JPS6364110A - Processing information generating system for free curved surface evading tool interference - Google Patents

Abstract

(57) [Abstract] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Industrial Field of Application] The present invention is an NC machining machine that uses a three-dimensional free-form surface. [Summary of the Invention] When generating tool path data for a numerically controlled machine tool from data of a three-dimensional free-form surface Next, we perform a polyhedral analysis consisting of surface elements for cutting, take out the surface elements one by one, and sample the planes parallel to the Z axis to find the (X
, Z") coordinates, and if the intersection lines on one sampling plane overlap with respect to the X coordinate, the tool interference is removed by taking the intersection line with the largest X coordinate. This system improves data generation efficiency and sampling accuracy, enabling high-speed processing.

[Conventional technology]

A CAD/CAM system that handles three-dimensional free-form surface data inside a computer and generates NC data (tool path data) for automatically machining final products or molds using NC machine tools, etc. is now in practical use. It is becoming more and more popular.

A conventionally known method for generating tool paths is APT (Automatically Prog.
The main body of APT is a general-purpose automatic programming language for multi-axis contour control that has a writing style similar to English. This language contains instructions regarding the geometry of the workpiece and tool, the movement of the tool relative to the workpiece, machine tool functions, tolerances, arithmetic calculations, etc.
Contains definitions. When a program written in this language is run on a large computer, it is possible to output NC tape.

On the other hand, when handling curved surfaces such as the outer diameter of a product in a computer, the B5zier formula and B-3pline formula have favorable properties for design such as good shape controllability (easy deformation and modification) and easy calculation. A parametric representation format using is often used.

[Problem that the invention seeks to solve]

The most fundamental problems inherent in tool path generation are the problem of data generation efficiency considering machining accuracy and the problem of tool interference determination.

In the APT described above, the user instructs (programs) the tool forward path, and as a result, cutting data for a free-form surface is generated, and the tool path is automatically generated from the geometric model generated within the computer. Not 0 originally CAD/CA
The M system improves efficiency as a whole by transmitting shape information during design to machining, but unlike APT, design is done separately and the tool path for machining is programmed while keeping the required shape in mind. Therefore, no improvement in efficiency can be expected.

On the other hand, a parametrically expressed curved surface is convenient for shape definition because it does not depend on the coordinate system.

However, since the coordinate system of machine tools that cut curved surfaces is fixed, machining data (
tool path data) cannot be converted with high accuracy.
For this reason, machining accuracy decreases.

In addition, when directly cutting based on parametric expression,
It is technically difficult to check for interference (collision) between the tool or tool holder and the finished shape, resulting in the inconvenience of cutting off the necessary portion.

In other known methods of surface representation using polyhedral approximation, sufficient machining accuracy cannot be obtained unless a huge amount of data that exceeds the processing capacity is handled. Therefore, it is impossible to expect to generate processing data in a short time that is practical. If the number of data representing the curved surface is reduced in order to perform high-speed processing, the processing accuracy will become rough, making it impossible to satisfy the designed tolerance of the curved surface.

SUMMARY OF THE INVENTION In view of the above-mentioned problems, it is an object of the present invention to generate tool path data that satisfies required machining accuracy at high speed while determining tool interference and non-interference.

[Means for solving problems]

The present invention processes data representing a three-dimensional free-form surface to
This is a system that generates tool path data for a numerically controlled machine tool that controls at least three axes, such as a C-milling machine.

A means is provided for dividing the free-form surface into cutting surface elements and generating an offset polyhedron offset from the free-form surface according to the shape of the tool.

For each of the above-mentioned surface elements, in order to set a tool path on the intersection line between the surface element and a group of planes that are parallel to one of the three axes (Z-axis) and spaced at a predetermined interval in the Y-axis direction, means for calculating and storing the orthogonal coordinate values (X, Z) of the starting end, P, and end of each intersection line.

When a plurality of intersection lines belonging to one of the plane groups overlap with respect to the X coordinate, means is provided for selecting the one having the maximum Z coordinate among them.

The method further includes means for generating tool path data along the selected intersection line.

[Effect]

It is a tool path generation system most suitable for numerically controlled machine tools with three-axis control J that has an orthogonal coordinate system (XYZ axes), and performs tool interference removal processing at high speed in an orthogonal coordinate system.

