Continuous fiber reinforced composite material FDM-3D printing path planning method and device based on stress field

Abstract

The invention provides a continuous fiber reinforced composite material FDM-3D printing path planning method and device based on a stress field, and the method comprises the steps: carrying out finite element simulation on a to-be-printed model according to the load condition of the to-be-printed model, and obtaining the stress tensor of each subunit of the to-be-printed model, each subunit comprises at least one grid unit divided in a finite element simulation process; determining the maximum principal stress of each subunit according to the stress tensor of each subunit; performing consistency processing on the maximum principal stresses of the adjacent subunits to obtain fitting principal stresses of the subunits; projecting the fitting principal stresses of the subunits to the corresponding 3D printing layers to obtain a scalar field of each 3D printing layer; and for each 3D printing layer, generating a printing path according to the scalar field of the 3D printing layer. In this way, the printing path is generated through the stress field obtained through finite element analysis, the strong anisotropic material characteristics of continuous fibers are fully considered, and the printing path and the stress field are consistent in distribution.

Description

Technical Field

[0001] The present invention relates to the technical field of 3D printing, and more particularly, to a method and device for path planning of fused deposition modeling (FDM) - 3D printing of continuous fiber reinforced composites based on a stress field. Background Art

[0002] Fused deposition modeling (FDM), as a widely used 3D printing technology, has been widely adopted due to its cost - effectiveness and rich material selection. In order to improve the mechanical strength of FDM models, in recent years, strengthening methods by combining high - performance materials with FDM technology have attracted wide attention. In particular, the behavior of continuous carbon fiber (CCF) reinforced thermoplastic composites has been deeply studied. Models reinforced with CCF can provide excellent tensile strength in the axial direction while maintaining light weight.

[0003] Currently, there are two main methods for 3D printing continuous fiber reinforced polymers: in - nozzle impregnation method and out - of - nozzle impregnation method. The out - of - nozzle impregnation method has the following advantages: on the one hand, the twin - extruder can separately control the temperatures of the thermoplastic material and the continuous fiber, thus optimizing the mechanical properties; on the other hand, the laying of fibers can be carried out only in key areas as needed. Therefore, this method has been widely used and there are already commercial products on the market.

[0004] However, existing methods for generating CCF printing paths, such as the hybrid printing path of contour parallel and zigzag parallel used in the Eiger software of Mark Forged company, do not fully optimize the performance of CCF reinforcement. Summary of the Invention

[0005] The present invention aims to at least solve the problem of inconsistency between the printing path and the stress field distribution in the prior art.

[0006] In view of this, an object of the present invention is to provide a method for path planning of FDM - 3D printing of continuous fiber reinforced composites based on a stress field.

[0007] Another object of the present invention is to provide a device for path planning of FDM - 3D printing of continuous fiber reinforced composites based on a stress field.

[0008] To achieve the above object, the technical solution of the first aspect of the present invention provides a method for path planning of FDM - 3D printing of continuous fiber reinforced composites based on a stress field, including:

[0009] According to the load conditions of the model to be printed, performing finite element simulation on the model to be printed to obtain the stress tensor of each sub - unit of the model to be printed, where the sub - unit includes at least one grid unit divided during the finite element simulation process;

[0010] Determine the maximum principal stress of each of the sub-units according to the stress tensor of each of the sub-units;

[0011] Perform consistency processing on the maximum principal stresses of adjacent sub-units to obtain the fitted principal stress of the sub-units;

[0012] Project the fitted principal stress of the sub-units onto the corresponding 3D printing layer to obtain the scalar field of each 3D printing layer;

[0013] For each of the 3D printing layers, generate a printing path according to the scalar field of the 3D printing layer.

[0014] Optionally, the generating a printing path according to the scalar field of the 3D printing layer includes:

[0015] Extract an isocurve in the scalar field through the following formula:

[0016]

[0017] where S min is the minimum scalar value in the scalar field, S max is the maximum scalar value in the scalar field, n is the number of isocurves, and n is determined by the following method:

[0018] n = D / W

[0019] where D is the maximum value of the first distances from the sub-units with the maximum scalar value to the set of sub-units with the minimum scalar value, and the set of sub-units with the minimum scalar value includes all sub-units with the minimum scalar value;

[0020] Determine the minimum distance d between adjacent isocurves;

[0021] If d ≤ W, then set n = n - 1, and re-extract the isocurves according to n and calculate the minimum distance d between adjacent isocurves, gradually reducing the number of isocurves until the minimum distance meets the requirements;

[0022] Determine the 3D printing path according to the updated isocurves.

