Printing path design method and system based on stress flow guidance

Abstract

The invention discloses a printing path design method and system based on stress flow guidance, and the design method comprises the steps: S1, carrying out the grid cell division, and determining a target printing point; determining principal stress data of the target printing point according to the stress field; s2, selecting a printing starting point as a current printing point, calculating a direction deflection coefficient according to the principal stress data, and selecting a target printing point with the minimum direction deflection coefficient in a neighborhood as a second printing point; s3, the second printing point serves as the current printing point, and after the direction deflection coefficient is calculated, the target printing point with the minimum direction deflection coefficient in the neighborhood is selected as a third printing point; s4, repeating S3, and connecting the printing points to form a printing path segment; determining at least one printing path fragment according to the steps; and S5, obtaining the printing path of the printing component from the determined at least one printing path segment. According to the method, the path design reasonability is improved, and the mechanical anisotropy distribution of the printing component is matched with the adaptive working condition.

Description

Technical Field

[0001] The present 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 Art

[0002] Concrete 3D printing is a method of stacking cement-based materials layer by layer along a preset printing path by extrusion, injection, etc. through a control system to eventually form a structural entity. It is one of the main means of intelligent construction with the advantages of digitization, automation, and intelligence. The 3D printing process has the characteristics of accumulating into layers and stacking layer by layer. This molding principle will lead to the appearance of a variety of weak mechanical properties in the molded structure, which are mainly distributed at the interface between the printed layers and the contact interface between the printed strips in the layer. The generation of structural weak areas leads to the anisotropy of the mechanical properties of the 3D printed products, which makes the force differences in different directions significant, thus affecting the force performance of the final molded components in certain directions. Therefore, related technologies to improve the mechanical properties of components by optimizing the printing path have gradually emerged.

[0003] At present, the research on 3D printing path design is mainly aimed at 3D printing processes such as stereolithography (SLA), fused deposition modeling (FDM), and selective laser sintering (SLS). The relatively mature path planning algorithms proposed, such as Zigzag, Hilbert, Contour, etc., focus more on molding accuracy and printing efficiency, lack consideration of the mechanical properties of printed components, and are more likely to have weak mechanical properties in the main stress-bearing parts. And due to the large differences in printing materials and the different levels of printing resolution, the above method is not applicable enough in the 3D printing path planning design of cement-based materials. The concrete 3D printing path optimization method based on the first principal stress vector distribution disclosed in Chinese patent 202110857585.9 obtains the three-dimensional model of the relevant components in the modeling software, and slices the three-dimensional model using the slicing software to obtain the slice information and layer thickness information of the model; after the above steps are completed, the three-dimensional model is imported into the finite element software for stress and strain calculation, and the stress vector information of the key nodes of each part is obtained, including size 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, and plans the printing path in combination with the characteristics of concrete 3D printing, so that the component obtained by concrete 3D printing can 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 direction (angle) of the stress vector is considered, without fully considering the magnitude; the stress situation is not considered enough, 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 the present invention is to overcome the problem that the stress considered in the path design process of the prior art is only the first principal stress, the stress situation is not sufficiently considered, and the problem based on the requirements of various stress fields is not considered, and to provide a printing path design method and system based on stress flow guidance.

[0005] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0006] A printing path design method based on stress flow guidance includes the following steps:

[0007] Step S1, dividing the printed layer of the printed component into grid units, and taking the geometric centroid of each unit as the target printing point; determining the principal stress data of all the target printing points according to the stress field of the printed component;

[0008] Step S2, selecting a target printing point as the printing starting point, taking the printing starting point as the current printing point, taking the adjacent grid cells of the cell where the current printing point is located as the neighborhood, calculating the directional deflection coefficients of all target printing points in the neighborhood of the current printing point according to the principal stress data, and selecting the target printing point with the smallest directional deflection coefficient in the neighborhood as the second printing point;

[0009] Step S3, taking the second printing point as the current printing point, calculating the directional deflection coefficients of all target printing points in the neighborhood of the current printing point, and selecting the target printing point with the smallest directional deflection coefficient in the neighborhood as the third printing point;

[0010] Step S4, repeating step S3 until there is no candidate target printing point in the neighborhood of the current printing point, obtaining m printing points, connecting the determined printing starting point, the second printing point, the third printing point, ..., the mth printing point to form a printing path segment; determining at least one printing path segment according to the above steps;

