A five-axis path planning method to reduce the staircase effect in 3D printed parts

Abstract

This invention relates to a five-axis path planning method for reducing the staircase effect in 3D printed parts. The method first acquires a 3D model of the printing target and extracts the vertex coordinates and normal vectors of each triangular facet on the surface of the 3D model. Then, the surface to be optimized is extracted from the 3D model, the topological relationship of all triangular facets on the surface to be optimized is established, and a complete five-axis 3D printing path is formed through steps such as projection, inverse projection, sorting, and connecting intersection points. The five-axis 3D printing path planned by this invention can perform surface optimization printing on a workpiece to be optimized formed by three-axis 3D printing, ensuring that the originally curved surface remains smooth after printing, effectively mitigating the impact of the staircase structure produced by traditional three-axis 3D printing on the accuracy and quality of the printed object.

Description

Technical Field

[0001] This invention relates to the field of 3D printing technology, and in particular to a five-axis path planning method for reducing the staircase effect in 3D printed parts. Background Technology

[0002] 3D printing technology can be used to process and manufacture required parts. In layman's terms, 3D printing is additive manufacturing, which involves layering and adding materials. However, in traditional three-axis 3D printing technology, which uses planar layering and step-by-step addition, the surface of the part will have uneven edges and a stepped structure between the layers. This is called the step effect. The step effect is an unavoidable problem in 3D printing technology, which can easily cause deviations in the accuracy of the printed parts, thus failing to meet the requirements for use. Summary of the Invention

[0003] Based on this, it is necessary to address the technical problem that traditional three-axis 3D printing is prone to printing accuracy deviation due to the step effect, thereby reducing the surface quality of objects. This invention provides a five-axis path planning method to improve the surface quality of 3D printed parts.

[0004] This invention discloses a five-axis path planning method for reducing the staircase effect in 3D printed parts. The five-axis path is used to perform surface optimization printing on a workpiece to be optimized, which has been formed by three-axis 3D printing. The planning method includes the following steps:

[0005] Obtain the 3D model of the target object and extract the vertex coordinates and normal vectors of each triangular facet on the surface of the 3D model. The 3D model exists in an XYZ coordinate system, with the Z-axis perpendicular to the horizontal plane containing the XY axes.

[0006] S1. Extract the surface to be optimized from the 3D model.

[0007] S2. Establish the topological relationships of all triangular faces on the surface to be optimized.

[0008] S3. Project all vertices of the triangular faces on the surface to be optimized onto the unit circle domain in the plane and establish a mapping relationship. Among them, two vertices that have a topological relationship on the surface to be optimized maintain their topological relationship when projected onto the unit circle domain.

[0009] S4. Connect the projection points that have topological relationships on the unit circle domain to form line segments, and find the intersection of the unit circle and the line segments to form the intersection point.

[0010] S5. Inverse map the intersection points onto the surface to be optimized, traverse the coordinates of all inverse-mapped intersection points, and extract the X and Y coordinates and normal vectors of the inverse-mapped intersection points.

[0011] S6. Calculate the angle between the vector formed by the intersection points after the inverse mapping and the X-axis on the horizontal plane, and sort the intersection points after the inverse mapping according to the size of the angle.

[0012] S7. Use straight lines to connect the intersection points of the sorted reverse mapping in sequence to form a closed polyline, which in turn constitutes a single printing path.

[0013] S8. Offset a series of concentric circles equidistantly inward from the unit circle, and form a printing path corresponding to each concentric circle in sequence, referring to the methods of S3 to S7, thereby forming a complete five-axis 3D printing path.

[0014] As a further improvement to the above scheme, the method for establishing the topological relationships of all triangular patches on the surface to be optimized includes the following process:

[0015] By iterating through the coordinates of each vertex of each triangular facet on the surface to be optimized, and analyzing the positional relationship between each triangular facet and the other triangular facets, the analysis results are as follows:

[0016] (a) If two triangular faces have the same vertex coordinates, it means that the two triangular faces have one corner that coincides.

[0017] (b) When two triangular faces have two identical vertex coordinates, it means that the two triangular faces are adjacent to each other by one edge.

[0018] Record the triangular facets that are adjacent to each other on each triangular facet, and then establish the topological relationship of all triangular facets.