The process of generating the offset polyhedron and the process of calculating the tool path from the offset polyhedron are separated, and the tool path is calculated using the orthogonal coordinate system, but the generation of the offset polyhedron uses Bezier surface, B-aplins surface, Co
It can be based on a representation format of a geometric surface such as an ons surface. Therefore, it is possible to process a wide variety of curved surfaces without depending on the data structure of the curved surface representation.

Furthermore, even if the workpiece is composed of multiple curved surfaces, it can be handled in the same way as a single curved surface.

Further, tool interference removal processing is performed only once for each surface element constituting the offset polyhedron, and redundant calculation processing does not occur, so tool path data can be generated efficiently and at high speed.

〔Example〕

G1 Overall configuration of the system> FIG. 1 shows the overall configuration of the CAD/CAM system of the embodiment. In FIG. 1, the free-form surface generation processing system 1 is
In the part corresponding to CAD, shape data of a geometric model expressing the three-dimensional free-form surface of the object is generated based on input operations by an operator, and is stored in a file. The objects are machined parts and molds.

The generated shape data is converted into machining data, that is, data for determining the movement path of the cutting tool, in the free-form surface cutting tool path generation system 2.

The processing data is downloaded to a floppy disk, and automatic processing is performed by loading the floppy disk into the NC milling machine 3 (NC milling machine or machining center).

The free-form surface generation processing system 1 and the free-form surface cutting tool path system 2 are actually computers, and are attached with an input device 4 such as a keyboard or digitizer, and a display device W5 such as a CRT for a user interface.

The tool path generation system 2 takes into account (1) the shape accuracy of the free-form surface (2), the surface roughness of the free-form surface (3), and tool interference check, and generates machining data at high speed. It works with a devised algorithm.

<G2: Configuration of tool path generation system> As shown in FIG. 2, the tool path generation system includes a plurality of program modules that are activated sequentially or in parallel. Each program module can be thought of as a dedicated data processor and will therefore be referred to hereinafter as a processor.

First, the accuracy determination preprocessor 21 and the surface roughness determination preprocessor 22 are activated in the preliminary processing stage.

The precision determination preprocessor 21 determines the division fineness for dividing the curved surface of the geometric model generated in the CAD stage into a large number of quadrilaterals (or triangles) based on the tolerance specified for the target workpiece. Determine. With this polyhedral division,
A cutting shape (cutting model) approximated within tolerances can be generated. By polyhedral approximation that takes tolerances into consideration, it is possible to determine an optimal tool path for performing cutting that is not unnecessarily highly accurate and satisfies design specifications.

When the error between the radius of curvature ρ of the geometric surface and the distance from its center to the approximate polyhedron is δ, the size of each side of the approximate polyhedron is determined so that δ is within the specified intersection according to the formula 2 = 2h−corot i. difference! , the finishing accuracy preprocessor 21 determines the sampling width on the hanging geometric model curved surface.

The tool path is set on the generated polyhedron.

In other words, the tool cuts a curved surface while moving minutely in a straight line from point to point in space. Such cutting processing can be realized with a normal three-axis controlled NC milling machine.

Note that the actual tool path is set on a virtual offset polyhedron offset from the cutting edge of the tool to the tool center (tool movement command position) with respect to the machining surface.

Next, the surface roughness determination preprocessor 22 determines the feed width (feed pitch) of the tool based on the surface roughness specified for the target workpiece. Generally, if the tool feed width is narrow,
The surface is cut more smoothly. However, if the tool feed width is halved, the amount of data defining the tool path will double. Therefore, the tool feed width must be set optimally to obtain the required finished surface roughness with minimum tool path data. The surface roughness determination preprocessor 22 includes an algorithm for calculating a tool feed width that satisfies a given surface roughness.

When using a ball end mill (radius R) as a cutting tool, the surface roughness determination preprocessor 22 determines the roughness so that the height H of the amount of uncut material on the machined surface satisfies the specified surface roughness.
Determine the tool feed width Δ using the formula.

