JPH052416A - Nc data producing method for 5-axis side cutting process - Google Patents

Abstract

PURPOSE:To prevent the interference between a tool and a bottom surface in the case of the side cutting process of the simultaneous 5-axis control by calculating the distance between the bottom surface and a free-form curved surface to be an object in the side cutting process and the position of the tool. CONSTITUTION:The XY coordinate values and the point TP2 on a bottom surface of a tool tip TP1 are found. When the bottom surface of the point TP2 is defined in its entire region, the coordinates of the tip TP1 are obtained according to the conventional method. When the bottom surface of a cutting object is a free-form curved surface, the coordinates of the TP1 is calculated using the coordinate values of the adjacent lattice points approximated by means of the coordinate values of a group of lattice points set at the four corners of patches formed by dividing the free-form curved surface. Based on the obtained coordinates of the TP1, a straight line formed by connecting the TP1 and a lower shape dividing point is supposed as a bottom surface continuous to the dividing point. Then the tool position is corrected so that the tip TP1 is in contact with the straight line. Thus it is possible to produce the NC data obtained by an automatic programming that can prevent the biting of the bottom surface by the tool.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for creating NC data for cutting a free-form surface by side cut of simultaneous 5-axis control by an automatic programming device for creating NC data.

[0002]

2. Description of the Related Art In creating NC data for cutting a free curved surface by simultaneous 5-axis control using a cutting tool such as a ball end mill or a flat end mill, an automatic programming device is used. Coordinate positions on the Y and Z axes and the inclination of the tool axis (A axis around the X axis, Y
The position and orientation are designated by the B axis around the axis.

When NC data for instructing the motion of a tool for cutting a free curved surface by side cutting is created by an automatic programming device, first, the upper and lower shapes (see FIG. 10) of the curved surface (side surface) are formed. Use as a reference curve. Then, the longer value of the upper and lower shapes is divided by the specified pitch, and the fraction is rounded up to an integer (n). Next, by dividing each of the upper shape and the lower shape from the start point to the end point by the above number n, the division points are formed along the upper and lower shapes. Then, the corresponding dividing points in the upper and lower shapes are connected to each other to form a connection. Then, this connection determines the inclination of the tool axis.

Further, the position of the tool tip is designated at a position designated by the lower shape. That is, as shown in FIG. 11, a point where a straight line v extending from the dividing point in the lower shape perpendicular to the line u connecting the dividing point in the lower shape and the dividing point in the upper shape intersects the tool axis s. It is designated as a point TP starting from p and descending from it by a certain distance h along its axis.

[0005]

[Problems to be Solved by the Invention] As shown in FIG.
When the bottom surface is connected to the curved surface (side surface) to be cut, if the position of the tool tip TP is specified to be a certain distance lower than the lower shape as in the conventional case (see FIG. 11),
As shown by hatching in FIG. 12, the tip of the side-cutting tool bites into this bottom surface and causes interference.

Therefore, an object of the present invention is to provide a method of creating NC data which can be side-cut so that the tool does not interfere with the bottom surface.

[0007]

According to the present invention, when a side surface of a free-form surface is side-cut, in order to eliminate the interference with the bottom surface of the tool as described above, the tool is pulled up to a position where the interference does not occur. This is a solution to this problem.

[0008]

First, the coordinate position (xi, yi, zi) of the tip TP of the tool in the connection (i-th) is determined by the conventional method. That is, the coordinate values on the X, Y and Z axes of the tool tip TP shown in FIGS. Then, a point TP3 (xi, yi, zi ') on the bottom surface having the same XY coordinate value as the XY coordinate value of the tool tip TP is obtained (FIG. 13).
reference). By the way, the point TP3 (xi, yi, zi ')
As for, if the bottom surface is defined in the entire region, the value of zi 'can be immediately obtained from the values of xi and yi. However, if the bottom surface is a free-form surface, the coordinate values of the grid points close to the above value zi 'are used for the calculation based on the coordinate values of the grid point groups at the four corners of the patch formed by dividing the free-form surface. To do.

The point TP3 (xi, yi, zi) thus obtained
') And the lower shape dividing point are assumed to be a bottom surface connected to the dividing point, and the tool position is corrected so that the tool tip TP is in contact with this straight line.

[0010]

2 is a block diagram of an essential part of an automatic programming apparatus according to an embodiment for carrying out the method of the present invention.

