JP2003067018A - Detecting method for unworkable area of numerically controlled working, generating method for shape data for the numerically controlled working, and computer program and program storage medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for detecting an unworkable area which is narrower than a working tool diameter from working shape data. SOLUTION: Voxels 11a showing a working area and voxels 11b showing an area other than the processing area are initially given as shown in (a). The minimum value of the distance of a voxel (1-pixel voxel) whose voxel value is 1 from a voxel (0-pixel voxel) whose voxel value is 0 is stored (distance conversion) (b). Then voxels whose minimum distances are smaller than a specific quantity are defined as 0-pixel voxels (reduction processing) (c). Then 1's and 0's of all the voxels are inverted (d). After the distance conversion and reduction processing, 1's and 0's of the voxels are inverted (3). Lastly, differences between the starting voxel data which are displayed in (a) last and voxel data after enlargement shown in (e) are calculated. The remaining 1-pixel voxels show the unworkable area (f).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for detecting a region which cannot be machined by a tool when preparing data for numerically controlled machining based on given machining shape data and tool information. The present invention relates to a method of creating shape data for numerically controlled machining that enables machining, a computer program describing these methods, and a program storage medium storing the computer program.

[0002]

2. Description of the Related Art For example, when treatment is performed by scraping off a caries part and covering the remaining abutment teeth with a crown, the shape of the tip of the remaining abutment teeth is modeled with plaster, and it is three-dimensionally shaped. The shape is obtained by measuring with a shape measuring device, the tooth profile has a normal outer shape, and the inside of which a hole having a shape that fits the remaining abutment tooth is processed is processed by the NC device, and this tooth crown is processed. A technique for fitting a tooth to an abutment tooth and fixing it with an adhesive has started to attract attention.

As described above, in order to perform the drilling having a predetermined shape by the NC device, the processed shape data describing the desired three-dimensional shape is given, and such a shape is processed by the computer. The posture and trajectory of the tool are calculated, and N is used as the processing data (data for numerical control processing).
It is usually provided to the C device, and the NC device is controlled accordingly.

[0004]

However, in the case of a small work piece such as a crown, the shape of the hole to be machined is small and has a complicated shape. When it is attempted to perform machining, there is a portion where the size to be machined is smaller than the size of the tool. That is, if you try to process this part,
The processing will be performed up to the portion that should have been not processed. In such a case, the program for calculating the machining data given to the normal NC device is designed to prepare the machining data so that the machining is performed such that the portion is left as a non-machinable portion.

This state is shown in FIG. FIG. 7 is a diagram showing the relationship between the inner working surface of the crown and the tool.
Reference numeral 1 represents a machined surface inside the crown cut by one surface (a surface parallel to the axis of the tool), and 32 represents a line of intersection with the cut surface. The tool 33 is visible from the cut portion. As shown in this figure, the size of the hole surrounded by the machining surface 31 and into which the tool 33 is inserted becomes smaller toward the upper part of the figure, and at the position shown in the figure, the outer surface of the tool 33 and the machining surface are machined. The surfaces 31 are in contact with each other, and whichever direction the tool 33 is moved, the outer surface of the tool 33 penetrates the processing surface 31. Therefore, no further processing is possible, and in the figure 34
The part indicated by is left as an unprocessed part that cannot be processed.

However, when there is a mating partner, such as a hole in the crown, if the unprocessed part remains, the mating convex part will not fit into that part, and the mating will not be performed sufficiently. Problems arise. In such a case, it is necessary to perform processing without leaving an unprocessed portion. If no unprocessed part is left, the part that was initially processed and the part that was not processed will be processed. That is, a gap is created when the mating member is fitted to the mating member, but since this portion is filled with the adhesive material, no problem occurs.

Therefore, in such a case, conventionally, from a shape measured by a three-dimensional shape measuring apparatus, a portion which is presumed to be an unprocessed portion by a human being is searched for, and processed by CAD so as to eliminate the unprocessed portion. The shape data was corrected. However, this process is troublesome.
In particular, if the processed shape is composed of a free-form surface that is not represented by a mathematical expression, it is difficult to determine whether or not it will be an unprocessed portion, and even if it is possible, it will take a lot of time.

The present invention has been made in view of the above circumstances, and a method of detecting a portion (referred to as a non-machinable area) narrower than a diameter of a machining tool from machining shape data, and a non-machinable area can be machined. It is an object of the present invention to provide a method for creating shape data for numerical control machining, a computer program describing these methods, and a program storage medium storing the computer program.

