to the overhanging area, the normal of each overhanging point of the overhanging area, and the corrected support force, a growth simulation of tree support is performed by using an improved space colonization algorithm to obtain a growth skeleton; the growth skeleton includes a plurality of nodes and connecting lines between the nodes;

[0012] The growth skeleton is optimized and verified by a multi-objective optimization algorithm, when the verification fails, a new growth skeleton is generated by the improved space colonization algorithm, and the new growth skeleton is optimized and verified by the multi-objective optimization algorithm, until the verification passes, and the final tree support structure is generated by iterative optimization.

[0013] In an optional manner, the step of analyzing the grid data of the three-dimensional mesh model, identifying all overhanging areas needing support in the three-dimensional mesh model, and calculating the normal and required support force of each overhanging point of the overhanging area, specifically includes:

[0014] An angle between the normal vector of each triangular facet in the three-dimensional mesh model and the normal vector of the printing platform is calculated;

[0015] The triangular facets with an angle greater than a dynamic angle threshold are marked as overhanging facets; the dynamic angle threshold is dynamically adjusted according to the local geometric features of the triangular facets; wherein the local geometric features include but are not limited to curvature, area, and continuity with adjacent facets;

[0016] The overhanging facets are voxelized or spatially sampled to generate a plurality of target points representing the overhanging area, thereby obtaining an overhanging area; the target points carry a support urgency weight, and the support urgency weight is determined according to the inclination angle, area, and curvature of the region where the overhanging facet is located.

[0017] In an optional manner, the step of calculating the required support force of each overhanging point of the overhanging area specifically includes:

[0018] According to the target point corresponding to the overhanging area, the model wall thickness empirical value, and the resin material density, the static gravity required to be borne by the target point is estimated;

[0019] determine a solidification shrinkage stress coefficient according to the solidification shrinkage characteristics of the resin material; the solidification shrinkage stress coefficient is calculated based on a shrinkage model of material properties and printing process parameters; the printing process parameters include layer thickness, exposure time per layer, and light intensity;

[0020] calculate the required support force of the target point by the static gravity and the solidification shrinkage stress coefficient.

[0021] In an optional manner, the mechanical model is a finite element model or a truss structure model; the simulation result of the mechanical model is used to correct the required support force of the overhanging point, and the corrected support force is fed back to the improved spatial colonization algorithm to guide the growth direction and diameter of the tree branch; the fluid static pressure of the resin liquid on the support structure and the equivalent shrinkage force corresponding to the solidification shrinkage in the printing process are simulated by the pre-constructed mechanical model, and the required support force is corrected according to the fluid static pressure and the solidification shrinkage stress to obtain the corrected support force, which specifically includes:

[0022] discretize the support structure into a finite number of units;

[0023] for each unit, calculate the fluid static pressure P it bears according to the depth h of its center point, the resin density p, and the gravitational acceleration g fluid :

[0024] P fluid = p * g * h;

[0025] wherein the depth h is the vertical distance from the unit to the resin liquid surface of the current printing layer;

[0026] convert the fluid static pressure into an equivalent node force.

[0027] In an optional manner, the simulation result of the mechanical model is used to correct the required support force of the overhanging point, and the corrected support force is fed back to the improved spatial colonization algorithm to guide the growth direction and diameter of the tree branch; the fluid static pressure of the resin liquid on the support structure and the equivalent shrinkage force corresponding to the solidification shrinkage in the printing process are simulated by the pre-constructed mechanical model, and the required support force is corrected according to the fluid static pressure and the solidification shrinkage stress to obtain the corrected support force, which specifically includes:

[0028] calculate the equivalent shrinkage force F generated on the support structure due to the solidification shrinkage of the resin based on the volume shrinkage rate β, the elastic modulus E, and the printing process parameters of the resin material cure :

[0029] F cure = ∑ (β * E * A element );

[0030] The printing process parameters include layer thickness, exposure time and light intensity. element To support the micro-element area on the structure in contact with the solidification area;

[0031] The equivalent node force and the equivalent shrinkage force are used to correct the required support force, and a corrected support force is obtained.

[0032] In an optional manner, the improved space colonization algorithm includes the following growth rules:

[0033] The overhanging point generates an attractive force to the growth node within a set search radius, and the attractive force is positively correlated with the required support force of the overhanging point;

[0034] The growth node generates a repulsive force between the body and other branch structures of the three-dimensional mesh model to ensure the generation distance;

[0035] The growth direction of each growth node is determined by the vector resultant of all attractive forces and repulsive forces acting on the growth node;

[0036] The cross-sectional diameter of the branch is dynamically adjusted according to the total support force of the overhanging points required to be supported by the branch.

[0037] In an optional manner, the optimization objectives of the multi-objective optimization algorithm include: minimizing the total volume of the tree support structure, minimizing the number of contact points between the tree support structure and the model surface, and maximizing the mechanical safety factor of the tree support structure; The mechanical safety factor is obtained by finite element analysis or truss structure buckling analysis; The number of contact points is minimized, including preferentially setting the contact points on the low-curvature area of the model surface or the non-critical area specified by the user.

[0038] In an optional manner, the growth skeleton is optimized and verified by the multi-objective optimization algorithm, and when the verification fails, a new growth skeleton is generated by the improved space colonization algorithm, and the new growth skeleton is optimized and verified by the multi-objective optimization algorithm until the verification passes, and the final tree support structure is generated by iterative optimization, including:

[0039] The growth skeleton is converted into a three-dimensional mesh model;

[0040] The three-dimensional mesh model is subjected to collision detection, and the branch path is adjusted to eliminate interference with the model body;

[0041] Redundant branches with too close distance are merged, and functional branches with length below a threshold value are deleted.

[0042] In an optional manner, after the three-dimensional mesh model to be printed is obtained, the method further includes:

[0043] receiving a user's instruction of adjusting the placement orientation of the three-dimensional mesh model, or receiving a user's instruction of marking a specific region of the model as forbidden to generate support.

