CN116533524A

CN116533524A - Five-axis path planning method for reducing 3D printing part ladder effect

Info

Publication number: CN116533524A
Application number: CN202310513876.5A
Authority: CN
Inventors: 韩江; 张文强; 田晓青; 夏链
Original assignee: Hefei University of Technology
Current assignee: Hefei University of Technology
Priority date: 2023-05-09
Filing date: 2023-05-09
Publication date: 2023-08-04

Abstract

The invention relates to a five-axis path planning method for reducing the stair effect of a 3D printing part. And then extracting the surface to be optimized from the three-dimensional model, establishing the topological relation of all triangular patches on the surface to be optimized, and sequentially forming a complete five-axis 3D printing path through the steps of projection, back projection, sequencing, line intersection and the like. The five-axis 3D printing path planned by the invention can carry out surface optimization printing on a workpiece to be optimized formed by three-axis 3D printing, so that the curved surface of the original object is also kept smooth after printing, and the influence of the stepped structure generated by the traditional three-axis 3D printing on the precision and quality of the object after printing is effectively relieved.

Description

Five-axis path planning method for reducing 3D printing part ladder effect

Technical Field

The invention relates to the technical field of 3D printing, in particular to a five-axis path planning method for reducing the stair effect of 3D printing parts.

Background

The 3D printing technology can be utilized to process and manufacture required parts and the like, and 3D printing is additive manufacturing with layering accumulation in popular terms. However, in the printing process, the traditional triaxial 3D printing technology with planar layering and gradual accumulation is adopted, an edge-unsmooth stepped structure is generated between the surface layers of the part, which is called a stepped effect, which is an unavoidable problem of the 3D printing technology, and the deviation of the precision of the printed part is easy to cause, so that the use requirement is not met.

Disclosure of Invention

Based on the above, it is necessary to solve the technical problem that the printing precision deviation is easily caused by the step effect in the traditional three-axis 3D printing in the prior art, so that the surface quality of an object is reduced.

The invention discloses a five-axis path planning method for reducing the stair effect of a 3D printing part, which is used for carrying out surface optimization printing on a workpiece to be optimized formed by three-axis 3D printing, and comprises the following steps:

and acquiring a three-dimensional model of the printing target, and extracting the vertex coordinates and normal vectors of each triangular patch on the surface of the three-dimensional model. The three-dimensional model is in an X-Y-Z coordinate system, and the Z axis is perpendicular to the horizontal plane where the X-Y is located.

S1, extracting a surface to be optimized from a three-dimensional model.

S2, establishing topological relations of all triangular patches on the surface to be optimized.

S3, all vertexes of all triangular patches on the surface to be optimized are projected on a unit circle domain on a plane, and a mapping relation is established. Wherein, two vertexes with topological relation on the surface to be optimized maintain the topological relation on the unit circle field projected.

S4, connecting projection points which are projected on the unit circle domain and have topological relation into line segments in pairs, and intersecting the unit circle with the line segments to form intersection points.

S5, inversely mapping the intersection points to the surface to be optimized, traversing the coordinates of all the inversely mapped intersection points, and extracting X, Y axis coordinates and normal vectors of the inversely mapped intersection points.

S6, calculating the included angle between the vector formed by the inverse mapped intersection points and the X axis on the horizontal plane, and sequencing the inverse mapped intersection points according to the included angle.

S7, sequentially connecting the sequenced inverse mapping intersection points by utilizing straight lines to form a closed multi-section line, so that a single printing path is formed.

S8, a series of concentric circles are offset inwards at equal intervals from the unit circle, and printing paths corresponding to the concentric circles are formed in sequence according to the method of S3-S7, so that a complete five-axis 3D printing path is formed.

As a further improvement of the above solution, the method for establishing the topological relation of all triangular patches on the surface to be optimized comprises the following steps:

traversing coordinates of each vertex of each triangular patch on the surface to be optimized, and analyzing the position relationship between each triangular patch and the rest triangular patches, wherein the analysis result is as follows:

(a) When two triangular panels have the same vertex coordinates, it means that the two triangular panels have an angle coincident.

(b) When two triangular patches have two identical vertex coordinates, it means that the two triangular patches are adjacent with one side.