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

[0012] In the technical solution of the present invention, the layer structure of the printed component to be designed for printing path is first divided into several units, and the geometric center of each unit is used as the target printing point to obtain the stress field of the printed component. The stress field expresses the magnitude and direction information of the principal stress, and 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 generation of the path, the layer shape filling is completed, and the printing path of the final printed component is obtained. This method fully considers the stress field of the printed component. The stress field can reflect the structural stress distribution corresponding to the printed component in the actual application conditions. The printing path is optimized according to the stress field, and the axial strength of the printing path is fully utilized, thereby improving the mechanical properties of the component, so that the mechanical anisotropy distribution of the 3D printed component matches the working conditions it adapts to.

[0013] It should be noted that the printed component in the present invention is a component of uniform cross-section, that is, the profiles of the cross-sections of each printed layer obtained by slicing along a parallel plane in the molding direction are exactly the same. The printing path is designed for the printed layer, and then different layers of the printed layer are printed according to the designed printing path to obtain the printed component.

[0014] As a preferred solution of the present invention, in the process of dividing the grid units, the printed layers of the printed component are divided into grid units according to the layer shapes and the printing ranges.

[0015] Furthermore, during the grid unit division process, the size of the grid unit is determined according to the width range of the print strip extruded by the print head of the printing device; for regular-shaped printed layers, they are divided into rectangular grid units, and for irregular printed layers, they are first divided into a plurality of regular curved quadrilaterals that are convenient for relatively uniform grid unit division according to the shape characteristics of the printed layers, and then the curved quadrilaterals are divided into grid units according to appropriate unit sizes. The above technical solution takes into account the unit division of regular and irregular two-dimensional shaped printed layers, is applicable to different 3D printed components, and improves the applicability of the method of the present invention.

[0016] As a preferred embodiment of the present invention, the stress field of the printed component expresses the principal stress information and realizes the visualization of the stress field of the magnitude and direction of the principal stress; the stress field is expressed in the form of directed line segments with the arrow pointing to the principal stress direction and the line segment length being the principal stress magnitude, and the principal stress information is at least one of the principal tensile stress, the principal compressive stress, and the absolute maximum principal stress information.

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

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

[0019] As a preferred solution of the present invention, the calculation formula of the direction deflection coefficient is as follows

[0020] λ=ω·l·sinα+(1-ω)·l·sinβ

[0021] Where λ is the directional deflection coefficient, ω is the weight 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 straight line where the stress direction corresponding to the current printing point is located and the straight line where the printing path segment to be connected is located, α∈[0,90°]; β is the angle between the straight line where the stress direction corresponding to the target printing point is located and the straight line where the printing path segment to be connected is located, β∈[0,90°].

[0022] As a more preferred embodiment of the present invention, the weight factor calculation formula is as follows:

[0023]

[0024] Among them, σ sp is the stress value corresponding to the current printing point s, σ pi The target printing point p in the neighborhood of the current printing point i The corresponding stress value.

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

[0026] Step S1, dividing the printed layer of the printed component into grid units, and taking the geometric centroid of each unit as the target printing point; determining the principal stress data of all the target printing points according to the stress field of the printed component;

[0027] Step S2, selecting a target printing point as the printing starting point, taking the printing starting point as the current printing point, taking the adjacent grid cells of the cell where the current printing point is located as the neighborhood, calculating the directional deflection coefficients of all target printing points in the neighborhood of the current printing point according to the principal stress data, and selecting the target printing point with the smallest directional deflection coefficient in the neighborhood as the second printing point;

[0028] Step S3, taking the second printing point as the current printing point, calculating the directional deflection coefficients of all target printing points in the neighborhood of the current printing point, and selecting the target printing point with the smallest directional deflection coefficient in the neighborhood as the third printing point;

[0029] Step S4, repeating step S3 until there is no candidate target printing point in the neighborhood of the current printing point, obtaining m printing points, connecting the determined printing starting point, the second printing point, the third printing point, ..., the mth printing point to form a printing path segment as the first printing path segment;

[0030] For the remaining target printing points in the printing layer that are not involved in the generation of the printing path segments, a new target printing point is selected near the starting point or the end point of the first printing path segment as the printing starting point, and steps S2 to S4 are repeated until there is no candidate target printing point in the neighborhood of the current printing point, or the existing candidate target printing point and the path segment of the current printing point overlap with the formed printing path segment, then the printing point search is stopped, and the second printing path segment, ..., the nth printing path segment are determined, and the number of the 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 printing path segments according to the endpoints of the printing path segments that are adjacent to each other, and obtain the printing path of the printing component under the condition that the number of printing paths is minimized.