[0044] According to another aspect of the embodiments of the present application, a system for automatically generating tree support for 3D printing based on SLA light curing process is provided, comprising:

[0045] an acquisition module configured to acquire a three-dimensional mesh model to be printed and placement orientation information of the three-dimensional mesh model;

[0046] a calculation module configured to identify all overhanging regions in the three-dimensional mesh model that need support by analyzing mesh data of the three-dimensional mesh model, and calculate normal of each overhanging point of the overhanging regions and required support force;

[0047] a simulation module configured to simulate fluid static pressure of resin liquid on support structure and equivalent shrinkage force corresponding to curing shrinkage in the printing process by a pre-constructed mechanical model, correct the required support force according to the fluid static pressure and the equivalent shrinkage force, and obtain a corrected support force;

[0048] a growth module configured to generate a growth skeleton by using an improved space colonization algorithm for growth simulation of tree support according to the overhanging regions, the normal of each overhanging point of the overhanging regions, and the corrected support force; the growth skeleton comprises a plurality of nodes and connecting lines between the nodes;

[0049] a verification module configured to optimize and verify the growth skeleton by a multi-objective optimization algorithm, continue to generate a new growth skeleton by the improved space colonization algorithm when the verification fails, optimize and verify the new growth skeleton by the multi-objective optimization algorithm, and iterate until the verification passes to generate a final tree support structure.

[0050] According to another aspect of the embodiments of the present application, a 3D printing device is provided, comprising the system for automatically generating tree support for 3D printing based on SLA light curing process.

[0051] The embodiments of the present application acquire a three-dimensional mesh model to be printed and placement orientation information, identify all overhanging regions in the three-dimensional mesh model that need support, and calculate normal of each overhanging point of the overhanging regions and required support force; simulate fluid static pressure of resin liquid on support structure and equivalent shrinkage force corresponding to curing shrinkage in the printing process by a pre-constructed mechanical model to obtain a corrected support force; generate a growth skeleton by using an improved space colonization algorithm for growth simulation of tree support; and optimize and verify the growth skeleton by a multi-objective optimization algorithm to iterate and generate a final tree support structure, thereby realizing an intelligent, automatic, and high-success-rate tree support generation method.

[0052] The above description is only a summary of the technical solutions of the embodiments of the present application, in order to more clearly understand the technical means of the embodiments of the present application, and to be implemented according to the content of the specification, and in order to make the above and other purposes, features and advantages of the embodiments of the present application more obvious and easy to understand, the specific embodiments of the present application are described below. BRIEF DESCRIPTION OF DRAWINGS

[0053] The accompanying drawings are included to provide a further understanding of the application and are incorporated herein and constitute a part of the detailed description. It should be noted that the accompanying drawings illustrate the embodiments of the present application and therefore are not to be considered limiting of the present application. In the drawings:

[0054] Figure 1 A flowchart of a method for automatically generating tree support for 3D printing based on an SLA light curing process is shown.

[0055] Figure 2 A structural diagram of a system for automatically generating tree support for 3D printing based on an SLA light curing process is shown. DETAILED DESCRIPTION

[0056] Exemplary embodiments of the present application will be described herein below with reference to the accompanying drawings. Although exemplary embodiments of the present application are illustrated in the drawings, it is understood that the present application can be implemented in various forms and should not be limited by the embodiments set forth herein.

[0057] Tree support is a kind of bionic support structure, which is characterized by taking tree trunk as the base point and supporting the model through tree branch fractal structure, and has the advantages of small contact point, easy peeling and less material consumption. However, the existing tree support generation algorithm is challenged: 1. Insufficient mechanical stability: when printing large or heavy models, the traditional tree support may collapse due to insufficient strength. 2. Contradiction between generation efficiency and reliability: it is difficult to find the optimal solution between "sufficient support" and "not excessive support" in automatic generation. 3. Lack of SLA process pertinence: the existing method does not fully consider the influence of resin viscosity, light curing shrinkage and other specific factors in SLA process on support stability. Based on this, the present application provides an intelligent system capable of automatically, efficiently and reliably generating tree support suitable for SLA process.

[0058] Figure 1 A flowchart of a method for automatically generating tree support for 3D printing based on an SLA light curing process is shown, which is executed by a 3D printing device. As shown in Figure 1 The method comprises the following steps:

[0059] Step 110: Obtain a three-dimensional grid model to be printed and placement orientation information of the three-dimensional grid model.

[0060] In the embodiment of the present application, after the system is started by the user, a three-dimensional mesh model in STL format can be imported through a user graphical interface. The system renders the model and displays its current orientation. After obtaining the three-dimensional mesh model to be printed, the embodiment of the present application further receives a user's instruction for adjusting the orientation of the three-dimensional mesh model, or receives a user's instruction for marking a specific region of the model as prohibited from generating support. The user can adjust the orientation of the model through the interface tool, and the system highlights the current overhanging region in real time according to a default overhanging angle threshold. The overhanging angle threshold can be set according to specific scenarios, such as 45° in an embodiment of the present application.

[0061] Step 120: identifying all overhanging regions that need support in the three-dimensional mesh model by analyzing the mesh data of the three-dimensional mesh model, and calculating the normal and required support force of each overhanging point of the overhanging region.

[0062] The method further comprises:

[0063] calculating the angle between the normal vector of each triangular facet of the three-dimensional mesh model and the normal vector of the printing platform; wherein the angle between the normal vector of each triangular facet of the three-dimensional mesh model and the Z-axis (printing direction) is calculated by traversing each triangular facet of the three-dimensional mesh model;

[0064] triangular facets with an angle greater than the dynamic angle threshold are marked as overhanging facets.

[0065] performing voxelization or spatial mesh sampling on all the overhanging facets to generate a plurality of target points representing the overhanging region, thereby obtaining an overhanging region; the target points carry a support urgency weight, and the support urgency weight is determined according to the inclination angle, area, and curvature of the region where the overhanging facet is located.

[0066] In the embodiment of the present application, the dynamic angle threshold is dynamically adjusted according to the local geometric features of the triangular facet; in the embodiment of the present application, the local geometric features include but are not limited to curvature, area, and continuity with adjacent facets.

[0067] In traditional support generation algorithms, the criterion for determining whether a triangular facet is a hanging facet is a fixed, globally uniform angle threshold, usually 45°. This method, although simple, ignores the complexity of the local geometric characteristics of the model, resulting in either "over-supporting", i.e. generating supports in unnecessary places, or "under-supporting", i.e. lacking supports in places where they are needed. Embodiments of the present invention introduce the concept of a dynamic angle threshold, which is no longer a fixed value, but an adaptive variable that is intelligently adjusted according to the local geometric characteristics in which each triangular facet is located. The local geometric characteristics include but are not limited to: curvature, area, and continuity with its adjacent facets, where any one or more local characteristics can be used as an adjustment factor to adjust the dynamic angle threshold. That is, dynamic threshold adjustment, rather than simply using a fixed threshold. For a large area (e.g. greater than 100mm 2 ) and low curvature (more flat) facet, even if its inclination is only 40° (<45°), the system will temporarily adjust its dynamic threshold to 40° and mark it as a hanging facet. Conversely, for a small area (e.g. <1mm 2 ) and high curvature edge facet, even if its inclination reaches 50°, it may be ignored.

