CN111145363A

CN111145363A - Rapid slicing method for 3DP additive manufacturing

Info

Publication number: CN111145363A
Application number: CN201911113105.7A
Authority: CN
Inventors: 徐杰
Original assignee: Beijing Hengchuang Additive Manufacturing Technology Research Institute Co ltd
Current assignee: Beijing Hengchuang Additive Manufacturing Technology Research Institute Co ltd
Priority date: 2019-11-14
Filing date: 2019-11-14
Publication date: 2020-05-12
Anticipated expiration: 2039-11-14
Also published as: CN111145363B

Abstract

A rapid 3DP slicing algorithm belongs to the technical field of additive manufacturing and 3D printing. The method specifically comprises the following steps: 1. screening out triangles crossing the cutting layer; 2. calculating a rectangular thick envelope of each triangle; 3. boundary pixels with thickness of thick are calculated. Compared with the existing popular slicing technology, the 3DP slicing method can distinguish the boundary part and the internal filling part of the three-dimensional model, and maintain the thickness consistency in the boundary part. This facilitates a color-slicing process, or a boundary-fine-printing process. The algorithm rapidly completes slicing, the calculation complexity and the number of the model triangular faces are in a linear relation and are only O (n x D), wherein n is the total number of the model triangular faces, and D is the slicing lattice resolution.

Description

Rapid slicing method for 3DP additive manufacturing

Technical Field

The invention belongs to the technical field of additive manufacturing and 3D printing, and particularly relates to a rapid slicing method for 3DP additive manufacturing.

Background

In 3D printing, the slice of the 3DP printing process (stereo inkjet printing) is a pixel lattice and the resolution is typically tunable.

In the current 3DP slicing technique, the boundary part and the inner filling part are not generally distinguished. However, the printing process of the boundary portion of the cut layer and the inside filling portion is sometimes different. For example, the boundary portion needs to be ejected more finely, while the inner filling portion can be ejected more coarsely to increase the printing speed; for another example, in color 3D printing, the boundary portion needs to eject color ink droplets, while the inner filling portion ejects white or colorless ink droplets.

Therefore, in the slicing algorithm, a boundary portion needs to be distinguished for specific processing, each layer of the slice is a lattice, and the boundary portion is also represented by the lattice, which has a certain thickness and is represented by discrete pixels. The difficulty of the problem is that the thickness of the boundary should be consistent in the direction perpendicular to the normal of the surface of the three-dimensional model, which increases the computational complexity, while the data volume of the three-dimensional model is often large, the number of triangular panels is generally hundreds of megabytes, and the processing speed is required to be fast. Therefore, there is an urgent need to provide a slicing method capable of distinguishing the boundary portion of the three-dimensional model from the internally filled portion and maintaining the thickness uniformity in the boundary portion to solve the above-mentioned problems.

Disclosure of Invention

The invention provides a rapid 3DP slicing algorithm, the normal thickness consistency is kept at the boundary part, the calculation complexity and the number of model triangular surfaces are in a linear relation of O (n x D), wherein n is the total number of the model triangular surfaces, and D is the slicing lattice resolution.

A fast 3DP slicing algorithm comprises the following specific steps:

step 1, screening out a triangle crossing a tangent layer:

let the model boundary need to be thick for thick, at each slice height (level millimeter), check whether each triangle in the three-dimensional model spans the level ± thick range of height. That is, assuming that the three vertices of the triangle are p1, p2 and p3, if the height coordinates of p1, p2 and p3 are simultaneously greater than level + thick or simultaneously less than level-thick, the triangle does not cross the level ± thick level height. Otherwise, if the triangle is crossed, the triangle is added into a slice operation set R ═ triangle to be calculated }.

