A method and system for designing printing paths based on stress flow guidance

Abstract

This invention discloses a printing path design method and system based on stress flow guidance. The design method includes: S1, performing mesh cell division and determining the target printing point; determining the principal stress data of the target printing point based on the stress field; S2, selecting the printing start point as the current printing point, calculating the direction deflection coefficient based on the principal stress data, and selecting the target printing point with the smallest direction deflection coefficient in the neighborhood as the second printing point; S3, using the second printing point as the current printing point, calculating the direction deflection coefficient, and then selecting the target printing point with the smallest direction deflection coefficient in the neighborhood as the third printing point; S4, repeating S3, connecting the printing points to form a printing path segment; determining at least one printing path segment according to the above steps; S5, obtaining the printing path of the printed component from the determined at least one printing path segment. This invention improves the rationality of path design, making the mechanical anisotropy distribution of the printed component match its applicable working conditions.

Description

Technical Field

[0001] This invention relates to the field of concrete 3D printing construction technology, and in particular to a printing path design method and system based on stress flow guidance. Background Technology

[0002] Concrete 3D printing is a key intelligent construction method that uses a control system to stack cement-based materials layer by layer along a pre-set printing path through extrusion, spraying, or other methods to ultimately form a structural entity. It boasts advantages such as digitalization, automation, and intelligence. The 3D printing process is characterized by layer-by-layer accumulation and stacking, which leads to various weak areas in the resulting structure, primarily located at the interfaces between printed layers and the contact interfaces between printed strips within the layers. These weak areas result in anisotropy in the mechanical properties of the 3D printed product, causing significant differences in stress in different directions and thus affecting the stress performance of the final component in certain directions. Therefore, technologies that optimize the printing path to improve the mechanical properties of components have gradually emerged.

[0003] Current research on 3D printing path design primarily focuses on 3D printing processes such as stereolithography (SLA), fused deposition modeling (FDM), and selective laser sintering (SLS). Relatively mature path planning algorithms, such as Zigzag, Hilbert, and Contour, focus more on forming accuracy and printing efficiency, lacking consideration for the mechanical properties of the printed components. This leads to a higher likelihood of weak mechanical properties in key stress areas. Furthermore, due to significant differences in printing materials and printing resolutions, the aforementioned methods have limited applicability to path planning and design in cement-based 3D printing. Chinese Patent 202110857585.9 discloses a concrete 3D printing path optimization method based on the distribution of the first principal stress vector. This method involves obtaining a 3D model of the relevant component using modeling software, and then slicing the model using slicing software to obtain slice information and layer thickness information. After these steps, the 3D model is imported into finite element software for stress and strain calculation, yielding stress vector information for key nodes at various locations, including magnitude and direction. The above method calculates the first principal stress vector of the component to obtain the stress magnitude and direction of each part of the component. Combined with the characteristics of concrete 3D printing, the printing path is planned to enable the concrete 3D printed component to withstand greater stress and improve the mechanical properties of the component. However, the stress considered in the path design process is only the first principal stress, and only the stress vector direction (angle) is considered, without fully considering the magnitude. The stress situation is not adequately considered, and the path design method based on multiple stress field requirements is not considered, resulting in unreasonable path planning for cement-based material 3D printing. Summary of the Invention

[0004] The purpose of this invention is to overcome the problem that the stress considered in the existing path design process is only the first principal stress, the stress situation is not adequately considered, and the requirements based on multiple stress fields are not taken into account. This invention provides a printing path design method and system based on stress flow guidance.

[0005] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0006] A stress-flow-guided printing path design method includes the following steps:

[0007] Step S1: Divide the printed layers of the printed component into grid cells and use the geometric centroid of each cell as the target printing point; determine the principal stress data of all target printing points based on the stress field of the printed component.

[0008] Step S2: Select a target printing point as the printing start point, take the printing start point as the current printing point, take the adjacent mesh cells of the cell where the current printing point is located as the neighborhood, calculate the direction deflection coefficient of all target printing points in the neighborhood of the current printing point according to the principal stress data, and select the target printing point with the smallest direction deflection coefficient in the neighborhood as the second printing point.

[0009] Step S3: Using the second printing point as the current printing point, calculate the direction deflection coefficient of all target printing points in the neighborhood of the current printing point, and select the target printing point with the smallest direction deflection coefficient in the neighborhood as the third printing point.

[0010] Step S4: Repeat step S3 until there are no candidate target printing points in the neighborhood of the current printing point, resulting in m printing points. Connect the determined printing start point, the second printing point, the third printing point, ..., the mth printing point to form a printing path segment; determine at least one printing path segment according to the above steps.

[0011] Step S5: When there is only one determined printing path segment, the printing path segment is the printing path of the printed component; when there are at least two determined printing path segments, the printing path segments are connected according to the endpoints of adjacent printing path segments, and the printing path of the printed component is obtained under the condition of minimizing the number of printing paths.

