JP3242162B2 - NC processing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an NC processing method which approximates a straight line and a smooth arc using a small number of sampling points (data) so that an original figure can be reproduced.

[0002]

2. Description of the Related Art FIG. 3 is an explanatory diagram of a sampling point selection method used in a conventional processing method. A point P moving on the curve from an arbitrary point P1 on the curve of the original figure
Assuming k, a sampling point P2 is created at a point Pk where the distance (D) between the curve and a line segment P1 - Pk connecting P1 and Pk is equal to or closest to a preset tolerance (L). . Next, the point Pk is moved on the curve from P2, and the sampling point P3 is set to a point Pk at which the distance (D) between the curve and the line segment P2 - Pk connecting P2 and Pk becomes equal to a predetermined tolerance (L). Is created. Similarly, sampling points P3 to Pn where the distance (D) between the line segment and the curve is equal to the tolerance (L) are sequentially created, and n sampling points P1 to Pn are selected on the original curve. .

FIGS. 4 and 5 are explanatory views of a typical approximation method used in a conventional processing method. Figure 4 is a three-point arc approximation, two sampling points P1 consecutive - P2 between is approximated by an arc passing through 3 points P1~P3 consecutive (the center of the arc c1, radius r1), P2 - P
The distance between three is approximated by an arc passing through the next three consecutive points P2 to P4 (an arc having a center c2 and a radius r2). In the same manner, thereafter, an approximation is made by an arc passing through three sampling points continuous between two points, a curve between P1 and Pn is created, and the original figure is reproduced.

FIG. 5 shows a four-point arc approximation method, in which P2 - P3
Between the arc of center C2 and radius R2, the center C3 and radius R3
Are approximated by two arcs. C2 and C3 and R2 and R3 can be obtained from the following equations.

[0005]

(Equation 1)

(Equation 2)

(Equation 3)

[0006] In the same manner, after that, three sampling points including an approximate symmetric point and a point immediately before the sampling point are included.
It is approximated by two arcs of an arc passing through a point and an arc passing through three points including two sampling points that are symmetrical to the approximation and the next point, a curve between P1 to Pn is created, and the original figure is created. Is reproduced.

In both the three-point circular approximation method of FIG. 4 and the four-point circular approximation method of FIG.
Basically, it is performed with an arc passing between points, but generally, the three-point arc approximation method has a feature that an original figure can be reproduced with a relatively small number of points (data). The method reproduces a figure with a relatively large number of points (data), and since the same approximation section is composed of two arcs and an appropriate one can be selected from among them, a figure closer to the original figure There is a feature that can reproduce. When the radius r of the arc to be approximated exceeds a certain value (R), the approximation between two points is performed by a straight line.

[0008]

The conventional NC processing method is as follows.
Although the original figure can be reproduced with a small number of sampling points (data) as in the three-point circular approximation method, when there is a sudden change between the approximated arcs, the reproduced figure lacks smoothness. is there. In addition, since the optimal section can be selected from the two arcs for the section to be approximated like the four-point arc approximation method, the connection between the points (data) is smooth and the figure with little difference in shape from the original figure is reproduced. However, there are problems such as an increase in the number of points (data) and an increase in the number of arcs and straight lines to be created.

An object of the present invention is to solve such a problem, and an object of the present invention is to provide an NC which reproduces a figure as close as possible to the original figure with a small number of points (data).
It is to provide a processing method.

[0010]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, an NC machining method according to the present invention provides a machining target for a workpiece.
Approximate the original figure representing the shape using a straight line or arc
To create NC data, and N
In the NC machining method for machining a workpiece with the C command, the original
Multiple sampling points on the curve of the figure
Of the line segment and curve when connecting the sampling points
Configured so that the distance is equal to the preset tolerance
And two adjacent sampling points on the curve
Samples for the distance between the sampling points
One of the ring points and another sampler next to it
If the ratio of the distance between
One sampling point and another sampling point
And providing a sampling point for a new approximation between.

Further, in the NC machining method according to the present invention, when the difference between the tangent angles of the two consecutive points exceeds a predetermined value, the four-point circular approximation method is applied to the two points. It is characterized by approximation using two arcs.

