A method for direction transformation of continuous carbon fiber additive manufacturing scan line paths

Abstract

The application discloses a kind of for continuous carbon fiber additive manufacturing scanning line path direction conversion method, belong to the field of additive manufacturing.This method is layered to three-dimensional model and obtains each layer two-dimensional contour path, determines the core area polygon that each layer needs scanning line filling and scanning direction;Geometric validization processing is executed to core area and its geometric center point is calculated, so that scanning line path generation under arbitrary direction is uniformly converted into regular scanning line filling problem in local coordinate system;In local coordinate system, according to predetermined filling rule, generate continuous, ordered path point sequence;Subsequently, the path point sequence is mapped back to original coordinate system in reverse direction, and the boundary projection correction is carried out to the out-of-boundary point generated after inverse transformation, so that continuous and geometrically valid scanning line filling path under arbitrary direction is obtained.The application can significantly reduce the implementation repetition and engineering complexity of multidirectional filling, improve the stability and reusability of path generation, and inhibit the out-of-boundary risk caused by numerical error.

Description

Technical Field

[0001] This invention relates to the field of additive manufacturing technology, and in particular to a method for changing the direction of scan line paths in additive manufacturing of continuous carbon fiber reinforced composite materials. Background Technology

[0002] Continuous carbon fiber reinforced polymer composites (CFRPs) are widely used in aerospace, automotive, and high-end equipment fields due to their high specific strength, high specific stiffness, and excellent fatigue properties. With the development of additive manufacturing (AM) technology, combining continuous carbon fibers with fused deposition modeling (FDM) processes has become an important approach for fabricating high-performance complex structural components.

[0003] In the additive manufacturing process of continuous carbon fiber reinforced composites, the printing path planning directly affects the fiber placement accuracy, continuity, and interlayer overlap morphology, playing a crucial role in the mechanical properties and molding quality of the component. Specifically, the direction of the filling path determines the fiber placement direction in the plane, the interlayer overlap morphology, and thus influences the anisotropic properties of the component.

[0004] Existing slice filling strategies typically generate scan lines in a fixed direction. When it is necessary to change the scan direction layer by layer to improve anisotropy or meet process constraints, if the scan line intersection and path continuity are implemented separately for each direction in the global coordinate system, it will not only easily lead to repetition and complexity in the algorithm implementation, but also easily cause problems such as local boundary overflow and path disconnection under the influence of polygon boundaries and numerical errors.

[0005] Therefore, it is necessary to propose a unified direction transformation method so that the generation of scan line filling paths in any direction can be reduced to the problem of intersection and continuous connection of regular scan lines in the same local coordinate system, and the boundary error can be corrected after the inverse transformation, thereby improving the stability and reusability of engineering implementation. Summary of the Invention

[0006] This invention proposes a method for transforming the direction of scan line paths in additive manufacturing of continuous carbon fiber reinforced composite materials, aiming to solve problems such as repetitive multi-directional scan line filling, unstable inter-column connections, and path point out-of-bounds errors in existing technologies. The core idea is to transform the direction of the polygon of the core area to be scanned in the nth layer around its geometric center point and map it to a local coordinate system, thus unifying the scan line path generation process under any direction into a scan line filling problem in the local coordinate system. In this local coordinate system, a continuous and ordered sequence of path points is generated according to predetermined scan line path filling rules. Subsequently, the path point sequence is mapped back to the original coordinate system in the reverse direction, and boundary projection corrections are performed on the out-of-bounds points generated after the inverse transformation, thereby obtaining a continuous and geometrically effective scan line filling path under any direction. To achieve the above objective, this invention adopts the following technical solution:

[0007] Step 1: Perform layer processing on the 3D model, with layer numbers n (n=0,1,2,…,N), where the maximum number of layers is N, and obtain the 2D contour path of each layer. Where i represents the point number on the nth layer contour path, This represents the coordinates of the i-th point on the contour path of the n-th layer in the two-dimensional slice plane.

[0008] Step 2: Based on the nth layer 2D contour path obtained in Step 1 The core region of this layer that needs scanline filling is identified and denoted as a simple polygon.

[0009]

[0010] Simultaneously determine the scanning direction angle of the nth layer. When using a layer-by-layer directional recursive strategy, the following can be defined:

[0011]

[0012] in The initial direction angle, This is the interlayer angle increment; or it can be directly given by the process strategy. .

