JPH03116305A - Control method for nc machine tool - Google Patents

Abstract

PURPOSE:To perform the working along an approximate working path of high precision by obtaining distances from the origin to two points to be connected with an arc and defining an average value of these two distances as the radius of curvature of the arc connecting both points. CONSTITUTION:A function to indicate the curve of a desired working path is defined, and this curve is divided by an angle DELTAtheta at which this curve is viewed from an origin 0, and coordinate values of each division point pi are obtained in the XY rectangular coordinate system. Distances Ri-1 and Ri from the origin 0 to adjacent division points Pi-1 and Pi are obtained from the expres sion in a polar coordinate form of the curve. The average value of these two distances Ri-1 and Ri is defined as the radius of curvature of the arc as the approximate working path connecting both division points Pi-1 and Pi. Thus, working along the approximate working path of high precision is possible.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a method for controlling an NC machine tool, and particularly to a method for controlling an NC machine tool that performs machining based on data consisting of a combination of orthogonal coordinate values and a radius of curvature. .

[Conventional technology]

NC machine tools are used for various purposes because they can freely perform machining along desired machining paths. Currently, commonly used NC machine tools require a series of data in the following format.

xO, yO xl, yl, rl x2. y2. r2 xi-L, yi-1, ri-1 xn, yn, rn Here, (x O, y O) indicates the starting point position, and the first two terms of each data string following this are in the XY orthogonal coordinate system. These are coordinate values, and the third item is the radius of curvature.

Here, for example, the i-th data column (X1+Yl+ri
) corresponds to the instruction to "perform processing while moving along the curve with radius of curvature ri from the point with coordinate values (xl-L, yi-1) to the point with coordinate values (xi, yi)" . In this way, the NC machine tool repeats the operation of machining along an arc or a straight line between two points.

In this way, in order to control the NC machine tool, it is necessary to generate a series of data strings as described above and provide them to the NC machine tool. These days, such control is generally performed by a computer. Usually, a personal computer is provided for this purpose, and the personal computer creates a series of data strings as described above.

[Problem to be solved by the invention]

However, in the conventional control method of NC machine tools performed using a personal computer, the radius of curvature r
The problem is that the value of i is inaccurate. If the work path is a perfect circle, it is possible to use an accurate radius of curvature, but if the work path is an ellipse or an Archimedean curve, it is necessary to approximate the partial portion to a circular arc. However, in the conventional method, this approximation is rough and it is difficult to perform accurate control along the true machining path.

Therefore, an object of the present invention is to provide a control method for an NC machine tool that can perform more accurate control.

[Means to solve the problem]

The present invention provides orthogonal coordinate values (xi, yi) and radius of curvature of a position point Pi to be moved next with respect to a current position point p i-t indicated by orthogonal coordinate values (xi-1, yi-1). ri
By inputting
In a method for controlling a machine tool, there is a step of defining a curve indicating the machine path as a function, and for this function, when an angle θ is given, the distance R from the origin is calculated.
a step of defining a polar coordinate operation that can uniquely determine a working path; a step of inputting an initial angle value θ0 corresponding to the starting point of the work path, an angle final value θmax corresponding to the end point, and an angular interval Δθ; a subscript i The angle θi expressed using Find the orthogonal coordinate values (xi, yi) corresponding to the polar coordinate values (θt, Ri), find the radius of curvature ri using the formula r i -l Ri +R1-L l /2, and output it to the NC machine tool. The procedure of creating data (xi, yi, ri) is repeated while increasing i by 1 from the initial value 1 until θi reaches the final angle value θmax.

[For production]

In the method according to the invention, first a function is defined that represents the curve of the desired machining path. This curve is divided by the angle Δθ at which this curve is viewed from the origin, and the coordinate values of each dividing point are
Obtained in Cartesian coordinate system. The method according to the present invention has two features:
The problem lies in how to give the radius of curvature of the arc that forms the approximate machining path connecting two adjacent dividing points. First, the distance from the origin is determined for each adjacent dividing point. This can be easily determined by using a polar coordinate representation of the curve.

