A continuous fiber 3D printing design method based on force and shape

Abstract

The present invention relates to a continuous fiber 3D printing design method based on force and shape, including: obtaining stress information of a part model through finite element simulation; mapping the stress information to a slice plane, and forming a continuous force streamline by calculating the force flow field direction of each node; forming the outer contour of the printed matrix material and the shell filling of the inner hole based on the contour boundary of the part obtained on the slice plane; defining the matrix material filling inside the part; planning the fiber path of the contour shape and the force streamline fiber; planning the corresponding printing sequence and performing fiber printing; dividing the slice plane into two categories: fiber layer and non-fiber layer; each fiber layer repeats the above process according to the force and shape design principle to obtain the overall continuous fiber printing path of the part, so as to update and modify the three-dimensional model of the part, and then slice according to the new three-dimensional model to output the path of the planned fiber printing sequence. Compared with the prior art, the present invention can effectively improve the specific strength of the part while ensuring the geometric requirements.

Description

Technical Field

[0001] The present invention relates to the technical field of 3D printing, and in particular to a continuous fiber 3D printing design method based on force and shape. Background Art

[0002] The emergence of 3D printing technology of continuous fiber composites (CFC) has endowed traditional plastic parts with the superior properties of continuous fibers, enabling them to obtain multifunctional customized design options such as mechanics, thermals, and electromagnetics. Different from the design and processing methods of traditional single-material additive manufacturing, its design process comprehensively considers the layout of composite materials and the printing process of parts. It is necessary not only to consider the improvement of part performance by the arrangement of materials, but also the possibility of 3D printing process. On the basis of the preliminary requirements for the appearance and size of the parts, combined with the characteristics of the matrix material used, a continuous fiber composite material with good compatibility is selected. While realizing the lightweight design of the part structure, it is also necessary to ensure the bonding effect of the composite material, thereby improving the overall strength of the part.

[0003] That is, the performance of continuous fiber reinforced parts is closely related to the filling style of the fiber and its content in the parts. The more mature continuous fiber 3D printing scheme in current research is based on spiral conformal filling, that is, the spiral filling of the set number of circles is carried out inward along the contour of the part after slicing; the second is based on unidirectional reciprocating internal filling, after determining the internal fiber reinforcement area, the filling angle, density and other parameters are set, but its regulation of part performance often requires multiple groups of experimental explorations, and the printing quality of continuous fiber is also restricted by parameters such as printing speed and filling. This reduces the efficiency of continuous fiber 3D printing path design for part performance to some extent, and cannot give full play to the bearing effect of continuous fiber on the working conditions of the part inside the part, and it is difficult to improve the specific strength of the part while ensuring the geometric requirements. Summary of the invention

[0004] The purpose of the present invention is to overcome the defects of the above-mentioned prior art and provide a continuous fiber 3D printing design method based on force and shape, which can improve the specific strength of parts while ensuring geometric requirements.

[0005] The purpose of the present invention can be achieved by the following technical solution: A continuous fiber 3D printing design method based on force and shape, comprising the following steps:

[0006] S1. Build a part model and obtain stress information of the part model through finite element simulation;

[0007] S2. Select the corresponding slicing plane according to the manufacturing-oriented 3D printing process constraints;

[0008] S3, mapping the stress information obtained in step S1 to the slice plane, and forming a continuous force streamline by calculating the force flow field direction of each node;

[0009] S4, based on the contour boundary of the part obtained on the slice plane, the outer contour of the printing base material and the shell filling of the inner hole are formed by reserving a set width;

[0010] S5. Determine the matrix material filling inside the part according to the force streamline aggregation state of each slice plane and the demand for side wall attachment under the continuous fiber printing process;

[0011] S6, planning the fiber path of the contour shape and the force streamline fiber, and obtaining the fiber distribution and quantity of the slice plane;

[0012] S7, further planning a corresponding printing sequence according to the planned continuous fiber path;

[0013] S8, printing the fibers according to the printing order;

[0014] S9, dividing the slice plane into two categories: fiber layer and non-fiber layer, setting the printing layer height to be consistent, and completing the inter-layer planning according to the preset judgment conditions;

[0015] S10. Customize and select the fiber layer to be enhanced according to the mechanical performance requirements. Repeat steps S4 to S8 for each fiber layer according to the force and shape design principle to obtain a continuous fiber printing path for the entire part.

