JP2007286858A - Preparation device and preparing method for surface model - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a technique capable of precisely preparing an offset surface model. <P>SOLUTION: The preparation device for an offset surface model comprises a means for setting three-dimensional lattice points and its neighboring range in a three-dimensional space in which curved surface data describes a curved surface; a means for preparing a pair of data groups for both a first lattice point in which the curved surface passes through the neighboring range and the nearest point on the curved surface; a data preparing means for describing a group of second lattice points in which temporary offset points offsetting the nearest point are located in the neighboring range; a data preparing means for describing a group of third lattice points in which distances to the first lattice point located at the nearest point among the group of second lattice points are within a designated offset determining range; a means for calculating the offset points offsetting the nearest point for every third three-dimensional lattice point and preparing offset surface model data describing a group of calculated offset points, and a means for adding a group of three-dimensional lattice points adjacent to the third three-dimensional lattice points to the group of second three-dimensional lattice points. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a technique for creating a surface model used in NC machining technology (numerical control machining technology) or the like. In particular, the present invention relates to a technique for creating an offset surface model offset by a predetermined distance from a curved surface based on data describing the curved surface.

The NC machining technique forms a predetermined machining surface on the material by relatively moving the tool and the material along a movement path taught in advance. The shape of the machined surface is represented by machined surface data created using a three-dimensional CAD (Computer Aided Design) apparatus or the like. In order to form a machining surface on a material using an NC machine tool, it is necessary to determine a movement path of the tool based on machining surface data describing the machining surface.
In the NC machining technique, a reference point is defined for a tool in order to describe the position of the tool with coordinates. Thereby, the movement path of the tool is determined by the movement path of the reference point of the tool. The movement path of the tool is equal to the path along which the tool reference point moves when the tool cutting edge surface is moved while being in contact with the machining surface. That is, the movement path of the tool is located on a surface offset by the tool shape from the machining surface. In order to determine the movement path of the tool, it is necessary to create an offset surface model that is offset from the machining surface by the tool shape based on the surface data describing the machining surface.
Patent Document 1 describes a technique for creating a tool reference plane model using an inverse offset method. In the reverse offset method, a virtual reversing tool is created by approximating the machining surface with an approximate element such as a point cloud or stereo plane group (STL: Stereo lithography), and reversing the tool shape with respect to the machining posture. It arranges so that it may be located in each approximate element. Then, by obtaining the envelope surface of the arranged virtual reversal tool shape group, an offset surface model is created that is offset from the machining surface by the tool shape.
JP-A-4-133103

Since the technique of Patent Document 1 cannot directly handle a curved surface, it is necessary to calculate an offset surface model based on an approximate model obtained by approximating a curved surface with an approximate element group. For this reason, an error due to the approximation process occurs in the created offset surface model. In order to reduce this error, it is necessary to finely approximate the curved surface. However, the calculation load increases as fine approximation processing is performed. There is a need for a technique for accurately creating an offset surface model without excessively increasing the calculation load.
The present invention solves the above problems. The present invention provides a technique for accurately creating an offset surface model without increasing the calculation load.

  The technology of the present invention can be embodied in an apparatus that creates an offset surface model offset from a curved surface by a predetermined offset distance based on curved surface data describing the curved surface. This offset surface model creating apparatus includes a storage means for storing curved surface data describing a curved surface arranged in a three-dimensional space, and three-dimensional lattice points at predetermined intervals in the three-dimensional space in which the curved surface data describes a curved surface. Means for arranging and setting a neighborhood area of a predetermined radius for each 3D grid point, a first 3D grid point where the curved surface passes through the neighborhood area, and a closest point on the curved surface with respect to the first 3D grid point; A first grid point data describing a data group of a pair of the first 3D grid point and the nearest point, and a first 3D grid point described in the first grid point data; For each pair of nearest point data, an offset direction is determined from the relative position of the first 3D lattice point and the nearest point, and a temporary offset point is obtained by moving the nearest point in the offset direction by the offset distance. The second 3D lattice point where the offset point exists in the neighborhood The first grid point data is generated from the means for creating the second grid point data that specifies the specified second 3D grid point group and the second 3D grid point group described in the second grid point data. The third three-dimensional lattice point group whose distance to the nearest first three-dimensional lattice point is a predetermined offset determination range among the first three-dimensional lattice point group described in FIG. Means for generating third lattice point data describing three 3D lattice point groups, and for each third three-dimensional lattice point described in the third lattice point data, the maximum number described in the first lattice point data; Offset point model data describing the calculated offset point group is created by calculating the offset point by moving the closest point in the point group by the offset distance toward the 3D grid point. Described in the third grid point data. And a third three-dimensional three-dimensional grid point group adjacent to the lattice point is, and means for adding the second grid point data.