[0068] Specifically, the dynamic angle threshold can be implemented in the following ways:

[0069] 1. Adjust the dynamic angle threshold based on curvature:

[0070] Curvature reflects the degree of bending of the surface. For high curvature areas such as sharp edges and sharp corners, they have higher structural rigidity by themselves, and even if the inclination is large, the risk of collapse is relatively low. Conversely, low curvature areas, such as flat large surfaces, lack inherent rigidity, and even if the inclination is small, they may sag due to gravity or liquid surface tension.

[0071] By calculating the local curvature value of the area where the triangular facet is located. For high curvature areas, for example, the curvature radius is less than 2mm, the system increases the angle threshold of the preset difference, for example, from 45° to 55° or 60°, which makes the algorithm more tolerant and avoids generating unnecessary supports at the edges and details of the model, thereby protecting the surface details of the model and saving materials. For low curvature areas, for example, the curvature radius is greater than 10mm, the angle threshold will be appropriately reduced, for example, from 45° to 40° or 35°, which makes the algorithm more "sensitive" and ensures that it can identify the collapse risk of large flat areas and provide support in time.

[0072] 2. Adjust the dynamic angle threshold based on area:

[0073] The overhanging area is a key factor affecting the risk of collapse. A large overhanging area, even if its inclination is only slightly higher than a fixed threshold, the central part is prone to sag due to its own weight and resin viscosity. While a small overhanging area, even if the inclination is large, may remain stable. By calculating the area of a single triangular facet or the total area of the continuous overhanging region it belongs to. When the overhanging area of the triangular facet is large (for example, greater than 100mm 2 ), the system will significantly reduce the angle threshold of this area (for example, to 30-40°), forcing the algorithm to generate support for this area to prevent it from collapsing. For a small isolated overhanging area (for example, less than 1mm 2 ), the system can increase the angle threshold, choose to ignore it, or mark it as a low-priority support point.

[0074] 3. Adjust the dynamic angle threshold based on the continuity of adjacent facets

[0075] Whether an overhanging area is isolated or part of a large overhanging region, the risk is also different. Continuous and large overhanging areas are at higher risk. In addition, overhanging areas connected to vertical walls are more stable than isolated overhanging areas.

[0076] Analyze the angle relationship between a triangular facet and its adjacent facets. If a triangular facet is closely connected to a nearly vertical facet (forming a "cliff" structure), the root of the overhanging area is strengthened, and its risk is relatively low, and the threshold can be slightly increased. Conversely, if a triangular facet is at the center of a continuous and extensive overhanging area, it is at the highest risk, and the threshold should be further reduced.

[0077] 4. Dynamic angle threshold of the comprehensive dynamic adjustment model:

[0078] In actual implementation, the above three factors are not independent, but through a weighted decision function to determine the final dynamic angle threshold. An exemplary implementation of the weighting function of the embodiment of the present application is as follows:

[0079] α dynamic = α base + k curvature *f(curvature) + k area *g(area) + k continuity *h(continuity);

[0080] Where, α baseis a base angle threshold, such as 45°; f(curvature) is a curvature-based adjustment function. The higher the curvature, the larger the return value; g(area) is an area-based adjustment function. The larger the area, the smaller the return value; h(continuity) is a continuity-based adjustment function. The better the continuity (the more flat and coherent), the smaller the return value; k curvature ,k area ,k continuity is a weight coefficient of each feature, which can be determined by experiment or machine learning optimization.

[0081] Wherein, after determining the dynamic angle threshold, the overhanging surface is marked, and the weighted target point is generated: voxel sampling is performed on all marked overhanging surfaces to generate a dense target point cloud. Each target point inherits a support urgency weight W from the overhanging surface to which it belongs. W = (θ / 90)*(Area)*(1 / Curvature). This means that the target point of the area with large area, steep angle and low curvature has the highest weight.

[0082] By introducing this dynamic angle threshold mechanism, the embodiment of the present application realizes higher printing reliability, effectively prevents the missing identification and collapse of large-scale, low-angle overhanging areas, and significantly improves the printing success rate. Extreme material saving, avoiding generating redundant support in non-risk areas such as high-curvature details and small-area protrusions of the model, reducing the consumption of support material. Excellent surface quality: reducing support contact on the key appearance surface of the model (usually with higher curvature), thereby minimizing the scars left after removing the support, and improving the surface quality of the final printed part. Intelligence and adaptability: the algorithm can adjust itself according to the geometric morphology of the model, reducing the workload of manual parameter adjustment by the user, and having stronger generalization ability for models of different shapes.

[0083] In the embodiment of the present application, the required support force of each overhanging point of the overhanging area is calculated, including:

[0084] According to the overhanging area corresponding to the target point, the model wall thickness empirical value and the resin material density, the static gravity required to be borne by the target point is estimated;

[0085] According to the curing shrinkage characteristics of the resin material, a curing shrinkage stress coefficient is determined; the curing shrinkage stress coefficient is calculated based on a shrinkage model of material properties and printing process parameters; the printing process parameters include layer thickness, exposure time and light intensity of each layer;

[0086] The static gravity and the curing shrinkage stress coefficient are calculated to obtain the required support force of the target point.

[0087] Specifically, in one embodiment of the present application, the system calculates the required support force for each target point:

[0088] where, static gravity (F gravity ) : F gravity = (area represented by the target point) * (average wall thickness) * (resin density) * (acceleration of gravity). The average wall thickness can be obtained from the model information or specified by the user.

[0089] Curing shrinkage stress (F cure ) : The system has a built-in material database. For the selected "Standard Resin" material, its curing shrinkage stress coefficient is preset to 1.5. This coefficient is measured by experiment based on the process parameters of layer thickness 50 μm and exposure time 8 seconds. Therefore, the shrinkage force F cure = F gravity * 1.5.

[0090] Total support force: The final required support force F total of the target point = F gravity + F cure .

[0091] Step 130: Simulate the fluid static pressure of the resin liquid on the support structure and the equivalent shrinkage force corresponding to the curing shrinkage during the printing process by the pre-constructed mechanical model, correct the required support force according to the fluid static pressure and the equivalent shrinkage force, and obtain the corrected support force.