[0009]

A first means for solving the above-mentioned problems is to create the numerically controlled machining data on the basis of given machining shape data and tool information, A reduced shape obtained by reducing (offset) a predetermined amount in the processing area side is obtained, and subsequently an enlarged shape obtained by expanding (offset) the reduced shape in the opposite direction to the processing area side is obtained, and further, the processing is performed. By taking the difference between the shape data and the enlarged shape data,
A method for detecting an unprocessable area, wherein the reduced shape, the enlarged shape, and the difference between the processed shape data and the enlarged shape data are obtained using binarized voxel data. This is a method for detecting a non-machinable area in controlled machining (claim 1).

In the present means, first, a reduced shape is obtained by reducing (offset) the processing shape data in the processing area side direction by a predetermined amount. This predetermined amount is an amount determined by the relationship with the tool, and by this, a shape representing the range of movement of the tool that does not machine an area other than the area to be machined is obtained as a reduced shape. Next, an enlarged shape obtained by enlarging (offseting) the reduced shape in the direction opposite to the processing region side by the predetermined amount is obtained. The enlarged shape corresponds to the area actually machined in accordance with the movement of the tool determined by the reduced shape. Therefore, the unprocessed portion can be extracted by taking the difference between the processed shape data and the enlarged shape data.

In the present means, these series of operations are performed using the binarized voxel data. The voxel data is data expressed by dividing a three-dimensional space at equal intervals in length, width, and height. The voxel in the i-th row, j-th column, and k-th row is f _ijk (1 ≦ i ≦ L, 1 ≦ j ≦ M 1 ≦ k ≦ N). In this means, the inside and outside of the machined surface is represented using the binarized data among these. For example, voxel data having a value of 1 inside the area to be processed and a value of 0 outside the area to be processed is used.

In this case, first, voxel data having a value of 1 inside the area to be processed and a value of 0 outside the area to be processed is created from the processed shape data. Then, among the voxels with a voxel data value of 1, the minimum value of the distance from the voxel with a voxel data value of 0 is less than or equal to the predetermined value by changing the data value of the voxel to 0. Ask for. next,
In this reduced shape, among voxels with a voxel data value of 0, the minimum value of the distance from the voxel with a voxel data value of 1 is less than or equal to the predetermined value by changing to 1 Find the enlarged shape.

Then, by changing the value of the voxel having a value of 1 in the voxel data corresponding to the processed shape data and having a value of 1 in the voxel data corresponding to the enlarged shape to 0, the difference is calculated. Ask. The voxel in which the voxel data is 1 in this difference corresponds to the unprocessable area. Performing the calculation using the voxel data in this way significantly simplifies the calculation.

A second means for solving the above-mentioned problem is the first means, wherein the voxel data value is inverted when the enlarged shape is obtained, and the inverted data is transferred in the opposite direction to the processing area side. Then, the enlarged shape is obtained by reducing the predetermined amount and further inverting the value of the voxel data (claim 2).

In the description of the example of the first means, when obtaining the enlarged shape, the minimum value of the distance from the voxel having the voxel data value of 1 among the voxels having the voxel data value of 0 is determined. The enlarged shape is obtained by changing the data value of voxels that is equal to or less than the predetermined value to 1. On the other hand, in this means, the value of the voxel data is inverted, the reduction processing is performed, and then the value of the voxel data is inverted again to obtain the enlarged shape. Therefore, since the enlargement process can be performed by the same process as the reduction process prior to that, the calculation process can be shared, and when the computer process is performed, the programs can be shared.

A third means for solving the above-mentioned problems is as follows.
The first means or the second means, characterized in that when the voxel data (corresponding to the processing area) is obtained from the processing shape data, Z buffer method data used for three-dimensional shape display is used. What does (claim 3).

In the Z-buffer method, three-dimensional shape data is converted into 2
A known method of displaying on a display device that is a three-dimensional plane,
When an object having a three-dimensional shape is viewed from a certain direction, the three-dimensional shape is x-, where the screen of the display device is the xy plane.
It is expressed in the yz Cartesian coordinate system, and the values of z are compared for the elements having the same coordinates (x, y), and the element with the smallest z value is displayed on the screen as it is in the front. is there.

That is, in the Z-buffer method, the three-dimensional coordinates of the three-dimensional shape in the x-y-z Cartesian coordinate system in which the screen of the display device is the xy plane is calculated no matter what direction it is viewed from. The function to do is included.