The offset surface model creating apparatus first arranges a three-dimensional lattice point in a three-dimensional space in which a curved surface is arranged, and for each three-dimensional lattice point, creates a region near a predetermined radius centered on the three-dimensional lattice point. Set.
Next, the offset surface model creation device identifies the first three-dimensional lattice point where the curved surface passes through the neighboring region and the closest point on the curved surface with respect to the first three-dimensional lattice point, and the first three-dimensional lattice point First grid point data describing a data group of a pair of nearest points is created. Thereby, data expressing the curved surface described by the curved surface data as a set of three-dimensional lattice points is obtained.
Next, the offset surface model creation device generates a relative value between the first 3D lattice point and the nearest point for each pair of data of the first 3D lattice point and the nearest point described by the first lattice point data. The offset direction is determined from the position, a temporary offset point obtained by moving the nearest point in the offset direction by the offset distance is determined, the second 3D lattice point where the temporary offset point exists in the vicinity region is specified, and the specified second Second grid point data describing a three-dimensional grid point group is created. The nearest point on the curved surface with respect to the first three-dimensional lattice point is a foot of a perpendicular line drawn from the first three-dimensional lattice point to the curved surface. Therefore, the normal direction at the nearest point of the curved surface can be obtained from the relative position between the first three-dimensional lattice point and the nearest point, that is, the vector connecting the first three-dimensional lattice point and the nearest point. From the relative position between the first three-dimensional lattice point and the nearest point, the offset direction at each nearest point can be obtained correctly without requiring complicated calculation.

  Next, the offset plane model creation device is closest to the first three-dimensional lattice point group described in the first lattice point data from the second three-dimensional lattice point group described in the second lattice point data. The third 3D lattice point group in which the distance to the first 3D lattice point located at is a predetermined offset determination range is specified, and the third lattice point data describing the specified third 3D lattice point group is created To do. Since each of the second 3D lattice point groups is located near the temporary offset point obtained by offsetting the nearest point on the curved surface, it becomes a 3D lattice point located near the offset surface obtained by offsetting the curved surface. obtain. On the other hand, the temporary offset point obtained by offsetting the nearest point on the curved surface may be closer to the other part of the curved surface than the offset distance, and each of the second three-dimensional lattice point groups is not necessarily It is not necessarily located near the offset surface. In this offset surface model creation device, the offset surface is identified by identifying a distance from the second 3D lattice point group to the nearest first 3D lattice point within a predetermined offset determination range. A third three-dimensional lattice point group located in the vicinity of is extracted.

Next, the offset surface model creation device is positioned closest to the third point lattice point described in the first lattice point data for each third three-dimensional lattice point described in the third lattice point data. An offset point obtained by moving the nearest point toward the third three-dimensional lattice point by an offset distance is calculated, and offset plane model data describing the calculated offset point group is created. The offset point group calculated here is a point obtained by offsetting the nearest point group located on the curved surface, and a point group located on the offset surface obtained by offsetting the curved surface can be obtained.
Next, the offset surface model creation device adds a three-dimensional lattice point group adjacent to the third three-dimensional lattice point described in the third lattice point data to the second lattice point data. Since the third three-dimensional lattice point is located in the vicinity of the offset surface, the three-dimensional lattice point group adjacent to the third three-dimensional lattice point can also be located in the vicinity of the offset surface. Therefore, a three-dimensional lattice point group adjacent to the third three-dimensional lattice point is added to the second lattice point data, and the above-described processing is executed for the three-dimensional lattice point group adjacent to the third three-dimensional lattice point. Thus, the offset point can be obtained without omission.
Finally, it is possible to obtain offset surface model data that expresses an offset surface obtained by offsetting a curved surface by an offset distance by an offset point group.
According to this creating apparatus, in the intermediate process of creating the offset surface model, the calculation process is reduced using the three-dimensional lattice points, and finally the offset surface model is created by the offset points obtained by offsetting the points on the curved surface. Compared to an offset surface model that is offset from an approximate element that approximates a curved surface as in the prior art, an accurate offset surface model can be obtained.

In the above apparatus, the offset determination range used by the third grid point data creation means is a value obtained by subtracting the diameter of the neighboring area from the offset distance, and a value obtained by adding the diameter of the neighboring area to the offset distance. It is preferable that it is the range to.
As a result, the third 3D lattice point group located in the vicinity of the offset plane can be extracted from the second 3D lattice point group described in the second lattice point data without excess or deficiency.