[0092] where, the required support force has been obtained by calculation, and the support structure is further simulated here. The final purpose of the pre-constructed mechanical model is not to output a complex stress cloud map, but to correct a more accurate and reliable total support force for each target point that needs support. The fluid static pressure is the pressure generated by the resin liquid on the immersed support structure due to its own weight. Its size is proportional to the depth of the resin, and the direction is perpendicular to the surface of the support structure. During the subsequent growth of the support structure, the lateral pressure that the branches may bear at different heights needs to be estimated. This will affect the design of the minimum diameter of the branches. A vertical support rod at a deep level must be thick enough to resist the lateral pressure at that depth without bending. Therefore, the fluid static pressure of the resin liquid on the support structure needs to be simulated in advance.

[0093] The simulation of the fluid static pressure (Hydrostatic Pressure) specifically includes the following steps:

[0094] a. Modeling and simplification:

[0095] Since it is extremely complex to calculate the fluid pressure at each moment, the embodiment of the present application adopts a static simplified model to simulate the moment when the support structure bears the maximum fluid static pressure during the printing process. Usually, this moment occurs when the support structure is almost completely covered, but before it is covered by the next layer of resin.

[0096] b. Pressure calculation:

[0097] For each micro-element on the support structure (e.g. each triangle after meshing the support), the hydrostatic pressure P fluid experienced by it can be calculated by the following formula:

[0098] P fluid = p * g * h;

[0099] where p is the density of the resin (a known material property, e.g. ~1.1 g / cm 3 for standard resin); g is the acceleration due to gravity (9.8 m / s 2 ); h is the depth of the micro-element, i.e. the vertical distance from the current resin level to the micro-element. In the simulation, the level is usually taken as the height of the current printing layer.

[0100] c. Force transformation and integration:

[0101] The calculated hydrostatic pressure P fluid acts in the normal direction of the support micro-element.

[0102] For subsequent mechanical analysis, this distributed pressure needs to be transformed into equivalent nodal forces, which are applied on the nodes of the finite element mesh or truss structure of the support. Ultimately, for the whole support structure, the effect of the hydrostatic pressure can be simplified as a combination of a vertical upward buoyancy (Archimedes principle) and a distributed lateral pressure. The lateral pressure is the main cause of buckling instability of the slender support rods.

[0103] where the solidification shrinkage stress is a more complex mechanical phenomenon specific to the SLA process. When the resin changes from liquid to solid, the intermolecular distance shortens and the volume shrinks (usually by 3-5%). This shrinkage is constrained by the already solidified part, thus generating internal stress within the support structure and the model. In the calculation of the "required support force" at the overhang point, the solidification shrinkage force F cure is a component that must be added to the total support force. This larger support force is directly passed to the space colonization algorithm: it makes the attractive force larger, and the algorithm will generate a more robust support to "grab" the model. It determines the diameter of the branches to be thicker to ensure that the support rods themselves have enough strength to withstand this shrinkage tension without being pulled apart or deformed too much. To further modify the total support force, the present embodiment also calculates the equivalent shrinkage force of the solidification shrinkage. The implementation steps of the simulation of the equivalent shrinkage force include:

[0104] a. Modeling and simplification:

[0105] Wherein, the precise simulation of the curing process needs complex multi-physical field simulation, the embodiment of the application adopts a simplified method based on experience coefficient and linear extension spring model, and the core idea is that the shrinkage effect is equivalent to generating a shrinkage force between the support point and the model, which is directed to the curing center (usually the solidified entity part).

[0106] b. Perform shrinkage force calculation:

[0107] Estimate shrinkage: for a specific support contact point, the corresponding model overhang area will shrink during curing. The shrinkage ΔL can be approximated as:

[0108] ΔL = β * L * C;

[0109] Wherein, β is the volume shrinkage rate of the resin (a known material property); L is the characteristic length, which can be taken as the size in the shrinkage direction of the overhang area during curing (for example, the distance from the support point to the model attachment point); C is the constraint coefficient (between 0 and 1). It represents the degree to which the shrinkage of the area is constrained by the surrounding solidified material. The free boundary is 0, and the complete constraint is 1.

[0110] Calculate the shrinkage force: treat the support structure as a spring that provides constraint. According to Hooke's law, to resist the shrinkage ΔL, the support point needs to provide the force F' cure :

[0111] F' cure = k * ΔL = ∑(β * E * A element )

[0112] Wherein, k is the equivalent stiffness. It represents the stiffness of the support rod, which is related to the elastic modulus E, cross-sectional area A and length L support of its material, for example, for a rod, k = (A * E) / L support , so it can be expressed as:

[0113] Based on the volume shrinkage rate β, the elastic modulus E of the resin material and the printing process parameters, calculate the equivalent shrinkage force F cure generated by the resin curing shrinkage on the support structure:

[0114] F cure = ∑(β * E * A element );

[0115] Wherein, the printing process parameters include layer thickness, exposure time and light intensity; A element is the micro-element area of the support structure in contact with the solidified area.

[0116] After the equivalent node force and the equivalent shrinkage force are obtained, the required support force is corrected according to the equivalent node force and the equivalent shrinkage force, and a corrected support force is obtained. That is, the support force obtained by calculation is F total ’=F gravity ’+F’ cure , and the final total support force F i =F total ’+F total .

[0117] Step 140: According to the overhanging region, the normal of each overhanging point of the overhanging region and the corrected support force, a growth simulation of tree support is performed by using an improved space colonization algorithm to obtain a growth skeleton; the growth skeleton includes a plurality of nodes and connecting lines between the nodes.

[0118] The improved space colonization algorithm includes the following growth rules:

[0119] The overhanging point generates an attractive force on a growth node within a set search radius, and the attractive force is positively correlated with the required support force of the overhanging point;

[0120] The growth node generates a repulsive force between the body of the three-dimensional mesh model and other branch structures to ensure a generation distance;

[0121] The growth direction of each growth node is determined by the vector resultant force of all attractive forces and repulsive forces acting on the growth node;

[0122] The cross-sectional diameter of the branch is dynamically adjusted according to the total support force of the overhanging points required to be supported by the branch.