The data on the division fineness of the offset polyhedron and the tool feed pinch obtained by the accuracy determination preprocessor 21 and the surface roughness determination preprocessor 22 are passed to a tool path generation processor consisting of a rough cutting processor 23 and a finishing processor 24. , based on these, the curved surface data of the geometric model is sequentially processed to finally generate tool path data. Note that rough machining and finish machining differ only in the size of the tool, the feed width, and the presence or absence of a finishing allowance, and the data processing algorithm can be considered to be the same. Additionally, tolerances and surface roughness do not need to be considered during the rough cutting process.

The most important function of these tool path generation processors 23 and 24 is to determine a tool path that avoids tool interference. Tool interference is most likely to occur during rough cutting processes where the outside diameter of the tool is large. Furthermore, by devising the tool path generation algorithm, these processors 23 and 24 can generate tool paths at high speed.

The generated tool path data is sent to the NC milling machine 3 shown in FIG. 1 using a floppy disk or the like as a medium in the order of rough cutting and finishing, and milling is performed on the block material.

Note that the tool path generation system shown in FIG. 2 is attached with a parameter cutting processor 25, and it is also possible to directly perform cutting based on the original curved surface shape data expressed in parameters. Although this processor 25 does not perform a tool interference check, for curved surfaces for which it is predicted that no interference will occur, parameter cutting can be selected depending on the shape of the curved surface.

Furthermore, the tool path generation system includes a tool path display processor 26 and an interference location display processor 27. By displaying three-dimensional images by these processors, tool paths and tool interference can be visually recognized.

Each processor or pre-processor of the tool path generation system can communicate with input/output devices through a user interface module 28 . Using input/output devices such as a keyboard, display, and XY plotter, an operator can operate each processor and obtain processing results.

FIG. 3 shows a processing flowchart of the tool path generation system of FIG. 2. First, curved surface data is read from a computer file (input Pi). Next, the curved surface data is displayed and the data is confirmed (display P2). Next, proceed to the roughing process,
Generates a tool path for rough cutting. In the rough cutting process, first, the finishing allowance and tool diameter are specified (operation P3). Based on these specified values and the curved surface data, the rough cutting processor 23 (routine P4) generates a tool path that avoids tool interference. Using the data generated, the rough cutting tool path, cutting start point, and cutting end point are displayed (display P
5). At this time, if there is an unavoidable tool interference location, this is displayed (display P6).

If tool interference occurs (judgment P7), the process returns to operation P3 to change the tool diameter and generates the tool path again.

If it is determined in determination P7 that there is no tool interference, the process proceeds to the next finishing process. In this process, first, the finishing tool diameter is specified (operation P8). Furthermore, the tolerance class (allowable tolerance) of the registered general tolerance table is specified (operation P9). Next, the buri processor 21 (
The routine P10) is started, and the finishing accuracy (fineness of division into offset polyhedrons) is determined by comparing the specified tolerance table with the cutting dimensions. Furthermore, the surface roughness value specified in the design drawing is manually determined (operation pH). Based on this specified surface roughness value, the tool feed width is determined by the finished surface roughness determination preprocessor 22 (routine P12).

Next, the finishing milling processor 24 (routine P13) is activated to generate a finishing milling tool path based on the polyhedral division fineness and tool feed width data determined by the allowable tolerance and designated surface roughness.

Based on the generated tool path data, the tool path for finish cutting is displayed, and the tool interference location is also displayed (displays P14, PI3). If tool interference has occurred, the process returns from judgment P16 to operation P8, partially changes the finishing tool path, and generates the tool path again. If the interference is removed by this tool change, the generated tool path data is written to a file and the series of processes ends.

<G.: Basic concept of tool path generation process> The tool path generation process consisting of the rough cutting processor 23 and the finish cutting processor 24 basically generates an offset polyhedron from the curved surface data of the geometric model, and generates the tool from this polyhedron. This is a procedure for generating interference-free tool path data at high speed.

When cutting point A of the free-form surface S with the ball end mill 10 as shown in FIG. 4, point A becomes the contact point between the free-form surface and the blade surface of the ball end mill. In this case, ball end mill 1
The vector AO connecting the center ○ of the sphere of 0 and point A becomes the normal vector at point A of the free-form surface. This vector is called an offset vector.

In general, an offset vector at a point on a curved surface is a vector that starts from that point and ends at a reference point set in the tool when a tool is brought into contact to cut that point. Vector F is generally a function F (n) of normal vector n.

In the case of a ball end mill, F (n)=rn (r is the radius of the spherical part).