The technique of the present invention can also be embodied in a method of creating an offset surface model that is offset from a curved surface by a predetermined offset distance based on curved surface data describing the curved surface. This method includes a step of preparing curved surface data describing a curved surface arranged in a three-dimensional space, and arranging three-dimensional lattice points at predetermined intervals in the three-dimensional space in which the curved surface data describes a curved surface. Identifying a neighborhood area of a predetermined radius for each original grid point, identifying a first 3D grid point where the curved surface passes through the neighborhood area, and a closest point on the curved surface with respect to the first 3D grid point; A step of creating first grid point data describing a data group of a pair of the first 3D grid point and the nearest point, and the first 3D grid point and the nearest point described in the first grid point data For each pair of data, the offset direction is determined from the relative position of the first 3D lattice point and the nearest point, and the temporary offset point is obtained by moving the nearest point in the offset direction by the offset distance. Identify the second 3D grid points that exist in the region, The first grid point data described in the first grid point data is generated from the step of creating the second grid point data describing the three-dimensional grid point group and the second three-dimensional grid point group described in the second grid point data. The third 3D lattice point group in which the distance to the nearest first 3D lattice point in the 3D lattice point group is within a predetermined offset determination range is specified, and the identified third 3D lattice point group is The step of creating the third grid point data to be described, and the third 3D grid point described in the third grid point data are the nearest among the nearest points described in the first grid point data. Calculating an offset point obtained by moving the nearest point located at the position of the third lattice point by an offset distance, creating offset plane model data describing the calculated offset point group, and a third lattice point Third 3D lattice described in the data A three-dimensional grid point group adjacent to, and a step of adding the second grid point data.
According to this method, in the intermediate process of creating the offset surface model, the calculation process is reduced using the three-dimensional lattice points, and finally the offset surface model is created by the offset points obtained by offsetting the points on the curved surface. Compared to an offset surface model that is offset from an approximate element that approximates a curved surface as in the prior art, an accurate offset surface model can be obtained.

  According to the present invention, based on data describing a curved surface, an offset surface model offset from the curved surface by an offset distance can be accurately created. By creating a tool path to be taught to the NC machine tool using the created offset surface model, it is possible to cause the NC machine tool to form a machining surface with high accuracy.

The main features of the embodiments described below are listed.
(Feature 1) Curved surface data is created using a three-dimensional CAD device.
(Feature 2) The three-dimensional lattice points are arranged at equal intervals in the three-dimensional direction.
(Characteristic 3) The diameter of the region near the three-dimensional lattice point is set to 3 ^1/2 times the interval of the three-dimensional lattice point.

FIG. 1 shows a functional configuration of an offset surface model creation apparatus 10 (hereinafter simply referred to as a creation apparatus) in which the present invention is implemented. The creation device 10 is a device that creates an offset surface model that is offset from the curved surface by a tool shape based on curved surface data describing a curved surface such as a machining surface, for example. The offset surface model created by the creation device 10 can be used to create a tool movement path for forming a machining surface on a material using, for example, a numerical control (NC) machine tool.
As shown in FIG. 1, the creation device 10 functionally includes a data storage unit 20, a data creation unit 50, and an input / output unit 70. The creation device 10 is mainly configured by using a computer device, and the data storage unit 20, the data creation unit 50, and the input / output unit 70 are configured by hardware, software, and the like of the computer device.

The data storage unit 20 includes curved surface data 22, curved surface lattice point data (first lattice point data) 24, temporary offset lattice point data (second lattice point data) 26, and offset lattice point data (third lattice point data). ) 28 and offset plane data 30 and the like can be stored. The curved surface data 22 is data describing a curved surface such as a desired machining surface, for example, and describes a curved surface arranged in a three-dimensional space in which xyz orthogonal coordinates are defined. The curved surface data 22 is taught to the creation apparatus 10 from the outside via the input / output unit 70. The curved surface grid point data 24, temporary offset grid point data 26, offset grid point data 28, and offset surface data 30 are created by the data creation unit 50.
The data creation unit 50 includes a grid point setting unit 52, a curved grid point data creation unit 54, a temporary offset grid point data creation unit 56, an offset grid point determination unit 58, and an offset point calculation unit 60. The data creation unit 50 performs various arithmetic processes based on the curved surface data 22 stored in the data storage unit 20 and finally creates the offset surface data 30. The offset surface data 30 describes an offset surface offset by a predetermined distance from the curved surface described by the curved surface data 22. In addition, the data creation unit 50 creates the curved surface grid point data 24, the temporary offset grid point data 26, and the offset grid point data 28 in the calculation process of creating the offset surface data 30.