[0023] Optionally, the generating a printing path according to the scalar field of the 3D printing layer further includes:

[0024] If d > W, then update and re-extract the isocurves according to n and calculate the minimum distance d between adjacent isocurves.

[0025] Optionally, the determining the maximum principal stress of each of the sub-units according to the stress tensor of each of the sub-units includes:

[0026] Perform eigenvalue decomposition on the stress tensor of the sub-unit to obtain three principal stresses (σ1, σ2, σ3) and their corresponding directions (τ1, τ2, τ2);

[0027] In the case where the principal stress σ1 is negative, but σ2 is positive and satisfies the preset condition, determine that σ2 is the maximum principal stress and τ2 is the maximum principal stress direction,

[0028] wherein, the preset condition is (|σ1 / σ2| < μ).

[0029] Optionally, the determining the maximum principal stress of each sub-unit according to the stress tensor of each sub-unit further includes:

[0030] In the case where both σ1 and σ2 are negative, determine that the maximum principal stress direction is τ1 and the maximum principal stress is set to a preset stress value.

[0031] Optionally, the performing consistency processing on the maximum principal stresses of adjacent sub-units to obtain the fitted principal stress of the sub-units includes:

[0032] Redirect the maximum principal stresses of the sub-units through the minimum spanning tree algorithm to obtain the fitted principal stress of each sub-unit.

[0033] Optionally, before projecting the fitted principal stress of the sub-unit onto the corresponding 3D printing layer to obtain the scalar field of each 3D printing layer, the method further includes:

[0034] In the case where the fitted stress direction of the sub-unit is inconsistent with the fitted principal stress direction of the adjacent sub-unit, set the fitted principal stress of the sub-unit to 0.

[0035] Optionally, before projecting the fitted principal stress of the sub-unit onto the corresponding 3D printing layer to obtain the scalar field of each 3D printing layer, the method further includes:

[0036] Calculate the energy function E for stress smoothing between adjacent faces σ and the energy function E for vector smoothing v , and minimize the energy function E σ and the energy function E v , wherein, the energy function E σ and the energy function E v are calculated by the following method:

[0037]

[0038]

[0039] where E σis the energy function for stress smoothing, E v is the energy function for vector smoothing, U f is the set of all adjacent faces of the polygon face f, |U f | represents the number of all adjacent faces of f.

[0040] The technical solution of the second aspect of the present invention provides a stress field-based continuous fiber reinforced composite material FDM-3D printing path planning device, including:

[0041] a processor;

[0042] a memory for storing executable instructions of the processor;

[0043] wherein, the processor is configured to load and execute the executable instructions to implement the steps of the stress field-based continuous fiber reinforced composite material FDM-3D printing path planning method provided by the first aspect of the present invention.

[0044] Through the above technical solution, a load-dependent printing path is generated based on the stress field obtained by finite element analysis, fully considering the strong anisotropic material properties of continuous fibers, and making the printing path consistent with the stress field distribution.

[0045] The additional aspects and advantages of the present invention will become apparent in the following description section, or be learned through the practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Figure 1 is a flowchart of a stress field-based continuous fiber reinforced composite material FDM-3D printing method according to an embodiment of the present invention;

[0047] Figure 2 is a flowchart of a stress field-based continuous fiber reinforced composite material FDM-3D printing method according to an embodiment of the present invention;

[0048] Figure 3 is a flowchart of a stress field-based continuous fiber reinforced composite material FDM-3D printing method according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0049] In order to more clearly understand the above objects, features, and advantages of the present invention, the present invention will be further described in detail below with reference to the drawings and specific embodiments. It should be noted that, without conflict, the embodiments of the present application and the features in the embodiments may be combined with each other.

[0050] In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention. However, the present invention may be practiced in other ways different from those described herein. Therefore, the scope of protection of the present invention is not limited by the specific embodiments disclosed below.

[0051] The inventors of the present application have found that in the related art, the research on load-dependent printing path generation is still not perfect. Although some existing studies use topology optimization to select key regions, when generating printing paths, they mainly rely on manually set regions and preset paths, which are not completely consistent with the actual stress field distribution. Therefore, the anisotropic characteristics and strengthening effects of the material cannot be fully utilized.