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

[0033] Determine data units for dividing the printed layers of the printed component into grid units, and use the geometric centroid of each unit as the target printing point; determine the principal stress data of all target printing points according to the stress field of the printed component;

[0034] A first calculation unit is used to select a target printing point as a printing starting point, take the printing starting point as a current printing point, take the adjacent grid cells of the cell where the current printing point is located as a neighborhood, calculate the directional deflection coefficients 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 directional deflection coefficient in the neighborhood as a second printing point;

[0035] A second calculation unit is used to use the second printing point as the current printing point, calculate the directional deflection coefficients of all target printing points in the neighborhood of the current printing point, and select the target printing point with the smallest directional deflection coefficient in the neighborhood as the third printing point;

[0036] A printing path segment determination unit is used to repeat step S3 until there is no candidate target printing point in the neighborhood of the current printing point, and m printing points are obtained, and the determined printing starting point, the second printing point, the third printing point, ..., the mth printing point are connected to form a printing path segment; at least one printing path segment is determined according to the above steps;

[0037] A printing path determination unit is used to determine that when the determined printing path segment is one, the printing path segment is the printing path of the printing component; when the determined printing path segment is at least two, the printing path segments are connected according to the endpoints of the printing path segments with adjacent endpoints, and the printing path of the printing component is obtained under the condition that the number of printing paths is minimized.

[0038] The present invention also provides an electronic device, comprising 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, and the instructions are executed by the at least one processor so that the at least one processor can execute the above-mentioned stress flow-guided printing path design method.

[0039] Compared with the prior art, the present invention has the following beneficial effects:

[0040] The present invention provides a printing path design method based on stress flow guidance. The method fully considers the stress field of the printed component. The stress field can reflect the structural stress distribution corresponding to the printed component in the actual application condition. The printing path is optimized according to the stress field, and the axial strength of the printing path is fully utilized to improve the mechanical properties of the component. Based on the process characteristics of 3D printing, the improvement of the mechanical properties of the component is considered to improve 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 condition it adapts to. BRIEF DESCRIPTION OF THE DRAWINGS

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

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

[0043] Figure 3 Schematic diagram of current printing point direction calculation and printing point selection for printing 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 force 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 absolute maximum principal stress field of the prism; (b) The direction of the principal stress flow at the target printing point;

[0046] Figure 6 The printing path fragment of the prism based on the principal tensile stress field;

[0047] Figure 7 is the printing path segment based on the absolute maximum principal stress field;

[0048] Figure 8 For the prismatic specimen, (a) the printing path guided by the principal tensile stress field; (b) the printing path guided by the absolute maximum principal stress field;

[0049] Fig. 9 This is a schematic diagram of the absolute maximum principal stress field of the topologically optimized pavement structure;

[0050] Fig.10 Schematic diagram of the plane design domain partition for topological optimization of pavement structure;

[0051] Fig.11 (a) Partition grid unit division diagram for topological optimization of pavement structure; (b) Target printing point layout diagram;

[0052] Fig.12 Schematic diagram of stress data screening and matching of target printing points for topological optimization of pavement structure plies;

[0053] Fig.13 Printing path segments generated for topologically optimized pavement structures based on the absolute maximum principal stress field;

[0054] Fig.14 Printing path guided by the absolute maximum principal stress field for topological optimization of pavement structures;

[0055] Fig.15 The finished product map of the topologically optimized pavement structure after printing the printing path obtained by the design method of the present invention. DETAILED DESCRIPTION

[0056] In order to more clearly describe the invention purpose, technical scheme and technical effect advantages in the specific implementation case of the present invention, the scheme in the specific embodiment will be described in detail in combination with the drawings of the specification of the present invention. The specific technical scheme involved in the following specific embodiments is only for a clear and complete description of the innovative technical scheme of the present invention. It is only a part of the specific implementation scheme that can be adopted by the present invention, not all embodiments, and should not be understood as a limitation on the innovative scheme of the present invention. Any scheme adopting the same inventive concept of the present invention should be included in the protection scope of the present invention.