Step 2, calculating the rectangular thick envelope of each triangle:

and performing XY plane projection on each triangle in the set R, and calculating the XY plane range of the projection triangle. I.e. let three vertices of a triangle be p₁、p₂、p₃They have a maximum value X in their X coordinate_maxMinimum value of X in X coordinate_minMaximum value of Y coordinate is Y_maxMinimum value of Y in Y coordinate_minThen the projection range of the triangle XY plane is [ X ]_min,X_max；Y_min,Y_max]. The required rectangular thick envelope of the triangle is then [ X_min-thick,X_max+thick；Y_min-thick,Y_max+thick]Rectangular.

Step 3, calculating boundary pixel with normal thickness of thick

The method comprises the steps of carrying out scanning line pixel filling on a three-dimensional model slice contour line obtained at a level (millimeter) height to obtain an entity part pixel point set V, calculating scanning line pixel point filling enveloped by a rectangle thick for each space triangle a of a set R, obtaining a pixel point set S, calculating a vertical q from a point p to a plane where the space triangle a is located, and if one of the following conditions is met, the pixel point is a boundary pixel point with a normal thickness of thick, wherein the pixel point belongs to a pixel point p belonging to the set V (inside an entity) and a pixel point p belonging to a set S (near the triangle a) and belongs to { V ∩ S }, the space coordinate is set as p ═ x, y, z ]:

1) the point q is in the triangle a, and the point-surface distance d from the point p to the point a is less than thick;

2) the point q is outside the triangle a, but inside the thick rectangle of a certain side of the triangle a, and the distance from the point p to the side is less than thick;

3) point q is outside triangle a, and q is outside the thick width rectangle of three sides of a, but p is the distance to some vertex. Less than thick.

The invention has the beneficial effects that:

compared with the existing popular slicing technology, the 3DP slicing method can distinguish the boundary part and the internal filling part of the three-dimensional model, and the normal thickness consistency is kept at the boundary part. This facilitates a color-slicing process, or a boundary-fine-printing process. The algorithm rapidly completes slicing, the calculation complexity and the number of the model triangular faces are in a linear relation and are only O (n x D), wherein n is the total number of the model triangular faces, and D is the slicing lattice resolution.

Drawings

FIG. 1: a closed model entity with blue as boundary part and transverse line as tangent plane

FIG. 2: selecting a triangle intersected with the level + -thick horizontal section, wherein the black bold line part is a triangle (silhouette) set R across the level + -thick to be calculated

FIG. 3: the space triangle has a thick rectangular envelope projected on the tangent plane, wherein the dotted rectangle is the thick envelope of the triangle.

FIG. 4: carrying out pixel line scanning on the model outline on the tangent plane to obtain an entity lattice

FIG. 5: the pixel point p to the foot q of the model triangle a is in the triangle area.

FIG. 6: the drop foot q is outside the triangular area but within the side click rectangle.

FIG. 7: the drop foot q is outside the triangle area and outside the side thick rectangle area, but within the vertex thick distance.

FIG. 8: an instance of a boundary pixel point near the spatial triangle is computed.

Detailed Description

The technical solution proposed by the present invention is further described below with reference to the accompanying drawings.

A fast 3DP slicing algorithm comprises the following specific steps:

step 1, screening out a triangle crossing a tangent layer:

as shown in FIG. 2, assuming that the model boundary needs to have a thickness of thick mm, at each slice height (level mm), it is checked whether each triangle in the three-dimensional model spans the level + -thick (mm) height range. That is, assuming that the three vertices of the triangle are p1, p2 and p3, if the height coordinates of p1, p2 and p3 are simultaneously greater than level + thick or simultaneously less than level-thick, the triangle does not cross the level ± thick level height. Otherwise, if the triangle is crossed, the triangle is added into a slice operation set R ═ triangle to be calculated }. The thick black line in fig. 2 is the triangle silhouette set R to be calculated.