[0019] As a further improvement to the above scheme, the method for establishing topological relationships also includes the following process:

[0020] Each triangular facet on the surface to be optimized is assigned a number. Specifically, the topological relationships of all triangular facets are established by recording the numbers of the triangular facets that are adjacent to each other on an edge.

[0021] As a further improvement to the above solution, the method for improving the surface quality of the object before performing surface optimization printing on the workpiece to be optimized also includes the following steps:

[0022] The process involves obtaining the three-axis 3D printing path of the 3D model and printing the workpiece to be optimized based on this path. The method for obtaining the three-axis 3D printing path includes the following steps:

[0023] By intersecting the triangular facets in the 3D model with multiple parallel planes, the corresponding intersection line segments are obtained on each plane.

[0024] Intersecting line segments are arranged and connected on each plane to generate a triaxial 3D printing slice outline.

[0025] The corresponding 3D printing infill path is generated based on the slice outline, and then a three-axis 3D printing path is formed.

[0026] As a further improvement to the above scheme, the 3D printing infill path type can be any one of the following: contour parallel infill path, direction parallel infill path, and a hybrid infill path of contour parallel and direction parallel.

[0027] As a further improvement to the above scheme, in step S3, the harmonic mapping algorithm is used to project all the vertices of the triangular facets on the surface to be optimized onto the unit circle on the plane.

[0028] As a further improvement to the above scheme, in S1, the STL format 3D model is processed by the Materialise Magics software to extract the surface to be optimized.

[0029] As a further improvement to the above scheme, in S6, when sorting the intersection points after the inverse mapping, the sorting index of the sorting algorithm is as follows:

[0030]

[0031] In the formula, (x, y) represents the vector formed by the intersection points after the inverse mapping. θ is the included angle.

[0032] As a further improvement to the above scheme, in S8, the unit circle is offset inward at equal intervals to form concentric circles according to the required path spacing.

[0033] As a further improvement to the above scheme, in S4, finding the intersection of the unit circle and the line segment yields three results: 0 intersection points, 1 intersection point, and 2 intersection points.

[0034] Compared with the prior art, the technical solution disclosed in this invention has the following beneficial effects:

[0035] This invention obtains a 3D model of the printing target and extracts the vertex coordinates and normal vectors of each triangular facet on the surface of the 3D model. Then, it extracts the surface to be optimized from the 3D model, establishes the topological relationship of all triangular facets on the surface to be optimized, and sequentially plans an optimized printing path based on five-axis 3D printing for the printing target through steps such as projection, inverse projection, sorting, and connecting intersection points. Then, it can perform secondary optimization printing on the workpiece obtained by traditional three-axis 3D printing according to the planned five-axis path. Compared with traditional standalone three-axis 3D printing, this invention can make the curved surface of the original object remain curved and smooth after printing, effectively mitigating the impact of the stepped structure produced by traditional three-axis 3D printing on the accuracy and quality of the printed object. Attached Figure Description

[0036] Figure 1This is a flowchart of a five-axis path planning method for reducing the staircase effect in 3D printed parts in an embodiment of the present invention;

[0037] Figure 2 This is an external view of the alveolar tooth STL model in an embodiment of the present invention;

[0038] Figure 3 for Figure 2 Internal view of the STL model of the central molar;

[0039] Figure 4 This is a diagram showing the filling path of a three-axis 3D printed tooth model in an embodiment of the present invention.

[0040] Figure 5 This is an optimized external surface image extracted from the STL model of the alveolar tooth in this embodiment of the invention;

[0041] Figure 6 for Figure 5 Optimized surface internal image extracted from the STL model of the molar tooth;

[0042] Figure 7 This is the projection of all triangular facet vertices on the optimized surface of the alveolar STL model in this embodiment of the invention onto the plane unit circle.

[0043] Figure 8 This is the projection of all triangular facets on the optimized surface of the alveolar tooth STL model in this embodiment of the invention onto the unit circle in the plane.

[0044] Figure 9 This is a schematic diagram showing the intersection of line segments projected onto the unit circle of the plane on all triangular facets on the optimized surface extracted from the alveolar tooth STL model in this embodiment of the invention with concentric circles.