[0057] Secondly, the description of the drawings in the specific embodiments of the present invention is only for the convenience of technical personnel to understand the solution of the present invention. The partial details in the drawings are for the convenience of clearly presenting the technical solution. It should not be considered that all technical features in the drawings must be included in the specific implementation cases, and the detailed features in the drawings should not be identified as additional limitations on the innovative technical solution of the present invention. The components in the various embodiments described and shown in the drawings can be combined and arranged according to different configurations, and these changes in combination and arrangement should be identified as part of the entire embodiment of the innovative solution of the present invention and included in the scope of protection of the present invention.

[0058] In summary, the schemes or descriptions presented in the specific embodiments and drawings of the present invention are not intended to limit the scope of protection claimed, but are merely selected embodiments / cases to help technicians understand the relevant innovative solutions. Based on these embodiments, all other equivalent or parallel embodiments obtained by those skilled in the art without creative work are within the scope of protection claimed by the present invention.

[0059] In addition, the expressions “first”, “second”, “third”, etc. that appear in the terms are merely descriptions used to distinguish the same or similar components and should not be understood as emphasizing or implying the relative importance of specific components.

[0060] In addition, in the description of the technical solution of the present invention, unless otherwise clearly specified / defined / restricted, the terms "set", "install", "connected" and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection, and can be welding, riveting, bolting, threading and other commonly used connection means in the field. This connection can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, and it can be the internal connection of two components.

[0061] Example 1

[0062] The 3D printing process of cement-based materials has the characteristic of good mechanical properties along the radial direction of the printed strip. Therefore, the force flow direction reflected by the stress field is used as the main direction basis of the printing path. After clarifying the stress field information based on which the structural printing path design is based, considering the characteristics of the 3D printing process of cement-based materials and equipment limitations, a printing path design method based on stress flow guidance is proposed, which includes the following steps:

[0063] Step S1, dividing the printed layer of the printed component into grid units, and taking the geometric centroid of each unit as the target printing point; determining the principal stress data of all the target printing points according to the stress field of the printed component;

[0064] Step S2, selecting a target printing point as the printing starting point, taking the printing starting point as the current printing point, taking the adjacent grid cells of the cell where the current printing point is located as the neighborhood, calculating the directional deflection coefficients of all target printing points in the neighborhood of the current printing point according to the principal stress data, and selecting the target printing point with the smallest directional deflection coefficient in the neighborhood as the second printing point;

[0065] Step S3, taking the second printing point as the current printing point, calculating the directional deflection coefficients of all target printing points in the neighborhood of the current printing point, and selecting the target printing point with the smallest directional deflection coefficient in the neighborhood as the third printing point;

[0066] Step S4, repeating step S3 until there is no candidate target printing point in the neighborhood of the current printing point, obtaining m printing points, connecting the determined printing starting point, the second printing point, the third printing point, ..., the mth printing point to form a printing path segment; determining at least one printing path segment according to the above steps;

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

[0068] The printed layer is divided into grid units according to the layer shape and printing range, and the centroid of each grid unit figure is set as the target printing point. It should be noted that the centroid of the surface is the geometric center of the cross-sectional figure. For shape units with two symmetry axes, the intersection of the two is the centroid of the cross section. For other shape units, the geometric centroid is calculated using corresponding calculation methods, such as integration or more advanced mathematical methods.

[0069] When the target printing point is a unit 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 a unit node or integration point in the finite element model, the point closest to the target printing point is screened out, and the principal stress data of the nearest point is used as the stress state of the target printing point for calculation. Because when the finite element method is used to calculate the internal stress state of the structure, the unit size of the model grid unit division is usually smaller than the printing strip width adapted to the cement-based material 3D printing port, that is, the model grid unit division density used for finite element analysis is significantly greater than the grid unit division density in path design.