Recording triangular patches with side adjacent position relation with each triangular patch, and further establishing topological relation of all triangular patches.

As a further improvement of the above scheme, the method for establishing a topological relation further includes the following steps:

numbering is added to each triangular patch on the surface to be optimized. And the topological relation of all triangular patches is established by recording the numbers of the triangular patches with the edge adjacent position relation with each triangular patch.

As a further improvement of the above solution, the method for improving the surface quality of the object before the surface-optimized printing of the workpiece to be optimized further comprises the steps of:

and acquiring a three-axis 3D printing path of the three-dimensional model, and printing out the workpiece to be optimized according to the three-axis 3D printing path. The method for acquiring the three-axis 3D printing path comprises the following steps:

and intercepting triangular patches in the three-dimensional model by utilizing a plurality of parallel planes, so as to obtain corresponding intercepting line segments on each plane.

And sequencing and connecting the intersecting line segments on each plane to generate the three-axis 3D printing slice outline.

And generating a corresponding 3D printing filling path according to the slice profile, and further forming a three-axis 3D printing path.

As a further improvement of the above solution, the type of 3D printing filling path employs any one of a contour parallel filling path, a direction parallel filling path, and a contour parallel and direction parallel mixed filling path.

As a further improvement of the above solution, in step S3, vertices of all triangular patches on the surface to be optimized are all projected on a unit circle on a plane using a harmonic mapping algorithm.

As a further improvement of the above scheme, in S1, the three-dimensional model in STL format is processed by materialise magics software, and the surface to be optimized is extracted.

As a further improvement of the above scheme, in S6, when sorting the inverse mapped intersecting points, a sorting index of the sorting algorithm is as follows:

where (x, y) represents a vector composed of the intersection points after the inverse mapping. θ is the included angle.

As a further improvement of the above scheme, in S8, the unit circles are offset inward equidistantly to form concentric circles according to the required path pitch.

As a further improvement of the above scheme, in S4, there are three results of intersection of the unit circle with the line segment: 0 intersections, 1 intersection, and 2 intersections.

Compared with the prior art, the technical scheme disclosed by the invention has the following beneficial effects:

according to the invention, the three-dimensional model of the printing target is obtained, the vertex coordinates and the normal vector of each triangular patch on the surface of the three-dimensional model are extracted, then the surface to be optimized is extracted from the three-dimensional model, the topological relation of all triangular patches on the surface to be optimized is established, and the steps of projection, back projection, sequencing, intersection of connecting lines and the like are sequentially carried out, so that an optimized printing path based on five-axis 3D printing is planned for the printing target, and further, secondary optimized printing can be carried out on a workpiece obtained by traditional three-axis 3D printing according to the planned five-axis path.

Drawings

FIG. 1 is a flow chart of a five-axis path planning method for reducing the stair effect of 3D printed parts in an embodiment of the invention;

FIG. 2 is an external view of a model of a tooth STL according to an embodiment of the present invention;

FIG. 3 is an internal view of the model of the socket STL of FIG. 2;

FIG. 4 is a filling path diagram of a three-axis 3D printed dental model in an embodiment of the present invention;

FIG. 5 is an exterior view of an optimized surface extracted from a model of a tooth STL in an embodiment of the invention;

FIG. 6 is an interior view of the optimized surface extracted from the model of the tooth STL of FIG. 5;

FIG. 7 is a projection of all triangular patch vertices on a planar unit circle on an optimized surface extracted from a model of a tooth STL in an embodiment of the invention;

FIG. 8 is a projection of all triangular patches on a planar unit circle on an optimized surface extracted from a model of a tooth STL in an embodiment of the invention;

FIG. 9 is a schematic diagram showing the intersection of concentric circles with line segments in projection on a planar unit circle on all triangular patches on an optimized surface extracted by a model of a tooth STL in an embodiment of the present invention;

FIG. 10 is a schematic view of the intersection points of the concentric circles and the line segments in the projections on the planar unit circles on all triangular patches on the optimized surface extracted by the model of the tooth STL in the embodiment of the present invention;

FIG. 11 is a schematic diagram of the inverse mapping back of the intersection points of the concentric circles and the line segments in the projections on the planar unit circles on all triangular patches on the optimized surface extracted by the model of the tooth STL in the embodiment of the present invention;

FIG. 12 is a five-axis 3D print path graph generated for an extracted external surface of a dental model in an embodiment of the present invention;

fig. 13 is a path diagram of a 3D printed tooth model using a three-axis five-axis hybrid in an embodiment of the invention.