FIG. 2 is a flowchart showing a flow of processing in which the creation apparatus 10 creates the offset surface data 30. A processing procedure in which the creation device 10 creates the offset surface data 30 based on the curved surface data 22 taught from the outside will be described along the flow shown in FIG.
First, in step S <b> 2, the creation apparatus 10 inputs the curved surface data 22 through the input / output unit 70 and stores it in the data storage unit 20. The curved surface data 22 is created by, for example, an external three-dimensional CAD (Computer Aided Design) device.
FIG. 3 shows an example of the processed surface 22a described by the curved surface data 22. As illustrated in FIG. 3, the curved surface data 22 describes the machining surface 22 a arranged in the xyz space by a plurality of basic shapes arranged in the xyz space. As the basic shape, for example, a vertex V, a ridge line C, a surface S, or the like is used. For example, a straight line or a curved line is used for the ridge line C, and a flat surface, a cylindrical surface, a spherical surface, a free curved surface, or the like is used for the surface S. The ridge line C is described by a curve expression C (t) using a parameter t. The surface S is described by a surface expression S (u, v) using parameters u and v. An identifier ID that can identify each of the basic shapes V, C, and S describing the processed surface 22a is assigned.
The curved surface data 22 may be data that approximates and describes the processing surface 22a by a point group arranged in the xyz space or a minute plane group (STL: Stereo lithography) arranged in the xyz space.

In step S4 of FIG. 2, the lattice point setting unit 52 of the data creation unit 50 converts the three-dimensional lattice point group into the xyz space described by the curved surface data 22, that is, the xyz space where the processed surface 22a is arranged. Set. The three-dimensional lattice point group is an intersection point group when a three-dimensional lattice is partitioned in the xyz space.
FIG. 4 shows an xyz space in which the three-dimensional lattice point g group is set by the lattice point setting unit 52. Note that FIG. 4 shows the interval of the three-dimensional lattice point group enlarged for the sake of clarity of illustration. As shown in FIG. 4, the lattice point setting unit 52 sets a three-dimensional lattice point g group arranged at a predetermined interval b with respect to each of the xyz directions in the xyz space where the processed surface 22 a is arranged. Each three-dimensional lattice point g is identified using integer coordinates (i, j, k). Here, i means a position in the x direction and indicates i-th position in the x direction. j means a position in the y direction and indicates the jth position in the y direction. k means a position in the z direction and indicates the kth position in the z direction. That is, the three-dimensional lattice point g: (i, j, k) means that it is located at the coordinates (b × i, b × j, b × k) in the xyz space.

  In step S <b> 6 of FIG. 2, the curved grid point data creation unit 54 creates curved grid point data 24. As shown in FIG. 5, the curved surface grid point data 24 indicates that the machining surface 22a is in the neighborhood region R when the neighborhood region R having the radius a (diameter 2a) is set for each of the three-dimensional lattice point g group set in step S4. Is a data describing a group of three-dimensional lattice points gm passing through. Further, the identifier ID of the nearest point p on the machining surface 22a and the basic shape (vertex V, ridge line C, surface S) where the nearest point p is located in association with the three-dimensional lattice point gm group. It is described. Hereinafter, the three-dimensional lattice point gm described in the curved surface lattice point data 24 may be referred to as a curved surface lattice point (first three-dimensional lattice point) gm.

Here, a procedure in which the curved surface grid point data creation unit 54 creates the curved surface grid point data 24 from the curved surface data 22 will be described. As described above, in the curved surface data 22, the machining surface 22a is described by the basic shape group such as the vertex V, the ridge line C, and the surface S arranged in the xyz space. Therefore, as illustrated in FIGS. 6A to 6C, the curved surface grid point data creation unit 54 first specifies the curved surface grid point gm with respect to the vertex V that configures the processed surface 22a, and then configures the processed surface 22a. The curved grid point gm is specified for the ridge line C to be performed, and finally, the curved grid point gm is specified for the surface S constituting the processed surface 22a.
As shown in FIG. 6A, first, the curved surface grid point data creation unit 54 has a vertex V described in the curved surface data 22 in the neighborhood region R in the three-dimensional grid point g group set in step S4. A three-dimensional lattice point g group existing in the inside is specified. FIG. 7 shows a three-dimensional lattice point g in which the vertex V exists in the neighboring region R. The curved surface grid point data creation unit 54 calculates the distance from the vertex V to each three-dimensional grid point g for each vertex V described in the curved surface data 22, and the calculated distance is equal to or less than the radius a of the neighboring region R. Are recorded in the curved surface grid point data 24 as curved surface grid points gm.