[0123] The improved space colonization algorithm of the embodiment of the application obtains the growth skeleton by defining the growth node, the improved growth rule and the output growth skeleton. In the embodiment of the application, the system takes the printing platform as the starting point and initializes a “root node”. According to the growth rule, the algorithm starts to iterate and grow. Each growth node finds all target points within its search radius (such as 5 mm). The target point generates an attractive force on the growth node, and the attractive force is positively correlated with the total support force. A target point with a high support force will more strongly “attract” the branch to grow towards it. The growth node is simultaneously subjected to repulsive forces from the “model body” (i.e. the original three-dimensional mesh model) and other generated branches to ensure a safety distance of 0.5 mm. For the growth direction, the next growth direction of the node is determined by the vector resultant force of all attractive forces and repulsive forces. For branching and diameter, when the resultant force direction forks, a new branch is generated. The diameter of each branch segment is calculated according to the sum of the total support forces of all target points required to be supported, to ensure the mechanical strength.

[0124] Specifically as follows:

[0125] Definition of Growth Nodes: Generate one or more initial growth nodes (called "root nodes") based on the print platform. These nodes are the starting points for tree branch growth. Among them, define Target Points: Identify all overhanging points as the target points of the algorithm. Each target point i is attached with the following attributes: spatial coordinates P i , normal vector N i (determine the optimal growth direction of support contact points), final required support force F i (obtained after correction by the mechanical model).

[0126] Improved growth rules (the process is an iterative process): The improved spatial colonization algorithm is performed in discrete iterative steps until all target points are "captured" or the stop condition is met. In each step, the following operations are performed for each growth node:

[0127] 1. Calculate the Attraction Force for determining the core drive.

[0128] Search for all uncaptured target points within a set search radius R centered on the current growth node.

[0129] For each target point j within the search radius, calculate its Attraction Force vector A j to the current growth node. The magnitude of the attraction force is positively correlated with the support force F j of the target point (e.g. |A j | = k * F j , where k is the proportionality coefficient), and the direction points to the target point j.

[0130] Sum all attraction forces to get the total Attraction Force vector A total .

[0131] 2. Calculate the Repulsion Force for collision avoidance.

[0132] Repulsion from the model body: Detect the distance d model between the current growth node and the model surface. If d model is less than the safety distance D min , a strong Repulsion Force vector R model is generated in the direction away from the normal direction of the model surface.

[0133] Repulsion from other tree branches: Detect the distance d branch between the current growth node and other existing tree branch nodes. If d branch is too close, a Repulsion Force vector R branch is generated in the direction away from other nodes.

[0134] Summing all repulsion forces, we get the total repulsion force vector R branch .

[0135] 3. Determine the growth direction

[0136] Calculate the resultant force vector F resultant experienced by the current growth node

[0137] F resultant = A total + R total .

[0138] Unitize the resultant force vector F resultant , we get the growth direction vector G direction for the current iteration step

[0139] 4. Generate a new node and connecting line (tree branch growth)

[0140] Move a fixed step length S along the growth direction vector G direction , and generate a new node.

[0141] Create a connecting line (Edge) between the current growth node and the new node. This connecting line represents a small section of tree branch.

[0142] Dynamically calculate the tree branch diameter: The diameter D of this connecting line (tree branch section) is not fixed, but is dynamically calculated according to the total support force it needs to bear. Specifically, the algorithm will track all target points ultimately supported by this tree branch, and sum the support forces F j of these target points to get ΣF. According to the simplified form of Euler's buckling formula, the tree branch diameter is adjusted to ensure its mechanical strength. Specifically, the cross-sectional diameter D of the tree branch is dynamically adjusted according to the total support force ΣF of all hanging points it needs to support; its adjustment is based on Euler's buckling theory to ensure that the critical buckling load of this tree branch section is always greater than the actual load ΣF it bears; in actual calculation, the diameter D is proportional to the fourth root of ΣF.

[0143] 5. Target point capture and branch formation

[0144] Capture: Check if any target points have entered the "capture range" (a very small radius) of the new node. If so, the target point is marked as "supported" and removed from the target point set for subsequent iterations.

[0145] Branching: If a growing node is simultaneously attracted by multiple different directions of strong force (indicating that it is at a position that needs to be bifurcated to support multiple target points), the algorithm creates multiple new growing nodes (representing new branches) instead of just a single node. Each new node grows along a direction of the respective differentiated force.

[0146] Output the growing skeleton:

[0147] When the iteration process ends (all target points are captured or the maximum number of iterations is reached), the algorithm outputs a complete growing skeleton.

[0148] Nodes: Record the three-dimensional coordinates of all key points on the tree support structure.

[0149] Edges: Record the connection relationship between nodes and store the diameter attribute of each branch.

[0150] This growing skeleton is a parameterized, lightweight intermediate representation that accurately describes the topological structure and physical properties of the tree support, laying the foundation for subsequent conversion to a triangular mesh model and optimization verification.

[0151] Step 150: Optimize and verify the growing skeleton through a multi-objective optimization algorithm. If the verification fails, continue to generate a new growing skeleton through an improved spatial colonization algorithm, and optimize and verify the new growing skeleton through a multi-objective optimization algorithm until the verification passes. Iterative optimization generates the final tree support structure.

[0152] Wherein, the optimization objectives of the multi-objective optimization algorithm include: minimizing the total volume of the tree support structure, minimizing the number of contact points between the tree support structure and the model surface, and maximizing the mechanical safety factor of the tree support structure. The mechanical safety factor is obtained through finite element analysis or truss structure buckling analysis; the number of contact points is minimized by preferentially setting the contact points in low-curvature areas of the model surface or user-specified non-critical areas.

[0153] In the embodiment of the application, the optimization of the growing skeleton through the multi-objective optimization algorithm comprises:

[0154] Converting the growing skeleton into a three-dimensional mesh model;

[0155] Performing collision detection on the three-dimensional mesh model and adjusting the branch path to eliminate interference with the model body;

[0156] Merging redundant branches that are too close in distance and deleting functional branches with lengths below a threshold value.

[0157] Specifically, the generated growth skeleton is converted into a triangular mesh model, and the support structure is evaluated by a multi-objective evaluation and verification module, and the main evaluation contents include:

[0158] Total volume V: calculate the total volume of all support structures.

[0159] Surface damage D: count the number of contact points and calculate the damage score D = Σ (curvature weight of each contact point), high curvature area weight is high.

[0160] Safety factor S: simplified truss buckling analysis is performed on the support structure. Calculate the ratio of the actual stress of each branch to the critical buckling stress, and take the minimum value of all branches as s min .

[0161] By defining the comprehensive objective function Fitness = (W1*1 / V) + (W2*1 / D) + (W3*S min ). If the evaluation result does not meet the requirements (such as S min <1.5 or D value is too large), the system will automatically adjust the parameters of the space colonization algorithm (such as increasing the repulsion force weight and reducing the search radius), and then return to step 140 to generate a new support structure and perform a new round of evaluation. This cycle continues until a solution that meets all optimization objectives is found.

