Path generation and 3D printing method of continuous fiber reinforced composite variable-density curved surface grating structure

Abstract

An existing method has defects in the aspect of continuous fiber reinforcement path planning of a grating structure, so that a path generation method capable of optimizing the fiber content and exerting the fiber continuity is needed, and efficient 3D printing forming is achieved. The invention provides a grating structure suitable for continuous fiber reinforced 3D printing and a printing method of the grating structure. According to the method, printing of a grid structure in two directions is achieved through optimized path planning, and the requirements of curved surface printing and multilateral grid expansion can be met. According to the structural design, structures such as auxiliary frames are allowed to be printed, and variable-thickness grating design can be achieved, so that the mechanical property of the overall structure is improved. The printing strategy is composite printing of resin and continuous fibers, the fibers form a main bearing structure through a one-stroke path, the resin is used for area filling, and the overall strength is improved. The high-performance composite material is suitable for the fields of aerospace, buildings and other fields needing high-performance composite material structures.

Description

Technical Field

[0001] The present invention relates to the field of additive manufacturing, and in particular to a 3D printed grid structure based on composite materials and a continuous fiber path planning method thereof. The method can be applied to the design and manufacture of high-performance composite material structures in the fields of aerospace, construction, and automobile manufacturing. Background Art

[0002] With the development of additive manufacturing (3D printing) technology, composite materials have gradually become the main choice for high-performance lightweight structures. Continuous fiber reinforced composites (CFRC) have shown great potential in engineering applications due to their excellent mechanical properties and lightweight characteristics. However, traditional manufacturing processes have problems such as complex processing steps and high mold costs, which limit their application in complex structures.

[0003] 3D printing technology can achieve rapid manufacturing of complex geometric shapes through computer-aided design and manufacturing (CAD / CAM), while allowing the integration of multiple materials, such as resin and continuous fiber, to form a composite structure during the manufacturing process. Especially in the grid structure, how to optimize the path planning of continuous fibers and the filling strategy of composite materials is crucial to improving the mechanical properties of the grid. Summary of the invention

[0004] The present invention relates to a composite material 3D printing path planning method for grid structures, which aims to improve structural performance through the coordinated printing of continuous fibers and resins, and is particularly suitable for lightweight structural design with high load-bearing requirements. The method generates a geometric model of grid cell structures with different numbers of edges through CAD software, and combines a path planning algorithm written in a programming language to determine the optimal direction of the fiber path and the resin filling area to achieve multi-objective optimization.

[0005] During the path planning process, the present invention can generate a path suitable for curved grilles, support adjustable design of grille thickness and density, and realize accessory structure design (such as frame, mounting holes, etc.). In the composite material printing strategy, the continuous fiber path serves as the supporting skeleton of the main structure, and the mechanical properties of the overall structure are improved by filling the resin area. The path data file thus generated can be used for direct manufacturing by a 3D printer.

[0006] In order to achieve the above object, the technical solution adopted by the present invention is:

[0007] The present invention proposes a method for generating a 3D printing path for a continuous fiber reinforced grid structure, which is characterized by comprising: a parametric design of the grid structure for preparing basic data for path planning; a path planning algorithm for generating an initial path for the grid structure and adjusting parameters such as printing spacing; a post-processing algorithm for adapting to curved grids, meeting special process code requirements, etc., and generating a G code for driving a machine to print.

[0008] The present invention provides a design method for a grid structure supporting variable unit cells.

[0009] In the first step: the grid can be a two-dimensional plane grid with two directional vectors intersecting, or it can be extended to a lattice structure composed of a multi-sided grid unit cell. By geometrically modeling the grid unit, the grid structure's border, basic directional vector, thickness range, density adjustment and other parameters are defined.

[0010] In the second step: use Rhino 3D modeling design software and its integrated graphic programming tool Grasshopper to perform preliminary design, preview whether the design meets the requirements, fit the surface parameters with tools such as MATLAB, and select the basic data required for the export path.

[0011] Preferably, the step 1 of the present invention also supports dynamic control of grid thickness and density. By adjusting the spacing of the fiber paths, the layer height and the number of stacked layers, the user can control the thickness and density of different areas during the CAD design process.

[0012] In order to ensure the mechanical properties of the grid structure, the present invention proposes a continuous fiber path planning strategy.

[0013] In step 1: Generate fiber path: The fiber path needs to be globally continuous to avoid breakpoints. By optimizing the geometric arrangement of the path, the smooth direction of the fiber in the grid is ensured.