Detailed Description

The following description of the embodiments of the present invention will be made clearly and completely with reference to the accompanying drawings, in which it is apparent that the embodiments described are only some embodiments of the present invention, but not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.

It is noted that when an element is referred to as being "mounted to" another element, it can be directly on the other element or intervening elements may also be present. When an element is referred to as being "disposed on" another element, it can be directly on the other element or intervening elements may also be present. When an element is referred to as being "secured to" another element, it can be directly secured to the other element or intervening elements may also be present.

Unless defined otherwise, 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 belongs. The terminology used herein in the description of the 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.

Referring to fig. 1, the present embodiment provides a five-axis path planning method for reducing a step effect of a 3D printed part, which includes the following steps: and planning a five-axis 3D printing path of the printing target, and carrying out surface optimization printing on a workpiece to be optimized formed by three-axis 3D printing by utilizing the five-axis path, so that the normal vector direction of the surface of the part in the path is smoothly transited to relieve the step effect of the surface of the part. As shown in fig. 2 and 3, the present embodiment takes the example of manufacturing the slot teeth by using the 3D printing technique.

Firstly, a three-dimensional model of a printing target is obtained, and the vertex coordinates and normal vectors of each triangular patch on the surface of the three-dimensional model are extracted. The three-dimensional model is in an X-Y-Z coordinate system, and the Z axis is perpendicular to the horizontal plane where the X-Y is located.

In this embodiment, a space rectangular coordinate system is constructed, a 3D model of an object is placed in the space rectangular coordinate system, coordinates of all points on an outer wall of the 3D model of the object are obtained, so as to obtain boundaries of the 3D model of the object in the space rectangular coordinate system, and coordinates and normal vectors of vertices of triangles in each triangular patch are obtained according to the space rectangular coordinate system.

A three-axis 3D print path of the tooth model may then be acquired first, as shown in fig. 4, fig. 4 being a filling path diagram of the three-axis 3D print tooth model. Specifically, the method for acquiring the three-axis 3D printing path comprises the following steps: a series of parallel planes are used for intersecting with triangular patches in the model, and a series of intersecting line segments are obtained on each plane; sequencing and connecting the cut line segments on each plane to generate a triaxial 3D printing slice contour, and then storing the slice contour in a data file named layer, namely an SLC file; slice contour information in the SLC file is read, a 3D printing filling path is generated by utilizing the slice contour, a common path comprises a contour parallel filling path, a direction parallel filling path and a contour parallel and direction parallel mixed filling path, and the contour parallel filling path is adopted in the embodiment.

S1, extracting a surface to be optimized from a three-dimensional model, wherein software materialise magics capable of processing STL data can be used for extracting the surface to be optimized, and the surface to be optimized is the surface required to be optimized of the tooth model as shown in fig. 5 and 6.

In this embodiment, the overall surface of the tooth model needs to be optimized, and in some embodiments, selective local optimization may also be performed for some conventional parts or workpieces.

S2, establishing topological relations of all triangular patches on the surface to be optimized, wherein the method for establishing the topological relations comprises the following steps:

(1) Adding a number to each triangular patch on the surface to be optimized;

(2) And traversing the coordinates of each vertex of each triangular surface patch on the surface to be optimized, analyzing the position relation between each triangular surface patch and the rest triangular surface patches, wherein the analysis result at least comprises the following two types (a) and (b).

So far, by recording triangular patches with edge adjacent position relation with each triangular patch, the topological relation of all triangular patches is established.

S3, all the vertexes of all triangular patches on the surface to be optimized are projected on a unit circle on a plane by using a harmonic mapping method, and a mapping relation is established, as shown in FIG. 7, the projection diagram of the vertexes on the unit circle is shown.

