3D printing method for automobile special-shaped thin-walled composite part

Abstract

The application discloses a 3D printing method for an automobile special-shaped thin-wall composite part, and comprises the following steps: creating a three-dimensional model of the thin-wall composite part by using software, importing the model into slicing software for layering processing, obtaining the outer contour and the inner contour of the thin slice, spline processing, calculating the slope of the contour line, determining the direction and thickness of the filling line through the slope, filling the area with a large slope and exceeding the specified threshold value by using a vertical center line, filling the area with a small slope by using a parallel center line, obtaining the filling path by using a smooth transition algorithm for the transition area, preparing the printing material, and starting layer-by-layer printing by the printer according to the printing instruction until the object shape is formed; the slope of the contour line is calculated to ensure that the direction of the filling line matches the geometric characteristics of the printed part, the surface quality and the structural strength are improved, the smooth transition algorithm is used to determine the filling path in the area with a large slope to a small slope, the filling mode mutation is reduced, and the risk of cracks and deformation of the printed part is reduced.

Description

Technical Field

[0001] This invention relates to the technical field of 3D printing methods for irregularly shaped thin-walled composite parts for automobiles, and particularly to a 3D printing method for irregularly shaped thin-walled composite parts for automobiles. Background Technology

[0002] 3D printing, also known as additive manufacturing, is a manufacturing technology that uses a 3D printer to transform a 3D digital model into a solid three-dimensional object by layering materials. Compared with traditional cutting and forming, 3D printing technology has advantages such as high design freedom and convenient personalization, and is widely used in industries such as automotive, aerospace, and medical.

[0003] Currently, 3D printing technology still faces certain limitations in printing complex, irregularly shaped, thin-walled structures. Traditional 3D printing methods are difficult to apply to printing irregularly shaped, thin-walled parts with irregular internal structures and fine features. The printing process of irregularly shaped, thin-walled composite parts in 3D printing involves several key technologies, such as model design, slicing, and infill strategies. Among these, model design is the foundation of the printing process, requiring designers to fully consider wall thickness, internal cavities, and necessary detailed features to ensure that the printed parts meet usage requirements. However, traditional model design methods often struggle to accurately predict potential deformation and stress issues during the printing process, leading to low printing efficiency and unstable print quality.

[0004] Common methods in existing technologies include: using uniform infill, which cannot meet the printing requirements of thin-walled structures and is prone to producing too much or too little material; using path infill, which is difficult to handle the complex changes in inner and outer contours and is difficult to achieve smooth transitions in transition areas; at the same time, the stacking method has poor support for thin-walled structures and has problems such as interlayer adhesion; and how to dynamically adjust the infill method to take into account the printing requirements of different areas and achieve high-quality 3D printing of irregular thin-walled structures still needs to be solved.

[0005] Meanwhile, in the transition area where the slope decreases, the sudden change in the filling method may cause discontinuity in the print path. Since the slope change of each slice is not linear, a slice is divided into many parts, which is not good for continuity, and the printing time is long, affecting the print quality. Summary of the Invention

[0006] This invention overcomes the shortcomings of the prior art and provides a 3D printing method for irregularly shaped thin-walled composite parts for automobiles.

[0007] To achieve the above objectives, the technical solution adopted by this invention is: a 3D printing method for irregularly shaped thin-walled composite automotive parts, comprising the following steps:

[0008] S1. Model Design: Based on the irregular thin-walled composite part to be printed, use CAD software to create a three-dimensional model of the irregular thin-walled composite part. During the model design process, the wall thickness, internal cavity and any necessary details also need to be considered.

[0009] S2. Slicing Processing: Import the designed 3D model of the composite part into the 3D slicing software for layer processing. That is, the slicing software horizontally cuts the 3D model of the composite part into a series of thin slices, each slice representing a layer to be printed, and obtains the outer contour and inner contour of each slice.

[0010] S3. Thin-piece filling: Spline the obtained outer and inner contours, calculate the slope of the thin-piece outer and inner contours, scan the thin part, and dynamically adjust the filling method according to the geometric features of the composite model. The slope determines the direction and thickness of the filling line.