[0014] In step 2: Use resin to strengthen the structural strength. In complex geometric structures, in areas that are mathematically disconnected and cannot form a single stroke, resin needs to be supplemented to ensure the strength and structural integrity of the printed part.

[0015] Preferably, in the step 1, the present invention can locally strengthen the area that needs to be strengthened by increasing the number of fiber layers or density, which can be achieved by adjusting the set fiber printing spacing, while in other areas, the use of materials can be reduced to save cost and weight.

[0016] The present invention proposes a composite printing method of resin and continuous fiber. The specific strategy is as follows:

[0017] In step 1: the fiber is the main load-bearing fiber. In path planning, the continuous fiber bears most of the load of the grid structure, and its path is designed to be continuous and cover the entire grid area.

[0018] In step 2: Resin filling is used to fill the gaps in the grid to improve local stiffness and compressive strength. Through the Python script-based path planning algorithm, the resin filling path for different areas is generated, and the filling density and filling strategy are adjusted as needed to reduce empty strokes and improve printing efficiency.

[0019] Preferably, all geometric and path planning data in the design process are processed by Python scripts. Data input includes geometric parameters of the grid, path planning parameters, printing process parameters, etc. Data output includes Gcode code generation and path code post-processing to facilitate reading by the printing machine.

[0020] The beneficial effects of the present invention are:

[0021] 1. Improve structural strength: By optimizing the path of continuous fibers, the fiber path maintains the advantage of continuity and improves the overall strength of the grid structure.

[0022] 2. Efficient composite printing: The composite printing process of resin and fiber optimizes printing efficiency and reduces the waste of empty strokes.

[0023] 3. Flexibility and scalability: It supports the structural design of grid cells with different numbers of edges and can be expanded to curved grids, which can meet the manufacturing needs of different complex structures.

[0024] 4. Cost saving: Through reasonable distribution of fibers and resins, such as using fewer fiber paths in places with less stress, material waste can be reduced and production costs can be reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art are briefly introduced below.

[0026] Figure 1 It is a general process step diagram of an embodiment of the present invention, showing the composite material 3D printing grid structure design and path planning process;

[0027] Figure 2 A flow chart for generating initial grid geometry and path planning data in the present invention;

[0028] Figure 3 The schematic diagram for explaining the coordinated printing of continuous fibers and resins of the present invention shows the continuous fiber area, resin area and frame area of ​​the grid. 1 is the fiber area, 2 is the discrete resin area, and 3 is the outer frame area of ​​the grid;

[0029] Figure 4 It is a schematic diagram of an example in which a variable density grid or a grid of a certain thickness may need to adjust the printing spacing in an embodiment of the present invention;

[0030] Figure 5 This is a schematic diagram of the fiber path result of a grid (including variable density) drawn in one stroke in an embodiment of the present invention. DETAILED DESCRIPTION

[0031] The method of the present invention is described in detail below in conjunction with the accompanying drawings, and each of the accompanying drawings does not constitute a limitation on the embodiments of the present invention. In the embodiments of the present invention, the design and path planning process of the grid structure is described by taking Rhino 3D modeling design software and Python as specific examples.

[0032] Process 1: Design of grille geometry model. In Rhino 3D modeling design software, define the design parameters of the grille such as boundary, thickness, direction, etc. through Grasshopper plug-in, and establish a preliminary geometric model. The grille model can be a two-dimensional plane structure or an n-dimensional curved grille. At the same time, define the auxiliary structure (such as the frame) and set the installation hole position on the frame to facilitate assembly requirements in subsequent manufacturing.

[0033] Process 2: Path planning and file generation. The path planning algorithm written in Python is used to calculate the generated grid geometry model to determine the continuous fiber path and resin filling area. During the path planning process, the continuous fiber path covers the entire grid structure through a "one-stroke" continuous direction, and the corners are processed to ensure a smooth transition of the path. The mounting holes on the frame are bypassed by the path algorithm to ensure the continuity of the fiber path around the hole.

[0034] Process 3: Composite material 3D printing and performance verification. The generated path data file is converted into G code for use in composite material 3D printers. During the printing process, the fiber path is used as a load-bearing support structure, and the overall performance is enhanced by filling the resin area. Constraint loads can be defined as needed to perform finite element analysis on the generated grid structure CAD to evaluate performance indicators such as stress distribution and displacement distribution of the printed structure.

[0035] Example 1

[0036] like Figure 1 As shown, the present invention can be roughly divided into five steps: inputting grid design parameters, geometric parameterized modeling, path planning, G code generation and post-processing, and 3D printing.