Considering offset vectors at all points on a free-form surface, the end points form one curved surface. If this curved surface is called an offset curved surface, the desired free-formed surface can be machined by moving the tool so that the center of the tool is clearly on the offset curved surface.

The simplest method for generating a tool path based on an offset-knot curved surface is to consider a sequence of points to be cut on a free-form surface, and use the end point of the offset vector at each point as the sequence as the tool path. This method is mainly used for free-form surfaces expressed by parametric lines.

For example, consider a free-form surface expressed parametrically as shown in FIG. The order 1P(x, t, 2) of a point on the surface is given as the period of parameters u, v by x=f, (u, v) )' = ft (us v) z” fs (uS v) .For such a curved surface, if u and v are given, the points on the curved surface and the normal direction can be easily found, so by changing u and v, the point sequence (A) as shown in Figure 6 can be obtained. , and the corresponding point sequence (0) at the center of the tool can be obtained as the tool path.

Another method, as shown in FIG. 7, is to generate a corresponding offset curved surface from a free-formed surface and designate points on the offset curved surface as parametric links to generate a tool path. For example, if the free-form surface is expressed by the following formula, x"" g+(u, v) = C
Eye u3+ Cl2u” V +Cl5uV” +c, 4
v” +C,su” +CIhuV+CBV” +C1
11u+c, 9v+c, ^y=gt<u,v)=C2,
uko+c2□u”v+cz3uv” +C! 4V'+
CBu” +cz6uv+CHV” +cBu+c2.
v+c2Az = g3(u+'/) = C
ff1u' + C3zu" V +c, 3u
v"+c34v'+c35u" 10 C34
uV+c,,v2+C,8u+c39v+
Considering the offset vector at points P, ˜P1° of the C3A free-form surface point 10, the offset curved surface can be obtained as a curved surface passing through the end points Q1˜Q1°. In this offset curved surface, a tool path can be generated by changing parameters U' and V''.

The tool path generation method described above does not take tool interference into consideration. For example, if an attempt is made to cut part A as shown in FIGS. 8a and 8b, a necessary part in the vicinity thereof will be cut off. This is tool interference caused by the tool shape. Alternatively, as shown in FIG. 9, unless the angle of the ball end mill is changed, there may be cases where it is impossible to avoid tool interference and cut part A. This is tool interference caused by the setting conditions of the machining axis.

To find tool interference, you can calculate the intersection of the ball end mill and the target free-form surface, but it takes a lot of calculation time to obtain a certain degree of accuracy, so tool interference is actually detected. The tool path is generated while being checked by humans to ensure that this does not occur.

In order to solve such a tool interference problem, a verification method in the Z-axis direction as shown in FIG. 10 can be used. In this method, the axis of the ball end mill is set in the Z-axis direction, a straight line l parallel to the Y-axis is considered, and the intersection of this line and the offset curved surface is determined. When tool interference occurs, the tool path on the offset curved surface draws a loop as shown in the figure, so a plurality of intersection points H1, H2, and H3 are found for one straight line l.

A point H3 having the largest value (height) in the Z-axis direction of these intersection points becomes a point on the offset surface where tool interference is avoided. Such an offset curved surface is x of straight line l,
It is expressed by the y coordinate and the two coordinates of the intersection.

<G4: Specific example of tool path generation process> A specific tool path generation process based on the above-mentioned principle basically consists of the following steps.

The first step is to generate an offset polyhedron from the two free-form surfaces.

Second step: Find the highest position of the offset curved surface at the top point of the XY 1000 screen.

As an algorithm for the second step, the ``segment height method'' in which the Y-axis is calculated with respect to a line segment on the offset plane drawn along the scanning line parallel to the X-axis will be described in detail below.

This algorithm basically provides a solution to the problem of finding the outer envelope of an offset surface.

That is, as shown in FIG. 11, there is a tool path free from interference on the upper surface in the Z-axis direction of the overlapping offset curved surfaces 1.2.

Figure 12 shows the characteristics of the segment height method. In this method, the offset surface is sampled only in one direction along the Y axis, for example, so that the tool path can be generated with high accuracy. That is, line sampling is performed. In other words, sampling is performed at equally spaced positions whose y coordinate is (y,). Consider a plane y=yJ at each position, and find a group of line segments corresponding to the intersection lines when the cross section of the offset polyhedron is taken along this plane.