[0011] S4. Contour Division: Contours are divided based on the obtained slope. Areas with a large slope that exceeds a specified threshold are filled with vertical center lines, while areas with a small slope that is within the threshold range are filled with parallel center lines. For transitional areas where the slope decreases, a smooth fill angle is calculated by linearly changing the slope and the rate of change of the slope to address the sudden change in the fill method. A fill path is then generated based on the fill angle for filling.

[0012] S5. Printing Preparation: After preparing the printing material, load the material into the 3D printer and set the printing speed, printing temperature and layer height according to the printing instructions generated by the slicing software.

[0013] S6. Layer-by-layer printing: The 3D printer begins printing layer by layer. In each layer, the printer precisely moves the print head on the printing platform according to the contour information generated by the slicing software. The print head moves along the path of the contour, accumulating material layer by layer and spraying the material to the designated position to gradually form the shape of the object.

[0014] In a preferred embodiment of the present invention, the method for filling the vertical center line in step S4 is as follows: insert several points into the center line array of the inner and outer contours in the region with a large slope and exceeding a specified threshold, that is, generate several vertical lines perpendicular to the center line at the point. The two ends of the vertical lines extend to intersect with the offset lines of the inner and outer contours to generate fill lines, and the fill lines pass through the thickness of the printed part and extend from the top to the bottom.

[0015] In a preferred embodiment of the present invention, the method for filling the parallel center lines in step S4 is as follows: the center lines of the outer contour and inner contour of the region with a small slope (i.e., within the threshold range) are offset to generate filling lines. The filling lines are connected as straight lines and are arranged along the X-axis or Y-axis to form a series of parallel lines.

[0016] In a preferred embodiment of the present invention, the slope of the contour line in step S3 is calculated as follows:

[0017] a. First, construct a rectangular coordinate system, divide the contour line into several points, each with coordinates (x, y). The slope of points far from the endpoints is considered zero. Add points near the endpoints, using the slope of the endpoints as the calculation value for each added point.

[0018] b. In 3D printing, the slope represents the change along the printing bed direction relative to the change perpendicular to the printing bed direction, and the slope is the ratio of the vertical change to the horizontal change between two points; except for the points with a slope of zero, other points are taken at equal intervals, and the calculation results are applied according to the slope calculation formula.

[0019] The formula for calculating the slope is:

[0020] Where (x1, y1) and (x2, y2) are the coordinates of two adjacent points on the contour line.

[0021] In a preferred embodiment of the present invention, the premise for achieving a smooth filling mode conversion in the transition region of slope change in step S4 is as follows: by calculating the slope change rate between two adjacent printing units, the obtained change rate value is compared with the slope change rate threshold, and the slope is compared with the slope threshold. If the slope is greater than the slope threshold and the slope change rate is greater than the change rate threshold, then the smooth transition algorithm is activated.

[0022] In a preferred embodiment of the present invention, the smooth transition algorithm is expressed as follows: First, the rate of change of the slope is calculated based on the starting point and the ending point of the printing unit. Then, the distance between any point in the transition area and the starting point is multiplied by the rate of change of the slope to calculate the fill angle that should be at that point. As the point moves from the starting point to the ending point of the printing unit, the fill angle will smoothly transition from the maximum value in the direction perpendicular to the center line to the minimum value in the direction parallel to the center line.

[0023] In a preferred embodiment of the present invention, in step S4, the contour is divided by the calculated slope. When the slope is greater than a specified threshold, the two ends of the contour are extended according to a specified length. If there are sample points with a slope greater than the specified threshold in the extended part, the part with a large slope is further extended until there are no sample points with a slope greater than the specified value. The other parts are contour parts with a small slope.

[0024] In a preferred embodiment of the present invention, the spline processing in step S3 uses an interpolation spline processing method.

[0025] In a preferred embodiment of the present invention, in step S5, the printing material is selected as PLA polylactic acid material, and the printing speed is set to 50-100 mm / s, the printing temperature is set to 190-230℃, and the layer height is set to 0.1-0.3 mm.

[0026] In a preferred embodiment of the present invention, the geometric features of the composite model include: wall thickness, internal cavity size, and fine features on the model; the wall thickness is 1-4 mm, the internal cavity is a hole structure inside the model, and the fine features are small holes, grooves, and chamfers on the model.