[0016] S11. Based on the overall continuous fiber printing path of the part, the three-dimensional model of the part is further updated and modified, and then sliced ​​according to the updated and modified three-dimensional model to output a path for planning the fiber printing sequence.

[0017] Furthermore, the step S1 specifically includes the following steps:

[0018] S101, constructing a part model according to part size data;

[0019] S102, setting constraints and applied loads, and setting material parameters, and obtaining a stress cloud diagram of the part model, that is, stress information of the part model, through finite element simulation.

[0020] Furthermore, the specific process of step S3 is as follows: after mapping the stress information obtained in step S1 to the slice plane in step S2, the node coordinates (x, y) extracted in the corresponding reference system and the normal stress of each point are obtained. and shear stress Information generation, through the formula tanθ = τ xy / σ x , calculate the force flow field direction of each node to form a continuous streamline.

[0021] Furthermore, the specific process of step S5 is as follows:

[0022] According to the force streamline aggregation state of each slice plane, the blank part is first extracted to fill the internal matrix; then the force streamline area that is not suitable for printing continuous fibers is optimized:

[0023] Change the force streamlines in the area where the distance between the inner and outer contours is less than or equal to the threshold to conformal;

[0024] Ignore the swirling force streamlines.

[0025] Furthermore, step S6 specifically performs theoretical calculations and experiments based on the printing layer height and temperature to determine the printing width of the fiber bundle of the contour shape; and optimizes the spiral connection of adjacent layers at the intersection point based on the filling area of ​​the matrix material to preliminarily obtain the fiber distribution and quantity of the slice plane.

[0026] Furthermore, the step S7 specifically includes the following steps:

[0027] S701, firstly, printing continuous fibers in the conformal area is performed using the inner and outer contours as bonding starting points;

[0028] S702, taking the long side whose internal filling smoothness is greater than or equal to the smoothness threshold as the printing start position, and setting the spiral strategy of the fiber path according to the force streamline trajectory;

[0029] S703. Finally, the internal matrix material filling area in step S5 is reversely optimized based on the local fiber unfilled area, and its boundary is adjusted to fit the fiber trajectory to improve the printing quality.

[0030] Furthermore, the determination condition preset in step S9 includes a first determination condition and a second determination condition, and the inter-layer planning specifically needs to satisfy the first determination condition or the second determination condition.

[0031] Furthermore, the first determination condition is specifically as follows: the non-fiber layer refers to a layer printed only with the matrix material, a grid is used for filling inside the part, and a dense filling is used near the outer surface.

[0032] Furthermore, the second determination condition is specifically: the fiber layers of the same style are printed in a continuous stack, otherwise a densely filled non-fiber layer needs to be printed on the top and bottom to ensure that the continuous fiber adheres to the bottom part during printing.

[0033] Furthermore, the step S11 specifically further updates and modifies the three-dimensional model of the part based on the overall continuous fiber printing path of the part;

[0034] Import the updated and modified 3D model into the slicing software to automatically generate a path for planning the fiber printing sequence.

[0035] Compared with the prior art, the present invention proposes a continuous fiber 3D printing design method based on force and shape, which not only considers the reinforcement of the part shell to improve the part stiffness, but also gives full play to the bearing effect of the continuous fiber inside the part under the working conditions of the part. Secondly, the fiber path design based on stress information of the present invention is also different from the traditional topological optimization of the lightweight of the single material structure and the change of the part shape. It can improve the specific strength of the part while ensuring the geometric requirements, and at the same time provide a reference method for the design optimization of subsequent composite material structures.

[0036] The present invention applies continuous fibers to the structural reinforcement of 3D printed parts, which not only changes the design and manufacturing methods of the parts, but also fills the side walls and bottom surfaces with matrix materials, which can effectively enhance the adhesion ability of the continuous fibers and make the printing process more stable and reliable.

[0037] After preliminarily determining the direction suitable for printing the part model, the present invention gives priority to considering the utilization rate of the force streamline plane formed by the stress information to the original stress information. The specific evaluation method can select indicators such as the maximum principal stress and strain energy based on the mapped stress information, and then quantify it in combination with the printability of fiber reinforcement.