Each of the line segment groups is obtained by sequentially connecting the intersection points of each side of the rectangle forming the offset polyhedron and the plane y''y.

Next, based on the group of line segments obtained in this way, the 13th
As shown in the figure, by generating a line segment group having the maximum height in the Z-axis direction, a tool path without tool interference can be obtained.

FIG. 14 shows the processing procedure of the segment height method.

Step 1 (Figure 15) Find the normal vector n at the grid point on the geometric model surface. Each grid point (sample point) is obtained by arranging the grid points on the curved surface in a grid pattern so as to satisfy the required tolerance based on the result (sampling interval β) of the accuracy determination preprocessor 21 described above. The lattice spacing, that is, the fineness of division into polyhedrons, is determined by the curvature of each curved surface and the specified tolerance class.

Note that FIG. 15 shows one sheet (punch) of surface elements constituting the geometric model, which is expressed in a libarametric manner by 16 control points. When this patch is subdivided into a grid, the results from the precision determining preprocessor 21 are used to perform division so that the final finished shape falls within the tolerance.

Step 2 (Fig. 16) Obtain an offset vector F from the normal vector n at each point. The function F (n) is determined by the tool shape.

Step 3 (FIG. 17) Each quadrilateral on the offset curved surface determined by the end point of the offset vector is divided into two to obtain an offset polyhedron whose surface elements are quadrilaterals. Note that since a quadrilateral does not form a plane, an offset polyhedron cannot be accurately generated.

Step 4 (18th flash) A memory array is prepared to store a group of line segments on the offset plane corresponding to each sampling position Wyj in the Y-axis direction. One line segment is represented by the coordinate values of the starting end (X18, z!3) and the coordinate values of the ending end (Xis, Z te).

Note that the sampling interval is equal to or less than the tool feed width Δ calculated by the surface roughness determining pre-processor 22 described above so as to satisfy the surface roughness specified in the drawing.

Step 5 (Figure 19) Take out one quadrilateral element from the grid on the offset plane,
The minimum value ymin and maximum value ymsx of the y coordinate are determined.

Step 6 (Fig. 20) For y that falls in the interval from sin to y□8, find the intersection points (two) between the plane y-yi and the quadrilateral, and store the coordinates of the intersection in the memory array for each y ( Xi,, Zil) (X
i23. ) and repeat this for all quadrilaterals.

Step 7 (FIGS. 21 and 22) For each yi, the line segment group data is used to convert to the highest line segment data in the Z-axis direction. In other words, if a plurality of line segment groups overlapping in the Z-axis direction are obtained for y as shown in Figure 21, all but the top line segment group are deleted and a new line is created as shown in Figure 22. Generate subgroup data. The obtained line segment group data represents a tool path that avoids tool interference.

Step 8 (23k) A tool path can be determined using the coordinate data of the group of line segments in the memory array of FIG. 18 thus obtained. For example, as shown in FIG. 23, while scanning the tool continuously in the X-axis direction at a constant speed, Z-axis control is performed so that the tool height in the Z-axis direction matches each line segment. The tool is moved in steps of pitch Δ in the Y-axis direction. In order to shorten machining time, it is preferable to move the tool along the X axis in a reciprocating manner.

Takarin performance algorithm of segment 1 method Next, a method for speeding up the arithmetic processing required in step 7 of FIG. 14 (FIG. 22) will be described.

The calculation performed in step 7 is a process of generating the highest line segment group with respect to the Z axis, and is the process that takes the most time. The arithmetic processing is performed on the positional relationships of line segments consisting of the two types shown in FIG. 24 a and b and their combinations. Type a is an overlamp of two line segments, and type b is a cross of two line segments. In either case, the line segment is redefined to eliminate the dotted line portion.

In type a, line segment P+Pz and QIQ2 overlap. If point P1 is above line segment Q+Qz, straight line x
The intersection point h' between =P+x and line segments Q and QZ is determined, and line segments P+Pz and Q+P+', which are located higher on the Z axis, are obtained as line segments with no overlap.

In type b, line segment P+Pz intersects Q and Q2, so first find the intersection R2. Among the four line segments generated in this way, the one located above with respect to the Z axis is selected to obtain two line segments P+Rz and R+Qz without a cross.