[0012]

According to the NC machining method of the first aspect of the present invention, a new portion having a distance corresponding to the ratio of the length of a curve having a large curvature to the length of a curve preceding or following the curve having a large curvature is provided for a curve portion having a large curvature. Sampling points can be provided before or after the two points that make up the large curvature curve. Therefore, since a new sampling point is added only to a portion having a large curvature, a figure as close as possible to the original figure can be reproduced by adding a minimum number of points (data).

In the NC machining method according to a second aspect of the present invention, when the difference in the tangent angle between the two symmetrical points of the circular arc approximation exceeds a predetermined value, the NC machining method is not required. Apply the point arc approximation method. Therefore, since the four-point arc approximation method is applied only to a portion where the tangent angle difference is large and the curve changes suddenly, a smooth figure as close as possible to the original figure can be obtained by adding a minimum number of arcs to be approximated. Can be reproduced.

[0014]

Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is an explanatory view of the NC processing method according to the first aspect. P1~P4 sampling point is, P1 using conventional methods - between P2, P2 - P3, and between P3 -
The distance (D) between the line segment between P4 and the curve is equal to a preset tolerance (L). Also,
The curve P2 - P3 is a portion where the curvature of the curve changes abruptly, and the curves P1 - P2 and P3 - P4 are portions where the curves change relatively gently.

On the curve, between P1 and P2, between P2 and P3,
The distances between 3 - P4 are ΔL1, ΔL2, and ΔL3, respectively, and the ratio of the distance ΔL1 to the distance ΔL2 is k1 (ΔL1 / ΔL
2 = k1) or the ratio of the distance ΔL3 to the distance ΔL2 is k2
When (ΔL3 / ΔL2 = k2) is equal to or larger than the set value K, the fixed distances d1 and d2 based on the ratios k1 and k2 are secured.

The point P2 from the curve P1 - at the distance d1 on P2, or curve P2 from point P2 - setting a new sampling point P 'at a distance d1 on P3. First, sampling point P 'of the curve when P1 - set between P2, 3 points P1, P' P1 arc passing through, P2 -
'Approximates the curve between three points P' P, P 'in an arc through the P2, P3 - approximating the curve between P2, P2 with arc through the P2, P3, P4 - approximate the curve between P3 . Next, the sampling point P 'the curve P2 - If set to between P3, 3 points P1, P2, P' P1 arc through - approximating the curve between P2, 3 points P2, P ', through P3 P2 with arc
- 'approximates the curve between, P' P, P in an arc through the P3, P4 '- approximating the curve between P3.

Furthermore, sampling point P 'the curve P1 - P2, and between the curve P2 - When set to both between P3, 3 points P1, P', P1 an arc passing through the P2 - P 'approximates the curve between , And P ′, P2, P ′ with a curve P ′ −
P2 is represented by P2, P ', P3, and the curve P2 - P' is represented by P ',
P3, P4 in the curve P '- each to approximate the P3.

A new sampling point P 'is represented by a curve P
1 - provided or between P2, the curve P2 - whether provided between P3,
Or curves P1 - P2 between the curve P2 - The choice to set both between P3 is a curve that approximates the increase of the number of data is determined by the balance of how close to the original curve. The distance d from the point P2 to the sampling point P '
1 can be set to different values d1 ′ and d1 ″ corresponding to k1 between the curves P1 and P2 and between the curves P2 and P3.

Similarly to the case of P ', a new sampling point P "is set at a position at a distance d2 from the point P3 on the curve P2 - P3 or at a position at a distance d2 on the curve P3 - P4 from the point P3. .

A new sampling point P ″ is represented by a curve P
2 - If provided between P3, P3-P4 provided between the case or curve P2 - P3 between the P3 - and the method of arc approximation for setting both between P4, the selection of the set position of the P "is the The distance d2 from the point P3 to the sampling point P ″ is calculated by the curve P2 − P3.
It is also possible to set different values d2 'and d2 "corresponding to k2 between the interval and the curves P3 - P4.