S4, connecting projection points which are projected on the unit circle domain and have topological relation into line segments in pairs, and intersecting the unit circle with the line segments to form intersection points. Fig. 8 is a schematic diagram of line segments formed by two pairs of projection points with topological relation on a unit circle domain. Three possibilities exist for intersecting the line segment with the circle: 0 intersection points, 1 intersection point and 2 intersection points.

S5, inversely mapping the intersection points to the surface to be optimized, traversing the coordinates of the intersection points after all inverse mapping, reserving normal vectors of the intersection points, and extracting X, Y axis coordinates of the intersection points after inverse mapping.

S6, calculating an included angle between a vector formed by the inverted mapped intersection points and an X axis on a horizontal plane, and sequencing the inverted mapped intersection points according to the included angle, wherein sequencing indexes of a sequencing algorithm are as follows:

wherein, (x, y) represents a vector composed of intersection points after inverse mapping; and theta is the included angle.

S8, a series of concentric circles are offset inwards at equal intervals according to the required path distance, printing paths corresponding to the concentric circles are formed in sequence according to the method of S3-S6, and then a complete five-axis 3D printing path is formed. Referring to fig. 9 and 10, fig. 9 is a schematic diagram of an intersection between concentric circles in a unit circle domain and the line segment, a1 is a schematic diagram of a unit circle, a2 is a schematic diagram of an offset concentric circle of the unit circle, and fig. 10 is a schematic diagram of an intersection between concentric circles in a unit circle domain and the line segment.

11-12, in this embodiment, after establishing the topological relation of triangular patches, the vertices of triangular patches on the tooth surface are quickly traversed, the vertices are all projected on a unit circle on a plane by using a space mapping method, then the vertices on the upper boundary of the tooth surface are projected on the unit circle, the internal vertices on the tooth surface are projected in the unit circle, two vertices with the topological relation on the tooth surface are projected, then the projected vertices are thrown to have the topological relation, then the unit circle is intersected with line segments formed by every two boundary vertices with the topological relation projected on the unit circle, then the intersection points are reversely mapped on the tooth model surface, the coordinates of the intersection points after all reverse mapping are traversed, the X-axis coordinates and the y-axis coordinates are extracted, then the vector formed by the X-axis coordinates and the X-axis clamping angles are calculated, the intersection points after reverse mapping are ordered according to the included angle, and then the intersection points are sequentially linked by straight lines, so as to form a five-axis 3D printing path; and then a series of concentric circles are offset inwards from the unit circle at equal intervals, and each circle in the concentric circles is intersected with line segments formed by every two internal vertexes with topological relation in the unit circle according to the flow, so that all five-axis 3D printing paths are formed.

After the three-axis 3D printing path is obtained and the five-axis 3D printing path is planned, the traditional three-axis 3D printing path can be used for printing the to-be-optimized tooth workpiece, then the five-axis 3D printing path is used for carrying out surface optimization printing on the to-be-optimized tooth workpiece, and the step effect of the 3D printing part is reduced.

In this embodiment, as shown in fig. 13, compared with the filling path diagram of the three-axis five-axis mixed 3D printing tooth model, the method of the present invention can make the curved surface of the original object remain curved smoothly after printing, and effectively alleviate the influence of the stepped structure generated by the traditional three-axis 3D printing on the precision and quality of the printed object.

The technical features of the above-described embodiments may be arbitrarily combined, and all possible combinations of the technical features in the above-described embodiments are not described for brevity of description, however, as long as there is no contradiction between the combinations of the technical features, they should be considered as the scope of the description.

The above examples merely represent a few embodiments of the present invention, which are described in more detail and are not to be construed as limiting the scope of the invention. It should be noted that it will be apparent to those skilled in the art that several variations and modifications can be made without departing from the spirit of the invention, which are all within the scope of the invention. Accordingly, the scope of the invention should be assessed as that of the appended claims.