The present means uses this well-known and commonly used means for determining binarized voxel data. That is, when the shape represented by the processed shape data is viewed from a certain direction, the z value of the voxel corresponding to each pixel of the shape displayed on the display screen which is the xy plane is read.
Now, if these data are (x _i , y _i , z _i ), all voxel values of voxels with z ≧ z _i among voxels having coordinates (x _i , y _i ) are set to 1. .
This operation is repeated by changing the viewing direction of the processed shape data. A voxel having a voxel value of 1 when viewed from all directions is defined as a portion surrounded by the processed shape, that is, a processed area. In this way, the voxel data can be easily obtained from the processed shape data by using the existing program.

Normally, the display of three-dimensional data by the Z-buffer method can be performed at a very high speed, so that this processing in the present invention is completed in a short time. Further, it is needless to say that this means does not need to actually display the processed shape on the display screen, and simply performs data processing.

The fourth means for solving the above-mentioned problems is as follows:
Any one of the first to third means is characterized in that the predetermined amount is equal to or larger than the radius of the tool (claim 4).

Many tools are cylindrical or rotationally symmetrical with respect to a rotation axis. In the case of such tools, the machining allowance in one direction is the radius of the tool. Therefore, by making the predetermined amount equal to or larger than the radius of the tool, it is possible to reliably obtain the unworkable region when such a tool is used.

A fifth means for solving the above-mentioned problems is as follows.
Numerical control characterized in that after the unmachined area is detected by using any of the first to fourth means, the original machined shape data is deformed so that the unmachined area can be machined. This is a method of creating processing data (claim 5).

In the present means, the unworkable area can be detected automatically with certainty. Therefore, the unworkable area is transformed by modifying the original working shape data so that the unworkable area can be worked. It can be surely eliminated.

A sixth means for solving the above-mentioned problems is as follows.
A computer program (claim 6) describing any one of the first to fifth means.

The seventh means for solving the above-mentioned problems is as follows.
A program storage medium (claim 7) that stores the computer program that is the sixth means.

[0027]

BEST MODE FOR CARRYING OUT THE INVENTION Preferred embodiments of the present invention will be described below with reference to the drawings. First, FIG. 1 shows an example of an apparatus configuration for executing a method for detecting a non-machinable area and a method for creating shape data for numerically controlled machining according to an embodiment of the present invention. This device has a computer main body 1, a display 2, a mouse 3, and a keyboard 4. The computer main body 1 includes a memory for storing programs and data for executing the design method according to the present invention. Specifically, MS-Windows NT (registered trademark)
However, the present invention is not limited to this. Further, here, the processing of the crown is taken as an example, but the present invention is not limited to the processing of the crown.

Consider, for example, designing the crown of the anterior tooth. Since the front tooth abutment tooth is usually thin, it often has a narrow shape as shown in FIG. Therefore, it is necessary to expand the processing area so that the processing tool can be inserted.

The machining shape data as shown in the photograph of FIG. 1 is loaded in the memory of the computer main body 1. This processed shape data is, for example, Japanese Patent Laid-Open No. 9-17844
The actual tooth model is three-dimensionally measured and input by the three-dimensional measuring machine described in Japanese Patent No.

In order to express this processed shape data in voxels, first, the voxel database is stored in the computer 1.
Is built on the memory that constitutes the. As shown in FIG. 2, each voxel has a structure capable of storing a value of 1 or 0 indicating inside or outside of design data and a distance value obtained by distance conversion, so that each voxel completely covers machining shape data. , L rows and M columns and N stages are prepared. The size of voxels depends on the number of voxels and the amount of available memory of the computer main body 1, but in the case of tooth shape data, one side of about 0.1 mm is preferable. In FIG. 2, 11 indicates voxels and 12 indicates processed shape data.

All the following processes including this process are also 3
Although it is a dimensional process, it is difficult to represent it in three dimensions in the figure, so it is represented in two dimensions. It is easy for a person skilled in the art to look at this two-dimensional representation and to infer the corresponding three-dimensional processing.

Hereinafter, the display surface of the display 2 will be considered as an xy plane. The computer main body 1 is provided with a Z buffer (not shown). When the processed shape data is displayed on the computer main body 1, the depth information (that is, the z-direction position of the displayed processed shape) is stored in the Z buffer. Therefore, the position (x, y) on the display when each voxel pixel is displayed on the display is calculated, and the depth information stored in the Z buffer 5 at that position is referred to. The referenced depth value and the depth value on the display of the voxel are compared, and if the voxel is in the back, 1 is stored in the voxel, and if it is in the front, 0 is stored.