[0052] The following refers to Figures 1 to 3 Describe some embodiments according to the present invention.

[0053] Refer to Figure 1 , embodiments of the first aspect of the present invention provide a method for planning a continuous fiber reinforced composite material FDM-3D printing path based on a stress field, including:

[0054] Step S11, according to the load conditions of the model to be printed, perform finite element simulation on the model to be printed to obtain the stress tensor of each sub-unit of the model to be printed, where the sub-unit includes at least one grid unit divided during the finite element simulation process;

[0055] For example, after modeling the model to be printed, the grid can be divided and the load conditions can be set in the finite element simulation software, and then the finite element simulation can be performed to obtain the stress tensors of each grid.

[0056] Step S12, determine the maximum principal stress of each sub-unit according to the stress tensor of each sub-unit;

[0057] Step S13, perform consistency processing on the maximum principal stresses of adjacent sub-units to obtain the fitted principal stress of the sub-units;

[0058] By performing consistency processing, the directions of the fitted principal stresses of each sub-unit can be made consistent, avoiding situations such as sudden changes in local stress directions.

[0059] Step S14, project the fitted principal stress of the sub-unit onto the corresponding 3D printing layer to obtain the scalar field of each 3D printing layer;

[0060] Step S15, for each 3D printing layer, generate a printing path according to the scalar field of the 3D printing layer.

[0061] In this embodiment, the maximum principal stress of each sub-unit is determined by finite element method simulation, and the maximum principal stress is processed for consistency, so that the fitting principal stress directions of each sub-unit are basically the same, avoiding local mutations, and making the printing path basically consistent with the stress field distribution. In this way, the strong anisotropic material characteristics of continuous fibers can be fully considered, and the printing path is made consistent with the stress field distribution.

[0062] In an alternative embodiment, generating a printing path according to the scalar field of the 3D printing layer includes:

[0063] Extracting an isocurve in the scalar field by the following formula:

[0064]

[0065] where S min is the minimum scalar value in the scalar field, S max is the maximum scalar value in the scalar field, n is the number of isocurves, and n is determined by the following method:

[0066] n = D / W

[0067] where D is the maximum value of the first distance from each sub-unit with the maximum scalar value to the set of sub-units with the minimum scalar value, and the set of sub-units with the minimum scalar value includes all sub-units with the minimum scalar value;

[0068] Determining the minimum distance d between adjacent isocurves;

[0069] If d ≤ W, then set n = n - 1, and re-extract the isocurve according to n and calculate the minimum distance d between adjacent isocurves, gradually reducing the number of isocurves until the minimum distance meets the requirements;

[0070] Determining the 3D printing path according to the updated isocurve.

[0071] In an alternative embodiment, generating a printing path according to the scalar field of the 3D printing layer further includes:

[0072] If d > W, then update and re-extract the isocurve according to n and calculate the minimum distance d between adjacent isocurves.

[0073] In this way, isocurves with appropriate density can be extracted, so that the printing path can effectively enhance the mechanical strength of the material and avoid overlap caused by over-dense paths.

[0074] In an alternative embodiment, a smooth scalar field s(x) that meets the stress distribution requirements is obtained by minimizing the difference between the scalar field gradient and the final vector field. To construct the scalar field, the following objective function is constructed:

[0075]

[0076] Among them, T is a set of polygon meshes obtained by the intersection of the slicing plane and the tetrahedral mesh, and x f is the center of the polygon face f, u f is the target vector field of the face f, and w f is the weight of the polygon face. By minimizing the objective function, a smooth scalar field can be generated on the entire plane, so that the scalar field can effectively reflect the change of the stress field in space, thereby providing a stable basis for subsequent tool path planning. Through the above formula, a piecewise linear scalar field can be obtained, whose value is defined at each grid node and calculated from the gradient terms of the polygon faces. Specifically, the generation of the scalar field needs to satisfy both the smoothness of the gradient and the consistency of the direction.

[0077] In an alternative embodiment, according to the stress tensor of each sub-unit, the maximum principal stress of each sub-unit is determined, including: performing eigenvalue decomposition on the stress tensor of the sub-unit to obtain three principal stresses (σ1, σ2, σ3) and their corresponding directions (τ1, τ2, τ2); when the principal stress σ1 is negative, but σ2 is positive and satisfies a preset condition, determining σ2 as the maximum principal stress and τ2 as the maximum principal stress direction, where the preset condition is (|σ1 / σ2| < μ).