[0012] In the technical solution of this invention, the layer structure of the printed component to be printed is first divided into several units, and the geometric center of each unit is used as the target printing point. The stress field of the printed component is obtained, which expresses the magnitude and direction information of the principal stress. The principal stress data expressed by the stress field is assigned to the target printing point. Then, the printing path is formed according to the stress flow direction of each target printing point. When all target points participate in the path generation, the layer shape filling is completed, and the final printing path of the printed component is obtained. This method fully considers the stress field of the printed component, which can reflect the structural stress distribution of the printed component in actual application conditions. The printing path is optimized according to the stress field, making full use of the axial strength of the printing path, thereby improving the mechanical properties of the component and matching the mechanical anisotropy distribution of the 3D printed component with its applicable working conditions.

[0013] It should be noted that the printed component in this invention is a component with a uniform cross-section, meaning that the outlines of the cross-sections of each printed layer obtained by slicing along the forming direction using parallel planes are completely identical. By designing the printing path for the printed layers, and then printing different layers according to the designed printing path, the printed component is obtained.

[0014] As a preferred embodiment of the present invention, during the grid cell division process, the printed layers of the printed component are divided into grid cells according to the layer shape and printing range.

[0015] Furthermore, during the mesh cell division process, the size of the mesh cell is determined based on the width range of the printed strip extruded by the print head of the printing equipment. For regularly shaped printed sheets, they are divided into rectangular mesh cells. For irregularly shaped printed sheets, they are first divided into multiple regular curved quadrilaterals that facilitate relatively uniform mesh cell division based on their shape characteristics. Then, the curved quadrilaterals are further divided into mesh cells according to appropriate cell sizes. The above technical solution considers the cell division of regular and irregular two-dimensional shaped printed sheets, is applicable to different 3D printed components, and improves the applicability of the method of this invention.

[0016] As a preferred embodiment of the present invention, the stress field of the printed component expresses principal stress information, realizing the visualization of the magnitude and direction of the principal stress; the stress field is expressed by a directed line segment method in which the arrow points to the direction of the principal stress and the line segment length is the magnitude of the principal stress, and the principal stress information is at least one of the principal tensile stress, principal compressive stress, and the principal stress with the maximum absolute value.

[0017] As a preferred embodiment of the present invention, when the target printing point is a node or integration point of a model element in the finite element analysis of the stress field, the principal stress data of the model element node or integration point is used as the stress state of the target printing point for calculation; when the target printing point is not a node or integration point in the finite element model, the principal stress data of the closest point to the target printing point is selected as the stress state of the target printing point for calculation. Considering that when calculating the internal stress state of a structure using the finite element method, the element size of the model mesh is usually smaller than the width of the printing strip adapted to the 3D printing port of cement-based materials, that is, the mesh element density used for finite element analysis is greater than the mesh element density in the path design, the closest point to the target printing point can be selected, and the principal stress data of the closest point can be used as the stress state of the target printing point for calculation.

[0018] As a preferred embodiment of the present invention, based on the stress field of the printed component, the printing starting point is selected as a target printing point with a large stress value located at the edge of the printed layer or at a structural turning point. This selection ensures that the printing path is preferentially constructed according to the force flow direction of the area with greater stress. It should be noted that the printing starting point is located at a non-stress concentration part of the printed component, and not at a stress concentration part of the printed component.

[0019] As a preferred embodiment of the present invention, the formula for calculating the direction deflection coefficient is as follows:

[0020] λ=ω·l·sinα+(1-ω)·l·sinβ

[0021] In the formula, λ is the direction deflection coefficient, ω is the weighting factor, l is the length of the line segment connecting the current printing point and the target printing point, α is the angle between the line containing the stress direction corresponding to the current printing point and the line containing the printing path segment to be connected, α∈[0,90°]; β is the angle between the line containing the stress direction corresponding to the target printing point and the line containing the printing path segment to be connected, β∈[0,90°].

[0022] As a more preferred embodiment of the present invention, the formula for calculating the weighting factor is as follows:

[0023]

[0024] Where, σ sp σ is the stress value corresponding to the current printing point s. pi For the target print point p within the neighborhood of the current print point i The corresponding stress value.

[0025] As a preferred embodiment of the present invention, the design method determines at least two printing path segments, and the design method includes the following steps:

[0026] Step S1: Divide the printed layers of the printed component into grid cells and use the geometric centroid of each cell as the target printing point; determine the principal stress data of all target printing points based on the stress field of the printed component.

[0027] Step S2: Select a target printing point as the printing start point, take the printing start point as the current printing point, take the adjacent mesh cells of the cell where the current printing point is located as the neighborhood, calculate the direction deflection coefficient of all target printing points in the neighborhood of the current printing point according to the principal stress data, and select the target printing point with the smallest direction deflection coefficient in the neighborhood as the second printing point.

[0028] Step S3: Using the second printing point as the current printing point, calculate the direction deflection coefficient of all target printing points in the neighborhood of the current printing point, and select the target printing point with the smallest direction deflection coefficient in the neighborhood as the third printing point.

[0029] Step S4: Repeat step S3 until there are no candidate target printing points in the neighborhood of the current printing point, and obtain m printing points. Connect the determined printing start point, the second printing point, the third printing point, ..., the mth printing point to form a printing path segment, which is used as the first printing path segment.