In the figure, 1 is a processor (CPU), 2 is an RO storing a control program of the programming device.
RAMs 3 and 3 store system programs and part programs loaded from the floppy disk 9, a part program interactively created by the CRT 7 and the keyboard 5, and various data, and a RAM 4 stores created NC data. The NC data storage memory 5 is a keyboard, which has ordinary character keys, ten keys, and various command keys. Reference numeral 6 is a disk controller, 7 is a graphic display (CRT), and these elements 1 to 7 are connected by a bus 8.

First, a flow chart of FIG. 1 shows an outline of creating NC data based on the method of the present invention.
It is assumed that the system program has already been loaded from the floppy disk 9 into the RAM 3 via the disk controller 6.

In step S1 of FIG. 1, curved surface information is input by the NC programming language. This curved surface information includes information about the upper shape and the lower shape of the curved surface (side surface) to be cut, and the bottom surface shape connected to the lower shape. This bottom surface information is given in the form of a set of position information (X, Y, Z coordinate values) of the lattice points of the curved surface forming the bottom surface.

Note that the position information of the bottom face may be given separately in advance for each grid point, for the convenience of considering the XY plane as will be described later. Further, as another method of giving the position information of the bottom surface, in step S1, a reference curve and an operation curve for the bottom surface are given as the curved surface information, and in the next step S2, the coordinates of the grid points are determined by the cutting pitch as the cutting information. You may give it.

In the next step S2, cutting information is input. This cutting information includes the pitch p along the vertical shape, the tool diameter D, the cutting start point, the tool feed rate, and other information.

Then, in the next step 3, the longer value (L) of the upper shape length and the lower shape length of the cutting side surface.
Is taken and divided by the pitch p, and the value is rounded up to the whole number (n).

As a result, the upper shape and the lower shape are each divided into n pieces, and when the corresponding division points are connected, the connection lines t (0), t (1) ... t (i) ... t ( n) can be done (see FIG. 9). In this way, the tool is given a command to move from one connection t (i) to the next connection t (i + 1) at regular intervals.

Next, in step 4 and subsequent steps, the tool tip position is corrected for each wire connection. First, in step S4, the index i representing the connection number is set to zero. In step 5, the tool tip position TP1 at the i-th connection t (i) is determined by the conventional method.
Find (i). That is, it is the coordinate position of a point (TP) that is a certain distance h downward from the point p on the axis in FIG. Then, in step S6, this TP1 (i) is corrected based on the bottom surface shape to obtain a new tool position NTP (i). The details of this procedure will be described later.

The NTP (i) thus obtained is subjected to post processing in step S7 to create NC data and output. If the NTP (i) obtained this time is not for the last connection t (n) (step S8), the next connection t (i + 1)
The same process is repeated for (step S9). When the processing for all the connection lines t is completed in this way, the entire processing ends.

Next, as shown in FIG. 3 for explaining a specific example of the processing in step S6 described below, a point TP2 (i) obtained by projecting the tool tip position TP1 (i) obtained by the conventional method on the XY plane is shown. ) And a grid point group G1 of the bottom surface SS1 projected on the XY plane.

Next, which grid point (four adjacent points) surrounds this point TP2 (i) is determined.

If four grids a, to which the point TP2 (i) is adjacent,
When surrounded by a quadrilateral consisting of b, c and d,
As shown in (a), the point TP2 (i) and the points a, b; b, c;
The sum of the areas S1, S2, S3, S4 of the four triangles formed by connecting c, d; d, a respectively is equal to the area S of the quadrangle consisting of a, b, c, d. The point TP2 (i)
Is the same even if is on the side of this quadrilateral. On the other hand, as shown in FIG. 4B, a point TP is placed outside the quadrangle.
If there are 2 (i), the sum of the areas S1, S2, S3, S4 will be larger than the area S of the quadrangle and will not be equal. In this case, try another quadrilateral.

When a quadrangle including the point TP2 (i), that is, four adjacent grid points a, b, c, d can be identified, the quadrangle abcd is determined as shown in FIG. Divide into two triangles with the diagonal line ac of the book, and point TP2
Find which of the triangles (i) belongs to. This determination is also made in the same manner as described above. First, this triangle ab
The areas of c and acd are obtained, and the area of the former is T1 and the area of the latter is T2. And FIG.
As shown in (b), if the point TP2 (i) is not inside the triangle abc, the areas S1 and S2 of the three triangles consisting of the point TP2 (i) and the points a, b; b, c; , S3 is not equal to the area T1 of this triangle abc. On the other hand, as shown in FIG. 5C, the point TP2 (i) is a triangle a.
If it is within bc, this point TP2 (i) and points a, c; c, d;
The sum of the areas S1, S2 and S3 of the three triangles consisting of d and a is equal to the area T2 of this triangle acd. The diagonal line that divides the quadrangle into two may be bd.