  Next, as shown in FIG. 6B, the curved surface grid point data creation unit 54 displays the ridge line C described in the curved surface data 22 in the neighborhood region R in the three-dimensional grid point g group set in step S4. A group of three-dimensional lattice points g passing through is specified. FIG. 8 shows a three-dimensional lattice point g where a ridge line C exists in the vicinity region R. As shown in FIG. 8, in the three-dimensional lattice point g where the ridge line C exists in the neighboring region R, the distance to the nearest point Ca on the ridge line C with respect to the three-dimensional lattice point g is larger than the radius a of the neighboring region R. Is also shortened. The nearest point Ca on the ridge line C with respect to the three-dimensional lattice point g is a constraint condition that the vector connecting the three-dimensional lattice point g and the nearest point Ca and the tangent vector C ′ at the nearest point Ca are perpendicular. It can be obtained by executing an analytical operation of the Newton-Raphson method. However, in the analysis calculation for obtaining the nearest point Ca, if the given initial point is inappropriate, the correct nearest point Ca may not be calculated. Therefore, the curved surface lattice point data creation unit 54 first determines at least one initial point on the ridge line C and specifies the three-dimensional lattice point g in which the initial point is located in the vicinity region R. Then, with respect to the specified three-dimensional lattice point g, an analysis calculation is performed using the initial point on the ridge line C previously determined, and the nearest point Ca is calculated. Thereby, one curved surface grid point gm related to the ridge line C and the nearest point Ca on the ridge line C can be correctly specified. The curved grid point data creation unit 54 records the identified curved grid point gm and the nearest point Ca in the curved grid point data 24. Next, the curved surface grid point data creation unit 54 performs an analysis operation on the three-dimensional grid point g adjacent to the previously specified curved surface grid point gm, using the previously specified nearest point Ca as an initial point, and is adjacent. The nearest point Ca with respect to the three-dimensional lattice point g is obtained. Then, the distance between the adjacent three-dimensional lattice point g and the nearest point Ca is calculated, and if the calculated distance is equal to or less than the radius a of the neighboring region R, the three-dimensional lattice point g is defined as the curved surface lattice point gm. Record in the point data 24. The curved surface grid point data creation unit 54 performs the same process for each of the 26 three-dimensional grid points g adjacent to the previously specified curved surface grid point gm. Thereafter, every time the curved surface grid point gm is specified, the 26 three-dimensional grid points g adjacent to the curved surface grid point gm are added to the object of the above-described analysis calculation processing, thereby being positioned along the ridge line C. Analysis operations are sequentially performed on the three-dimensional lattice point g. Thereby, the curved surface grid point gm group regarding the ridgeline C can be specified correctly without omission.

  As shown in FIG. 6 (c), finally, the curved surface grid point data creation unit 54 includes the surface S described in the curved surface data 22 in the neighborhood region in the three-dimensional grid point g group set in step S4. A group of three-dimensional lattice points g passing through R is specified. FIG. 9 shows a three-dimensional lattice point g where the surface S exists in the neighboring region R. As shown in FIG. 9, in the three-dimensional lattice point g where the surface S exists in the neighboring region R, the distance to the nearest point Sa on the surface S with respect to the three-dimensional lattice point g is larger than the radius a of the neighboring region R. Is also shortened. The nearest point Sa on the surface S with respect to the three-dimensional lattice point g is a vector connecting the three-dimensional lattice point g and the nearest point Sa, a tangent vector Su in the s direction and a tangent vector Su in the u direction at the nearest point Sa. Can be obtained by executing analytical operations of the Newton-Raphson method, with the constraint that the angle is vertical. However, in the analysis calculation for obtaining the nearest point Sa, if the given initial point is inappropriate, the correct nearest point Sa may not be calculated. Therefore, the curved lattice point data creation unit 54 first determines at least one initial point on the surface S and specifies a three-dimensional lattice point g in which the initial point is located in the vicinity region R. Then, with respect to the identified three-dimensional lattice point g, an analysis calculation is performed using the initial point on the surface S previously determined, and the nearest point Sa is calculated. Thereby, one curved surface grid point gm related to the surface S and the nearest point Sa on the surface S can be correctly specified. The curved grid point data creation unit 54 records the identified curved grid point gm and the nearest point Sa in the curved grid point data 24. Next, the curved surface grid point data creation unit 54 performs an analysis operation on the three-dimensional grid point g adjacent to the previously specified curved surface grid point gm, using the previously specified nearest point Sa as an initial point, The nearest point Sa with respect to the three-dimensional lattice point g is obtained. If the distance between the three-dimensional lattice point g and the nearest point Sa is equal to or less than the radius a of the neighboring region R, it is recorded in the curved surface lattice point data 24 as the curved surface lattice point gm. The curved surface grid point data creation unit 54 performs the same process for each of the 26 three-dimensional grid points g adjacent to the previously specified curved surface grid point gm. Thereafter, every time the curved surface grid point gm is specified, the 26 three-dimensional grid points g adjacent to the curved surface grid point gm are added to the object of the above-described analysis calculation processing, thereby positioning along the surface S. Analysis operations are sequentially performed on the three-dimensional lattice point g. Thereby, the curved surface grid point gm group regarding the surface S can be correctly specified without omission.