[0030] For the remaining target printing points within the printing layer that did not participate in the generation of printing path segments, a new target printing point is selected near the start or end point of the first printing path segment as the printing start point. Steps S2 to S4 are repeated until there are no candidate target printing points in the neighborhood of the current printing point, or when the existing candidate target printing points and the path segments of the current printing point overlap with the already formed printing path segments, the printing point search is stopped, and the second printing path segment, ..., the nth printing path segment are determined. The number of determined printing path segments is n, where n is an integer ≥ 2, that is, there are two or more printing path segments.

[0031] Step S5: Connect the determined at least two print path segments according to the endpoints of adjacent print path segments to obtain the print path of the print component while minimizing the number of print paths.

[0032] Another aspect of the present invention provides a stress-flow-guided printing path design system, the system comprising:

[0033] The data units are defined to divide the printed layers of the printed component into grid units, and the geometric centroid of each unit is used as the target printing point; based on the stress field of the printed component, the principal stress data of all target printing points are determined.

[0034] The first calculation unit is used to select a target printing point as the printing start point, take the printing start point as the current printing point, take the adjacent grid cells of the cell where the current printing point is located as the neighborhood, calculate the direction deflection coefficient of all target printing points in the neighborhood of the current printing point according to the principal stress data, and select the target printing point with the smallest direction deflection coefficient in the neighborhood as the second printing point.

[0035] The second calculation unit is used to calculate the direction deflection coefficient of all target printing points in the neighborhood of the current printing point, taking the second printing point as the current printing point, and select the target printing point with the smallest direction deflection coefficient in the neighborhood as the third printing point.

[0036] A print path segment unit is determined to repeat step S3 until there are no candidate target print points in the neighborhood of the current print point, resulting in m print points. The determined print start point, second print point, third print point, ..., m-th print point are connected to form a print path segment. At least one print path segment is determined according to the above steps.

[0037] The print path determination unit is used to determine the print path of the printed component when there is only one print path segment; when there are at least two print path segments, the print path segments are connected according to the endpoints of adjacent print path segments to obtain the print path of the printed component under the condition of minimizing the number of print paths.

[0038] The present invention also provides an electronic device, including at least one processor and a memory communicatively connected to the at least one processor; the memory stores instructions executable by the at least one processor, the instructions being executed by the at least one processor to enable the at least one processor to perform the stress flow-guided printing path design method described above.

[0039] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0040] This invention provides a printing path design method based on stress flow guidance. This method fully considers the stress field of the printed component, which can reflect the structural stress distribution of the printed component in actual application conditions. The printing path is optimized according to the stress field, making full use of the axial strength of the printing path to improve the mechanical properties of the component. Based on the process characteristics of 3D printing, this method also considers the improvement of the mechanical properties of the component, thereby improving the rationality of the path design based on the improvement of the mechanical properties of the component, so that the mechanical anisotropy distribution of the 3D printed component matches the working conditions it is adapted to. Attached Figure Description

[0041] Figure 1 Process flow diagram of stress flow guided printing path;

[0042] Figure 2(a) Neighborhood diagram of the current print point; (b) Schematic diagram of target point direction deflection coefficient calculation for the printing path design;

[0043] Figure 3 A schematic diagram illustrating the calculation of the current print point direction and the selection of print points for the print path design;

[0044] Figure 4 (a) The magnitude and direction of the principal stress matching the target printing point in the principal tensile stress field of the prism; (b) The direction of the principal stress flow at the target printing point;

[0045] Figure 5 (a) The magnitude and direction of the principal stress matching the target printing point in the maximum absolute principal stress field of the prism; (b) The direction of the principal stress flow at the target printing point;

[0046] Figure 6 A printed path segment for a prism based on the principal tensile stress field;

[0047] Figure 7 This is a printed path segment based on the maximum absolute value principal stress field;

[0048] Figure 8 For prism specimens, (a) printing path guided by principal tensile stress field; (b) printing path guided by principal stress field with maximum absolute value;

[0049] Figure 9 A schematic diagram of the maximum principal stress field for topology-optimized pavement structures;

[0050] Figure 10 A schematic diagram of the planar design domain partitioning for topology-optimized road surface structure;

[0051] Figure 11 (a) Partitioning of the grid cell structure for topology optimization of the road surface; (b) Target printing point layout.

[0052] Figure 12 A schematic diagram illustrating the screening and matching of target printing point stress data for topology-optimized pavement structure layers;

[0053] Figure 13 Printed path segments generated based on the maximum absolute value principal stress field for topology optimization of road surface structure;

[0054] Figure 14 A printing path guided by the maximum absolute value principal stress field for topology-optimized road surface structure;

[0055] Figure 15 This is a topology-optimized road surface structure printout image obtained by using the design method of this invention. Detailed Implementation

[0056] To more clearly describe the inventive objectives, technical solutions, and advantages of the specific embodiments of this invention, the solutions in the specific embodiments will be described in detail below with reference to the accompanying drawings. The specific technical solutions involved in the following embodiments are merely for the purpose of clearly and completely describing the innovative technical solutions of this invention. They are only a part of the specific implementation methods that this invention can adopt, not all embodiments, and should not be construed as limiting the innovative solutions of this invention. Any solution that adopts the same inventive concept as this invention should be included within the protection scope of this invention.

