JPH07276506A - Data processing method and photo-shaping device - Google Patents

Abstract

PURPOSE:To improve the dimensional accuracy of a photo-shaped matter by a method wherein a polygonal patch locating at the base of a shaped matter is judged by the positive or negative Z-component of a normal vector after the apices are rearranged and rewritten in nodes and finally correction is performed to the Z-distance of the node of a negative patch. CONSTITUTION:By specifying a surface shape data file, the apex coordinates of a patch and normal vectors are read and the total number of patches are counted. Next, node numbers are given to apex coordinates so as to memorize which nodes compose respective patches. Further, in order to detect overhanging, positive or negative Z-distance of normal vector is checked so as to be up a flag to a node constituting a negative patch. The above-mentioned procedure is repeated on all the patches. Next, all the nodes are checked so as to set the amounts of correction to the nodes, in which the flag is up, in order to add the amount of correction to the Z-distance of the node and to be rearranged as the new values of the coordinates, apex coordinates consisting of patches are rewritten. In this case, the normal vector of the patch is calculated with the corrected Z-distance.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a stereolithography method and apparatus for curing a UV-curable resin by laser irradiation to create a three-dimensional model, and particularly by correcting a dimension deviation due to excessive curing due to laser transmitted light. The present invention relates to a data processing method and apparatus for providing a stereolithography object with excellent accuracy.

[0002]

2. Description of the Related Art Conventionally, as a stereolithography method and apparatus, there has been known a method of converting three-dimensional shape model data into contour line data and sequentially laminating the contour model data according to the sectional shape of each contour line to create a three-dimensional model.

Regarding measures for improving accuracy, Japanese Patent Publication No. 5-339.
No. 00 and Japanese Patent Publication No. 5-33901.

Also, at the RP & M / SLA Special Seminar: Japan 3D System Sponsor: '92 .10.29-30,
It is described that the curing depth in the case where the resin layer is scanned once by laser irradiation and the curing depth when the laser intersects is such that the curing depth of the intersecting portion is deeper.

[0005]

In the stereolithography technique, there is a problem that the bottom surface of the horizontal plate or the bottom surface of the overhang portion is excessively hardened due to the accumulation of leakage light of the laser which has passed through the hardened material at the time of stacking. This problem appears as dimensional deviation and is an essential problem of stereolithography.

The above-mentioned prior art does not consider the correction of the excess cured thickness by the laser transmitted light on the bottom surface of the overhang portion. Therefore, in the lower part of the portion, the uncured resin is hardened by the laser transmitted light and becomes the designed thickness or more,
There was a problem of reducing the dimensional accuracy.

Further, in order to make the dimensions of the modeled object equal to the design value, a secondary machining step such as shaving is required, but in some cases it is impossible to shave in a narrow gap, and it is necessary to correct the dimensional deviation. It was

A three-dimensional CA is used as a method for correcting the dimensional deviation.
There is a method to modify the design dimension in D, but C
There is a problem that the dimension correction by AD is not easy and takes time.

An object of the present invention is to solve the above problems and provide a method for automatically detecting the bottom surfaces of a modeled object and an overhang portion and automatically correcting the dimensional deviation which is an essential feature of the optical modeling technique. Especially.

[0010]

In order to achieve the above object, the direction of the normal vector of the patch surface of the polygon patch forming the surface shape data is checked to determine whether it is an overhang or not. Arrange the vertices that make up the patch by replacing them with nodes, identify whether that node is the node that makes up the polygon patch located at the bottom of the overhang, and then configure the polygon patch located at the bottom of the overhang. If the node is a node that does, the shape and position of the polygon patch are changed by moving the node according to the inclination of the patch surface by a movement amount determined by a predetermined rule. At this time, in the node shared by multiple patches, by checking the direction of the normal vector of the patch surface that moves at the maximum value from the movement amount determined by the inclination of the patch surface, the direction I know what I'm doing. If the Z-axis component of the normal vector is negative, the patch surface is Z
Facing downwards to the axis. That is, if the Z-axis direction is taken in the vertical direction, it can be identified that the patch is located at the bottom of the overhang. If the vertices forming the patch are simply moved and corrected by determining the orientation of the patch, the vertices shared by a plurality of patches may have different amounts of movement, resulting in a disordered shape. Therefore, the vertices of the polygon patch are arranged as nodes, and whether the node is located on the bottom surface of the overhang is identified by checking the direction of the patch by the above-described method, and the node is moved. After that, by returning to the patch vertex coordinates again, the shape can be corrected without disturbance. The above-mentioned dimensional deviation is automatically corrected in the surface shape data by the method as described above, and modeling is performed based on the data.