Then, the average value of these two distances is determined as the radius of curvature of the arc connecting the points on both sides.

By taking the average of both in this way, machining can be performed along a highly accurate approximate machining path.

〔Example〕

The present invention will be described below based on illustrated embodiments. 1st
The figure is a flowchart showing the procedure of a method for controlling an NC machine tool according to the present invention. Hereinafter, control for performing processing along the Archimedes curve will be explained according to this flowchart.

First, in step S1, a function representing the curve of the work path is defined. This function may be defined in any format, but in the case of an Archimedean curve, it is convenient to define it in polar coordinate format Rmaθ. Here, R is the distance from the origin 0, θ is the counterclockwise angle from the X axis,
a is a coefficient. FIG. 2 shows an example of an Archimedes curve. The starting point PO of this Archimedean curve coincides with the origin O of the XY coordinate system, and when it rotates one and a half times counterclockwise from this starting point PO, it reaches the ending point P max. On this curve, the distance Rk from the origin of the point Pk located at the angle θ is determined as Rk−a θ, so the position of the point Pk is uniquely determined.

Subsequently, in step S2, polar coordinate calculations for this curve are defined. In the case of the Archimedes curve in this embodiment, the function defined in step S1 is originally expressed in polar coordinate format. Therefore, there is virtually no need to perform any work in this step S2. However, for boat fishing, the polar coordinate format is not necessarily defined in step S1, so R-f
(θ), that is, when an arbitrary angle θ is given, it is necessary to define an operation that can uniquely determine the corresponding distance R from the origin.

In the next step S3, the initial angle value θ0, the final angle value θW
aX and the angular interval Δθ are input. Here, the initial angle value θ0 is a value indicating the angle of the starting point position of the work path on the polar coordinate system, and the final angle value θIIaX is a value indicating the angle of the end point position of the work path on the polar coordinate system. In this example, as shown in FIG. 2, θo-o', θmax-54
It becomes 0°. Further, the angular interval Δθ corresponds to the unit of angle by which the work path is divided, and the finer the setting, the higher the accuracy. However, if the settings are made more detailed, the number of steps will increase and the time will increase. In the case of an Archimedes curve as in this embodiment, a practically sufficient accuracy can be obtained by setting it to about Δθ−5″.

In step S4, the control parameter i is an initial value of 1.
is set to This control parameter i increases by 1 each time the loop from steps 85 to S9 is completed (step 510).

During this cycle, instruction data (Xl + Y i + rL) for moving the NC machine tool by an angular interval Δθ
is created. If it is necessary to specify the starting point coordinates of the machining path to the NC machine tool, data indicating the starting point coordinate values is created in step S4. In this example, the coordinate coordinates of the origin O (xO, yO)
is created as the starting point coordinate value.

In step S5, the angle θi is calculated by the following calculation: θi=θ0+i·Δθ. for example,
If Δθ-5°, if i-5, θ5-25'
becomes.

In the following step S6, the orthogonal coordinate values (xi, yi) of the dividing point Pi on the workpiece at the angle θi are derived. This is done by finding Ri corresponding to θi using the expression R-f(θ) in polar coordinate format derived in step S2, and defining it as a point located on the angle θi counterclockwise from the X axis and at a distance Ri from the origin O. It is sufficient to recognize the dividing point Pi.

in particular, xi-Ri・cos (θ1) yi=RiΦ5in(θi) It is derived as

In the following step S7, the radius of curvature ri is determined as follows.

ri=lRi −R1−1l/2 Thus, in step S8, the coordinate values (xt, yi) derived in step S6 and the radius of curvature ri obtained in step S7 are combined and outputted to the NC machine tool. set of instruction data (x i.

yi, ri) are created.

Finally, in step S9, θi is the final angle value θma
It is determined whether or not the fork has been reached. If it has not been reached, i is updated by 1 in step SIO, and the operations from step S5 are repeated.

If θmax has been reached, all work is complete. Thus, x O+ y O xi, yl.

x2. y2゜ 1 2 xi-1, yi-1, rl-1 xn, yn, rn A series of data columns will be created.