[0078] In this solution, when the principal stress σ1 is negative, it means that the principal stress σ1 is a compressive stress. To make the planned printing path adapt to the profit direction, it is selected to determine σ2 as the maximum principal stress and τ2 as the maximum principal stress direction.

[0079] In an alternative embodiment, according to the stress tensor of each sub-unit, the maximum principal stress of each sub-unit is also determined, including: when both σ1 and σ2 are negative, determining the maximum principal stress direction as τ1 and setting the maximum principal stress to a preset stress value. For example, the preset stress value can be a pre-assigned minimum value.

[0080] In this way, numerical instability or singularity can be avoided in the subsequent reorientation process.

[0081] In an alternative embodiment, the maximum principal stresses of adjacent sub-units are processed for consistency to obtain the fitted principal stress of the sub-unit, including: reorienting the maximum principal stresses of the sub-units through the minimum spanning tree algorithm to obtain the fitted principal stress of each sub-unit.

[0082] Through the minimum spanning tree algorithm, the ambiguity of the vector direction can be resolved and the turbulent change of the vector direction can be processed, making the vector transition between different sub-units smoother.

[0083] In an alternative embodiment, before projecting the fitted principal stress of the subunit onto the corresponding 3D printing layer to obtain the scalar field of each 3D printing layer, the method further includes:

[0084] In the case where the fitted stress direction of the subunit is inconsistent with the fitted principal stress directions of adjacent subunits, set the fitted principal stress of the subunit to 0.

[0085] In this way, it is possible to ensure that the vector directions of adjacent subunits are consistent and improve the printing quality.

[0086] In an alternative embodiment, before projecting the fitted principal stress of the subunit onto the corresponding 3D printing layer to obtain the scalar field of each 3D printing layer, the method further includes:

[0087] Calculate the energy function E for stress smoothing between adjacent faces σ and the energy function E for vector smoothing v , and minimize the energy function E σ and the energy function E v , where the energy function E σ and the energy function E v are calculated by the following method:

[0088]

[0089] where E σ is the energy function for stress smoothing, E v is the energy function for vector smoothing, U f is the set of all adjacent faces of the polygon face f, and |U f | represents the number of all adjacent faces of f.

[0090] In this solution, during the process of minimizing the energy function E σ and the energy function E v , the incompatible regions in the stress field are gradually optimized to make their stress values and stress vectors smoother and more consistent. Set the boundary conditions by fixing the stress and vector of the face with the maximum stress value. Minimize the energy function in an iterative manner. In each iteration, by updating the stress value and stress vector, the smoothness of the stress field is continuously improved until the preset convergence condition is reached. Specific embodiments

[0092] Referring to Figure 2 and Figure 3 , in a specific embodiment of the present invention, the FDM-3D printing path planning method for continuous fiber reinforced composites based on the stress field includes:

[0093] Step S1: Generate basic data and guidance for subsequent printing paths by calculating the stress field.

[0094] Specifically, finite element simulation (FEA) is used to calculate the stress distribution of the input three-dimensional solid model under given loading conditions and export it as the stress tensor of each element. This stress data provides key input for further analysis and optimization, ensuring that the generated continuous carbon fiber (CCF) reinforced printing path can be optimized according to the actual mechanical requirements;

[0095] Step S2: Provide key directional data for generating an optimized printing path, thereby ensuring that the 3D printed continuous carbon fiber reinforced thermoplastic composites (CFRTPCs) have excellent mechanical properties.

[0096] Specifically, the calculation of the maximum principal stress direction involves the following aspects:

[0097] Eigenvalue decomposition of the stress tensor: By performing eigenvalue decomposition on the stress tensor of each element in the finite element analysis, three principal stresses (σ1, σ2, σ3) and their corresponding directions (τ1, τ2, τ2) are obtained. These principal stresses and principal stress directions determine the stress state of the material under loading conditions.

[0098] Determination of the maximum principal stress direction: The maximum principal stress (σ1) usually points in the direction where the material is most vulnerable to tension. Therefore, when the principal stress σ1 is positive, the maximum principal stress direction is given by τ1, and this direction is used for subsequent printing path design. By choosing the maximum principal stress direction as the dominant direction of the printing path, it can be ensured that the tensile capacity of the material under external forces can be effectively enhanced during fiber laying.