  In step S <b> 8 of FIG. 2, the temporary offset grid point data creation unit 56 creates temporary offset grid point data 26 using the curved grid point data 24. As shown in FIG. 10, the temporary offset grid point data 26 is moved by the offset distance r in the normal direction of the machining surface 22a for each nearest point p on the machining surface 22a described in the curved surface grid point data 24. This is data describing a three-dimensional lattice point gf group in which the temporary offset point h group is located in the vicinity region R when the provisional offset point h group is determined. Hereinafter, the three-dimensional lattice point gf described in the temporary offset lattice point data 26, that is, the three-dimensional lattice point gf where the temporary offset point h is located in the vicinity region R may be referred to as the temporary offset lattice point gf. Here, the offset distance r can be determined in advance according to the tool shape or the like. The temporary offset grid point data creation unit 56 first determines an offset direction for offsetting the nearest point p from the relative position between the curved grid point gm described in the curved grid point data 24 and the nearest point p. A relative position between the curved surface grid point gm and the nearest point p, that is, a vector connecting the curved surface grid point gm and the nearest point p indicates a normal direction at the nearest point p of the processed surface 22a. Therefore, the temporary offset point h determined in a straight line passing through the curved lattice point gm and the nearest point p is offset from the nearest point p on the machining surface 22a in the normal direction of the machining surface 22a. . Next, a temporary offset point h obtained by moving the nearest point p by the offset distance r in the offset direction is obtained. Then, the three-dimensional lattice point gf where the temporary offset point h is located in the vicinity region R is specified, and is recorded in the temporary offset lattice point data 26 as the temporary offset lattice point gf.

In steps S10 and S12 of FIG. 2, the offset grid point determination unit 58 determines whether or not each temporary offset point grid gf described in the temporary offset grid point data 26 is an offset grid point. . Each of the temporary offset lattice points gf group obtained in the previous step S8 is positioned in the vicinity of the temporary offset point h obtained by offsetting one nearest point p on the processed surface 22a, so that the processed surface 22a is offset. It can be a three-dimensional lattice point located in the vicinity of the offset plane. On the other hand, the temporary offset point h obtained by offsetting one nearest point p on the processed surface 22a may be closer to the other portion of the processed surface 22a than the offset distance r, and the temporary offset lattice point Each of the gf groups is not necessarily located near the offset surface. Therefore, in the processing of steps S10 and S12, the temporary offset lattice point gf group is extracted that is located in the vicinity of the offset surface obtained by offsetting the machining surface 22a by the offset distance.
First, in step S <b> 10 of FIG. 2, the offset grid point determination unit 58 selects one temporary offset grid point gf from the temporary offset grid point data 26.
Next, in step S12, the offset grid point determination unit 58 determines whether or not the selected temporary offset grid point gf is an offset grid point. This determination process will be described with reference to FIG. As shown in FIG. 11, the offset grid point determination unit 58 has a first determination area U1 having a radius r-2a obtained by subtracting the diameter 2r of the neighboring area R from the offset distance r around the selected temporary offset grid point gf. Then, a second determination region U2 having a radius r + 2a obtained by adding the diameter 2r of the neighboring region R to the offset distance r is determined. The curved grid point gm described in the curved grid point data 24 does not exist in the first determination area U1 and is selected in the difference area between the first determination area U1 and the second determination area U2. The provisional offset grid point gf is determined to be an offset grid point. That is, the distance to the curved grid point gm closest to the temporary offset grid point gf among the curved grid points gm described in the curved grid point data 24 is not less than the radius r-2a of the first determination region U1. If the radius r + 2a of the second determination region U2 is greater than or equal to, the selected temporary offset grid point gf is determined to be an offset grid point. At the same time, among the curved surface lattice points gm described in the curved surface lattice point data 24, those existing in the second determination region U2 (the curved surface lattice points gm with hatching in FIG. 11) are specified. To do. Then, the offset grid point determination unit 58 associates the temporary offset grid point gf determined to be an offset grid point with the curved grid point gm group existing in the second determination region U2, and associates the data storage unit 20 To record. Thereby, the offset grid point data 28 describing the offset grid point gf and the curved grid point gm group existing in the second determination region U2 in association with each other is created. On the other hand, when the curved grid point gm exists in the first determination area U1, or when the curved grid point gm does not exist in the second determination area U2, the selected temporary offset grid point gf is not an offset grid point. Judge that there is no. In this case, the process returns to step S10.