[0027] This invention addresses the shortcomings of the prior art and has the following beneficial effects:

[0028] (1) This invention proposes a 3D printing method for automotive irregular thin-walled composite parts. By calculating the slope of the contour line, the direction of the filling line can be ensured to match the geometric features of the printed part, thereby improving the surface quality and structural strength of the printed part. The 3D printing method that dynamically adjusts the filling method according to the slope of the contour line divides the region by calculating the slope, and realizes the smooth transition of different regions. In the region where the slope changes from large to small, the smooth transition algorithm can reduce the abrupt change of the filling method, avoid stress concentration points in the printed part, reduce the risk of cracks and deformation in the printed part, and effectively solve the problems of traditional methods in printing complex irregular thin-walled structures.

[0029] (2) For the transition region where the slope decreases from large to small, the present invention calculates a smooth filling angle by linearly changing the slope and the rate of change of the slope to address the sudden change in the filling method. The filling path is generated based on the filling angle for filling. For irregular thin-walled parts with complex geometric features, the slope analysis and smooth transition algorithm can ensure that the filling strategy adapts to the local changes of the model, thereby maintaining the functional characteristics of the printed part. At the same time, the slope analysis helps to maintain the consistency of the wall thickness during the printing process, which improves the printing efficiency to a certain extent, reduces the idle movement of the print head, and shortens the printing time.

[0030] (3) The smooth transition algorithm proposed in this invention not only reduces the frequency of filling mode switching, making the printing process smoother, but can also be adjusted according to different printed parts designs and material properties, which has strong adaptability and improves the overall printing efficiency to a certain extent. Attached Figure Description

[0031] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0032] Figure 1 This is a perspective structural diagram of a preferred embodiment of the present invention;

[0033] Figure 2 This is a schematic diagram of a contour filling path according to a preferred embodiment of the present invention.

[0034] In the diagram: 1. Outer contour; 2. Inner contour; 3. Parallel center line fill line; 4. Transition area. Detailed Implementation

[0035] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0036] In the description of this application, it should be understood that the terms "center," "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicating orientation or positional relationships based on the orientation or positional relationships shown in the accompanying drawings, are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as limiting the scope of protection of this application. Furthermore, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Therefore, features defined with "first," "second," etc., may explicitly or implicitly include one or more of that feature. In the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0037] like Figure 1 As shown, a 3D printing method for irregularly shaped thin-walled composite automotive parts includes the following steps:

[0038] S1. Model Design: Based on the irregular thin-walled composite part to be printed, use CAD software to create a three-dimensional model of the irregular thin-walled composite part. During the model design process, the wall thickness, internal cavity and any necessary details also need to be considered.

[0039] S2. Slicing Processing: Import the designed 3D model of the composite part into the 3D slicing software for layer processing. That is, the slicing software horizontally cuts the 3D model of the composite part into a series of thin slices, each slice representing a layer to be printed, and obtains the outer contour and inner contour of each slice.

[0040] S3. Thin-piece filling: Spline the obtained outer and inner contours, calculate the slope of the thin-piece outer and inner contours, scan the thin part, and dynamically adjust the filling method according to the geometric features of the composite model. The slope determines the direction and thickness of the filling line.

[0041] S4. Contour Division: Contours are divided based on the obtained slope. Areas with a large slope that exceeds a specified threshold are filled with vertical center lines, while areas with a small slope that is within the threshold range are filled with parallel center lines. For transitional areas where the slope decreases, a smooth fill angle is calculated by linearly changing the slope and the rate of change of the slope to address the sudden change in the fill method. A fill path is then generated based on the fill angle for filling.

[0042] S5. Printing Preparation: After preparing the printing material, load the material into the 3D printer and set the printing speed, printing temperature and layer height according to the printing instructions generated by the slicing software.

[0043] S6. Layer-by-layer printing: The 3D printer begins printing layer by layer. In each layer, the printer precisely moves the print head on the printing platform according to the contour information generated by the slicing software. The print head moves along the path of the contour, accumulating material layer by layer and spraying the material to the designated position to gradually form the shape of the object.