[0099] Optimization of stress turning: In some cases, if the principal stress σ1 is negative (i.e., in a compressive state), but σ2 is positive and satisfies certain conditions (|σ1 / σ2| < μ), then the secondary principal stress direction τ2 is selected as the direction of the printing path. This turning treatment can avoid unreasonable fiber laying in the material under compressive state and further enhance the stability and mechanical properties of the overall structure.

[0100] Avoiding singularity problems: If the principal stress direction cannot be effectively determined (for example, when both σ1 and σ2 are negative), then by assigning a very small stress value (σ e = 10 -5 ) and a default direction (v e = τ1), numerical instability or singularity during subsequent reorientation is avoided.;

[0101] Step S3: Used for vector reorientation, aiming to solve the vector compatibility problem in the discrete stress field and ensure the consistency of the printing path directions of adjacent elements. Specifically,

[0102] Resolving the ambiguity of vector directions: In finite element analysis, the principal stress directions (such as τ1) are obtained through eigenvalue decomposition. However, due to the directionality of vectors, there may be multiple direction choices (such as τ1 or -τ1), resulting in inconsistent vector directions between adjacent elements. Through the MST redirection method, these directions can be reasonably adjusted to make the vector directions consistent between adjacent elements and eliminate contradictions.

[0103] Handling the turbulent changes of vector directions: In some regions, the principal stress directions may change drastically, especially in regions where the stress distribution changes significantly. The MST redirection method uses graph traversal techniques to avoid propagating inconsistent directions in these regions, thus ensuring smoother and more stable vector changes.

[0104] Eliminating the ambiguity in isotropic stress regions: In some regions, the principal stress values may be close (such as |σ1|≈|σ2|), resulting in unclear directions or an approximately isotropic stress state. In such cases, MST redirection can effectively handle the contradictions in these regions and maintain vector consistency;

[0105] Step S4: By filtering out locally incompatible vectors, ensure that during the subsequent print path generation process, the vector directions of all adjacent elements are consistent, thereby improving the overall quality of the print path and the mechanical properties of 3D printed composites.

[0106] Step S5: Since the 3D printing process is carried out layer by layer, in order for the fiber arrangement direction to be more in line with the plane stress state, and to simplify the calculation and help intuitively understand and analyze the plane stress state, project the stress vectors in three-dimensional space onto a two-dimensional plane, so that during the 3D printing process, the generation of the print path can be optimized and controlled at the two-dimensional level.

[0107] Step S6: Through Step S4, for incompatible regions, the calculated values of stress and vectors are undefined and need to be further processed to optimize the incompatible regions, eliminate or reduce the directionality and numerical inconsistencies caused by incompatible vectors, thereby enhancing the consistency and stability of the entire vector field in the neighborhood and ensuring that the generated print path better meets the requirements of stress distribution. The optimization process is achieved by minimizing two energy functions: Stress difference energy (E σ ): Measures the difference in stress values (σ f and ) between adjacent faces. Vector difference energy (E v ): Measures the difference in stress vectors (v f and ) between adjacent faces. To achieve the above optimization goals, the following energy functions are constructed:

[0108]

[0109] Among them, E σ is the energy function for stress smoothing, and E v is the energy function for vector smoothing, and U f is the set of all adjacent faces of the polygon face f, and |U f | represents the number of all adjacent faces of f. This process gradually optimizes the incompatible regions in the stress field to make its stress values and stress vectors smoother and more consistent. The boundary conditions are set by fixing the stress and vector of the face with the maximum stress value. The energy function is minimized in an iterative manner. In each iteration, by updating the stress values and stress vectors, the smoothness of the stress field is continuously improved until the preset convergence condition is reached. After 50 iterations, the calculation results will converge to a stable state, thereby obtaining the stress field of the processed incompatible region;

[0110] Step S8: By minimizing the difference between the scalar field gradient and the final vector field, a smooth scalar field s(x) that meets the stress distribution requirements is obtained. To achieve the construction of the scalar field, the following objective function is proposed:

[0111]