FIG. 25 shows details of the processing procedure in step 7.

In step 6, the end points of the group of line segments representing the offset surface are stored in the memory array in the order determined for each y. Each line segment is P isP , e (i = 1.2-・
・−・−・−・・n, s represents the start end, and e represents the end point), the coordinate data of each end point in the memory is P
1s=(Xis, 21.) Pis=(x盈"is).

Step 7-1 Xis and X, so that Xis becomes Xie. exchange with. In other words, for a line segment whose direction from the starting end to the ending point is in the negative direction of the X axis, X. 〈X, . Therefore, orientation is performed so that only the X coordinates of the starting end and the ending end are exchanged so that all line segments face in the positive direction of the X axis. Since the two coordinates do not change, the height of each line segment, that is, the tool path itself does not change. The purpose of orientation is to limit the tool path to one direction of the X-axis.

Step 7-2 Each line segment p is p is is converted to X8. Sort (rearrange) in ascending order of (starting end coordinate). Through this sorting, regardless of the order in which the line segments are sampled, the line segments are rearranged in the order of increasing X coordinates, and tool paths are generated in that order.

Step 7-3 1st and 1+1st adjacent line segments PisPi P phase
, P... 1... Take out... ■ In the case of X 111 = Since there is not, increment i by 1 and extract two new line segments.

■ When X i@<X i,, + * (Figure 27) If the X coordinates of the end of the previous line segment and the start of the next line segment are far apart, the predetermined 2i,, A line segment Q with a height of
+ Insert QZ after p is p , . Due to the insertion, Q+ QZ becomes P i and 1+ S P i. 1
．． .

, and subsequent subscripts are shifted by month.

Furthermore, i is incremented by +1 and the next process is performed. Note that in order to facilitate the insertion and movement of data within the memory, line segment arrangement and data management are actually performed using a pointer structure.

■ In the case of Xie 〉xi+l+s (Fig. 28) If the end of the previous line segment is behind the start end of the next line segment with respect to the X-axis, there will be an overlamp between the line segments and tool interference will occur. ing. In this case, as shown in Figure 28, 2
A line segment is divided into a maximum of four sections I to ■.

(a) If Xis≠Pi41+1, section I exists.

(b), line segment PisPi. and P i+l+ S P i
41+ @ intersects, there is an intersection R8,
Sections ■ and ■ can be created. If they do not intersect, ■ and ■ are 1.
There will be two sections.

(C), Xzl≠X, and 11. In the case of , an interval ■ exists.

Next, select the line segment above the X-axis in the sections ■ and ■. Furthermore, the original line segments PisPi* and Pi+l+IP.

1. . is deleted from the data, and the newly obtained four line segments S1 to Sv are x! Insert in the interval 1≠X1+1+@.

The above step 7-3 is repeated until i=n. However, the value of n (tt number) changes during processing.

Through the above processing, it is possible to detect the portion where tool interference occurs and eliminate the interference. Note that in areas where there is no interference, the process simply goes through a loop that goes through the process 1 or 2 in FIG. 25, so very high-speed processing is possible.

In contrast, in the segment height method as described above, as shown in the outline in Figure 29, one quadrilateral is extracted from the offset polyhedron, sampled on the plane y, and once all the quadrilaterals are stored in the memory area corresponding to yj. The line segment data of is stored, and calculations to remove tool interference are performed based on this data. Since the line segment data is stored in the memory in an appropriate order, it is necessary to perform sorting on the X coordinate as described above. However, since the segment height method handles only the coordinate data of both ends of the line segment, the memory area may be small. Therefore, the segment height method is more efficient in generating tool paths, and can generate highly accurate tool paths with a small-capacity data processor.

FIG. 30 shows a block diagram of a tool path generation system using the segment height method. Each block corresponds to the following program module.

IVIDE B6zi Generate an offset polyhedron from the er curved surface (note that the surface element is a quadrilateral and not a plane).

In addition, an offset polyhedron is generated to compensate for discontinuous positions and tangential planes at the silicon boundary.

LICE Offset/Cut the polyhedron on a plane perpendicular to the Y axis,
Generate line segments.

PVECT Perform calculations to remove tool interference.