As shown in FIG. 1, a new sampling point P 'is provided at a distance d1 from the point P2, or a new sampling point P "is provided at a distance d2 from the point P3.
Is provided, the increase in the number of sampling points (data) can be minimized and a smooth curve close to the original figure can be reproduced.

FIG. 2 is an explanatory view of the NC machining method according to the second aspect. P5~P8 sampling point is, P5 using conventional methods - between P6, P6 - P7 and between P7 -
The distance (D) between the line segment between P8 and the curve is configured to be equal to a preset tolerance (L).

Next, the tangent angles (α, β, γ, δ) of the curves at the sampling points P5 to P8 are determined, and the differences (α-β, β-γ) of the tangent angles of the curves between two consecutive points are determined. ,
If the absolute value of [gamma]-[delta] exceeds a preset value [theta], a curve is approximated by applying a four-point circular approximation method to the corresponding section. For example, in the case of | β−γ | ≧ θ, the curve between the approximate target sections P6 and P7 is approximated by two arcs using the four-point arc approximation method using the four points P5 to P8.

Similarly, when the absolute value of the difference between the tangent angles exceeds the set value θ, two additional sampling points are used without adding new sampling points to the corresponding approximate symmetry section. Create an arc of.

As described above, as shown in FIG. 2, for an approximation target section having a large difference in tangent angle between two points, the same section is approximated by two arcs without adding a new sampling point. It is possible to reproduce a smooth figure with a small difference in shape from the original figure.

[0026]

As described above, the NC according to the first aspect is described.
The processing method configures a new sampling point having a distance corresponding to the ratio of the length of the curve having a large curvature to the length of the curve preceding or following the curve having a large curvature for a curve having a large curvature. It can be provided before or after the two points. Therefore, since a new sampling point is added only to a portion having a large curvature, a figure as close as possible to the original figure can be reproduced by adding a minimum number of points (data).

Further, the NC machining method according to the second aspect monitors the difference between the tangent angles of two points that are symmetrical to the circular arc approximation, and if the value of the tangent angle difference exceeds a predetermined value, the corresponding NC processing method is performed. The four-point circular approximation method can be applied between the two points. Therefore, the four-point arc approximation method is applied only to the part where the tangent of the two points has a large tangent and the curve changes abruptly. A close and smooth figure can be reproduced.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of an NC processing method according to claim 1;

FIG. 2 is an explanatory view of an NC processing method according to claim 2;

FIG. 3 is an explanatory diagram of a sampling point selection method used in a conventional processing method.

FIG. 4 is an explanatory diagram of a typical approximation method (three-point approximation method) used in a conventional processing method.

FIG. 5 is an explanatory diagram of a typical approximation method (four-point approximation method) used in a conventional processing method.

[Explanation of symbols]

 P1 to Pn Sampling points P ′, P ″ Newly added sampling points ΔL1 to ΔL3 Curve distance D Maximum distance between curve and straight line between two points | β−γ | C2, C3 Center of arc R1, R2, R3 Radius of arc c1, c2 Center of arc r1, r2 Radius of arc

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) G05B 19/18-19/46 B25J 3/00-3/04 B25J 9/10-9/22 B25J 13 / 00-13/08 B25J 19/02-19/06

Claims (2)

(57) [Claims] 1. An element representing a shape to be a processing target of a workpiece.
NC The figure was approximated to reproduce with a linear or arc
Creates data and precedes it with an NC command consisting of the NC data.
In the NC processing method for processing the workpiece, the original figure
Adjacent multiple sampling points on the shape curve
The distance between the line segment and the curve connecting the sampling points
Configuration so that the separation is equal to the preset tolerance
And adjacent ones of the sampling points on the curve
The two relative to the distance between two sampling points
One sampling point and another adjacent to it
When the ratio of the distance between sampling points is greater than the set value
The one sampling point and the another sample point.
An NC processing method characterized by providing a sampling point for a new approximation between a ring point and a ring point . 2. When the difference between the tangent angles of two consecutive sampling points exceeds a predetermined value, approximating the two sampling points with two arcs. The NC machining method according to claim 1, wherein