[0112] Among them, T is the set of polygon meshes obtained by the intersection of the slicing plane and the tetrahedral mesh, x f is the center of the polygon face f, u f is the target vector field of the face f, and w f is the weight of the polygon face. By minimizing the objective function, a smooth scalar field can be generated on the entire plane, so that the scalar field can effectively reflect the changes in the stress field in space, thereby providing a stable basis for subsequent tool path planning. Through the above formula, a piecewise linear scalar field can be obtained, whose value is defined at each grid node and is calculated from the gradient terms of the polygon faces. Specifically, the generation of the scalar field needs to satisfy both the smoothness of the gradient and the consistency of the direction. This scalar field provides a basis for the subsequent generation of the printing path, ensuring that the generated printing path has a high density in the key areas and can accurately reflect the stress distribution characteristics;

[0113] Step S9: Generate an adaptive printing path (CCF printing path) according to the distribution of the scalar field to optimize the structural performance of fiber-reinforced thermoplastic composites (CFRTPCs) during 3D printing.

[0114] First, store the nodes corresponding to the minimum value S min in the scalar field S(x) in the set S. Next, for each node with the maximum value S max , calculate the distance from this node to the set S, and record the maximum value of the distance as D.

[0115] Then, set the initial number of contour lines \(n = D / W\), extract the contour lines in the scalar field, and the values of the contour lines are given by the following formula:

[0116]

[0117] Calculate the minimum distance \(d\) between adjacent contour lines. If \(d > W\), then update and re-extract the contour lines according to \(n\) and calculate the minimum distance \(d\) between adjacent contour lines. If \(d \leq W\), then set \(n = n - 1\), re-extract the contour lines according to \(n\) and calculate the minimum distance \(d\) between adjacent contour lines, gradually reducing the number of contour lines until the minimum distance meets the requirements.

[0118] By extracting the contour curves with appropriate density, it is ensured that the generated printing paths can effectively enhance the mechanical strength of the material and avoid the overlapping phenomenon caused by overly dense paths. This kind of overlapping will reduce the adhesion between the CCF and the resin matrix, thus affecting the final mechanical properties. By gradually adjusting the density of the contour curves, it is ensured that the minimum distance between adjacent printing paths meets the manufacturing requirements, and finally, efficient material strengthening and optimized printing quality are achieved.

[0119] An embodiment of the present invention also provides a continuous fiber reinforced composite material FDM-3D printing path planning device based on a stress field, including: a processor; a memory for storing executable instructions of the processor; wherein, the processor is configured to load and execute the executable instructions to implement the steps of the method of the above embodiment of the present invention.

[0120] Those skilled in the art should understand that the embodiments of the present invention can be provided as a method, a system, or a computer program product. Therefore, the present invention can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Moreover, the present invention can take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0121] Those skilled in the art should understand that the embodiments of the present invention can be provided as a method, a system, or a computer program product. Therefore, the present invention can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Moreover, the present invention can take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0122] The present invention is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the invention. It should be understood that each flow and / or block in the flowchart illustrations and / or block diagrams, and combinations of flows and / or blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions may be provided to a processor of a general purpose computer, special purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions executed by the processor of the computer or other programmable data processing apparatus create means for implementing the functions specified in the flow Figure 1 a flow or flows and / or blocks Figure 1 or blocks specified in the claims.

[0123] These computer program instructions may also be stored in a computer-readable memory that can direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer-readable memory produce an article of manufacture including instruction means that implement the functions specified in the flow Figure 1 a flow or flows and / or blocks Figure 1 or blocks specified in the claims.

[0124] These computer program instructions may also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer-implemented process, such that the instructions executed on the computer or other programmable apparatus provide steps for implementing the functions specified in the flow Figure 1 a flow or flows and / or blocks Figure 1 or blocks specified in the claims.

[0125] It should be noted that, in the claims, any reference signs placed between parentheses shall not be construed as limiting the claim. The word "comprising" does not exclude the presence of elements or steps not listed in a claim. The word "a" or "an" preceding an element does not exclude the presence of a plurality of such elements. The present invention can be implemented by means of hardware comprising several distinct elements and by means of a suitably programmed computer. In the unit claims listing several means, several of these means can be embodied by one and the same item of hardware. The use of the words first, second, and third, etc. do not denote any order. These words can be interpreted as names.