[0037] Step 1: Boundary definition. Use Rhino 3D modeling design software and its integrated graphics programming tool Grasshopper to define the grid boundary, geometric parameters and preliminary fiber path. Figure 4 As shown, in actual design, since the grid has an arbitrary numerical thickness, and the thickness of the fiber and the thickness of the printing nozzle both affect the printing effect, the flexible adjustment of the printing spacing will affect the molding quality of the fiber printing.

[0038] Step 2: Parametric modeling. The geometric design and data generation of the grid are the basis and premise for path planning of grid printing. Figure 2 As shown, the definition of the grid can first use a closed geometric boundary to constrain the range of grid generation. In order to apply parametric design to any grid generation, the minimum geometric bounding box of the closed geometric boundary is used as a reference, and parallel line grids in different directions are generated by defining the grid direction vector. Note that since the grid is defined by the direction vector, when printing, one layer is the grid fiber with the same direction vector, so the two-dimensional grid can be extended to n-dimensional, and the grids with different direction vectors can be processed in the same way to obtain G code for layered interlaced printing.

[0039] In step 3: path optimization, the designed geometric parameters are input into the Python script, and the path planning is performed using mathematical algorithms to ensure the continuity and integrity of the fiber path. Figure 3 , Figure 4 As shown, the overall strategy is zigzag printing, but the printing spacing can be flexibly adjusted according to the different thicknesses of the grids; in addition, the discrete areas of the grid parts that are not connected will be identified and printed with resin.

[0040] In step 4: composite printing is performed. The grid structure is printed out according to the generated gcode file through a 3D printer. The fiber part is printed using a continuous path, and the resin is used for regional filling to achieve the molding of the overall composite structure. Figure 5 The figure shows a schematic diagram of the result of drawing a path in the fiber area of ​​the grid piece in one stroke.

Claims

1. A 3D printing method for continuous fiber reinforced composite materials, for generating a path file of a grid structure with variable density or curved surface features, characterized in that: The following steps are involved: (1) Establishing a geometric model of the grid structure in a three-dimensional modeling software, and determining the fiber path and resin filling area through a path planning algorithm written in a programming language; (2) Generate path codes for composite 3D printing equipment and output simulation analysis files to verify structural performance.

2. The method according to claim 1, wherein the grid structure is defined by a lattice structure of periodic unit arrangements, and the geometric characteristics of the grid are described by unit cell type or number of unit cells, wherein the unit cell type includes various lattice arrangement forms such as square and triangle, and each unit cell is a structural unit with n sides.

3. The method according to claim 1 or 2, wherein the continuous fiber path serves as a skeleton support structure for the load-bearing grid, and the path is continuously arranged in a one-stroke manner within the lattice structure to ensure smooth transitions at path nodes and corners, avoid fiber breakage and reduce stress concentration within the structure.

4. The method according to any one of claims 1 to 3, wherein the printing strategy is cross-printing of fibers and resin, the fiber path is used as the main load-bearing part of the structure, and the stability and mechanical properties of the structure are further enhanced by filling the non-connected areas with resin areas.

5. The method according to any one of claims 1 to 4, wherein the geometric model of the grid structure is suitable for curved grid design, and the path planning algorithm can generate a fiber orientation consistent with the curved surface according to the curved surface morphology, so as to ensure that the fibers can fit the curved surface structure during printing and improve the overall stability of the structure.

6. The method according to any one of claims 1 to 5, wherein the grid density and thickness in the lattice structure are adjustable, and variable density design of local areas is achieved by adjusting the spacing and stacking times of the fiber paths in path planning, thereby meeting the load-bearing requirements and material usage control of different areas.

7. A method according to any one of claims 1 to 6, wherein the grid structure includes a frame design and a plurality of mounting holes are provided in the frame, each mounting hole being a circular hole of a specific diameter for structural installation; the path planning algorithm can realize a path around the mounting hole near the mounting hole so that the fibers are evenly distributed along the periphery of the hole, thereby ensuring the structural strength of the installation area.

8. The method according to any one of claims 1 to 7, wherein the path data file can automatically export a simulation analysis file after being generated, so as to be used for structural performance simulation of CAE tools, especially for analyzing the influence of grid thickness, fiber orientation and filling area on structural stress distribution.

9. The method according to any one of claims 1 to 8, wherein the generated path data file includes file formats such as path codes, which are used for 3D printing equipment, finite element analysis, etc. to ensure the feasibility of the designed path in 3D printing manufacturing and its effectiveness in mechanical properties.

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