Similarly, the same processing is repeated while changing the display direction. From the second time onward, if only voxels in which 1 is already stored are calculated, the processing efficiency can be improved. Then, the voxels in which 1 is stored for all the displayed directions are set as the voxels inside the processed shape, that is, the voxels indicating the processed region. By the above processing, 1 is set to the voxel inside the processed shape, and voxel data is obtained as shown in FIG. In the case of the crown shape data, it is sufficient to display about 5 directions from the top, the front, the back, the left and the right.

The procedure of the processing for extracting the unprocessed area from the obtained voxel data will be described with reference to FIGS. 3 and 4. FIG. 3 is a flowchart showing the processing procedure, and FIG. 4 is the voxel data at each stage of the processing. FIG.

First, the voxel 11a indicating the processed region and the voxel 11b indicating the outside of the processed region are given as initial states by the above-described processing, as shown in FIG. 4 (a). In FIG. 4, voxels having a value of 1 are shown in gray, and voxels having a value of 0 are shown in white. First, FIG.
Distance conversion is performed in step S11. This is because the voxel indicating the processing area, that is, the voxel with a voxel value of 1 (sometimes referred to as “1 pixel voxel”) is changed from the voxel with a voxel value of 0 (sometimes referred to as “0 pixel voxel”). This is a process of calculating the distance and storing the minimum value.

The voxel at the i-th row and the j-th column of the k-th row is defined as f _ijk (1
≦ i ≦ L, 1 ≦ j ≦ M, 1 ≦ k ≦ N). Also, the entire three-dimensional space is written as F = {f _ijk }. When the distance transformation of the three-dimensional space F = {f _ijk } is D = {d _ijk }, d _ijk is the minimum value of the distance values from all 0 pixel voxels of the three-dimensional space F to (i, j, k). Is. Ie

[0037]

[Equation 1]

F _pqr = 0, 1 ≦ p ≦ L, 1 ≦ q ≦ M, 1 ≦ r ≦ N.

By this distance conversion, one pixel voxel has 0
The shortest distance from the pixel voxel is stored. This state is shown in FIG. The number written in one pixel voxel is the standardized shortest distance.

An example of a method for realizing distance conversion is the Institute of Electronics, Information and Communication Engineers, Journal Vol.J76-D-II No.3 pp.445-453.

Next, reduction processing is performed in step S12 of FIG. This can be easily performed by setting a voxel in which the shortest distance d _ijk is smaller than the amount to be reduced as a voxel of 0 pixel. FIG. 4C shows the result of reduction processing by setting the voxel having the shortest distance of 2 or less as a voxel of 0 pixel. Here, the area corresponding to one pixel voxel indicates an area in which the tool can be moved under the condition that the area other than the processing area is not processed.

When machining with a rotating tool, the distance to be reduced should be the same as the radius of the tool, or with a margin,
The distance is larger than the radius of the tool. In this case, the voxel of 1 pixel remaining as a result of the reduction processing corresponds to the space in which the center tip of the tool can move under the condition that the area other than the processing area is not processed.

Next, the enlarging process is started. In the present embodiment, the enlarging process is performed by converting it into a reducing process. First, in step S13 of FIG.
Invert 1s and 0s in all voxels. The inverted result is shown in FIG. Then, in step S14 of FIG. 3, the distance conversion and reduction processing described above are performed on the voxels after the inversion, and then the voxels 1 and 0 are inverted again. At this time, the distance to be reduced used in the reduction processing is the same as the distance to be reduced used in the reduction processing in step S12. The result of performing these series of processes is shown in FIG. In FIG. 4E, the area indicated by one pixel voxel indicates an area that is actually machined when the tool moves under the condition that the area other than the machining area is not machined.

Finally, the difference between the first voxel data shown in FIG. 4A and the enlarged voxel data shown in FIG. 4E is calculated. That is, of the former 1-pixel voxels, those that are also the latter 1-pixel voxels are changed to 0-pixel voxels. The result is shown in FIG. The remaining 1-pixel voxel indicates an unprocessable area. In this way, the unprocessable area can be extracted by a simple method.

Next, FIGS. 5 (a) and 5 (b) show an example in which the machining shape data is transformed so that the machining tool can be inserted by utilizing the remaining one pixel voxel in FIG. 4 (f). Figure 5 (a)
In, the voxels 11c to 11g as unworkable regions
It is assumed that the area corresponding to is left. The tool has a cylindrical shape centered on the shaft 14 as shown in 13,
It is assumed that the tip has a hemispherical shape, and that processing is performed vertically from the lower side toward the upper side.