[0162] The final generated support is post-processed and optimized, including: performing accurate collision detection to ensure no interference, merging adjacent branches that are too close, and deleting extremely short invalid branches. After optimization, the system merges the final tree support mesh with the original model and outputs a new.slcp project file that can be directly used in slicing software (such as Chitubox), which contains the model and the generated optimized tree support.

[0163] The embodiment of the application obtains a three-dimensional grid model to be printed and placement orientation information; analyzes grid data of the three-dimensional grid model, identifies all overhanging areas that need to be supported in the three-dimensional grid model, and calculates normal and required support force of each overhanging point of the overhanging area; simulates fluid static pressure and solidification shrinkage stress of a resin liquid on a support structure in a printing process through a mechanical model; generates a growth skeleton through growth simulation of tree support by using an improved space colonization algorithm; optimizes and verifies the growth skeleton through a multi-objective optimization algorithm, and when the verification fails, a new growth skeleton is continuously generated through the improved space colonization algorithm, and a final tree support structure is generated through iterative optimization, so that an intelligent, automated, and high-success-rate tree support generation method can be realized.

[0164] Figure 2 The structure of the 3D printing tree support automatic generation system based on the SLA light curing process provided by the embodiment of the application is shown. As shown inFigure 2 As shown, the system 200 comprises:

[0165] An acquisition module 210 is configured to acquire a three-dimensional grid model to be printed and placement orientation information of the three-dimensional grid model.

[0166] A calculation module 220 is configured to identify all overhanging regions needing support in the three-dimensional grid model by analyzing grid data of the three-dimensional grid model, and calculate a normal and a required support force of each overhanging point of the overhanging regions.

[0167] A simulation module 230 is configured to simulate a hydrostatic pressure and a solidification shrinkage stress of a resin liquid on a support structure in a printing process by a pre-constructed mechanical model.

[0168] A growth module 240 is configured to perform growth simulation of a tree support according to the overhanging regions, the hydrostatic pressure and the solidification shrinkage stress by an improved spatial colonization algorithm to obtain a growth skeleton; the growth skeleton comprises a plurality of nodes and connecting lines between the nodes.

[0169] A verification module 250 is configured to optimize and verify the growth skeleton by a multi-objective optimization algorithm, when the verification fails, continue to generate a new growth skeleton by the improved spatial colonization algorithm, and optimize and verify the new growth skeleton by the multi-objective optimization algorithm until the verification passes, and iteratively optimize to generate a final tree support structure.

[0170] In an optional manner, the step of identifying all overhanging regions needing support in the three-dimensional grid model by analyzing grid data of the three-dimensional grid model, and calculating a normal and a required support force of each overhanging point of the overhanging regions, specifically comprises:

[0171] calculating an included angle between a normal vector of each triangular facet in the three-dimensional grid model and a normal vector of a printing platform;

[0172] marking a triangular facet with an included angle greater than a dynamic angle threshold as an overhanging facet; the dynamic angle threshold is dynamically adjusted according to local geometric features of the triangular facet; wherein the local geometric features include but are not limited to curvature, area, and continuity with adjacent facets;

[0173] performing voxelization or spatial grid sampling on all the overhanging facets to generate a plurality of target points representing the overhanging regions, thereby obtaining overhanging regions; the target points carry a support urgency weight, and the support urgency weight is determined according to an inclination angle, an area and a curvature of a region of the overhanging facet.

[0174] In an optional manner, the step of calculating a required support force of each overhanging point of the overhanging regions specifically comprises:

[0175] estimating a static gravity that the target point needs to bear according to the overhanging area corresponding to the target point, a model wall thickness empirical value and a resin material density;

[0176] determining a solidification shrinkage stress coefficient according to a solidification shrinkage characteristic of the resin material; the solidification shrinkage stress coefficient is calculated based on a shrinkage model of material properties and printing process parameters; the printing process parameters include layer thickness, exposure time per layer and light intensity;

[0177] calculating the required support force of the target point by using the static gravity and the solidification shrinkage stress coefficient.

[0178] In an optional manner, the mechanical model is a finite element model or a truss structure model; a result simulated by the mechanical model is used to correct the required support force of the overhanging point, and the corrected support force is fed back to the improved spatial colonization algorithm to guide the growth direction and diameter of the tree branch; the fluid static pressure of the resin liquid on the support structure and the equivalent shrinkage force corresponding to the solidification shrinkage in the printing process are simulated by using the pre-constructed mechanical model, the required support force is corrected according to the fluid static pressure and the solidification shrinkage stress, and the corrected support force is obtained, which specifically includes:

[0179] discretizing the support structure into a finite number of units;

[0180] for each unit, calculating the fluid static pressure P of the unit according to the depth h of the center point of the unit, the resin density ρ and the gravity acceleration g fluid :

[0181] P fluid = ρ * g * h;

[0182] wherein the depth h is the vertical distance from the unit to the resin liquid surface of the current printing layer;

[0183] converting the fluid static pressure into an equivalent node force.

[0184] In an optional manner, the result simulated by the mechanical model is used to correct the required support force of the overhanging point, and the corrected support force is fed back to the improved spatial colonization algorithm to guide the growth direction and diameter of the tree branch; the fluid static pressure of the resin liquid on the support structure and the equivalent shrinkage force corresponding to the solidification shrinkage in the printing process are simulated by using the pre-constructed mechanical model, the required support force is corrected according to the fluid static pressure and the solidification shrinkage stress, and the corrected support force is obtained, which specifically includes:

[0185] calculating the equivalent shrinkage force F generated on the support structure due to the solidification shrinkage of the resin based on the volume shrinkage rate β of the resin material, the elastic modulus E and the printing process parameterscure :

[0186] F cure =∑(β*E*A element );

[0187] wherein the printing process parameters include layer thickness, exposure time and light intensity; A element is the microelement area on the support structure in contact with the solidification area;

[0188] The required support force is corrected according to the equivalent node force and the equivalent shrinkage force to obtain a corrected support force.