[0044] The geometric features of the composite model in this invention include: wall thickness, internal cavity size, and small features on the model; the wall thickness is selected as 2mm, the internal cavity is the hole structure inside the model, and the small features are small holes, grooves, and chamfers on the model. These structures require special attention during printing; and in step S5, the printing material is selected as PLA polylactic acid material, the printing speed is set to 60mm / s, the printing temperature is set to 210℃, and the layer height is set to 0.2mm.

[0045] The contour is divided by the calculated slope. When the slope of the contour is greater than a specified threshold, the two ends are extended by a specified length. If there are sample points with a slope greater than the specified threshold in the extended part, the part with a large slope is extended further until there are no sample points with a slope greater than the specified value. The other parts are contour parts with a small slope.

[0046] The method for filling the vertical center line in step S4 is as follows: Insert several points into the center line array of the inner and outer contours in the area with a large slope and exceeding the specified threshold, that is, generate several vertical lines perpendicular to the center line at the point. The two ends of the vertical lines extend to intersect with the offset lines of the inner and outer contours to generate fill lines. The fill lines pass through the thickness of the printed part and extend from the top to the bottom.

[0047] The method for filling parallel center lines is as follows: offset the center lines of the outer and inner contours of the region with a small slope (i.e., within the threshold range) to generate fill lines. The fill lines are connected by straight lines and are arranged along the X-axis or Y-axis to form a series of parallel lines.

[0048] The spline processing in step S3 of this invention uses the following interpolation spline processing method:

[0049] First, a series of discrete data points are obtained from the slicing software. These points constitute the original shapes of the outer and inner contours, and the data points are usually selected at equal intervals on the contour line.

[0050] Secondly, using the interpolation spline method, a continuous spline curve is constructed from discrete data points; where the spline curve is a curve defined by a series of control points, passing precisely through these control points and being smooth between the control points;

[0051] Then, based on the accuracy and efficiency requirements of printing, a suitable spline type is selected. In this invention, a cubic interpolation spline is selected. Based on the selected spline type and the given data points, the parameters of the spline curve are calculated.

[0052] Finally, the constructed initial spline curve is optimized to ensure that the curve meets specific requirements, and the final contour lines are generated based on the optimized spline curves; these contour lines will be used for subsequent selection of fill paths and generation of printing instructions.

[0053] In one embodiment, the slope of the contour line in step S3 is calculated as follows:

[0054] a. First, construct a rectangular coordinate system, divide the contour line into several points, each with coordinates (x, y). The slope of points far from the endpoints is considered zero. Add points near the endpoints, using the slope of the endpoints as the calculation value for each added point.

[0055] b. In 3D printing, the slope represents the change along the printing bed direction relative to the change perpendicular to the printing bed direction, and the slope is the ratio of the vertical change to the horizontal change between two points; except for the points with a slope of zero, other points are taken at equal intervals, and the calculation results are applied according to the slope calculation formula.

[0056] The formula for calculating the slope is:

[0057] Where (x1, y1) and (x2, y2) are the coordinates of two adjacent points on the contour line.

[0058] After calculating the slope of the contour line using the above method, it is compared with the corresponding slope threshold; where the slope threshold specifies the value of the slope threshold.

[0059] In one embodiment, the premise for achieving a smooth fill mode transition in the transition region of slope change in step S4 is as follows: by calculating the slope change rate between two adjacent printing units, the obtained change rate value is compared with the slope change rate threshold, and the slope is compared with the slope threshold. If the slope is greater than the slope threshold and the slope change rate is greater than the change rate threshold, then the smooth transition algorithm is activated.

[0060] It should be noted that the slope threshold needs to take into account the requirements of print quality, material properties, and printing speed. Before specifying the slope threshold, test pieces are printed to adjust the slope threshold and observe the printing effect before determining the value of the slope threshold. The slope change rate threshold needs to consider the need for smooth transition and printing effect. If the setting value is too high, the smooth transition algorithm will be frequently activated, affecting printing efficiency; if the setting value is too low, it may not be able to effectively smooth the slope change of the contour line, resulting in a decrease in print quality. Therefore, the slope change rate threshold is observed by printing some test pieces with different slope changes and adjusted as needed.

[0061] The specific prerequisites for using the smooth transition algorithm are as follows:

[0062] A1. After processing the inner and outer contours of each thin slice with interpolation splines, several spline curves are obtained. The coordinate values ​​of the two endpoints of each spline curve are obtained, the slope is calculated and compared with the slope threshold. The area with a large slope that exceeds the specified threshold is filled with a vertical centerline, and the area with a small slope that is within the threshold range is filled with a parallel centerline.