[0057] Secondly, the descriptions in the accompanying drawings of the specific embodiments of this invention are merely for the convenience of those skilled in the art to understand the invention. The details shown in the drawings are for the purpose of clearly presenting the technical solution, and should not be construed as including all technical features in the drawings in the specific implementation examples, nor should the details in the drawings be considered as additional limitations on the innovative technical solution of this invention. The components in the various embodiments described and shown in the drawings can be combined and arranged in different configurations. These variations in combination and arrangement should be considered as part of all embodiments of the innovative solution of this invention and included within the scope of protection of this invention.

[0058] In summary, the solutions or descriptions presented in the specific embodiments and accompanying drawings of this invention are not intended to limit the scope of protection claimed, but merely to illustrate selected embodiments / examples to help those skilled in the art understand the relevant innovative solutions. All other equivalent or parallel embodiments obtained by those skilled in the art based on these embodiments without inventive effort are within the scope of protection claimed by this invention.

[0059] Furthermore, the use of terms such as "first," "second," "third," etc. in terminology is merely for distinguishing identical or similar components and should not be interpreted as emphasizing or implying the relative importance of a particular component.

[0060] Furthermore, in the description of the technical solution of this invention, unless otherwise explicitly specified / limited / restricted, the terms "set," "install," "connect," and "link" should be interpreted broadly. For example, they can refer to fixed connections, detachable connections, or integral connections; they can refer to common connection methods in the art, such as welding, riveting, bolting, and threaded connections. Such connections can be mechanical or electrical; they can be direct connections or indirect connections through an intermediate medium; and they can refer to the internal communication between two components.

[0061] Example 1

[0062] Cement-based 3D printing technology is characterized by good radial mechanical properties along the printed strip. Therefore, the direction of force flow along the stress field is used as the main direction of the printing path. After clarifying the stress field information on which the structural printing path design is based, and considering the characteristics of cement-based 3D printing technology and equipment limitations, a stress flow-guided printing path design method is proposed, including the following steps:

[0063] Step S1: Divide the printed layers of the printed component into grid cells and use the geometric centroid of each cell as the target printing point; determine the principal stress data of all target printing points based on the stress field of the printed component.

[0064] Step S2: Select a target printing point as the printing start point, take the printing start point as the current printing point, take the adjacent mesh cells of the cell where the current printing point is located as the neighborhood, calculate the direction deflection coefficient of all target printing points in the neighborhood of the current printing point according to the principal stress data, and select the target printing point with the smallest direction deflection coefficient in the neighborhood as the second printing point.

[0065] Step S3: Using the second printing point as the current printing point, calculate the direction deflection coefficient of all target printing points in the neighborhood of the current printing point, and select the target printing point with the smallest direction deflection coefficient in the neighborhood as the third printing point.

[0066] Step S4: Repeat step S3 until there are no candidate target printing points in the neighborhood of the current printing point, resulting in m printing points. Connect the determined printing start point, the second printing point, the third printing point, ..., the mth printing point to form a printing path segment; determine at least one printing path segment according to the above steps.

[0067] Step S5: When there is only one determined printing path segment, the printing path segment is the printing path of the printed component; when there are at least two determined printing path segments, the printing path segments are connected according to the endpoints of adjacent printing path segments, and the printing path of the printed component is obtained under the condition of minimizing the number of printing paths.

[0068] The printing layers are divided into grid cells based on their shape and printing area, and the centroid of each grid cell is set as the target printing point. It should be noted that the centroid of a surface is the geometric center of the cross-section; for a shape cell with two axes of symmetry, the intersection of these axes is the centroid of the cross-section. For other shape cells, the geometric centroid is calculated using appropriate methods, such as integration or more advanced mathematical methods.

[0069] When the target printing point is an element node or integration point in the finite element analysis model, its principal stress data is directly calculated based on the stress state obtained by the numerical method. When the target printing point is not an element node or integration point in the finite element model, the point closest to the target printing point is selected, and the principal stress data of the closest point is used as the stress state of the target printing point for calculation. This is because when calculating the internal stress state of a structure using the finite element method, the element size of the model mesh is usually smaller than the width of the printing strip adapted to the 3D printing port of cement-based materials; that is, the mesh element density used for finite element analysis is significantly greater than the mesh element density in path design.

[0070] To design a printing path along the stress flow direction, starting from the selected printing start point, a weighted average search is performed on the neighboring target points of each current printing point to select the next printing point that best matches the stress flow direction. These points are then connected to generate a printing path segment, as follows:

[0071] After selecting the starting point for printing, during the search for the next printing point, a direction deflection coefficient λ is defined as the discrimination criterion. The neighboring grid cells of the current printing point are taken as the neighborhood, and the direction deflection coefficients of all candidate target printing points in the neighborhood are calculated according to the direction deflection coefficient calculation formula. The parameters involved in the calculation are illustrated in the diagram below. Figure 2 As shown, the formula for calculating the direction deflection coefficient is as follows:

[0072] λ=ω·l·sinα+(1-ω)·l·sinβ

[0073] In the formula, λ is the direction deflection coefficient, ω is the weighting factor, l is the length of the line segment connecting the current printing point and the target printing point, α is the angle between the line containing the stress direction corresponding to the current printing point and the line containing the proposed connected printing path segment, α∈[0,90°]; β is the angle between the line containing the stress direction corresponding to the target printing point and the line containing the proposed connected printing path segment, β∈[0,90°]. The l·sinα term represents the degree of deviation of the stress direction between the target point and the current printing point; the l·sinβ term represents the degree of deviation of the stress direction between the current printing point and the target point. The weighting factor ω∈[0,1] is calculated based on the absolute values ​​of the principal stresses corresponding to the current printing point and the target printing point. The formula for calculating the weighting factor is as follows:

[0074]

[0075] Where, σ sp σ is the stress value corresponding to the current printing point s. pi For the target print point p within the neighborhood of the current print point i The corresponding stress value.

[0076] The smaller the calculated direction deflection coefficient λ of the target printing point in the neighborhood, the smaller the direction deflection of the line segment connecting the two points compared to the stress flow direction at the two points. Therefore, the target printing point with the smallest direction deflection coefficient λ in the neighborhood is selected as the end of the printing path of this segment, which is the second printing point. Then, the second printing point is removed from the subsequent neighborhood search range and used as the starting point for generating the next path segment. This process continues to search for the next target printing point to form a path segment until there are no candidate target printing points in the neighborhood of the current printing point. At this point, the search stops, the connection generation of the path segment is completed, and the printing path segment is used as the first printing path segment.

[0077] like Figure 3 In the example shown, assuming that the absolute values ​​of the principal stresses at each point in the stress field are the same, and s is the current printing point, the direction deflection coefficients λ of all target printing points p1 to p8 in the neighborhood of the current printing point are calculated according to the direction deflection coefficient calculation formula. It can be found that p3 has the smallest direction deflection coefficient in the neighborhood of the current printing point s. Therefore, sp3 is connected to form a printing path segment, and p3 is made the current printing point. At the same time, point s is removed from the set of target printing points.

[0078] For the remaining target print points within the print layer design domain that did not participate in the generation of print path segments, select a new path start point near the start or end point of the formed print path segment, and repeat the above steps until all target print points within the design domain have been traversed, i.e., all target print points have participated in print path generation.

[0079] In some embodiments, at least two print path segments are determined. In step S4, after determining the first print path segment, for the remaining target print points in the print layer that did not participate in the generation of the print path segment, a new target print point is selected near the start or end point of the first print path segment as the print start point. This continues until there are no candidate target print points in the neighborhood of the current print point, or when the existing candidate target print points and the path segment of the current print point overlap with the formed print path segments, then the print point search is stopped, and steps S2 to S4 are repeated to determine the second print path segment, ..., the nth print path segment. The number of determined print path segments is n, where n is an integer ≥ 2, meaning there are two or more print path segments.

[0080] The above steps determine the printed path segments that have been generated throughout the printed layer design domain and pass through all printing points. Connect the endpoints of adjacent printed path segments. During the connection process, the condition that must be met is to generate as continuous printed paths as possible, that is, to minimize the number of printed paths, so as to reduce the number of structural weak parts caused by path breaks during printing. In other words, the number of printed paths for the determined printed component is at least one.

[0081] In some embodiments, after confirming the number and direction of the printing path segments of the printed component, it is also necessary to check and adjust the spacing between the parallel printing path segments to ensure that the spacing meets the requirements. This prevents excessive compression of the cement-based material after printing due to insufficient spacing, which can cause "overfilling" of the material and result in surface protrusions, affecting the printing quality. Adjusting the spacing of the parallel printing path segments is done manually. Taking a square cell as an example with a side length of d, the spacing of printing path segments parallel to the cell's side length is equal to the cell's side length. Since the cell size design already considers that it needs to be within the width range of the printing strip, no adjustment is needed to meet the spacing requirements for this type of printing path. For parallel printing path segments parallel to the cell's diagonal, the spacing is less than the cell's side length, and therefore may be less than the lower limit of the printing strip width range. Therefore, it is necessary to check the spacing of these parallel printing path segments and adjust it to the width range suitable for the printing opening to generate the final printing path.

[0082] It should be noted that the stress field expresses principal stress information. The principal stress information is at least one of principal tensile stress, principal compressive stress, and maximum absolute value principal stress. The stress field of the printed component in step S1 can be one of principal tensile stress field, principal compressive stress field, and maximum absolute value principal stress field. Different printing paths are designed using different stress fields. In practical applications, different stress fields are selected for printing path design according to the requirements of the printed component.

[0083] The stress flow-guided printing path design method provided in this embodiment first divides the layer structure of the 3D printed component into several units, using the geometric center of each unit as the target printing point. The stress field of the 3D printed component is then obtained, representing the magnitude and direction of the principal stresses. This principal stress data is assigned to the target printing points, and a printing path is formed according to the stress flow direction of each target printing point. When all target points participate in path generation, the layer shape filling is completed, resulting in the final printing path of the 3D printed component. This method fully considers the stress field of the 3D printed component, which reflects the structural stress distribution under actual application conditions. By optimizing the printing path design according to the stress field, the axial strength of the printing path is fully utilized, thereby improving the mechanical properties of the component and ensuring that the anisotropic distribution of the 3D printed component matches its applicable working conditions.