Tool shape data 35 of the same shape as this tool
Is prepared in the memory of the computer main body 1. Then, the voxels 11c to 11g are arranged so that the tool shape data is in contact with the machining shape data at a point P on the machining shape data closest to the top voxel (that is, the farthest from the machining side). All of the machining shape data inside it is moved to the position of the tool shape data (that is, the position representing the surface of the tool). The remaining voxels (ie,
The same processing is performed for all voxels 11c to 11g).

Since the unprocessed area is eliminated by the above processing, if the processed data is created based on the processed shape data after such deformation, the necessary area is prevented from being left unprocessed. it can. FIG. 5B shows a two-dimensional data diagram of such processed shape data after conversion.

FIG. 6A shows a data diagram before the more complex machining shape data is deformed, and FIG. 6B shows a data diagram after the deformation is three-dimensionally. It can be seen that the pointed part of the central part (the part where the gap is narrowed when viewed from the inside) bulges due to deformation. That is, when viewed from the inside, the processing area is widened and the processing shape is such that the portion to be processed does not remain. As described above, in the present embodiment, the result of the deformation is displayed on the display 2
The effect can be confirmed by displaying in.

[0049]

As described above, according to the present invention,
When cutting with numerical control, it becomes possible to automatically detect the unmachined area that cannot be machined because it is narrower than the machining tool, and based on this, the machined area is automatically expanded and the unmachined area is It is possible to lose it.

[Brief description of drawings]

FIG. 1 is a diagram showing an example of an apparatus configuration for executing a method for detecting a non-machinable region and a method for creating shape data for numerical control machining in numerical control machining according to an embodiment of the present invention.

FIG. 2 is a schematic diagram showing voxels and processed shape data.

FIG. 3 is a flowchart showing a procedure of processing for extracting an unprocessable area from voxel data.

FIG. 4 is a diagram showing voxel data at each stage of the processing shown in FIG.

FIG. 5 is a diagram showing an example in which machining shape data is deformed so that a machining tool is inserted based on a voxel indicating a non-machinable region, (a) is a data diagram before deformation, and (b) is a data diagram after deformation. is there.

FIG. 6 is a data diagram showing an effect of an example of the present invention.

FIG. 7 is a diagram for explaining a cause of occurrence of an unprocessable area.

[Explanation of symbols]

1 ... Computer body 2 ... Display 3 ... mouse 4 ... keyboard 11, 11a to 11g ... Voxels 12 ... Curved surface represented by machining shape data 13 ... Tool 14 ... Axis of curved surface represented by tool shape data 35 ... Curved surface represented by tool shape data

Claims (7)

[Claims] 1. When a numerical control machining data is created based on given machining shape data and tool information, a reduced shape is obtained by reducing (offsetting) the machining shape data by a predetermined amount in the machining region side direction. Then, it is impossible to process by obtaining the enlarged shape obtained by enlarging (offseting) the reduced shape by the predetermined amount in the direction opposite to the machining area side, and further obtaining the difference between the machining shape data and the enlarged shape data. A reduced area, the reduced shape,
A method for detecting an unprocessable region in numerical control machining, wherein an enlarged shape and a difference between the processed shape data and the enlarged shape data are obtained by using binarized voxel data. 2. When obtaining the enlarged shape, the value of voxel data is inverted, the inverted data is reduced by the predetermined amount in the direction opposite to the processing region side, and the value of voxel data is further inverted. The method for detecting an unprocessable region in numerical control processing according to claim 1, wherein the enlarged shape is obtained by. 3. The numerical control machining according to claim 1 or 2, wherein when the voxel data is obtained from the machining shape data, the Z buffer method data used for three-dimensional shape display is used. How to detect unprocessable area. 4. The method according to claim 1, wherein the predetermined amount is the same as the radius of the tool or larger than the radius of the tool. 5. Any one of claims 1 to 4
A numerical value characterized by deforming the initial machining shape data so that the unmachined area can be machined after detecting the unmachined area using the method for detecting the unmachined area in the numerically controlled machining described in the paragraph. How to create data for control processing. 6. Any one of claims 1 to 4
A computer program which describes the method for detecting an unworkable region in the numerically controlled machining according to claim 5 or the method for creating the numerically controlled machining data according to claim 5. 7. A program storage medium storing the computer program according to claim 6.