[0063] A2. For transition regions where the slope decreases from large to small, the slope and slope change rate are calculated to address the sudden change in filling method. These are then compared with the slope threshold and slope change rate threshold. If the slope is greater than the slope threshold and the slope change rate is greater than the change rate threshold, a smooth transition algorithm is used.

[0064] It should be noted that the smooth transition algorithm is as follows: First, the rate of change of the slope is calculated based on the start and end points of the printing unit. Then, the distance between any point in the transition area and the start point is multiplied by the rate of change of the slope to calculate the fill angle that should be at that point. As the point moves from the start point to the end point of the printing unit, the fill angle will smoothly transition from the maximum value in the direction perpendicular to the center line to the minimum value in the direction parallel to the center line.

[0065] The calculation method for the fill angle is as follows:

[0066] A. For two adjacent spline curves, the slopes k1 and k2 are obtained from the coordinates of the two endpoints of each spline curve, and the slope change δ = |k1-k2|; calculate the smooth transition distance d, where the magnitude of the distance d is related to the data points selected at equal intervals during the interpolation spline processing;

[0067] B. For each printed cell within the smooth transition region, calculate its distance x relative to the transition start point;

[0068] C. Calculate the fill angle using linear interpolation. Generate the corresponding fill path based on the obtained fill angle;

[0069] Where θ1 is the angle when filling vertically, θ2 is the angle when filling horizontally, x is the distance from the current printing cell to the transition start point, d is the total distance of the smooth transition, and S is the smoothing factor used to control the smoothness of the filling mode transition.

[0070] The linear interpolation (lerp) function is defined as: lerp(a, b, S·t) = a + S × t × (ba);

[0071] Here, a and b are the two values ​​to be interpolated; t is the interpolation parameter, ranging from 0 to 1.

[0072] After obtaining the filling angle according to the above calculation method, for each printing unit, the direction of the filling line is determined according to the calculated filling angle, which determines the movement direction of the print head in this area. For vertical filling areas, the filling line will be perpendicular to the print bed. For parallel filling areas, the filling line will be parallel to the X-axis or Y-axis of the print bed. For smooth transition areas, the direction of the filling line will be linearly interpolated between vertical and parallel according to the filling angle.

[0073] In the vertical infill region, a series of vertical lines are generated, extending from the top to the bottom of the printing unit and traversing the entire thickness of the printed part. In the parallel infill region, a series of parallel lines are generated, arranged along the X-axis or Y-axis. In the smooth transition region, the infill direction at each point is calculated based on the infill angle, generating a series of polygonal lines that smoothly transition between vertical and parallel. The infill path is optimized during the transition to ensure no abrupt changes occur, thus avoiding unnecessary movement of the print head. This is then used to generate printing instructions for 3D printing. Before actual printing, test pieces are printed to verify the accuracy of the infill path and print quality. The infill angle and path are adjusted based on the printing results to optimize the printing effect.

[0074] Based on the preferred embodiments of the present invention described above, those skilled in the art can make various changes and modifications without departing from the inventive concept. The technical scope of this invention is not limited to the contents of the specification, but must be determined according to the scope of the claims.