By the above procedure, as shown in FIG. 6, a point T on the XY plane regarding the position TP1 (i) of the tool tip TP is shown.
This means that the three closest lattice points (points a, c, d on the XY plane) surrounding P2 (i) can be specified. Next, this point TP2
The coordinate position of the point TP3 (i) obtained by projecting (i) on the bottom surface SS1 is obtained. However, the position of the point TP3 (i) on the X and Y axes is TP2.
Since it is already given at the point (i), the position z on the Z axis may be obtained.

Regarding the value of z, the point T on the XY plane is
The three closest lattice points surrounding P2 (i) (point a on the XY plane,
c, d) points projected on the bottom surface SS1, that is, the bottom surface SS
It is calculated by using the coordinate values za, zc, and zd on the Z axis of the grid points G (a), G (c), and G (d) on 1 respectively. By the way, as described above, all the lattice points on the bottom surface SS1 have already been given the positions on the X, Y, and Z axes. Assuming that the XY plane is located at the position of z = 0 in FIG. 6, the values of za, zc, and zd are points a, c, d, and G.
It is equal to the length of the line connecting (a), G (c), and G (d).

Here, as shown in FIG. 6, the area of a triangle formed by points a, c, and d on the XY plane including the point TP2 (i) inside is S, and the point TP2 (i) and the points a, c. C, d; area of three triangles consisting of d, a respectively S1, S2, S3
Assuming that (S = S1 + S2 + S3), the coordinate value z of the point TP3 (i) on the Z axis can be obtained by the following equation. z = [za * S2 + zc * S3 + zd * S1] / S When the coordinate position of the point TP3 (i) on the bottom surface SS1 is determined in this way, as shown in FIG. ) And the point TP3 (i) are connected by a straight line m. Then, the straight line m is considered as the bottom face connected to the division point (i-th).

In the above example, z is the area S1 of the triangle.
, S2, S3 were used, but the calculation method is not limited to this. In short, the grid points G (a), G (c),
Any value can be obtained by the interpolation method based on the coordinate values za, zc and zd of G (d) on the Z axis.

Here, if the tool to be used is a ball end mill, as shown in FIG. 8, a straight line u and a straight line m connecting the dividing points of the lower shape and the upper shape are inscribed and the radius is the tool diameter D. Find a circle C1 equal to 1/2 of. Of the points where a line passing through the center o of the circle C1 and parallel to the line u (this is the tool axis) intersects the circle C1, the lower one is the new tool tip NTP (i).

If the tool used is a flat end mill, the angle θ formed by the line u and the straight line m is determined. If this angle is 90 degrees or more, no interference occurs, but 90
If it is less than 100 degrees, interference will occur, so correct the tool position. In this case, as shown in FIG. 9, from the point p ′ at which the line v ′ obtained by extending the tool perpendicularly to the line u from the dividing point of the lower shape intersects the tool axis s ′, D / tan θ ( However, D is positioned so that the tip comes to the point where it is pulled up by the diameter of the tool (point NTP (i) in FIG. 9).

In the embodiments described above, the bottom surface SS
The coordinate position (value of z) of the point TP3 (i) on 1 was estimated from the coordinate value of each of the three lattice points surrounding it,
Alternatively, it may be obtained from four grid points. In this case, as shown in FIG. 5, the quadrilateral consisting of four grid points can be divided into two triangles, and the procedure for determining where the point TP2 (i) exists can be omitted. Then, in order to calculate the z value from the positions of these four points (a, b, c, d) on the Z axis, for example, considering in which direction of the quadrangle the point TP2 (i) is biased. It suffices to take the weighted average of the four points.

Furthermore, when the shape of the bottom surface is defined not by the information of the grid point group as described above but by the whole area by a function, the X and Y coordinate values of the point TP2 (i) are immediately determined. The X, Y, Z coordinate values of the point TP3 (i) can be obtained.

[0032]

According to the present invention, when the bottom surface is connected to the free-form surface (side surface) to be side-cut, the position of the tool is set in the axial direction of the tool in order to eliminate interference with the bottom surface of the tool. Since it is decided by calculation how much to raise along the side, it is possible to create a program of the operation command of the tool that does not cause interference during the side cut in such a case.

[Brief description of drawings]

FIG. 1 is a flowchart showing an outline when NC data is created based on the method of the present invention.

FIG. 2 is a block diagram of an essential part of an automatic programming device for implementing an embodiment of the present invention.