RPATH Remove incorrect line segment data caused by calculation errors, etc.

It also removes useless data such as integrating parallel line segments.

〔Effect of the invention〕

As described above, the present invention separates the process of approximating a geometric surface with an offset polyhedron and the process of generating a tool path from the offset polyhedron. Tool path data can be generated.

Tool interference removal processing is performed only once for each surface element constituting the offset polyhedron, and no duplicate calculation processing occurs, so tool path generation is efficient (and high-speed processing is possible).

The tool path is expressed as line segment data (coordinates at both ends of a straight line) obtained by cutting an offset polyhedron for each sampling plane, so there is no deterioration in accuracy due to sampling, and the processor that handles the data can be small-sized, making it extremely easy to use. A practical automatic addition system is obtained.

[Brief explanation of drawings]

FIG. 1 is a block diagram of the overall configuration of a CAD/CAM system showing an embodiment of the tool path generation system of the present invention, FIG. 2 is a block diagram of the tool path generation system, and FIG.
The figure is a flowchart of the data processing procedure of the tool path generation system. Figure 4 is a diagram showing the relationship between a free-form surface and an offset curved surface, and Figure 5 is a diagram showing a free-form surface expressed parametrically.
Fig. 6 is a diagram showing one method of generating a tool path from a free-form surface, Fig. 7 is a diagram showing one method of generating a tool path from an offset curved surface, and Fig. 8 is a diagram showing a method of generating a tool path from an offset curved surface. FIG. 9 is a cross-sectional view showing tool interference caused by the setting conditions of the machining axis, and FIG. 10 is a cross-sectional view showing a tool interference verification method. Fig. 11 is a line diagram showing the outer surface of an offset curved surface that avoids tool interference, Fig. 12 is a line diagram showing the principle of the segment height method, Fig. 13 is a line diagram of a group of line segments with tool interference removed, and Fig. 12 is a line diagram showing the principle of the segment height method. FIG. 14 is a flowchart showing the processing procedure of the segment height method. Fig. 15 is a diagram of the geometric surface corresponding to step 1 of the flowchart in Fig. 14, Fig. 16 is a ria diagram of the offset vector corresponding to step 2, and Fig. 17 is a diagram of the offset polyhedron corresponding to step 3. , FIG. 18 is a diagram showing the sampling position and data memory arrangement corresponding to step 4, FIG. 19 is a diagram showing the quadrilateral plane elements of the offset polyhedron corresponding to step 5, and FIG. 20 is a diagram corresponding to step 6. Fig. 21 is a diagram showing the position of the line segment group corresponding to step 7.
2 is a diagram of a line segment group subjected to tool interference removal processing corresponding to step 7, and FIG. 23 is a diagram of a tool path corresponding to step 8. 24a and 24b are diagrams showing overlap and crossing of line segments in the segment height method, FIG. 25 is a flowchart showing details of the processing procedure of step 7 in FIG. 33,
FIGS. 26 to 28 are diagrams showing various B types of positional relationships between two adjacent line segments. FIG. 29 is a diagram showing an outline of the processing procedure of the segment height method, and FIG. 30 is a block diagram of the tool path generation system. In addition, in the symbols used in the drawings, 1-・-・・・・・・・・・・Free-form surface generation processing system 2・・・・・・・・・・・・Free-form surface cutting tool Path generation system 3・・・・・・・・・NC milling machine 4・・・・・・・−・・・・・Human power device 5・・・・・・--- Display 21 --- Accuracy determination preprocessor 22 --- Surface roughness determination pre-processor 23 - - - - - - - Processor for rough cutting 24 - - - - - Processor for finish cutting.

Claims (1)

[Claims] A system for processing data representing a three-dimensional free-form surface to generate tool path data for a numerically controlled machine tool with at least three-axis control, which divides the free-form surface into cutting surface elements. and means for generating an offset polyhedron offset from the free-form surface according to the shape of the tool; means for calculating and storing orthogonal coordinate values (X, Z) of the starting and ending points of each line of intersection on each of the planes in order to set a tool path on the line of intersection with the group of planes; When a plurality of intersection lines belonging to one overlap with respect to the X coordinate, means for selecting the one with the largest Z coordinate among them, and means for generating tool path data along the selected intersection line. A free-form surface machining information generation system that avoids tool interference.