[0013] Step 3: Analyze the polygonal core area. Perform geometry simplification to obtain the effective region:

[0014]

[0015] like If not, no scanline fill path will be generated for that layer. Calculate the geometric center point (centroid) of the effective region:

[0016]

[0017] Step 4: Define the two-dimensional rotation matrix:

[0018]

[0019] For any point Define its orbit around the geometric center point Rotation The rotation operator is:

[0020]

[0021] Based on this, the effective core region polygon of the nth layer is... Contour points within the area According to the direction angle By performing a directional transformation, the core region polygon in the local coordinate system is obtained:

[0022]

[0023] Step 5: In the core area polygon of the local coordinate system Within, a continuous and ordered sequence of path points is generated according to the predetermined scan line path filling rules.

[0024]

[0025] Where M+1 represents the total number of path points filled in this layer. For any All have . Indicates the starting point of the local path. Indicates the number arranged in the order of printing motion. Local path points.

[0026] Step 6: Calculate the local path point sequence obtained in Step 5. All points in the array revolve around the same geometric center. according to Perform a direction transformation to obtain the path points in the original coordinate system:

[0027]

[0028] Obtain the path point set in the original coordinate system:

[0029]

[0030] Step 7: To eliminate the numerical error introduced by the inverse transform, if there exists Then it is corrected to be at the boundary. The nearest point on:

[0031]

[0032] And order

[0033]

[0034] in, express The boundary set, This represents the two-dimensional Euclidean norm. Detailed Implementation

[0035] Example:

[0036] This embodiment provides a specific application scenario to illustrate the application process of the above-mentioned inflection point smoothing method in actual continuous carbon fiber 3D printing.

[0037] Step 1: Select an inclined cylinder with non-parallel upper and lower end faces as the model. The lower end face has a diameter of 40 mm and a total axial length of 20 mm. The effective axial length of the other end is 10 mm, resulting in an angle of approximately 14.04° between the two end faces. Place the model on its side on a platform and slice it along the Z-direction in 0.2 mm thick layers, for a total of 200 layers. Each layer has a trapezoidal outer contour. The following explanation uses layer 100 as an example. The filling path within this layer is generated using a scanline algorithm, and the filling direction forms a fixed angle with the geometric feature lines of the model.

[0038] Step 2: Based on the 2D contour path of layer 100 obtained in Step 1, determine the core area of ​​this layer that needs to be filled with scan lines, denoted as a simple polygon. Simultaneously determine the scanning direction angle of the 100th layer. Initial direction angle And set the inter-layer angle increment Then the scanning direction angle of the 100th layer is:

[0039]

[0040] Step 3: Analyze the polygonal core area. Perform geometry simplification to obtain the effective region. .like If not, then no scanline fill path will be generated for that layer. The calculated geometric center point (centroid) of the effective region is... .

[0041] (In this embodiment, the "core area with the largest cross-section" is defined as four points.) Its centroid is taken as the center of rotation according to the above coordinates.

[0042] Step 4: Define the two-dimensional rotation matrix:

[0043]

[0044] For any point Define its orbit around the geometric center point Rotation The rotation operator is:

[0045]

[0046] Based on this, the polygon of the effective core area of ​​the 100th layer is... Each contour point within the area is arranged according to its direction angle. By performing a directional transformation, the core region polygon in the local coordinate system is obtained:

[0047]

[0048] In this embodiment ,therefore .Depend on , ,get:

[0049]

[0050] Taking the four vertices of the core region with the largest cross-section as an example (unit: mm), let Then through The vertices of the local coordinate system after the orientation transformation are:

[0051]

[0052] Step 5: In the core area polygon of the local coordinate system Within, a continuous and ordered sequence of path points is generated according to the predetermined scan line path filling rules.

[0053]

[0054] in Fill the total number of path points for this layer, and for any All have . Indicates the starting point of the local path. Indicates the number arranged in the order of printing motion. Local path points.

[0055] To better demonstrate the effect of "bringing in data", this embodiment takes several horizontal scan lines in a local coordinate system (example takes...). By forming a continuous scan line path according to the rule of "alternating connection of adjacent scan line endpoints", a set of exemplary local path points (unit: mm) can be obtained:

[0056]

[0057] Note: The above is only a "partial list" for demonstration purposes; in actual engineering... The spacing between the scan lines and the cut lines is determined by the process and slicing parameters.

[0058] Step 6: Calculate the local path point sequence obtained in Step 5. All points in the array revolve around the same geometric center. according to Perform a direction transformation to obtain the path points in the original coordinate system:

[0059]

[0060] Obtain the path point set in the original coordinate system:

[0061]

[0062] In this embodiment ,Depend on , After inversely transforming the above example point sequence back to the original coordinate system, the corresponding path points in the original coordinate system can be obtained (unit: mm, rounded):

[0063]

[0064] Step 7: To eliminate the numerical error introduced by the inverse transform, if there exists Then it is corrected to be at the boundary. The nearest point on:

[0065]

[0066] And order

[0067]

[0068] in, express The boundary set, This represents the two-dimensional Euclidean norm.