[0189] In an alternative way, the improved space colonization algorithm comprises the following growth rules:

[0190] The overhanging point generates an attractive force to the growth node within a set search radius, and the attractive force is positively correlated with the required support force of the overhanging point;

[0191] The growth node generates a repulsive force between the body of the three-dimensional mesh model and other branch structures to ensure the generation distance;

[0192] The growth direction of each growth node is determined by the vector resultant of all attractive forces and repulsive forces acting on the growth node;

[0193] The cross-sectional diameter of the branch is dynamically adjusted according to the total support force of the overhanging points required to be supported by the branch.

[0194] In an alternative way, the optimization objectives of the multi-objective optimization algorithm include: minimization of the total volume of the tree support structure, minimization of the number of contact points between the tree support structure and the model surface, and maximization of the mechanical safety factor of the tree support structure; the mechanical safety factor is obtained by finite element analysis or truss structure buckling analysis; the minimization of the number of contact points includes preferentially setting the contact points on the low-curvature area of the model surface or the non-critical area specified by the user.

[0195] In an alternative way, the growth skeleton is optimized and verified by the multi-objective optimization algorithm, and when the verification fails, a new growth skeleton is generated by the improved space colonization algorithm, and the new growth skeleton is optimized and verified by the multi-objective optimization algorithm until the verification passes, and the final tree support structure is generated by iterative optimization, comprising:

[0196] Converting the growth skeleton into a three-dimensional mesh model;

[0197] Performing collision detection on the three-dimensional mesh model and adjusting the branch path to eliminate interference with the model body;

[0198] Merge redundant branches that are too close together and delete functional branches that are below a threshold length.

[0199] The embodiment of the present application obtains a three-dimensional grid model to be printed and placement orientation information; analyzes grid data of the three-dimensional grid model to identify all overhanging areas needing support in the three-dimensional grid model, and calculates normal and required support force of each overhanging point of the overhanging areas; simulates fluid static pressure and solidification shrinkage stress of resin liquid to support structure in a printing process through a mechanical model; obtains a growing skeleton through growth simulation of tree support by using an improved space colonization algorithm; optimizes and verifies the growing skeleton through a multi-objective optimization algorithm, and when the verification fails, continues to generate a new growing skeleton through the improved space colonization algorithm, iteratively optimizes to generate a final tree support structure, and a smart, automated and high-success-rate tree support generation method can be realized.

[0200] According to another aspect of the embodiment of the present application, a 3D printing device is provided, which comprises the 3D printing tree support automatic generation system based on the SLA light curing process.

[0201] The embodiment of the present application provides a 3D printing tree support automatic generation device based on the SLA light curing process, which is used to execute the 3D printing tree support automatic generation method based on the SLA light curing process.

[0202] The embodiment of the present application provides a computer program, which can be called by a processor to make a computer device execute the 3D printing tree support automatic generation method based on the SLA light curing process in any method embodiment.

[0203] The embodiment of the present application provides a computer program product, which comprises a computer program stored on a computer readable storage medium, and the computer program comprises program instructions, when the program instructions run on a computer, make the computer execute the 3D printing tree support automatic generation method based on the SLA light curing process in any method embodiment.

[0204] The algorithms or displays provided herein are not inherently related to any particular computer, virtual system, or other apparatus. Various general purpose systems can be used with programs in accordance with the teachings herein, or it can prove convenient to construct more specialized apparatus to perform the required method steps. The required structure for a variety of these systems will be apparent from the description above. In addition, the present embodiment is not intended to be limited to any particular programming language. It will be appreciated that there are many programming languages that can be used to implement the teachings herein, and any such programming language can be used in connection with the various aspects of the present embodiment.

[0205] In the description provided herein, numerous specific details are set forth. However, it is understood that embodiments of the application can be practiced without these specific details. In some instances, well-known methods, structures and techniques have not been described in detail in order not to obscure the understanding of this description.

[0206] Similarly, it is to be understood that the embodiments of the application can be adapted to other applications and that their features can be interchanged in any way. In the description provided herein, numerous specific details are set forth. However, it is understood that embodiments of the application can be practiced without these specific details. In some instances, well-known methods, structures and techniques have not been described in detail in order not to obscure the understanding of this description.

[0207] Those skilled in the art will appreciate that modules in the apparatuses in the embodiments can be adapted and arranged in one or more apparatuses other than the embodiments. Modules or units or components in the embodiments can be combined into one module or unit or component, and can be divided into a plurality of sub-modules or sub-units or sub-components. All the features disclosed in this specification (including the claims, abstract and drawings) can be combined in any combination, except where such features are mutually exclusive. Each feature disclosed in this specification (including the claims, abstract and drawings) can also be replaced by an alternative feature providing the same, equivalent or similar functionality, unless expressly stated otherwise.

[0208] It is noted that the foregoing examples have been provided merely for the purpose of explanation and are in no way to be construed as limiting of the present application. While the application has been described with reference to preferred embodiments, it is understood that the words, which have been used herein, are words of description and illustration, rather than words of limitation. Changes can be made, within the purview of the appended claims, as presently set forth or as amended, without departing from the scope and spirit of the present application in its aspects. Accordingly, the disclosed application is not to be restricted except in the spirit of the appended claims. In the claims, any reference sign placed between two elements being compared is to be interpreted to mean that the elements are to be compared. The word comprising does not exclude the presence of elements or steps not listed in a claim. The word "a" or "an" preceding an element does not exclude the presence of a plurality of such elements. The application can be implemented by means of hardware comprising several distinct elements, and by means of a suitably programmed computer. In the claims, the word "first", "second", "third", etc. does not imply any order. The terms first, second, third, etc. are to be interpreted as names. The steps of the methods described herein do not have to be performed in the exact order described.

Claims

1. A method for automatically generating a 3D printing tree support based on an SLA light curing process, characterized in that, The method comprises: acquiring a three-dimensional grid model to be printed and placement orientation information of the three-dimensional grid model; identifying all overhanging areas needing support in the three-dimensional grid model by analyzing grid data of the three-dimensional grid model, and calculating a normal and a required support force of each overhanging point of the overhanging areas; correcting the required support force according to a hydrostatic pressure of resin liquid on the support structure and an equivalent shrinkage force corresponding to solidification shrinkage in a printing process simulated by a pre-constructed mechanical model, to obtain a corrected support force; generating a growth skeleton by growing simulation of tree support using an improved space colonization algorithm according to the overhanging areas, the normal of each overhanging point of the overhanging areas and the corrected support force; the growth skeleton comprises a plurality of nodes and connecting lines between the nodes; optimizing and verifying the growth skeleton by a multi-objective optimization algorithm, and when the verification fails, continuously generating a new growth skeleton by the improved space colonization algorithm, and optimizing and verifying the new growth skeleton by the multi-objective optimization algorithm until the verification passes, to iteratively optimize and generate a final tree support structure.