Claims

1. A continuous fiber-reinforced composite material FDM-3D printing path planning method based on a stress field, characterized in that, Including: Performing finite element simulation on the model to be printed according to the load condition of the model to be printed, and obtaining the stress tensor of each sub-unit of the model to be printed, where the sub-unit includes at least one mesh unit divided during the finite element simulation process; Determining the maximum principal stress of each sub-unit according to the stress tensor of each sub-unit; Performing consistency processing on the maximum principal stresses of adjacent sub-units to obtain the fitted principal stress of the sub-units; Projecting the fitted principal stress of the sub-units onto the corresponding 3D printing layer to obtain the scalar field of each 3D printing layer; For each 3D printing layer, generating a printing path according to the scalar field of the 3D printing layer.

2. The continuous fiber reinforced composite material FDM-3D printing path planning method based on stress field according to claim 1, characterized in that The generating a printing path according to the scalar field of the 3D printing layer includes: Extracting an isocurve in the scalar field through the following formula: Among them, S min is the minimum scalar value in the scalar field, S max is the maximum scalar value in the scalar field, n is the number of contour lines, and n is determined by the following method: n = D / W where D is the maximum value of the first distances from each sub-unit with the maximum scalar value to the set of sub-units with the minimum scalar value, and the set of sub-units with the minimum scalar value includes all sub-units with the minimum scalar value; Determining the minimum distance d between adjacent isocurves; If d ≤ W, then set n = n - 1, re-extract the isocurve according to n, and calculate the minimum distance d between adjacent isocurves, gradually reducing the number of isocurves until the minimum distance meets the requirement; Determining the 3D printing path according to the updated isocurve.

3. The continuous fiber reinforced composite material FDM-3D printing path planning method based on the stress field according to claim 2, wherein The generating a printing path according to the scalar field of the 3D printing layer further includes: If d > W, update and re-extract the contour lines according to n and calculate the minimum distance d between adjacent contour lines.

4. The continuous fiber reinforced composite material FDM-3D printing path planning method based on stress field according to any one of claims 1 to 3, characterized in that, The determining the maximum principal stress of each sub-unit according to the stress tensor of each sub-unit includes: Performing eigenvalue decomposition on the stress tensor of the sub-unit to obtain three principal stresses (σ1, σ2, σ3) and their corresponding directions (τ1, τ2, τ2); In the case where the principal stress σ1 is negative, but σ2 is positive and meets the preset condition, determining σ2 as the maximum principal stress and τ2 as the maximum principal stress direction, where the preset condition is (|σ1 / σ2| < μ).

5. The continuous fiber reinforced composite material FDM-3D printing path planning method based on the stress field according to claim 4, wherein The determining the maximum principal stress of each sub-unit according to the stress tensor of each sub-unit further includes: In the case where both σ1 and σ2 are negative, determining the maximum principal stress direction as τ1 and setting the maximum principal stress to a preset stress value.

6. The continuous fiber reinforced composite material FDM-3D printing path planning method based on stress field according to any one of claims 1 to 3, characterized in that, The performing consistency processing on the maximum principal stresses of adjacent sub-units to obtain the fitted principal stress of the sub-units includes: Redirecting the maximum principal stresses of the sub-units through the minimum spanning tree algorithm to obtain the fitted principal stress of each sub-unit.

7. The continuous fiber reinforced composite material FDM-3D printing path planning method based on the stress field according to claim 6, characterized in that Before the projecting the fitted principal stress of the sub-units onto the corresponding 3D printing layer to obtain the scalar field of each 3D printing layer, the method further includes: In the case where the fitted stress direction of the sub-unit is inconsistent with the fitted principal stress direction of the adjacent sub-unit, setting the fitted principal stress of the sub-unit to 0.

8. The continuous fiber reinforced composite material FDM-3D printing path planning method based on the stress field according to claim 7, characterized in that Before the projecting the fitted principal stress of the sub-units onto the corresponding 3D printing layer to obtain the scalar field of each 3D printing layer, the method further includes: Calculate the energy function E for stress smoothing between adjacent faces σ and the energy function E for vector smoothing v and minimize the energy function E σ and the energy function E v where the energy function E σ and the energy function E v is calculated as follows: Among them, E σ is the energy function for stress smoothing, and E v is the energy function for vector smoothing, and U f is the set of all adjacent faces of the polygon face f, and |U f | represents the number of all adjacent faces of f.

9. A continuous fiber reinforced composite material FDM-3D printing path planning device based on a stress field, characterized in that Including: A processor; A memory for storing executable instructions of the processor; Wherein, the processor is configured to load and execute the executable instructions to implement the steps of the method according to any one of claims 1-8.

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