[0038] In the present invention, the number of fibers can be further controlled within the layer in combination with the reinforcement target of the part, so as to reduce the number of continuous fibers generated according to the force streamlines by expanding the range of each matrix material filling sub-region outward; in addition, each sub-region of the matrix material can choose to adjust the grid filling style and density to achieve further lightweight requirements.

[0039] The present invention divides the slicing plane into fiber layers and non-fiber layers, and designs corresponding judgment conditions for inter-layer planning. In simple parts of stretching modeling, continuous fiber layer printing is generally adopted, while complex part structures adopt alternating combinations to reduce the total number of fiber layers and improve slicing efficiency, thereby effectively balancing mechanical properties and economic applicability. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 It is a schematic diagram of the method flow of the present invention;

[0041] Figure 2a A schematic diagram of a parts model constructed in the embodiment;

[0042] Figure 2b is a stress cloud diagram of the part model in the embodiment;

[0043] Figure 3a A schematic diagram of a three-dimensional force flow field in an embodiment;

[0044] Figure 3b A schematic diagram of force streamlines on a two-dimensional slice plane in an embodiment;

[0045] Figure 4a It is a schematic diagram of contour matrix filling in the embodiment;

[0046] Figure 4b This is a schematic diagram of internal matrix filling in the embodiment;

[0047] Figure 4c Schematic diagram of conformal path fiber in the embodiment;

[0048] Figure 4d This is a schematic diagram of the force flow path fiber in the embodiment;

[0049] Figure 5a A schematic diagram of continuous fiber printing path planning based on force and shape in an embodiment;

[0050] Figure 5b A schematic diagram of conventional shape-conforming continuous fiber printing path planning in an embodiment;

[0051] Figure 6 A schematic diagram of a simulation process for designing an embodiment;

[0052] Figure 7 Schematic diagram of the continuous fiber 3D printing design workflow in the embodiment. DETAILED DESCRIPTION

[0053] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments.

[0054] Example

[0055] like Figure 1 As shown, a continuous fiber 3D printing design method based on force and shape includes the following steps:

[0056] S1. Build a part model and obtain stress information of the part model through finite element simulation;

[0057] S2. Select the corresponding slicing plane according to the manufacturing-oriented 3D printing process constraints;

[0058] S3, mapping the stress information obtained in step S1 to the slice plane, and forming a continuous force streamline by calculating the force flow field direction of each node;

[0059] S4, based on the contour boundary of the part obtained on the slice plane, the outer contour of the printing base material and the shell filling of the inner hole are formed by reserving a set width;

[0060] S5. Determine the matrix material filling inside the part according to the force streamline aggregation state of each slice plane and the demand for side wall attachment under the continuous fiber printing process;

[0061] S6, planning the fiber path of the contour shape and the force streamline fiber, and obtaining the fiber distribution and quantity of the slice plane;

[0062] S7, further planning a corresponding printing sequence according to the planned continuous fiber path;

[0063] S8, printing the fibers according to the printing order;

[0064] S9, dividing the slice plane into two categories: fiber layer and non-fiber layer, setting the printing layer height to be consistent, and completing the inter-layer planning according to the preset judgment conditions;

[0065] S10. Customize and select the fiber layer to be enhanced according to the mechanical performance requirements. Repeat steps S4 to S8 for each fiber layer according to the force and shape design principle to obtain a continuous fiber printing path for the entire part.

[0066] S11. Based on the overall continuous fiber printing path of the part, the three-dimensional model of the part is further updated and modified, and then sliced ​​according to the updated and modified three-dimensional model to output a path for planning the fiber printing sequence.

[0067] This embodiment applies the above technical solution, and takes the wrench condition of tightening the hexagonal nut as an example for explanation, and mainly includes the following contents:

[0068] (1) Establish a wrench-hexagonal nut model as shown in 2a. Assume that there is no frictional slip between the wrench and the nut. Select the two end faces of the wrench as fixed constraints. Set the load applied to the part as a unilateral uniform load in the hole. After setting the material parameters, obtain the stress contour of the model through finite element simulation (see Figure 2a). Figure 2b shown).