[0045] Figure 10 This is a schematic diagram of the intersection points of line segments projected onto the unit circle on the optimized surface of all triangular facets extracted from the STL model of the alveolar tooth in this embodiment of the invention and the concentric circles.

[0046] Figure 11 This is a schematic diagram showing the inverse mapping of the intersection points of the line segments in the projections of all triangular facets on the optimized surface of the alveolar tooth STL model extracted in this embodiment of the invention with the concentric circles back to the surface of the alveolar tooth model.

[0047] Figure 12 This is a five-axis 3D printing path diagram generated from the extracted outer surface of the molar tooth model in an embodiment of the present invention;

[0048] Figure 13 This is a path diagram of a tooth model printed using a hybrid 3D printing method based on three-axis and five-axis axes in an embodiment of the present invention. Detailed Implementation

[0049] 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.

[0050] It should be noted that when a component is said to be "installed on" another component, it can be directly on the other component or it may be in a component that is centered on it. When a component is said to be "set on" another component, it can be directly set on the other component or it may also be in a component that is centered on it. When a component is said to be "fixed to" another component, it can be directly fixed to the other component or it may also be in a component that is centered on it.

[0051] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the specification of this invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "or / and" as used herein includes any and all combinations of one or more of the associated listed items.

[0052] Please see Figure 1 This embodiment provides a five-axis path planning method to reduce the step effect in 3D printed parts, including the following steps: planning a five-axis 3D printing path for the printing target and using the five-axis path to perform surface optimization printing on a workpiece to be optimized formed by three-axis 3D printing, so that the path transitions smoothly perpendicular to the normal vector direction of the part surface, thereby alleviating the step effect on the part surface. Figure 2 and Figure 3 As shown, this embodiment takes the use of 3D printing technology to process and manufacture alveolar teeth as an example.

[0053] First, obtain the 3D model of the target object and extract the vertex coordinates and normal vectors of each triangular facet on the surface of the 3D model. The 3D model exists in an XYZ coordinate system, with the Z-axis perpendicular to the horizontal plane containing the XY axes.

[0054] In this embodiment, by constructing a spatial rectangular coordinate system, the 3D model of the object is placed in the spatial rectangular coordinate system, and the coordinates of all points on the outer wall of the 3D model of the object are obtained to obtain the boundary of the 3D model of the object in the spatial rectangular coordinate system. Based on the spatial rectangular coordinate system, the coordinates of each vertex of the triangle in each triangular facet and its normal vector are obtained.

[0055] Then you can first obtain the three-axis 3D printing path of the tooth model, such as Figure 4 As shown, Figure 4 This is the infill path diagram for a triaxial 3D printed tooth model. Specifically, the method for obtaining the triaxial 3D printing path includes the following process: using a series of parallel planes to intersect with the triangular facets in the model, a series of intersection line segments are obtained on each plane; the intersection line segments are sorted and connected on each plane to generate a triaxial 3D printing slice outline, and then the slice outline is saved in a data file named layer, which is the SLC file; the slice outline information in the SLC file is read, and the 3D printing infill path is generated using the slice outline. Common paths include contour parallel infill path, direction parallel infill path, and a mixed infill path of contour parallel and direction parallel. This embodiment uses the contour parallel infill path.

[0056] S1. Extract the surface to be optimized from the 3D model. This can be done using software like Materialise Magics, which can process STL data. Figure 5 and Figure 6 As shown, this is the surface that needs to be optimized for the molar tooth model.

[0057] In this embodiment, the entire surface of the tooth model needs to be optimized. In some embodiments, selective local optimization can also be performed for some conventional parts or workpieces.

[0058] S2. Establish the topological relationships of all triangular faces on the surface to be optimized. The methods for establishing the topological relationships may include the following procedures:

[0059] (1) Add numbers to each triangular facet on the surface to be optimized;

[0060] (2) Traverse the coordinates of each vertex of each triangular facet on the surface to be optimized, and analyze the positional relationship between each triangular facet and the other triangular facets. The analysis results should include at least the following two types: (a) and (b).

[0061] (a) If two triangular faces have the same vertex coordinates, it means that the two triangular faces have one corner that coincides.

[0062] (b) When two triangular faces have two identical vertex coordinates, it means that the two triangular faces are adjacent to each other by one edge.