[0084] Example 2

[0085] This embodiment adopts the design scheme of Embodiment 1 for printing path design. The printed component is a prism used in the flexural strength test, which has a regular shape and the size of the prism specimen is 100mm×100mm×400mm.

[0086] First, the stress field of the prism is obtained. To obtain the stress distribution inside the prism under four-point bending loading in the flexural strength test, numerical simulation analysis is performed using the finite element analysis software ABAQUS. In the finite element model, the Z-direction represents the forming direction, and the planar design domain size for the printing layer path design is 100mm × 400mm. The coordinates and stress data of a layer element node parallel to the XY plane in the finite element analysis results are exported and visualized to obtain the stress field of the prism. This embodiment shows the principal tensile stress field and the absolute maximum principal stress field of the prism. The principal tensile stress field mainly reflects the flow direction of the maximum tensile stress inside the structure; the absolute maximum principal stress field reflects the magnitude and direction of the absolute maximum principal stress in each part of the structure. Both stress fields reflect the different maximum principal stress flow directions inside the structure to a certain extent, therefore, the printing path design is based on these two cases.

[0087] The 3D printing of the prism uses a print head with an inner diameter of 16mm and an outer diameter of 26mm. The width of the printing strip is 20mm ± 2mm. Therefore, square units with a side length of 20mm are designed as the grid units for printing layers. The center point of each numbered unit is the target printing point that the printing path needs to traverse.

[0088] Since the target printing points correspond to element nodes in a partial finite element analysis, the target printing point numbers are matched with the element node numbers. The corresponding nodal stress data represents the magnitude and direction of the principal stresses at the target printing point in that stress field. The matching of principal stress information for target printing points is as follows: Figure 4 , 5 As shown, Figure 4 (a) and Figure 5 (a) The arrows in the middle represent the magnitude and direction of the principal stress at the printing point. Figure 4 (b) and Figure 5 (b) The arrows in the diagram only indicate the direction of the principal stress at the printing point.

[0089] The printing start point should preferably be a target printing point with a high stress value at the edge of the printing layer or at a structural transition point, and it should be a non-stress concentration area. Figure 4 (a) The principal tensile stress at the bottom of the prism is relatively large. Several printing points at locations with high stress are selected as starting points. Using the printing point search method in steps S2-S4, four printing path segments based on the principal tensile stress field are generated, such as... Figure 6 As shown. According to Figure 4 (a) The maximum absolute principal stress field of the displayed prism is used as a starting point by selecting several printing points with large absolute principal stress values. The printing point search method in steps S2-S4 is then used to generate four printing path segments based on the maximum absolute principal stress field, such as... Figure 7 As shown.

[0090] Observe all printed path segments generated at the target printing point, and select the most suitable endpoints to connect them using the reference direction deflection coefficient. Minimize the stress direction deflection between the connecting line segments and their endpoints to reduce the number of independent printed paths. Also, place the starting points of remaining printed path segments as close as possible to the endpoints of existing printed path segments to reduce print head bounce during printing and improve the overall integrity and continuity of the structure. The stress flow-guided printed path based on the above post-processing is as follows: Figure 8 As shown, the single-layer printing path under both stress fields consists of two continuous printing paths.

[0091] Example 3

[0092] This embodiment uses the design scheme of Embodiment 1 for printing path design. The printed component is a topology-optimized cement pavement structure with an irregular shape. The topology-optimized pavement structure is generated based on the variable density method and has symmetry. Based on known stress data, the stress field method of Embodiment 2 is used to obtain the distribution of the generated stress field as follows: Figure 9 As shown, the stress field is the principal stress field with the largest absolute value.

[0093] In step S1, unlike the planar design domain with a regular contour shape in Example 2, the topology-optimized pavement structure has an irregular two-dimensional planar design domain. Consider first dividing the planar design domain into regions, dividing the irregular printed layer contour shape into multiple regular, easily uniformly meshed curved quadrilaterals, such as... Figure 10 As shown, the topology-optimized pavement structure planar design domain is divided into six regions enclosed by curved quadrilaterals. Based on this, each region is further divided into relatively uniform grid cells. The grid cell division and target printing point layout results are shown below. Figure 11 As shown.

[0094] Compared to the method of setting target printing points using square elements, the method of dividing and distributing grid cells into partitioned grid cells exhibits greater irregularity in the target printing points, and the overlap rate between the element division and the element nodes and integration points in the finite element analysis process is lower. Therefore, the point closest to all target printing points is selected, and its stress state is matched to that of the target printing point as the stress state of the target printing point, such as... Figure 12 As shown.