[0070] To design a printing path along the stress flow direction, starting from the selected printing starting point, a weighted average search is performed in the neighborhood target points of each current printing point, and the next printing point that best matches the stress flow direction is selected and connected to generate printing path segments, as follows:

[0071] After selecting the printing starting point, in the process of searching for the next printing point, the direction deflection coefficient λ is defined as the discrimination criterion, and the adjacent grid cells of the cell where the current printing point is located are taken as the neighborhood. 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 as follows: Figure 2 As shown, the calculation formula of the direction deflection coefficient is as follows

[0072] λ=ω·l·sinα+(1-ω)·l·sinβ

[0073] Where λ is the directional deflection coefficient, ω is the weight 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 straight line where the stress direction corresponding to the current printing point is located and the straight line where the printing path segment to be connected is located, α∈[0,90°]; β is the angle between the straight line where the stress direction corresponding to the target printing point is located and the straight line where the printing path segment to be connected is located, β∈[0,90°]. Among them, 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 weight factor ω∈[0,1] is calculated according to the absolute value of the principal stress corresponding to the current printing point and the target printing point. The weight factor calculation formula is as follows:

[0074]

[0075] Among them, σ sp is the stress value corresponding to the current printing point s, σ pi The target printing point p in the neighborhood of the current printing point i The corresponding stress value.

[0076] The smaller the calculated result of the directional deflection coefficient λ of the target printing point in the neighborhood, the smaller the deflection of the direction 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 directional deflection coefficient λ in the neighborhood is selected as the end of the segment printing path, that 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. The next target printing point is continuously searched in this step to form a path segment until there is no candidate target printing point in the neighborhood of the current printing point. Then, the search is stopped, 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 case shown, it is assumed that the absolute values ​​of the principal stresses at each point in the stress field are the same, s is the current printing point, and the directional deflection coefficient λ of all target printing points p1 to p8 in the neighborhood of the current printing point is calculated according to the directional deflection coefficient calculation formula. It can be found that p3 has the smallest directional deflection coefficient in the neighborhood of the current printing point s. Therefore, sp3 is connected to form a printing path segment, and p3 becomes the current printing point, and point s is removed from the target printing point set.

[0078] For the remaining target printing points in the printing layer design domain that do not participate in the generation of the printing path segments, a new path starting point is selected near the starting point or end point of the formed printing path segment, and the above steps are repeated until all the target printing points in the design domain are traversed, that is, all the target printing points are involved in the generation of the printing path.

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

[0080] Through the above steps, it is determined that a print path segment that passes through all print points throughout the print layer design domain has been generated, and the end points of the print path line segments with adjacent end points are connected. During the connection process, the condition that a continuous print path is generated as much as possible, that is, the number of print paths is minimized, so as to reduce the number of structural weak points caused by path breakpoints during the printing process, that is to say, the number of print paths of the determined printing component is at least one.

[0081] In some embodiments, after confirming the number and direction of the printing path segments of the printing component, it is also necessary to check and adjust the spacing between the parallel printing path segments so that the spacing meets the requirements, to prevent the spacing from being too small, resulting in excessive extrusion of the cement-based material after printing, causing "overfilling" of the material to cause surface bulges, and affecting the printing quality. The adjustment of the spacing of the parallel printing path segments is artificial. For example, the grid unit is a square unit with a side length of d. For the printing path segments parallel to the unit side length, the spacing is equal to the unit side length, and the unit size design has considered that it needs to be within the printing strip width range. Therefore, for this type of printing path, the spacing does not need to be adjusted to meet the spacing requirements; for the parallel printing path segments parallel to the unit diagonal, the spacing is less than the unit side length, so it may be less than the lower limit of the printing strip width range, so it is necessary to check the spacing of the parallel printing path segments and adjust the spacing to the strip width range adapted to the printing port to generate the final printing path.

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

[0083] The printing path design method based on stress flow guidance provided in this embodiment first divides the layer structure of the printing component to be designed for the printing path into several units, and takes the geometric center of each unit as the target printing point to obtain the stress field of the printing component. The stress field expresses the magnitude and direction information of the principal stress, assigns the principal stress data expressed by the stress field to the target printing point, and then forms a printing path according to the stress flow direction of each target printing point. When all target points participate in the generation of the path, the layer shape filling is completed, and the printing path of the final printing component is obtained. This method fully considers the stress field of the printing component. The stress field can reflect the structural stress distribution corresponding to the printing component in the actual application conditions. The printing path is optimized according to the stress field, and the axial strength of the printing path is fully utilized, thereby improving the mechanical properties of the component, so that the mechanical anisotropy distribution of the 3D printed component matches the working conditions it adapts to.