[0063] Thus, by recording the triangular facets that are adjacent to each other on each triangular facet, the topological relationship of all triangular facets is established.

[0064] S3. Project all vertices of the triangular faces on the surface to be optimized onto the unit circle on the plane using the harmonic mapping method, and establish the mapping relationship, such as... Figure 7 The figure shown is a projection of the aforementioned vertex onto the unit circle.

[0065] S4. Connect each pair of projection points that have topological relationships onto the unit circle's domain to form line segments, and then find the intersection points between the unit circle and the line segments. For example... Figure 8 The diagram shows a line segment formed by pairwise projection points with topological relationships on the unit circle domain. There are three possibilities for the line segment to intersect the circle: 0 intersection points, 1 intersection point, and 2 intersection points.

[0066] S5. Inverse map the intersection points onto the surface to be optimized, traverse the coordinates of all inverse-mapped intersection points, retain the normal vectors of the intersection points, and then extract the X and Y coordinates of the inverse-mapped intersection points.

[0067] S6. Calculate the angle between the vector formed by the intersection points after the inverse mapping and the X-axis on the horizontal plane, and sort the intersection points after the inverse mapping according to the size of the angle. The sorting index of the sorting algorithm is as follows:

[0068]

[0069] In the formula, (x, y) represents the vector formed by the intersection points after the inverse mapping; θ is the included angle.

[0070] S7. Use straight lines to connect the intersection points of the sorted reverse mapping in sequence to form a closed polyline, which in turn constitutes a single printing path.

[0071] S8. Based on the required path spacing, offset the unit circle inwards with a series of concentric circles at equal intervals, and sequentially form the printing path corresponding to each concentric circle, referring to methods S3 to S6, thus forming a complete five-axis 3D printing path. Please refer to... Figure 9 and Figure 10 , Figure 9 The diagram shows the intersection of concentric circles within the unit circle and the aforementioned line segments. a1 is a schematic diagram of the unit circle, and a2 is a schematic diagram of a concentric circle offset from the unit circle. Figure 10 This is a schematic diagram showing the intersection points formed by the unit circle, the concentric circles within the circular domain, and the aforementioned line segments.

[0072] like Figures 11 to 12As shown, in this embodiment, after establishing the topological relationship of the triangular facets, the vertices of the triangular facets on the alveolar tooth surface are quickly traversed. All vertices are projected onto a unit circle on the plane using a spatial mapping method. Thus, the vertices on the boundary of the alveolar tooth surface are projected onto the unit circle, and the vertices inside the alveolar tooth surface are projected into the unit circle. Two vertices on the alveolar tooth surface with a topological relationship still retain this relationship after projection. Then, the line segments formed by the pairwise projections of the unit circle and the boundary vertices with a topological relationship onto the unit circle intersect. Finally, the intersection points are inversely mapped onto the alveolar tooth model. On the surface of the model, the coordinates of all intersection points after inverse mapping are traversed, the x and y coordinates are extracted, and then the angle between the vector composed of the x and y coordinates and the X-axis on the plane is calculated. The intersection points after inverse mapping are sorted according to the size of the angle, and then connected with straight lines in sequence to form a closed polyline, thus forming a five-axis 3D printing path. Then, a series of concentric circles are offset inward from the unit circle at equal intervals. Each circle in the concentric circle intersects with the line segments formed by the internal vertices with topological relationships mapped to the unit circle in the above process, thus forming the entire five-axis 3D printing path.

[0073] After obtaining the three-axis 3D printing path and planning the five-axis 3D printing path, the workpiece to be optimized can be printed first using the traditional three-axis 3D printing path. Then, the surface of the workpiece to be optimized can be printed using the five-axis 3D printing path to reduce the step effect of 3D printed parts.

[0074] In this embodiment, as Figure 13 As shown, the filling path diagram of the three-axis and five-axis hybrid 3D printed tooth model shows that, compared with traditional three-axis 3D printing, the method of this invention can make the curved surface of the original object remain curved and smooth after printing, effectively mitigating the impact of the stepped structure produced by traditional three-axis 3D printing on the accuracy and quality of the printed object.

[0075] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0076] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the appended claims.