[0095] Based on the maximum principal stress field of absolute value after stress matching of the printed points in the topology-optimized pavement structure, different printing starting points are selected sequentially in each partition. Within each partition, the printing point search method of steps S2-S4 is used, taking the target printing points in the adjacent grid cells of the current printing point cell as the neighborhood, and generating printing path segments. When the most suitable next printing point in the neighborhood is a point in another partition, the printing point search for that segment stops, completing the generation of the current printing segment. This process continues until all target printing points in each partition are traversed, generating a total of 14 printing path segments, as shown below. Figure 13 As shown. Observe the generated print path segments, select the most suitable endpoints to connect adjacent print path segments, and reduce the number of independent print paths while minimizing the stress direction deflection corresponding to the connecting line segments and endpoints. Based on this, this embodiment further optimizes the post-processing connections of the print paths generated by this method according to design experience, thereby reducing print breakpoints and ultimately forming a complete single print path for the layer. After confirming the number of print paths, adjust the spacing between adjacent paths according to the print strip width range to ensure that each spacing meets the print strip width requirements. Simultaneously, adjust the outer contour boundary path to make it as parallel as possible to the outer contour. The resulting continuous stress flow guided print path based on the maximum absolute value principal stress field is shown below. Figure 14 As shown, the final printed product after printing according to the printing path is as follows. Figure 15 As shown.

[0096] Example 4

[0097] This embodiment provides a stress-flow-guided printing path design system, the system comprising:

[0098] The data units are defined to divide the printed layers of the printed component into grid units, and the geometric centroid of each unit is used as the target printing point; based on the stress field of the printed component, the principal stress data of all target printing points are determined.

[0099] The first calculation unit is used to select a target printing point as the printing start point, take the printing start point as the current printing point, take the adjacent grid cells of the cell where the current printing point is located as the neighborhood, calculate the direction deflection coefficient of all target printing points in the neighborhood of the current printing point, and select the target printing point with the smallest direction deflection coefficient in the neighborhood as the second printing point.

[0100] The second calculation unit is used to calculate the direction deflection coefficient of all target printing points in the neighborhood of the current printing point based on the principal stress data, taking the second printing point as the current printing point, and selecting the target printing point with the smallest direction deflection coefficient in the neighborhood as the third printing point.

[0101] A print path segment unit is determined to repeat step S3 until there are no candidate target print points in the neighborhood of the current print point. The determined print start point, second print point, third print point, ..., m-th print point are connected to form a print path segment. At least one print path segment is determined according to the above steps.

[0102] The print path determination unit is used to determine the print path of the printed component when there is only one print path segment; when there are at least two print path segments, the print path segments are connected according to the endpoints of adjacent print path segments to obtain the print path of the printed component under the condition of minimizing the number of print paths.

[0103] The systems or modules described in the above embodiments can be implemented by computer chips or physical entities, or by products with certain functions. For ease of description, the above devices are described in terms of function, divided into various modules. Of course, in implementing this application, the functions of each module can be implemented in one or more software and / or hardware, or the module that implements the same function can be implemented by a combination of multiple sub-modules, etc. The system of this embodiment is used to implement the stress flow-guided printing path design method provided in Embodiment 1.

[0104] An electronic device is also provided, including at least one processor and a memory communicatively connected to the at least one processor; the memory stores instructions executable by the at least one processor, the instructions being executed by the at least one processor to enable the at least one processor to perform the stress flow-guided printing path design method provided in Embodiment 1.

[0105] For those skilled in the art, when understanding the solutions described in the specific embodiments of the present invention, conventional technical manuals in the field can be consulted. At the same time, appropriate understandings or adjustments can be made to the above-mentioned terms to deduce the same or similar technical solutions without creative effort.

[0106] The above embodiments describe only the basic principles, main features and / or advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and the description of the invention content in the specification are only the principles or specific cases of the present invention. Without departing from the essence of the innovative idea of ​​the present invention, there are various changes and improvements to the innovative solution of the present invention, and all such changes and improvements fall within the scope of protection claimed by the present invention.

Claims

1. A printing path design method based on stress flow guidance, characterized in that, Includes the following steps: Step S1: Divide the printed layers of the printed component into grid cells, and use the geometric centroid of each cell as the target printing point; Based on the stress field of the printed component, determine the principal stress data for all target printing points; Step S2: Select a target printing point as the printing start point, take the printing start point as the current printing point, take the adjacent mesh cells of the cell where the current printing point is located as the neighborhood, calculate the direction deflection coefficient of all target printing points in the neighborhood of the current printing point according to the principal stress data, and select the target printing point with the smallest direction deflection coefficient in the neighborhood as the second printing point. Step S3: Using the second printing point as the current printing point, calculate the direction deflection coefficient of all target printing points in the neighborhood of the current printing point, and select the target printing point with the smallest direction deflection coefficient in the neighborhood as the third printing point. Step S4: Repeat step S3 until there are no target printing points in the neighborhood of the current printing point, resulting in m printing points. Connect the determined printing start point, the second printing point, the third printing point, ..., the mth printing point to form a printing path segment; determine at least one printing path segment according to the above steps. Step S5: When there is only one determined printing path segment, the printing path segment is the printing path of the printed component; when there are at least two determined printing path segments, the printing path segments are connected according to the endpoints of adjacent printing path segments, and the printing path of the printed component is obtained under the condition of minimizing the number of printing paths.

2. The printing path design method based on stress flow guidance according to claim 1, characterized in that, During the grid cell division process, the printed layers of the printed component are divided into grid cells according to the layer shape and printing range.