[0069] (2) Selecting the slice plane based on the manufacturing-oriented 3D printing process constraints. Due to the symmetry of the parts and working conditions in this embodiment, the generated three-dimensional force streamlines can be subdivided into sliced ​​two-dimensional planes, such as Figure 3a and 3b As shown. For the three-dimensional force streamlines of complex structural parts, the slicing plane with greater stress can be selected in combination with the direction requirements suitable for the printing process, and then the three-dimensional stress information is mapped to the two-dimensional plane, that is, the stress information is transformed from the part model coordinate system to the slicing plane coordinate system.

[0070] (3) After mapping the stress information in step (1) to the slice plane in step (2), the node coordinates (x, y) extracted in the corresponding reference system and the normal stress of each point are obtained. and shear stress Information generation, through the formula tanθ = τ xy / σ xCalculate the force flow field direction of each node to form a continuous streamline;

[0071] (4) Based on the contour boundary of the part obtained on the slice plane, a certain width is reserved to form Figure 4a Printing the outer contour of the substrate material and the shell filling of the inner hole can ensure the dimensional accuracy and surface roughness of the parts while enhancing the adhesion reliability of the continuous fibers that follow the inner wall;

[0072] (5) According to the force streamline aggregation state of each slice plane and the demand for side wall attachment under the continuous fiber printing process, the matrix material filling inside the part is defined. Figure 4b As shown, most areas are based on Figure 3b The blank part is extracted, and the rest is optimized for the continuity of fiber printing to optimize the force streamline areas that are not suitable for printing continuous fibers. The force streamlines in the upper semicircular area where the inner and outer contours are close are changed to follow the shape, and the vortex-shaped force streamlines in the lower right corner are ignored.

[0073] (6) Planning Figure 4c The fiber path and Figure 4d The fiber bundle printing width of the force streamline fiber shown is determined by theoretical calculation and experimental verification based on parameters such as printing layer height and temperature. The offset and spiral connection of adjacent layers at the intersection point are optimized based on the filling area of ​​the matrix material, and the fiber distribution and quantity on the slice plane are preliminarily obtained.

[0074] (7) The printing sequence of the initially obtained continuous fiber path is planned. First, the continuous fibers in the conformal area are printed using the inner and outer contours as the bonding starting points. Then, the relatively flat long side of the internal filling is used as the printing starting position and the spiral strategy of the fiber path is set according to the force streamline trajectory. Finally, the internal matrix material filling area in the reverse optimization step (5) of the local fiber unfilled area is adjusted to make it fit the fiber trajectory to improve the printing quality.

[0075] (8) The planned continuous fiber printing path is as follows Figure 5a As shown in the figure, the fiber printing is carried out according to the number sequence 1 to 7 in the figure. Figure 5b As shown, only the reinforcement strategy of contour following is compared. By adjusting parameters such as fiber length, volume fraction, and density of matrix material filling, the superiority of the continuous fiber 3D printing path design based on the force and shape strategy proposed in this technical solution can be verified.

[0076] (9) The slice plane is divided into two categories: fiber layer and non-fiber layer, and the printing layer height is consistent. The inter-layer planning must meet one of the following two judgment conditions: 1. The non-fiber layer refers to the layer printed only with the matrix material. Grid filling can be used inside the part, and dense filling is required near the outer surface; 2. Fiber layers of the same style can be printed in a continuous stack. Otherwise, a densely filled non-fiber layer must be printed on the top and bottom to ensure that the continuous fiber adheres to the bottom part during printing.

[0077] (10) Customize and select the fiber layer to be reinforced according to the mechanical performance requirements. Repeat steps (4) to (8) for each fiber layer based on the 3F (Fiber follows Force and Form) principle to obtain the overall continuous fiber printing path of the part, which is then input into the developed slicing plug-in.

[0078] (11) Figure 6 The process shown in the figure modifies the 3D model in combination with the continuous fiber design results, and the model saved in ".stl" format is imported into the slicing software to generate the ".gcode" file required for printing. Figure 7 This is a schematic diagram of the design workflow. The part model obtains the fiber layout of each layer according to the 3F principle, and then the model slices are updated to obtain the path of the planned fiber printing order.

[0079] In summary, this technical solution is based on the 3F strategy of force and shape, which applies continuous fibers to the structural reinforcement of 3D printed parts, and can improve the specific strength of parts while fully ensuring geometric requirements.