[0011]

In the present invention, it becomes possible to automatically correct the dimensional deviation which is an essential feature of the stereolithography technique on the surface shape data, and by performing the shaping based on the corrected surface shape data, the stereolithography object is produced. Dimensional accuracy is improved. Further, since the above-mentioned correction processing can be automatically performed, the efficiency of dimensional deviation correction is improved. Further, a secondary processing step such as shaving is omitted.

[0012]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows a first embodiment of the present invention, in which the dimensional deviation due to the excessive hardening of the bottom surface of the overhang portion or the bottom surface of the shaped article is one of the inclinations of the patches on the bottom surface of the adjacent overhang portion. FIG. 9 is a PAD diagram when the surface shape data is corrected with a value determined by a predetermined rule according to the largest inclination with respect to the modeling direction axis.

First, a surface shape data file for performing correction processing is designated. The surface shape data represents the surface of the three-dimensional shape model by a set of polygonal patches having at least three vertices, and this embodiment shows a triangular patch. The format of the surface shape data file is shown in FIG. Configure normal vector and patch 3
The three-dimensional coordinates of the vertices are described, and the data of each patch are distinguished by a delimiter mark. Next, the coordinates and normal vectors of the three vertices of the patches in the surface shape data file are sequentially read, and the total number of patches is counted. next,
A node number is added to the vertex coordinates that have been read, and the same node number is given to the one that matches the vertex coordinates of the patch that was previously read. Further, it stores which node each patch is composed of. Next, in order to detect the overhang portion, the positive / negative of the Z component of the normal vector is checked. When the patch is located on the bottom surface of the overhang portion or the bottom surface of the modeled object, that is, when the patch surface faces downward, the Z component is negative, so that automatic detection is possible. A flag indicating that the patch is located on the bottom surface of the overhang portion is set on the nodes constituting the patch. Repeat this for all patches. The above operation is the same as the entire processing even if it is performed at any time while reading the patch data.

Next, the flags of all the nodes are checked, and the surplus hardening thickness α is set as a correction amount for the node having the flag. The surplus cured thickness α will be described later. The correction amount at this time is a value determined by a predetermined rule according to the angle of each patch surface. A value determined by a predetermined rule according to the inclination of the patch is initialized to 0 for all nodes constituting the patch. A value according to the inclination of the patch is set in the node. Further, for a node shared by each patch, a re-larger value among the values according to the inclination of each patch surface is set in the node. A correction amount determined by a predetermined rule is added to the Z coordinate of the node, and the corrected Z coordinate value is replaced as a new coordinate value of each node. Rewrite the vertex coordinates that make up the patch with the new coordinates of the replaced node. Here, since the surface inclination of the patch is changed, the normal vector of the patch is calculated using the corrected Z coordinate.
Create a new surface shape data file in the same format as the read data format from the corrected vertex coordinates and normal vector.

Regarding the setting of the correction amount, the overall processing is the same regardless of which stage is performed before the Z correction.

First, the reason why node numbers are assigned to the vertices of the patch and the Z coordinate correction is processed by the nodes will be described. FIG. 3 is a diagram of the triangular patch of the surface shape data. FIG. 3A shows two adjacent patches A,
The patch A is located on the bottom surface of the overhang portion, and the patch B is not the overhang portion. The vertices of each patch are a1, a2, a3, b
1, b2, b3. Here, when changing the shape of the patch A on the bottom surface of the overhang portion, the vertices a1, a
When the coordinate values of 2 and a3 are moved, although the shape of the triangular patch A is changed, the triangular patch A is separated from the patch B, and the relationship between the patch A and the patch B is not maintained, resulting in incorrect data. Ordinary surface shape data patch is at least 3
Although composed of vertices, there is no realization that adjacent patches share these vertices. In FIG. 3B, the vertices shared by the triangular patches A and B are replaced with nodes n1 and n3, and the nodes n1, n2, and n3 are moved to change the shape of the patch A. As a result, the shape of the patch B is also changed at the same time, the patches A and B are not separated, and the relationship between both patches is maintained and correct data is obtained. In this way, in the triangular patch representing the surface of the model, by replacing the vertices shared by adjacent patches with nodes and moving the nodes, the positions of both patches can be changed without leaving or intersecting each other. . Here, an inclined overhang bottom surface is shown as an example, but the same applies to a horizontal case.