[0084] Example 2

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

[0086] First, the stress field of the prism is obtained. In order to obtain the stress distribution inside the prism under the four-point bending loading condition in the flexural strength test, numerical simulation analysis is performed using the finite element analysis software ABAQUS. The Z direction in the finite element model represents the forming direction, and the plane design domain size of the printing layer path design is 100mm×400mm. The coordinates and stress data of a layer unit 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, where the principal tensile stress field mainly reflects the flow direction of the maximum tensile stress borne inside the structure; the absolute maximum principal stress field reflects the size and direction of the absolute maximum principal stress borne by each part of the structure. Both stress fields reflect the different maximum principal stress flow directions inside the structure to a certain extent, so the printing path design is based on the two situations.

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

[0088] Since the target printing point corresponds to some unit nodes in the finite element analysis, the target printing point number is matched with the unit node number, and the corresponding node stress data is the principal stress magnitude and direction corresponding to the target printing point in the stress field. Figure 4 , 5 As shown, Figure 4 (a) and Figure 5 The arrows in (a) represent the magnitude and direction of the principal stress at the printing point. Figure 4 (b) and Figure 5 The arrows in (b) only represent the principal stress directions at the printing points.

[0089] The starting point of printing should be the target printing point with larger stress value at the edge of the printing layer or at the turning point of the structure, and it should be a non-stress concentration part. Figure 4 (a) shows that the principal tensile stress at the bottom of the prism is relatively large. Several printing points at the locations with relatively large stress are selected as starting points. The printing point search method of steps S2-S4 is used to generate four printing path segments based on the principal tensile stress field, as shown in FIG. Figure 6 As shown. Figure 4 (a) shows the absolute maximum principal stress field of the prism. Similarly, several printing points with large absolute principal stress values ​​are selected as starting points. The printing point search method of steps S2-S4 is used to generate four printing path segments based on the absolute maximum principal stress field, as shown in FIG. Figure 7 shown.

[0090] Observe all the printing path segments generated by the target printing point, refer to the direction deflection coefficient to select the most appropriate endpoints to connect, and try to minimize the stress direction deflection corresponding to the connecting line segment and the connecting endpoint, which can reduce the number of independent printing paths, and try to set the starting point of the remaining printing path segments close to the endpoints of the formed printing path segments, reduce the jump of the print head during printing, and improve the integrity and continuity of the structure. The stress flow-guided printing path based on the two stress fields after the above post-processing is as follows Figure 8 As shown, the single-layer printing paths under the two stress fields are composed of two continuous printing paths.

[0091] Example 3

[0092] This embodiment adopts the design scheme of embodiment 1 to design the printing path. The printed component is a topologically optimized cement pavement structure with an irregular shape. The topologically optimized pavement structure is generated based on the variable density method and has symmetry. Based on the known stress data, the stress field method of embodiment 2 is used to obtain the distribution of the generated stress field as shown in FIG. Fig. 9 As shown, the stress field is the absolute maximum principal stress field

[0093] In step S1, unlike the plane design domain with regular contour shape in Example 2, the topology optimization pavement structure has an irregular two-dimensional plane design domain. Consider firstly dividing the plane design domain into regions, dividing the irregular print layer contour shape into a plurality of regular curved quadrilaterals that are convenient for uniform grid unit division, such as Fig.10 As shown in the figure, the plane design domain of the topological optimization pavement structure is divided into 6 areas surrounded by curved quadrilaterals. Based on this, each partition is divided into relatively uniform grid units. The grid unit division and target printing point layout results are shown in Fig.11 shown.

[0094] The target printing points of the partitioned grid unit layout are more irregular than the square unit target printing point layout method, and the unit division and the unit nodes, integration points, etc. in the finite element analysis process have a low overlap rate. Therefore, the points closest to all the target printing points are selected, and their stress states are matched to the target printing points as the stress states of the target printing points, such as Fig.12 shown.