In step S14 shown in FIG. 2, the offset point calculation unit 60 calculates an offset point whose shortest distance to the processing surface 22a is approximately the offset distance r using the offset grid point gf determined in step S12.
With reference to FIG. 12 and FIG. 13, a process in which the offset point calculation unit 60 calculates an offset point will be described. As shown in FIG. 12, first, the offset point calculation unit 60 subtracts the radius r of the neighboring region R from the offset distance r around the offset grid point gf determined to be the offset grid point in step S10. A third determination region U3 of −a and a fourth determination region U4 of radius r + a obtained by adding the radius a of the neighboring region R to the offset distance r are determined. Next, the offset point calculation unit 60 determines that the nearest point p on the processing surface 22a is out of the third determination region U3 from the curved lattice point gm group existing in the second determination region U2 specified in step S12. And located within the fourth determination region U4. In the example shown in FIG. 12, the closest point p1 with respect to the curved grid point gm1 and the closest point p2 with respect to the curved grid point gm2 are located outside the third determination region U3 and within the fourth determination region U4. Two curved surface grid points gm1 and gm2 are specified.

As illustrated in FIG. 13, the offset point calculation unit 60 then calculates offset candidate points q1 and q2 for each of the two specified curved surface grid points gm1 and gm2. The offset candidate point q1 is a point obtained by offsetting the nearest point p1 on the processing surface 22a with respect to the curved lattice point gm1 by an offset distance r toward the offset lattice point gf. Similarly, the offset candidate point q2 is a point obtained by offsetting the nearest point p2 on the processing surface 22a with respect to the curved grid point gm2 by the offset distance r toward the offset grid point gf.
Next, the offset point calculation unit 60 calculates signed distance values d1 and d2 from the offset candidate points q1 and q2 to the offset grid point gf for each of the offset candidate points q1 and q2. The signed distance values d1 and d2 are calculated using the following formula, di = (distance between the nearest point pi and the offset grid point gf) − (offset distance r). That is, the signed distance values d1 and d2 indicate the distance between the offset candidate points q1 and q2 and the offset grid point gf, and the offset candidate points q1 and q2 are farther from the machining surface 22a than the offset grid point gf. If it is located, it takes a negative value, and if the offset candidate points q1, q2 are located closer to the machining surface 22a than the offset grid point gf, it takes a positive value.
Finally, the offset point calculation unit 60 determines the offset point having the smallest signed distance values d1 and d2 from the offset candidate points q1 and q2. In the example shown in FIG. 14, the offset candidate point q1 is determined as the offset point from the offset candidate points p1 and p2. That is, the offset point q1 is moved by the offset distance r toward the offset grid point gf, the closest point p1 located closest to the offset grid point gf among the nearest points p1 and p2 on the processing surface 22a. It will be a thing. The offset point calculation unit 60 records the calculated offset point q1 in the offset plane data 30 of the data storage unit 20. Thus, one offset point q1 is obtained for the offset grid point gf.

In step S16 of FIG. 2, as shown in FIG. 15, the temporary offset grid point data creation unit 56 uses the 26 three-dimensional grid point g groups adjacent to the offset grid point gf as temporary offset grid points. It is added to the point data 26. The 26 three-dimensional lattice points g adjacent to the offset lattice point gf may be offset lattice points. Therefore, the 26 three-dimensional lattice points g adjacent to the offset lattice point gf are recorded in the temporary offset lattice point data 26, and the above-described processing is applied to the 26 three-dimensional lattice points g adjacent to the offset lattice point gf. By executing the above, it is possible to obtain the offset grid point gf and the offset point q without omission.
In step S18 of FIG. 2, it is determined whether or not the processing has been completed for all temporary offset grid points gf described in the temporary offset grid point data 26. Until the processing is completed for all the temporary offset grid points gf, the processing in steps S <b> 10 to S <b> 16 is repeatedly performed, and the offset point q is recorded in the offset plane data 30. Finally, the offset surface q 30 is recorded with an offset point q group offset by the offset distance r from the processing surface 22a. That is, an offset surface model is obtained in which an offset surface offset by an offset distance r from the processing surface 22a is expressed by the offset point q group.

Specific examples of the present invention have been described in detail above, but these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and changes of the specific examples illustrated above.
The technical elements described in this specification or the drawings exhibit technical usefulness alone or in various combinations, and are not limited to the combinations described in the claims at the time of filing. In addition, the technology illustrated in the present specification or the drawings achieves a plurality of objects at the same time, and has technical utility by achieving one of the objects.

The block diagram which shows the structure of the preparation apparatus of an offset surface model. The figure which shows the processing flow which the preparation apparatus of an offset surface model performs. The figure which shows an example of the curved surface which curved surface data describes. The figure which shows the three-dimensional lattice point group set to the three-dimensional space. The figure which illustrates a curved surface lattice point group. The figure which shows the procedure which specifies a curved surface grid point group. The figure which shows the three-dimensional lattice point in which the vertex of a basic shape exists in a near region. The figure which shows the three-dimensional lattice point in which the ridgeline of a basic shape exists in a near region. The figure which shows the three-dimensional lattice point in which the surface of a basic shape exists in a near region. The figure which illustrates a temporary offset lattice point. The figure which illustrates the 1st judgment field and the 2nd judgment field. The figure which illustrates the 3rd judgment field and the 4th judgment field. The figure explaining the process which selects an offset point from an offset candidate point. The figure which illustrates the three-dimensional lattice point adjacent to an offset lattice point.