Here, the meaning of the above data string 0 (i, yi, ri) will be briefly explained. This data string is data that instructs the operation of the NC machine tool in the section from points P1-1 to Pi in FIG. The state immediately before the NC machine tool executes the instruction of this data string is the previous data string (x
i-1, yl-1.

This is the state immediately after executing rI-L). therefore,
In FIG. 3, the machining up to point P1-1 has been completed. The data string (xi, y'1ri) is the point P
From i-1 (xl-L, yi-1) to point Pi (xi
, yi) is an instruction to perform machining along an approximate machining path that connects the range up to yi) with a circular arc having a radius of curvature ri. In this way, the NC machine tool does not perform machining completely along the Archimedean curve shown in FIG. 3, but performs machining along an approximate machining path formed by a circular arc. The situation is shown in Figure 4.

The NC machine tool has two points P1-1. It has the function of finding a center point Oi for drawing an arc based on the coordinate values of Pi and the radius of curvature ri, and drawing an arc of radius ri centered on this center point O1.

The feature of the present invention is that this radius "i" is the distance Ri between the origin O and the point Pi, and the distance Ri between the origin O and the point Pi-1.
This point is the average value of -1.

In the conventional method, the value of radius ri is R1-1 or R
Since i was used, the approximation was rough, but the present invention improves the approximation accuracy by using these average values. As mentioned above, if the value is set to about Δθ-5″, extremely high-precision control becomes possible in practice.

Although the embodiments related to Archimedes curves have been described above, the present invention can be applied to any curves. For example, in the case of an ellipse as shown in FIG. 5, the definition in step S1 is generally defined by the function ax''+by2-c in the XY orthogonal coordinate system.

When such a function is defined in step S1, the polar coordinate calculation in step S2 may be performed, for example, as follows. That is, if an arbitrary angle θ is given, as shown in Fig. 5, if the coordinates (x, y) of the intersection point P between the straight line g having this angle θ and the ellipse are found by geometric calculation, then R can be determined from the coordinate values (x, y). In step S3, θ0
−0゜θmax−360@, and Δθ is, for example, 5″
You can set it as . And point PO (xo.

yO) and perform the steps from step 85 onwards. The subsequent steps are exactly the same as in the previous embodiment.

〔Effect of the invention〕

As described above, according to the control method for an NC machine tool according to the present invention, the distance from the origin is determined for each of two points to be connected by a circular arc, and the average value of the two determined distances is used to form an arc connecting the two points. Since the radius of curvature is set to , machining can be performed along a highly accurate approximate machining path.

[Brief explanation of drawings]

FIG. 1 is a flowchart showing the steps of the method for controlling an NC machine tool according to the present invention, FIG. 2 is a diagram showing an Archimedean curve drawn by the method according to the present invention, and FIG. 3 is a diagram showing the basic principle of the method according to the present invention. FIG. 4 is a diagram showing an approximate machining path drawn using the method according to the present invention, and FIG. 5 is a diagram showing an elliptic curve drawn using the method according to the present invention.

Claims (1)

[Claims] The orthogonal coordinate values (xi, yi) and curvature of the position point Pi to be moved next relative to the current position point Pi-1 indicated by the orthogonal coordinate values (xi-1, yi-1) A method for controlling an NC machine tool having the function of performing machining while moving from point Pi-1 to point Pi with a radius of curvature ri by inputting a radius ri, in which a curve indicating a machining path is defined as a function. a step of defining a polar coordinate operation that can uniquely determine the distance R from the origin when an angle θ is given for the function; The step of inputting the final angle value θmax and the angular interval Δθ corresponding to Based on the polar coordinate calculation, find Ri corresponding to θi, find the orthogonal coordinate value (xi, yi) corresponding to this polar coordinate value (θi, Ri), and calculate ri=|Ri+Ri−1|/ 2. The procedure of calculating the radius of curvature ri using the formula and creating data (xi, yi, ri) to be output to the NC machine tool is performed by increasing θi by 1 from the initial value 1.
A method for controlling an NC machine tool, comprising: repeating the step until the final angle value θmax is reached.