Claims

1. A continuous fiber 3D printing design method based on force and shape, characterized in that: The following steps are involved: S1. Build a part model and obtain stress information of the part model through finite element simulation; S2. Select the corresponding slicing plane according to the manufacturing-oriented 3D printing process constraints; S3, mapping the stress information obtained in step S1 to the slice plane, and forming a continuous force streamline by calculating the force flow field direction of each node; S4, based on the contour boundary of the part obtained on the slice plane, the outer contour of the printing base material and the shell filling of the inner hole are formed by reserving a set width; S5. Determine the matrix material filling inside the part according to the force streamline aggregation state of each slice plane and the demand for side wall attachment under the continuous fiber printing process; S6, planning the fiber path of the contour shape and the force streamline fiber, and obtaining the fiber distribution and quantity of the slice plane; S7, further planning a corresponding printing sequence according to the planned continuous fiber path; S8, printing the fibers according to the printing order; S9, dividing the slice plane into two categories: fiber layer and non-fiber layer, setting the printing layer height to be consistent, and completing the inter-layer planning according to the preset judgment conditions; S10. Customize and select the fiber layer to be enhanced according to the mechanical performance requirements. Repeat steps S4 to S8 for each fiber layer according to the force and shape design principle to obtain a continuous fiber printing path for the entire part. S11, based on the overall continuous fiber printing path of the part, further updating and modifying the three-dimensional model of the part, and then slicing the updated and modified three-dimensional model to output a path for planning the fiber printing sequence; The preset judgment conditions in step S9 include a first judgment condition and a second judgment condition. The inter-layer planning needs to satisfy the first judgment condition or the second judgment condition. The first judgment condition is specifically: a non-fiber layer refers to a layer printed only with matrix material, a grid filling is used inside the part, and a dense filling is used near the outer surface; The second judgment condition is specifically: the same style fiber layers are printed in a continuous stack, otherwise a densely filled non-fiber layer needs to be printed on the top and bottom to ensure that the continuous fiber adheres to the bottom part during printing.

2. A continuous fiber 3D printing design method based on force and shape according to claim 1, characterized in that: The step S1 specifically includes the following steps: S101, constructing a part model according to part size data; S102, setting constraints and applied loads, and setting material parameters, and obtaining a stress cloud diagram of the part model, that is, stress information of the part model, through finite element simulation.

3. The method for continuous fiber 3D printing design based on force and shape according to claim 1, characterized in that: The specific process of step S3 is as follows: after mapping the stress information obtained in step S1 to the slice plane in step S2, the node coordinates (x, y) extracted in the corresponding reference system and the normal stress of each point are obtained. and shear stress Information generation, through the formula tanθ = τ xy / σ x , calculate the force flow field direction of each node to form a continuous force streamline.

4. The method for designing continuous fiber 3D printing based on force and shape according to claim 1, characterized in that: The specific process of step S5 is as follows: According to the force streamline aggregation state of each slice plane, the blank part is first extracted to fill the internal matrix; then the force streamline area that is not suitable for printing continuous fibers is optimized: Change the force streamlines in the area where the distance between the inner and outer contours is less than or equal to the threshold to conformal; Ignore the swirling force streamlines.

5. The method for continuous fiber 3D printing design based on force and shape according to claim 4, characterized in that: The step S6 specifically performs theoretical calculations and experiments based on the printing layer height and temperature to determine the printing width of the fiber bundle of the contour shape; and optimizes the spiral connection of adjacent layers at the intersection point based on the matrix material filling area to preliminarily obtain the fiber distribution and quantity of the slice plane.

6. The method for continuous fiber 3D printing design based on force and shape according to claim 5, characterized in that: The step S7 specifically includes the following steps: S701, firstly, printing continuous fibers in the conformal area is performed using the inner and outer contours as bonding starting points; S702, taking the long side whose internal filling smoothness is greater than or equal to the smoothness threshold as the printing start position, and setting the spiral strategy of the fiber path according to the force streamline trajectory; S703. Finally, the internal matrix material filling area in step S5 is reversely optimized based on the local fiber unfilled area, and its boundary is adjusted to fit the fiber trajectory to improve the printing quality.

7. The method for continuous fiber 3D printing design based on force and shape according to claim 1, characterized in that: The step S11 specifically further updates and modifies the three-dimensional model of the part based on the overall continuous fiber printing path of the part; Import the updated and modified 3D model into the slicing software to automatically generate a path for planning the fiber printing sequence.

Images