Next, the reason why the value given to the node is set to a value having the largest inclination of the patch sharing the node will be described. Assuming that the values according to the patch inclination by the patch A, C, and D processing are β, β, γ and β <γ, FIG.
As shown in (b), the order of patch processing is patch C, D,
If A, the value according to the patch slope to the node n2 is β,
γ, β, and β, γ at node n5, n2, n
The Z coordinate of 5 is different and the patch tilts, which is a problem. Figure 3
(C) is an example when the value according to the inclination with respect to the shared nodes n2 and n5 is set to the maximum value. Even if the order of patch processing is different from A, C, D or C, D, A, the values according to the patch inclination given to the nodes n2, n5 on the same height are both γ, and the corrected node n2, n5 z
Coordinates are at the same height, and shape distortion can be avoided.

By the processing method as described above, the bottom surface of the modeled object and the bottom surface of the overhang portion can be automatically detected, and the dimensional deviation can be efficiently corrected on the surface shape data, and the modeling is performed based on this data. Thus, a stereolithography product with high dimensional accuracy can be obtained.

In this embodiment, the triangular patch is shown, but the same effect can be obtained with a polygon patch.

The surplus cured thickness will be described below.
FIG. 4A shows the principle of surplus curing by stereolithography. Excessive curing is caused by the leakage light of the laser which has passed through the bottom surface of the overhang portion of the molded article and cures the uncured resin on the bottom surface of the overhang portion. Next, how to obtain the surplus cured thickness α is shown in FIG.
An explanation will be given using (b).

The stacking pitch is P, the depth from the upper surface of the first cured layer is D, and the number of stacks is N. The light absorption coefficient of the resin is k. The transmitted light energy En (D, D
N) is En (D, N) = EXP (−k (D + (N−1) P) / λ).

Here, since the transmitted light is irradiated many times in the lower part of the first layer due to the stacking, the accumulated energy is E
If total (D, N) is given, Etotal (D, N) = EXP (−kD / λ) + EXP (−k (D + P) / λ) + ... + EXP (−k (D + (n−1) P) / λ) If A = EXP (−kD / λ) B = EXP (−kP / λ), then Etotal (D, N) = A (1 + B + B ^ 2 + ... + B ^ (n-1)) on both sides Taking the logarithm, ln (Etotal (D, N)) =-kD / λ + ln (C) where c = (1-B ^ n) / (1-B) Therefore, D = -λ / k (ln (Etotal (D, N) -ln
(C)) D is the depth from the top surface of the first layer, and Etota
If l (D, N) is the critical curing power (ratio to the irradiation power), the surplus curing thickness α when N layers are stacked is α = DP (n-1) ...・ ・ It becomes (1).

FIG. 5 shows the relationship between laminated thickness and dimensional deviation.
This data is for a horizontal overhang bottom. From this, it can be seen that the calculation result of the equation (1) is in good agreement with the actually measured value.

FIG. 6A is a cross-sectional view of model data obtained by performing the above correction on the surface shape data of a model having a hole of radius r = 3.0 with the correction amount being 1 and being constant irrespective of the inclination of the patch. . However, the surplus cured thickness depends on the inclination of the bottom surface of the overhang portion, and therefore, when stereolithography is performed based on this data, the dimensional deviation is not uniform, and the stereolithography model as shown in FIG. turn into. In FIG. 6C, the correction amount is set after comparing the inclination of the bottom surface of the overhang portion,
It is a cross-sectional view of the model data that has been subjected to the above correction. When stereolithography is performed based on this data, a smooth hole shape as shown in FIG. 6D is created, and a stereolithography model with good dimensional accuracy can be obtained. You can

The setting of the correction amount here is the same as that of the whole process regardless of which stage the correction amount is set after the detection of the patch located on the bottom surface of the overhang portion.