[0069] In this embodiment, the aforementioned exemplary inverse transformation point sequence was checked and found to fall within the core region of the largest cross-section. Therefore, no boundary projection correction is required; if a point exceeds the boundary due to floating-point error during the engineering implementation, the correction can be performed according to the projection formula above.

Claims

1. A method for changing the direction of scan line paths in continuous carbon fiber additive manufacturing, characterized in that, Includes the following steps: Step 1: Perform layering on the 3D model to obtain the... Two-dimensional contour path of the layer; Step Two: Based on the aforementioned... The two-dimensional contour path of the layer determines the core area that needs to be filled by scan lines in the layer, and determines the scan direction angle of the layer; Step 3: Perform geometric activating processing on the core region to obtain the effective region; when the effective region is empty, do not generate a scan line fill path for that layer; and calculate the geometric center point of the effective region; Step 4: Using the geometric center point as the rotation center, perform directional transformation on the effective area according to the scanning direction angle to obtain the core area in the local coordinate system; Step 5: Within the core area of ​​the local coordinate system, generate a continuous and ordered sequence of local path points according to the predetermined scan line path filling rules; Step 6: Using the same geometric center point as the rotation center, perform an inverse transformation on the local path point sequence to obtain the scan line filling path point set in the original coordinate system; Step 7: To eliminate the numerical error introduced by the inverse direction transformation, the path points falling outside the effective area are corrected to obtain the corrected scan line filling path point set. This set is then superimposed with the planning results of other contour paths, filling paths, and cross-layer paths in the same layer to generate G-code control instructions suitable for 3D printing of continuous carbon fiber reinforced composite materials.

2. The method for changing the direction of a scan line path in continuous carbon fiber additive manufacturing according to claim 1, characterized in that, The first The two-dimensional contour path is composed of several discrete sampling points arranged in the printing motion sequence, with adjacent sampling points connected sequentially to form a closed polyline contour; the core area is a simple polygon defined by the contour path. .

3. The method for changing the direction of a scan line path in continuous carbon fiber additive manufacturing according to claim 1, characterized in that, The scanning direction angle The direction is determined using a layer-by-layer recursive strategy, that is, it is obtained by recursively calculating the initial direction angle and the inter-layer angle increments, and the recursive results are periodically processed to ensure... fall into Within the range.

4. The method for changing the direction of a scan line path in continuous carbon fiber additive manufacturing according to claim 1, characterized in that, The scanning direction angle The process strategy is directly given by the process strategy, which includes any one of the following: fixed direction strategy, partition orientation strategy, or layer-based preset direction table strategy.

5. The method for changing the direction of a scan line path in continuous carbon fiber additive manufacturing according to claim 1, characterized in that, The geometry activation process in step three is used to eliminate self-intersections, duplicate edges, or degenerate boundaries of the core region polygons and output the effective region. ;when When this happens, the orientation transformation, local filling, and inverse transformation steps for that layer are skipped, and the scan line filling path for that layer is not generated.

6. The method for changing the direction of a scan line path in continuous carbon fiber additive manufacturing according to claim 1, characterized in that, The geometric center point is the effective area. center of mass The centroid is used as the common rotation center for the direction transformation and the reverse direction transformation in steps four and six.

7. The method according to claim 1, characterized in that, The direction transformation in step four uses a two-dimensional rotation matrix to construct a rotation operator, rotating any point within the effective region around the geometric center point by an angle. Rotate to obtain the core region polygon in the local coordinate system. .

8. The method according to claim 7, characterized in that, The reverse direction transformation in step six uses the same rotation center as in step four, and transforms each point in the local path point sequence by angle. Rotate and map back to the original coordinate system to obtain the scan line fill path point set in the original coordinate system. .

9. A method for changing the direction of a scan line path in continuous carbon fiber additive manufacturing according to claim 1, characterized in that, The scan line path filling rules in step five include: generating a set of parallel scan lines in the local coordinate system; calculating the polygon of the core area of ​​the local coordinate system for each scan line. The intersection points of the scan lines are used to form fill line segments; and the endpoints of the fill line segments of adjacent scan lines are connected in an alternating manner to generate a continuous and ordered sequence of local path points. .

10. A method for changing the direction of a scan line path in continuous carbon fiber additive manufacturing according to claim 1, characterized in that, Step seven's boundary correction includes: ensuring that the area falls within the effective region after the inverse direction transformation. Calculate the path points outside the boundary. The nearest point is projected onto the path and replaced with the nearest point to eliminate the out-of-bounds error introduced by the inverse transformation and floating-point calculation, thereby ensuring the geometric validity of the final scan line filling path.

Images