[0095] According to the absolute maximum principal stress field after the topological optimization of the pavement structure printing point stress matching, different printing starting points are selected in each partition in turn, and the printing point search method of steps S2-S4 is used in each partition. The target printing point in the adjacent grid unit of the current printing point unit is used as the neighborhood to generate a printing path segment. When the most suitable next printing point in the neighborhood is a point in another partition, the printing point search of the segment is stopped, and the current printing segment generation is completed until all target printing points in each partition are traversed, and a total of 14 printing path segments are generated as shown in FIG. Fig.13 As shown. Observe the generated printing path segments, select the most appropriate endpoints to connect adjacent printing path segments, and reduce the number of independent printing paths while ensuring that the stress direction deflection corresponding to the connecting line segments and the connecting endpoints is minimized. On this basis, this embodiment further performs post-processing connection optimization on the printing paths generated by this method based on design experience, thereby reducing printing breakpoints so that the layer eventually forms a complete single printing path. After confirming the number of printing paths, the spacing between adjacent routes is adjusted according to the printing strip width range so that each spacing meets the printing strip width requirements. At the same time, the outer contour boundary path is adjusted to be as parallel to the outer contour as possible. The resulting continuous stress flow-guided printing path based on the absolute maximum principal stress field is shown as follows. Fig.14 As shown, the final printed product after printing according to the printing path is as follows Fig.15 shown.

[0096] Example 4

[0097] This embodiment provides a printing path design system based on stress flow guidance, the system comprising:

[0098] Determine data units for dividing the printed layers of the printed component into grid units, and use the geometric centroid of each unit as the target printing point; determine the principal stress data of all target printing points according to the stress field of the printed component;

[0099] A first calculation unit is used to select a target printing point as a printing starting point, take the printing starting point as a current printing point, take the adjacent grid cells of the cell where the current printing point is located as a neighborhood, calculate the direction deflection coefficients 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 a second printing point;

[0100] A second calculation unit is used to use the second printing point as the current printing point, calculate the directional deflection coefficients 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 directional deflection coefficient in the neighborhood as the third printing point;

[0101] A printing path segment determination unit is used to repeat step S3 until there is no candidate target printing point in the neighborhood of the current printing point, and connect the determined printing starting 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;

[0102] A printing path determination unit is used to determine that when the determined printing path segment is one, the printing path segment is the printing path of the printing component; when the determined printing path segment is at least two, the printing path segments are connected according to the endpoints of the printing path segments with adjacent endpoints, and the printing path of the printing component is obtained under the condition that the number of printing paths is minimized.

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

[0104] Also provided is an electronic device comprising 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, and the instructions are executed by the at least one processor so that the at least one processor can execute the stress flow-guided printing path design method provided in Example 1.

[0105] For those skilled in the art, when understanding the solutions described in the specific embodiments of the present invention, they can refer to the conventional technical manuals in the field. At the same time, for the places where the above-mentioned terms appear, they can make appropriate understandings or adjustments for reference, and deduce the implementation of the same or similar technical solutions without paying any creative work.

[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 above embodiments and the invention content of the specification only describe the principles or specific cases of the present invention. Without departing from the essence of the innovative idea of ​​the present invention, the innovative scheme of the present invention may be subject to various changes and improvements, and these changes and improvements all fall within the scope of protection required by the present invention.

Claims

1. A printing path design method based on stress flow guidance, characterized in that: The following steps are involved: Step S1, dividing the printed layer of the printed component into grid units, and taking the geometric centroid of each unit as the target printing point; According to the stress field of the printed component, the principal stress data of all target printing points are determined; Step S2, selecting a target printing point as the printing starting point, taking the printing starting point as the current printing point, taking the adjacent grid cells of the cell where the current printing point is located as the neighborhood, calculating the directional deflection coefficients of all target printing points in the neighborhood of the current printing point according to the principal stress data, and selecting the target printing point with the smallest directional deflection coefficient in the neighborhood as the second printing point; Step S3, taking the second printing point as the current printing point, calculating the directional deflection coefficients of all target printing points in the neighborhood of the current printing point, and selecting the target printing point with the smallest directional deflection coefficient in the neighborhood as the third printing point; Step S4, repeating step S3 until there is no target printing point in the neighborhood of the current printing point, obtaining m printing points, connecting the determined printing starting point, the second printing point, the third printing point, ..., the mth printing point to form a printing path segment; determining at least one printing path segment according to the above steps; Step S5: when the determined printing path segment is one, the printing path segment is the printing path of the printing component; when the determined printing path segment is at least two, the printing path segments are connected according to the endpoints of the printing path segments with adjacent endpoints, and the printing path of the printing component is obtained under the condition that the number of printing paths is minimized.