FIG. 3 is a conceptual diagram showing a grid point group of the bottom surface and a grid point group projected on the XY plane when the bottom surface is connected to a free-form surface (side surface) to be side-cut. is there.

FIG. 4 is a diagram illustrating a method for determining whether or not the point of the tool tip projected on the XY plane shown in FIG. 2 is included in a quadrilateral formed by four specific grid points projected on the same plane. Is.

5 is a diagram illustrating a method for further determining which one of the triangles divided by the diagonal of the quadrangle the tool tip point determined to be included in the quadrangle of FIG. 3 belongs to. Is.

FIG. 6 is a conceptual diagram showing that the point of the tool tip is surrounded by three lattice points (on the bottom surface and on the XY plane) that are close to each other.

FIG. 7 is a diagram for explaining a point obtained by projecting the point of the tool tip on the bottom surface and assuming the shape of the bottom surface at the division point based on this point.

FIG. 8 is a diagram illustrating that the correction position of the tip of the ball end mill is calculated using the shape of the bottom surface assumed in FIG.

FIG. 9 is a conceptual diagram showing that the correction position of the tip of the flat end mill is obtained using the shape of the bottom surface assumed in FIG.

FIG. 10 is a diagram illustrating a conventional technique related to creation of NC data for cutting a side surface (free curved surface) by simultaneous 5-axis side cutting.

FIG. 11 is a diagram for explaining designation of a tip position of a tool in the above-mentioned conventional technique.

FIG. 12 is a diagram showing a case where a bottom surface is connected to a side surface to be cut.

FIG. 13 is a diagram illustrating that the tool interferes with the bottom surface when the side surface of FIG. 12 is cut based on the conventional technique.

[Explanation of Codes] 1 Processor 2 ROM 3 RAM 4 NC Data Storage Memory 5 Keyboard 6 Disk Controller 7 Graphic Display 9 Floppy Disk SS1 Bottom TP Tool Tip TP1 (i) Tool Tip Position Obtained by Conventional Method (XYZ
Coordinate position) TP2 (i) Point TP3 (i) TP1 (i) is projected on the XY plane TP3 (i) Point TP2 (i) is projected on the bottom surface SS1 NTP (i) Tool tip position G obtained by the present invention G Lattice point t (i) A line connecting the i-th dividing points of the upper and lower shapes m A line connecting the i-th dividing point of the lower shape and TP3 (i) s Tool axis u The lower shape dividing point (i-th) and the upper shape A line connecting the division point (i-th) of

Claims (3)

[Claims] 1. Automatic programming device for simultaneous 5
In the NC data creation method that cuts a free-form surface with an axis control side cut, when the bottom surface extends to the free-form surface to be cut, the upper shape and the lower shape that form the reference curve of this curved surface are common. The free-form surface cutting is performed by setting the tip position of the tool whose axis is parallel to the connection line that connects each of the divided points divided by the number, to a position that does not interfere with the bottom surface using the information related to the bottom surface. NC
NC data creation method in 5-axis side cut to create data. 2. Simultaneous 5 by automatic programming device
In the NC data creation method that cuts a free-form surface with an axis control side cut, when the bottom surface extends to the free-form surface to be cut, the upper shape and the lower shape that form the reference curve of this curved surface are common. For the tool whose tool side is in contact with the connection line that connects each of the divided points divided by the number of points, project the tool tip point at the position specified distance based on the lower shape on the bottom surface, and the projection point The coordinate position of the tool is indexed from the bottom surface information, and the straight line connecting the dividing point of the lower shape and the projected point of the index is positioned so that the tip of the tool does not cross to create NC data of free-form surface cutting. Method for creating cutting NC data for 5-axis side cut. 3. Automatic programming device simultaneously 5
In the NC data creation method that cuts a free-form surface with an axis control side cut, when the bottom surface extends to the free-form surface to be cut, the upper shape and the lower shape that form the reference curve of this curved surface are common. For a tool in which the tool side is in contact with the connection line that connects each of the divided points divided by the number of points, project the tool tip point at the distance specified based on the lower shape onto the bottom surface, and then project it. The grid point is selected by determining which grid point is surrounded by the grid point group that gives the information of the bottom surface, and then the coordinate value of the projected point is selected using the coordinate value of the grid point thus selected. Then, the NC of free-form surface cutting is determined by positioning so that the tip of the tool does not cross the straight line connecting the dividing point of the lower shape and the calculated projection point. Creating a chromatography data, cutting NC data creation method in the 5-axis side cut.