Claims

1. A method for 3D printing irregularly shaped thin-walled composite parts for automobiles, comprising the following steps: S1. Model Design: Based on the irregular thin-walled composite part to be printed, use CAD software to create a three-dimensional model of the irregular thin-walled composite part; S2. Slicing Processing: Import the designed 3D model of the composite part into the 3D slicing software for layer processing. That is, the slicing software horizontally cuts the 3D model of the composite part into a series of thin slices, each slice representing a layer to be printed, and obtains the outer contour and inner contour of each slice. S3. Thin-piece filling: Spline the obtained outer and inner contours, calculate the slope of the thin-piece outer and inner contours, scan the thin part, and dynamically adjust the filling method according to the geometric features of the composite model. The slope determines the direction and thickness of the filling line. S4. Contour Division: Contours are divided based on the obtained slope. Areas with a larger slope, exceeding a specified threshold, are filled with vertical center lines, while areas with a smaller slope, within the threshold range, are filled with parallel center lines. For transitional areas where the slope decreases, a smooth fill angle is calculated by linearly changing the slope and the rate of change of the slope to address the sudden change in fill method. A fill path is then generated based on the fill angle for filling. S5. Printing Preparation: After preparing the printing material, load the material into the 3D printer and set the printing speed, printing temperature and layer height according to the printing instructions generated by the slicing software. S6. Layer-by-layer printing: The 3D printer begins printing layer by layer. In each layer, the printer moves the print head precisely on the printing platform according to the contour information generated by the slicing software. The print head moves along the path of the contour, stacking material layer by layer and spraying the material to the designated position to gradually form the shape of the object. The method for filling the vertical centerline in step S4 is as follows: insert several points into the centerline array of the inner and outer contours in the region with a large slope that exceeds the specified threshold, thereby generating several vertical lines perpendicular to the centerline at that point. The two ends of the vertical lines extend to intersect with the offset lines of the inner and outer contours to generate filling lines. The method for filling parallel center lines in step S4 is as follows: offset the center lines of the outer contour and inner contour of the region with a small slope (i.e., within the threshold range) to generate filling lines. The filling lines are connected by straight lines and are arranged along the X-axis or Y-axis to form a series of parallel lines.

2. The 3D printing method for automotive irregular thin-walled composite parts according to claim 1, characterized in that: In step S3, the slope of the contour line is calculated as follows: a. First, construct a rectangular coordinate system, divide the contour line into several points, each with coordinates (x, y). The slope away from the endpoint is considered zero. Add points near the endpoint, and use the slope of the endpoint as the calculation value for the added points. b. In 3D printing, the slope represents the change along the print bed direction relative to the change perpendicular to the print bed direction, while the slope is the ratio of the vertical change to the horizontal change between two points. Apart from the points where the slope is considered zero, other points are taken at equal intervals, and their calculation results are applied according to the slope calculation formula. The formula for calculating the slope is: ;in,( , )and( , ) represents the coordinates of two adjacent points on the contour line.

3. The 3D printing method for automotive irregular thin-walled composite parts according to claim 1, characterized in that: The premise for achieving a smooth filling mode transition in the transition region of slope change in step S4 is as follows: by calculating the slope change rate between two adjacent printing units, the obtained change rate value is compared with the slope change rate threshold, and the slope is compared with the slope threshold. If the slope is greater than the slope threshold and the slope change rate is greater than the change rate threshold, then the smooth transition algorithm is activated.

4. The 3D printing method for automotive irregular thin-walled composite parts according to claim 3, characterized in that: The smooth transition algorithm is as follows: First, the rate of change of the slope is calculated based on the starting point and ending point of the printing unit. Then, the distance between any point in the transition area and the starting point is multiplied by the rate of change of the slope to calculate the fill angle that should be at that point. As the point moves from the starting point to the ending point of the printing unit, the fill angle will smoothly transition from the maximum value in the direction perpendicular to the center line to the minimum value in the direction parallel to the center line.

5. The 3D printing method for automotive irregular thin-walled composite parts according to claim 2, characterized in that: In step S4, the contour is divided by the calculated slope. When the slope of the contour is greater than a specified threshold, both ends are extended according to a specified length. If there are sample points with a slope greater than the specified threshold in the extended part, the part with a large slope is further extended until there are no sample points with a slope greater than the specified value. The other parts are contour parts with a small slope.

6. The 3D printing method for automotive irregular thin-walled composite parts according to claim 3, characterized in that: The spline processing in step S3 uses the interpolation spline processing method.

7. The 3D printing method for automotive irregular thin-walled composite parts according to claim 1, characterized in that: In step S5, PLA (polylactic acid) is selected as the printing material, and the printing speed is set to 50-100 mm / s, the printing temperature is set to 190-230℃, and the layer height is set to 0.1-0.3 mm.

8. The 3D printing method for automotive irregular thin-walled composite parts according to claim 1, characterized in that: The geometric features of the composite model include: wall thickness, internal cavity size, and fine features on the model; the wall thickness is 1-4 mm, the internal cavity is a hole structure inside the model, and the fine features are small holes, grooves, and chamfers on the model.

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