Explanation of symbols

10. · Offset surface model creation device 20 ·· Data storage unit 22 · Curved surface data 24 ·· Curved surface lattice point data 26 ·· Temporary offset lattice point data 28 ·· Offset lattice point data 30 ·· Offset surface data 50 · -Data creation unit 52-Grid point setting unit 54-Curved grid point data creation unit 56-Temporary offset grid point data creation unit 58-Offset grid point data creation unit 60-Offset point calculation unit

Claims (3)

An apparatus for creating an offset surface model offset from a curved surface by a predetermined offset distance based on curved surface data describing the curved surface,
Means for storing curved surface data describing curved surfaces arranged in a three-dimensional space;
Means for arranging three-dimensional lattice points at predetermined intervals in a three-dimensional space in which the curved surface data describes a curved surface, and setting a neighborhood region of a predetermined radius for each three-dimensional lattice point;
A first three-dimensional lattice point where the curved surface passes through the vicinity region and a nearest point on the curved surface with respect to the first three-dimensional lattice point are specified, and a data group of a pair of the first three-dimensional lattice point and the nearest point is obtained. Means for creating first grid point data to be described;
For each pair of data of the first 3D grid point and the nearest point described in the first grid point data, an offset direction is determined from the relative position of the first 3D grid point and the nearest point, and the nearest point Is obtained by calculating a temporary offset point obtained by moving an offset distance in the offset direction by the offset distance, specifying a second 3D lattice point where the temporary offset point exists in the vicinity region, and describing a specified second 3D lattice point group Means for creating grid point data;
From the second three-dimensional lattice point group described in the second lattice point data to the first three-dimensional lattice point located closest in the first three-dimensional lattice point group described in the first lattice point data Means for identifying a third three-dimensional lattice point group whose distance is a predetermined offset determination range, and creating third lattice point data describing the identified third three-dimensional lattice point group;
For each third 3D grid point described in the 3rd grid point data, the nearest point located in the nearest point group described in the 1st grid point data is determined as the third 3D grid point. Means for calculating an offset point moved by an offset distance toward the point, and creating offset plane model data describing the calculated offset point group;
Means for adding a three-dimensional lattice point group adjacent to the third three-dimensional lattice point described in the third lattice point data to the second lattice point data;
A device for creating an offset surface model.   The offset determination range used by the third grid point data creation means is a range from a value obtained by subtracting the diameter of the neighboring area from the offset distance and a value obtained by adding the diameter of the neighboring area to the offset distance. The creating apparatus according to claim 1. A method of creating an offset surface model offset from a curved surface by a predetermined offset distance based on curved surface data describing the curved surface,
Preparing curved surface data describing curved surfaces arranged in a three-dimensional space;
Placing three-dimensional grid points at predetermined intervals in a three-dimensional space in which the curved surface data describes a curved surface, and setting a neighborhood area of a predetermined radius for each three-dimensional grid point;
A first three-dimensional lattice point where the curved surface passes through the vicinity region and a nearest point on the curved surface with respect to the first three-dimensional lattice point are specified, and a data group of a pair of the first three-dimensional lattice point and the nearest point is obtained. Creating a first grid point data to be described;
For each pair of data of the first 3D grid point and the nearest point described in the first grid point data, an offset direction is determined from the relative position of the first 3D grid point and the nearest point, and the nearest point Is obtained by calculating a temporary offset point obtained by moving an offset distance in the offset direction by the offset distance, specifying a second 3D lattice point where the temporary offset point exists in the vicinity region, and describing a specified second 3D lattice point group Creating grid point data;
From the second three-dimensional lattice point group described in the second lattice point data to the first three-dimensional lattice point located closest in the first three-dimensional lattice point group described in the first lattice point data Identifying a third three-dimensional lattice point group whose distance is a predetermined offset determination range, and creating third lattice point data describing the identified third three-dimensional lattice point group;
For each third 3D grid point described in the third grid point data, the nearest third point in the nearest point group described in the first grid point data is determined as the third tertiary grid point. A step of calculating an offset point moved by an offset distance toward, and creating offset plane model data describing the calculated offset point group;
Adding a three-dimensional lattice point group adjacent to the third three-dimensional lattice point described in the third lattice point data to the second lattice point data;
A method of creating an offset surface model comprising:

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