2. The method of claim 1, wherein, The method of identifying all overhanging areas needing support in the three-dimensional grid model by analyzing grid data of the three-dimensional grid model, and calculating a normal and a required support force of each overhanging point of the overhanging areas, specifically comprises: calculating an included angle between a normal vector of each triangular facet in the three-dimensional grid model and a normal vector of a printing platform; marking a triangular facet with an included angle greater than a dynamic angle threshold as an overhanging facet; the dynamic angle threshold is dynamically adjusted according to local geometric features of the triangular facet; the local geometric features include but are not limited to curvature, area and continuity with adjacent facets; voxelizing or spatial grid sampling all the overhanging facets to generate a plurality of target points representing the overhanging areas, to obtain overhanging areas; the target points carry a support urgency weight determined according to an inclination angle, an area and a curvature of a region of the overhanging facet.

3. The method of claim 2, wherein, The method of calculating a required support force of each overhanging point of the overhanging areas specifically comprises: estimating a static gravity required to be borne by the target point according to an overhanging area corresponding to the target point, a model wall thickness empirical value and a resin material density; determining a solidification shrinkage stress coefficient according to solidification shrinkage characteristics of the resin material; the solidification shrinkage stress coefficient is calculated based on a shrinkage model of material properties and printing process parameters; the printing process parameters include layer thickness, exposure time per layer and light intensity; calculating the required support force of the target point from the static gravity and the solidification shrinkage stress coefficient.

4. The method of claim 1, wherein, The mechanical model is a finite element model or a truss structure model; the simulation result of the mechanical model is used to correct the required support force of the overhanging point, and the corrected support force is fed back to the improved spatial colonization algorithm, which is used to guide the growth direction and diameter of the branch; the mechanical model simulates the fluid static pressure of the resin liquid on the support structure and the equivalent shrinkage force corresponding to the solidification shrinkage during the printing process, and corrects the required support force according to the fluid static pressure and the solidification shrinkage stress to obtain the corrected support force, which specifically includes: Discretize the support structure into a finite number of units; For each cell, the hydrostatic pressure P it is subjected to is calculated from the depth h of its center point, the resin density p and the gravitational acceleration g fluid : P fluid = p * g * h; Wherein, the depth h is the vertical distance from the unit to the resin liquid surface of the current printing layer; Convert the fluid static pressure into an equivalent node force.

5. The method of claim 4, wherein, The simulation result of the mechanical model is used to correct the required support force of the overhanging point, and the corrected support force is fed back to the improved spatial colonization algorithm, which is used to guide the growth direction and diameter of the branch; the mechanical model simulates the fluid static pressure of the resin liquid on the support structure and the equivalent shrinkage force corresponding to the solidification shrinkage during the printing process, and corrects the required support force according to the fluid static pressure and the solidification shrinkage stress to obtain the corrected support force, which specifically includes: Based on the volume shrinkage rate β, the elastic modulus E of the resin material, and the printing process parameters, the equivalent shrinkage force F generated on the support structure due to the shrinkage of the resin curing is calculated cure : F cure =∑(β*E*A element ); The printing process parameters include layer thickness, exposure time and light intensity. element To support the micro-element area on the structure in contact with the curing area; According to the equivalent node force and the equivalent shrinkage force, the required support force is corrected to obtain the corrected support force.

6. The method according to any one of claims 1 to 5, characterized in that, The improved spatial colonization algorithm includes the following growth rules: The overhanging point generates an attractive force to the growth node within a set search radius, and the attractive force is positively correlated with the required support force of the overhanging point; The growth node generates a repulsive force between the body of the three-dimensional grid model and other branch structures to ensure the generation distance; The growth direction of each growth node is determined by the vector resultant force of all attractive forces and repulsive forces acting on the growth node; The cross-sectional diameter of the branch is dynamically adjusted according to the total support force of the overhanging point required by the branch.

7. The method according to any one of claims 1 to 5, characterized in that, The optimization objectives of the multi-objective optimization algorithm include: minimizing the total volume of the tree support structure, minimizing the number of contact points between the tree support structure and the model surface, and maximizing the mechanical safety factor of the tree support structure; the mechanical safety factor is obtained by finite element analysis or truss structure buckling analysis; the number of contact points is minimized, including preferentially setting the contact points in the low-curvature area of the model surface or the non-critical area specified by the user.

8. The method according to any one of claims 1 to 5, characterized in that, The growth skeleton is optimized and verified by the multi-objective optimization algorithm, and when the verification fails, a new growth skeleton is generated by the improved spatial colonization algorithm, and the new growth skeleton is optimized and verified by the multi-objective optimization algorithm until the verification passes, and the final tree support structure is generated by iterative optimization, including: Convert the growth skeleton into a three-dimensional grid model; Perform collision detection on the three-dimensional grid model and adjust the branch path to eliminate interference with the model body; Merge redundant branches that are too close in distance, and delete functional branches whose length is below a threshold value.

9. A system for automatic generation of 3D printing tree support based on SLA light curing process, characterized in that, The system includes: An acquisition module for acquiring a three-dimensional grid model to be printed and the placement orientation information of the three-dimensional grid model; A computing module is configured to identify all overhanging areas needing support in the three-dimensional mesh model by analyzing mesh data of the three-dimensional mesh model, and calculate a normal and a required support force of each overhanging point of the overhanging areas; A simulation module is configured to simulate, by a pre-constructed mechanical model, a hydrostatic pressure of resin liquid on the support structure and an equivalent shrinkage force corresponding to a solidification shrinkage in a printing process, correct the required support force according to the hydrostatic pressure and the equivalent shrinkage force, and obtain a corrected support force; A growing module is configured to perform growing simulation of tree support by using an improved space colonization algorithm according to the overhanging areas, the normal of each overhanging point of the overhanging areas, and the corrected support force, and obtain a growing skeleton; the growing skeleton includes a plurality of nodes and connecting lines between the nodes; A verifying module is configured to optimize and verify the growing skeleton by a multi-objective optimization algorithm, continue to generate a new growing skeleton by the improved space colonization algorithm when the verification fails, optimize and verify the new growing skeleton by the multi-objective optimization algorithm, and iterate until the verification passes, so as to generate a final tree support structure.

10. A 3D printing device, characterized by A 3D printing tree support automatic generation system based on an SLA light solidification process, including the system as claimed in claim 9.

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