3. The printing path design method based on stress flow guidance according to claim 2, characterized in that, During the grid cell division process, the size of the grid cell is determined based on the width range of the printed strip extruded by the print head of the printing equipment. For regular-shaped printed sheets, the printed sheets are divided into grid cells according to rectangular cells. For irregular printed sheets, the printed sheets are first divided into multiple regular curved quadrilaterals that are easy to divide into uniform grid cells according to their shape characteristics. Then, the curved quadrilaterals are divided into grid cells according to appropriate cell sizes.

4. The printing path design method based on stress flow guidance according to claim 1, characterized in that, The stress field of a printed component expresses principal stress information, including the direction and magnitude of the principal stresses. The principal stress information includes at least one of the principal tensile stress, principal compressive stress, and the principal stress with the maximum absolute value.

5. The printing path design method based on stress flow guidance according to claim 1, characterized in that, In step S2, based on the stress field of the printed component, the printing starting point is the target printing point with a large stress value located at the edge of the printed layer or at the structural turning point.

6. The printing path design method based on stress flow guidance according to claim 1, characterized in that, The formula for calculating the direction deflection coefficient is as follows: λ=ω·l·sinα+(1-ω)·l·sinβ In the formula, λ is the direction deflection coefficient, ω is the weighting factor, l is the length of the line segment connecting the current printing point and the target printing point, α is the angle between the line containing the stress direction corresponding to the current printing point and the line containing the printing path segment to be connected, α∈[0,90°]; β is the angle between the line containing the stress direction corresponding to the target printing point and the line containing the printing path segment to be connected, β∈[0,90°].

7. The printing path design method based on stress flow guidance according to claim 6, characterized in that, The formula for calculating the weighting factor is as follows: Where, σ sp σ is the stress value corresponding to the current printing point s. pi For the target print point p within the neighborhood of the current print point i The corresponding stress value.

8. The printing path design method based on stress flow guidance according to any one of claims 1-7, characterized in that, The design method identifies at least two print path segments and includes the following steps: Step S1: Divide the printed layers of the printed component into grid cells and use the geometric centroid of each cell as the target printing point; determine the principal stress data of all target printing points based on the stress field of the printed component. Step S2: Select a target printing point as the printing start point, take the printing start point as the current printing point, take the adjacent mesh cells of the cell where the current printing point is located as the neighborhood, calculate the direction deflection coefficient of all target printing points in the neighborhood of the current printing point according to the principal stress data, and select the target printing point with the smallest direction deflection coefficient in the neighborhood as the second printing point. Step S3: Using the second printing point as the current printing point, calculate the direction deflection coefficient of all target printing points in the neighborhood of the current printing point, and select the target printing point with the smallest direction deflection coefficient in the neighborhood as the third printing point. Step S4: Repeat step S3 until there are no target printing points in the neighborhood of the current printing point, and obtain m printing points. Connect the determined printing start point, the second printing point, the third printing point, ..., the mth printing point to form a printing path segment, which is used as the first printing path segment. For the remaining target printing points within the printing layer that did not participate in the generation of printing path segments, a new target printing point is selected near the start or end point of the first printing path segment as the printing start point. Steps S2 to S4 are repeated until there are no candidate target printing points in the neighborhood of the current printing point, or when the existing candidate target printing points and the path segments of the current printing point overlap with the already formed printing path segments, the printing point search is stopped, and the second printing path segment, ..., the nth printing path segment are determined. The number of determined printing path segments is n, where n is an integer ≥ 2, that is, there are two or more printing path segments. Step S5: Connect the determined at least two print path segments according to the endpoints of adjacent print path segments to obtain the print path of the print component while minimizing the number of print paths.

9. A printing path design system based on stress flow guidance, characterized in that, The system includes: The data units are defined to divide the printed layers of the printed component into grid units, and the geometric centroid of each unit is used as the target printing point; based on the stress field of the printed component, the principal stress data of all target printing points are determined. The first calculation unit is used to select a target printing point as the printing start point, take the printing start point as the current printing point, take the adjacent grid cells of the cell where the current printing point is located as the neighborhood, calculate the direction deflection coefficient of all target printing points in the neighborhood of the current printing point according to the principal stress data, and select the target printing point with the smallest direction deflection coefficient in the neighborhood as the second printing point. The second calculation unit is used to calculate the direction deflection coefficient of all target printing points in the neighborhood of the current printing point, taking the second printing point as the current printing point, and select the target printing point with the smallest direction deflection coefficient in the neighborhood as the third printing point. A print path segment unit is determined to repeat step S3 until there is no target print point in the neighborhood of the current print point, resulting in m print points. The determined print start point, second print point, third print point, ..., m-th print point are connected to form a print path segment. At least one print path segment is determined according to the above steps. The print path determination unit is used to determine the print path of the printed component when there is only one print path segment; when there are at least two print path segments, the print path segments are connected according to the endpoints of adjacent print path segments to obtain the print path of the printed component under the condition of minimizing the number of print paths.

10. An electronic device comprising at least one processor and a memory communicatively connected to said at least one processor; said memory storing instructions executable by said at least one processor, characterized in that, The instructions are executed by the at least one processor to enable the at least one processor to perform the stress flow-guided print path design method according to any one of claims 1-8.

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