By correcting the surface shape data and performing modeling by the above-described processing method, it is possible to obtain an optical modeling product with high dimensional accuracy.

FIG. 7 shows a second embodiment of the present invention.
This is a procedure of performing correction processing on the above surface shape data to perform stereolithography. A three-dimensional CAD is used to create a shape model, which is converted into surface shape data for stereolithography, and the data is subjected to correction processing such as automatic detection of overhangs and automatic correction of dimensional deviation to perform stereolithography. FIG. 8 is a cross-sectional view of a model having a hole with a design value D = 10.0 of the diameter.
FIG. 8A is a cross-sectional view of a model that has been modeled by performing the above-described correction process without correction. As described above, by performing the modeling according to the procedure of the present invention, it is possible to obtain an optical modeling product with high dimensional accuracy.

[0029]

According to the present invention, it is possible to automatically detect the bottom surface of a modeled object and the bottom surface of an overhang portion, and correct the essential dimensional deviation of the optical modeling technique generated on the bottom surface on the surface shape data. Therefore, there is an effect that a stereolithography product with high dimensional accuracy can be obtained.

Further, the correction of the dimensional deviation does not need to be manually corrected by returning to the three-dimensional CAD, and there is an effect that it can be automatically processed in a short time.

[Brief description of drawings]

FIG. 1 is a PAD of a processing method for correcting with a surface shape model.
It is a figure.

FIG. 2 is a format of surface shape data in the first embodiment of the present invention.

FIG. 3 is a diagram showing triangular patches and nodes according to the first embodiment of this invention.

FIG. 4 is a diagram showing a surplus cured thickness in the first embodiment of the present invention.

FIG. 5 is a graph showing a relationship between a laminated thickness and a dimensional deviation in the first embodiment of the present invention.

FIG. 6 is a cross-sectional view of a model when the correction amount in the first embodiment of the present invention is a value depending on the inclination of the bottom surface of the overhang portion.

FIG. 7 is a diagram showing a procedure for performing optical shaping by performing surface shape data correction processing according to the second embodiment of the present invention.

FIG. 8 is a cross-sectional view of a modeling model with and without surface shape data correction processing according to the second embodiment of the present invention.

[Explanation of symbols]

a1, a2, a3, b1, b2, b3, c1, c2, c
3, d1, d2, d3 ... Vertex, a ... Normal vector, n
1, n2, n3, n4, n5, n6 ... node, Za ... normal vector Z component, α ... surplus hardening thickness, A, B, C, D
... patch, β, γ ... values depending on the patch inclination.

 ─────────────────────────────────────────────────── --- Continuation of the front page (72) Inventor Kentsugu Okubo 4, 6 Kanda Surugadai, Chiyoda-ku, Tokyo Stock company Hitachi Ltd. (72) Inventor Toshiro Endo 292 Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa Hitachi, Ltd. AV Equipment Division

Claims (2)

[Claims] 1. A data processing for modeling a three-dimensional shape model using surface shape data representing a surface of a three-dimensional shape model as a set of polygonal patches having at least three vertices, the vertices of the patches are arranged and nodes are arranged. , The polygon patch located on the bottom surface of the modeled object or on the bottom surface of the overhang portion is determined by the positive / negative of the Z component of the normal vector of the patch, and the Z component is negative, that is, for the patch located on the bottom surface of the overhang portion, Set a flag that the node that constitutes the patch is located at the bottom of the overhang,
The amount of correction applied to the Z coordinate value of the node at this time by changing the shape and the position of all the polygonal patches having the node as a vertex by examining all the nodes and correcting the Z coordinate value of the node where the flag stands. Is set to a predetermined value according to the inclination of the patch, and is corrected with the maximum correction amount according to the maximum inclination of the inclinations of some of the overhanging part bottom surface patches that share the node. A data processing method characterized in that surface shape model data is corrected by a processing method in which a patch is restored so as to be expressed in coordinates depending on coordinates. 2. A stereolithography method and apparatus for producing a stereolithography model by irradiating an ultraviolet curable resin with a laser to cure it and stacking the cured products, and having the data processing function of claim 1. Stereolithography device characterized by pre-correction.