Claims

1. A five-axis path planning method for reducing the stair effect of a 3D printing part is characterized in that the five-axis path is used for carrying out surface optimization printing on a workpiece to be optimized formed through three-axis 3D printing; the planning method comprises the following steps:

acquiring a three-dimensional model of a printing target, and extracting the vertex coordinates and normal vectors of each triangular patch 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 vertical to the horizontal plane where X-Y is located;

s1, extracting a surface to be optimized from the three-dimensional model;

s2, establishing topological relations of all triangular patches on the surface to be optimized;

s3, all vertexes of all triangular patches on the surface to be optimized are projected on a unit circle domain on a plane, and a mapping relation is established; wherein, two vertexes with topological relation on the surface to be optimized keep the topological relation on the unit circle field projected to the unit circle field;

s4, connecting projection points projected on the unit circle domain and having topological relation into line segments in pairs, and intersecting the unit circle with the line segments to form intersection points;

s5, inversely mapping the intersection points to the surface to be optimized, traversing the coordinates of all the inversely mapped intersection points, and extracting X, Y axis coordinates and normal vectors of the inversely mapped intersection points;

s6, calculating an included angle between a vector formed by the inverse mapped intersection points and an X axis on the horizontal plane, and sequencing the inverse mapped intersection points according to the included angle;

s7, sequentially connecting the sequenced inverse mapping intersection points by utilizing a straight line to form a closed multi-section line, so as to form a single printing path;

s8, biasing the unit circles inwards at equal intervals to form a series of concentric circles, and sequentially forming printing paths corresponding to each concentric circle by referring to the method of S3-S7, so that the complete five-axis 3D printing path is formed.

2. The five-axis path planning method for reducing the stair effect of 3D printed parts according to claim 1, wherein the method for establishing the topological relation of all triangular patches on the surface to be optimized comprises the following steps:

traversing the coordinates of each vertex of each triangular patch on the surface to be optimized, and analyzing the position relationship between each triangular patch and the rest triangular patches, wherein the analysis result is as follows:

(a) When two triangular patches have the same vertex coordinates, the two triangular patches are shown to have an angle coincidence;

(b) When two triangular patches have two identical vertex coordinates, the two triangular patches are adjacent by one side;

3. The five-axis path planning method for reducing the stair effect of 3D printed parts according to claim 2, wherein the method for establishing the topological relation further comprises the following steps:

adding a number to each triangular patch on the surface to be optimized; and the topological relation of all triangular patches is established by recording the numbers of the triangular patches with the edge adjacent position relation with each triangular patch.

4. The five-axis path planning method for reducing the stair effect of the 3D printed part according to claim 1, wherein before the surface optimization printing is performed on the workpiece to be optimized, the workpiece to be optimized is printed out according to the three-axis 3D printing path by acquiring the three-axis 3D printing path of the three-dimensional model; the method for acquiring the three-axis 3D printing path comprises the following steps:

utilizing a plurality of parallel planes to intercept triangular patches in the three-dimensional model, thereby obtaining corresponding intercepting line segments on each plane;

sequencing and connecting the intersecting line segments on each plane to generate a triaxial 3D printing slice contour;

and generating a corresponding 3D printing filling path according to the slice profile, and further forming the three-axis 3D printing path.

5. The five-axis path planning method for reducing the stair-step effect of 3D printed parts according to claim 4, wherein the type of 3D printed 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.

6. The five-axis path planning method for reducing the stair-step effect of 3D printed parts according to claim 1, wherein in step S3, vertices of all triangular patches on the surface to be optimized are all projected on a unit circle on a plane using a harmonic mapping algorithm.

7. The five-axis path planning method for reducing the stair effect of 3D printed parts according to claim 1, wherein in S1, the three-dimensional model in STL format is processed by materialise magics software to extract the surface to be optimized.

8. The five-axis path planning method for reducing the stair effect of 3D printed parts according to claim 1, wherein in S6, when sorting the inverse mapped intersection points, a sorting index of a sorting algorithm is as follows:

wherein, (x, y) represents a vector formed by the intersection points after the inverse mapping; and theta is the included angle.

9. The five-axis path planning method for reducing the stair effect of 3D printed parts according to claim 1, wherein in S8, the unit circles are equally offset inward according to the required path pitch to form the concentric circles.

10. The five-axis path planning method for reducing the stair effect of 3D printed parts according to claim 1, wherein in S4, there are three results of intersecting the unit circle with the line segment: 0 intersections, 1 intersection, and 2 intersections.