Step 2, calculating rectangular thick envelope of each triangle

And performing XY plane projection on each triangle in the set R, and calculating the XY plane range of the projection triangle. Namely, the three vertexes of the triangle are p1, p2 and p3, the maximum value of the triangle in the X coordinate is Xmax, the minimum value of the triangle in the X coordinate is Xmin, the maximum value of the triangle in the Y coordinate is Ymax, and the minimum value of the triangle in the Y coordinate is Ymin, so that the XY plane projection range of the triangle is [ Xmin, Xmax; ymin, Ymax ]. The required rectangular thick envelope of the triangle is [ Xmin-thick, Xmax + thick; ymin-thick, Ymax + thick rectangle. FIG. 3 is a schematic diagram of a thick rectangular envelope for calculating the projection of the space triangle on the tangential plane.

Step 3, calculating boundary pixel with thickness of thick

As shown in fig. 4, scanning line pixel filling is performed on a three-dimensional model slice contour line obtained at a level (millimeter) height to obtain a solid part pixel set V, scanning line pixel filling of rectangular thick envelope is calculated for each space triangle a of a set R to obtain a pixel set S, for each pixel p belonging to both the set V (inside the solid) and the set S (near the triangle a), a space coordinate is set as p ═ x, y, z, and a vertical q from the point p to a plane where the space triangle a is located is calculated, and if one of the following conditions is satisfied, the pixel is a boundary pixel with a normal thickness of thick brick:

1) as shown in fig. 5, the point q is within the triangle a, and the point-surface distance d from p to a is less than thick;

2) as shown in FIG. 6, point q is outside triangle a, but within the thick rectangle of one side of triangle a, and the distance from p to the point side of that side is less than thick;

3) as shown in FIG. 7, point q is outside triangle a, and q is outside the thick rectangle of a, but the distance of p to a vertex is less than thick.

As shown in fig. 8, the hatched area is the boundary of the thickness of the thick thread of the three-dimensional model (here, the boundary is the thickness increased from the shell to the inside), the equally spaced horizontal lines are the slice height, the bold line represents the side view of a triangle, and the light bold line represents the side view of the rectangular envelope of the thick thread with the increased width of the thick thread after the triangle is projected to the horizontal XY plane. the pixels on the rectangular envelope of the thick are all possible boundary pixels.

Claims

1. A fast 3DP slicing algorithm, comprising the steps of:

step 1, screening out a triangle crossing a tangent layer:

setting the required thickness of the model boundary as thick millimeter, and checking whether each triangle in the three-dimensional model spans the height range of level +/-thick (millimeter) at each slice height (level millimeter); the three vertexes of the triangle are p1, p2 and p3, and if the height coordinates of p1, p2 and p3 are simultaneously greater than level + thick or simultaneously less than level-thick, the triangle does not cross the level +/-thick level height; if not, adding the triangle into a slice operation set R ═ triangle to be calculated };

step 2, calculating the rectangular thick envelope of each triangle:

carrying out XY plane projection on each triangle in the set R, and calculating the XY plane range of the projection triangle; namely, the three vertexes of the triangle are p1, p2 and p3, the maximum value of the triangle in the X coordinate is Xmax, the minimum value of the triangle in the X coordinate is Xmin, the maximum value of the triangle in the Y coordinate is Ymax, and the minimum value of the triangle in the Y coordinate is Ymin, so that the XY plane projection range of the triangle is [ Xmin, Xmax; ymin, Ymax ]; the required rectangular thick envelope of the triangle is [ Xmin-thick, Xmax + thick; ymin-thick, Ymax + thick rectangle;

and 3, calculating boundary pixels with normal thickness of thick:

the method comprises the steps of performing scanning line pixel filling on a three-dimensional model slice contour line obtained at a level (millimeter) height to obtain an entity part pixel point set V, calculating scanning line pixel point filling enveloped by a rectangle thick of each space triangle a of a set R to obtain a pixel point set S, calculating a vertical q from a point p to a plane of the space triangle a to obtain a boundary pixel point with a normal thickness of thick for each pixel point p belonging to the set V (inside an entity) and the set S (near the triangle a) belonging to { V ∩ S }, setting a space coordinate as p ═ x, y, z, and if one of the following conditions is met:

3) point q is outside triangle a and q is outside the thick rectangle of three sides of a, but the distance of p to a certain vertex is less than thick.