Claims

1. A five-axis path planning method for reducing staircasing of 3D printed parts, characterized in that, The five-axis path is used for surface optimization printing of a workpiece to be optimized formed by three-axis 3D printing; the planning method comprises the following steps: acquire a three-dimensional model of a printing target, and extract vertex coordinates and normal vectors of each triangular facet on the surface of the three-dimensional model; wherein the three-dimensional model is in an X-Y-Z coordinate system, and the Z axis is perpendicular to the horizontal plane on which the X-Y is located; S1. extracting a surface to be optimized in the three-dimensional model; S2. establishing a topological relationship of all triangular facets on the surface to be optimized; S3. projecting all vertices of all triangular facets on the surface to be optimized on a unit circle domain on a plane, and establishing a mapping relationship; wherein two vertices having a topological relationship on the surface to be optimized maintain a topological relationship after being projected onto the unit circle domain; S4. connecting the projected points having a topological relationship on the unit circle domain into line segments two by two, and performing intersection between the unit circle and the line segments to form intersection points; S5. inversely mapping the intersection points to the surface to be optimized, traversing the coordinates of all inversely mapped intersection points, and extracting the X, Y axis coordinates and normal vectors of the inversely mapped intersection points; S6. calculating the included angle of the vector composed of the inversely mapped intersection points with the X axis on the horizontal plane, and sorting the inversely mapped intersection points according to the included angle size; S7. connecting the sorted inversely mapped intersection points in sequence by using straight lines to form a closed multi-segment line, and then forming a single printing path; S8. offsetting a series of concentric circles inward from the unit circle by an equal distance, and referring to the methods of S3-S7 to form a printing path corresponding to each concentric circle in sequence, and then forming a complete five-axis 3D printing path; wherein, before surface optimization printing of the workpiece to be optimized, a three-axis 3D printing path of the three-dimensional model is acquired, and the workpiece to be optimized is printed according to the three-axis 3D printing path; wherein the acquisition method of the three-axis 3D printing path comprises the following process: intersecting triangular facets in the three-dimensional model with a plurality of parallel planes to obtain corresponding intersection line segments on each plane; sorting and connecting the intersection line segments on each plane, and then generating a three-axis 3D printing slice contour; generating a corresponding 3D printing filling path according to the slice contour, and then forming the three-axis 3D printing path; The type of the 3D printing filling path adopts any one of a contour parallel filling path, a direction parallel filling path, and a contour parallel and direction parallel mixed filling path; In step S3, the vertices of all triangular facets on the surface to be optimized are projected onto a unit circle on a plane by using a harmonic mapping algorithm.

2. The five-axis path planning method for reducing staircasing of 3D printed parts of claim 1, wherein, The method for establishing the topological relationship of all triangular facets on the surface to be optimized comprises the following process: traverse the coordinates of each vertex of each triangular facet on the surface to be optimized, analyze the positional relationship between each triangular facet and the remaining triangular facets, and the analysis result is as follows: (a) when two triangular facets have a same vertex coordinate, it indicates that the two triangular facets have an angle coincidence; (b) When two triangular facets have two same vertex coordinates, it means that the two triangular facets are adjacent with one edge; The triangular facets adjacent with each triangular facet in edge position relationship are recorded, and the topological relationship of all the triangular facets is established.

3. The method of claim 2, wherein, The method for establishing the topological relationship further comprises the following process: Each triangular facet on the surface to be optimized is added with a number; wherein, the numbers of the triangular facets adjacent with each triangular facet in edge position relationship are recorded, and the topological relationship of all the triangular facets is established.

4. The method of claim 1, wherein, In S1, the three-dimensional model in STL format is processed by materialise magics software, and then the surface to be optimized is extracted.

5. The method of claim 1, wherein, In S6, when the intersection points after the inverse mapping are sorted, the sorting index of the sorting algorithm is as follows: θ = arctan y / x In the formula, (x, y) represents a vector composed of the intersection points after the inverse mapping; and θ is the included angle.

6. The method of claim 1, wherein, In S8, the unit circle is equally offset inward to form the concentric circles according to the required path interval.

7. The method of claim 1, wherein, In S4, the intersection of the unit circle and the line segment has three results: 0 intersection point, 1 intersection point and 2 intersection points.

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