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

3. The printing path design method based on stress flow guidance according to claim 2 is characterized in that: During the grid unit division process, the size of the grid unit is determined according to the width range of the print bar extruded by the print head of the printing device; for regular-shaped printing layers, the printing layers are divided into grid units according to rectangular units, and for irregular printing layers, they are first divided into multiple regular curved quadrilaterals that are easy to evenly divide into grid units according to the shape characteristics of the printing layers, and then the curved quadrilaterals are divided into grid units according to the appropriate unit size.

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

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

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

7. The printing path design method based on stress flow guidance according to claim 6 is characterized in that: The weight factor calculation formula is as follows: Among them, σ sp is the stress value corresponding to the current printing point s, σ pi The target printing point p in the neighborhood of the current printing point i The corresponding stress value.

8. The printing path design method based on stress flow guidance according to any one of claims 1 to 7, characterized in that: The design method determines at least two printing path segments, and the design method comprises the following steps: Step S1, dividing the printed layer of the printed component into grid units, and taking the geometric centroid of each unit as the target printing point; determining the principal stress data of all the target printing points according to the stress field of the printed component; Step S2, selecting a target printing point as the printing starting point, taking the printing starting point as the current printing point, taking the adjacent grid cells of the cell where the current printing point is located as the neighborhood, calculating the directional deflection coefficients of all target printing points in the neighborhood of the current printing point according to the principal stress data, and selecting the target printing point with the smallest directional deflection coefficient in the neighborhood as the second printing point; Step S3, taking the second printing point as the current printing point, calculating the directional deflection coefficients of all target printing points in the neighborhood of the current printing point, and selecting the target printing point with the smallest directional deflection coefficient in the neighborhood as the third printing point; Step S4, repeating step S3 until there is no target printing point in the neighborhood of the current printing point, obtaining m printing points, connecting the determined printing starting point, the second printing point, the third printing point, ..., the mth printing point to form a printing path segment as the first printing path segment; For the remaining target printing points in the printing layer that are not involved in the generation of the printing path segments, a new target printing point is selected near the starting point or the end point of the first printing path segment as the printing starting point, and steps S2 to S4 are repeated until there is no candidate target printing point in the neighborhood of the current printing point, or the existing candidate target printing point and the path segment of the current printing point overlap with the formed printing path segment, then the printing point search is stopped, and the second printing path segment, ..., the nth printing path segment are determined, and the number of the 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 printing path segments according to the endpoints of the printing path segments that are adjacent to each other, and obtain the printing path of the printing component under the condition that the number of printing paths is minimized.

9. A printing path design system based on stress flow guidance, characterized in that: The system comprises: Determine data units for dividing the printed layers of the printed component into grid units, and use the geometric centroid of each unit as the target printing point; determine the principal stress data of all target printing points according to the stress field of the printed component; A first calculation unit is used to select a target printing point as a printing starting point, take the printing starting point as a current printing point, take the adjacent grid cells of the cell where the current printing point is located as a neighborhood, calculate the directional deflection coefficients 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 directional deflection coefficient in the neighborhood as a second printing point; A second calculation unit is used to use the second printing point as the current printing point, calculate the directional deflection coefficients of all target printing points in the neighborhood of the current printing point, and select the target printing point with the smallest directional deflection coefficient in the neighborhood as the third printing point; A printing path segment determination unit is used to repeat step S3 until there is no target printing point in the neighborhood of the current printing point, and m printing points are obtained, and the determined printing starting point, the second printing point, the third printing point, ..., the mth printing point are connected to form a printing path segment; at least one printing path segment is determined according to the above steps; A printing path determination unit is used to determine that when the determined printing path segment is one, the printing path segment is the printing path of the printing component; when the determined printing path segment is at least two, the printing path segments are connected according to the endpoints of the printing path segments with adjacent endpoints, and the printing path of the printing component is obtained under the condition that the number of printing paths is minimized.

10. An electronic device comprising at least one processor and a memory in communication with the at least one processor; the memory stores instructions executable by the at least one processor, characterized in that: The instructions are executed by the at least one processor so that the at least one processor can execute the stress flow-guided printing path design method described in any one of claims 1-8.

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