JP2002258925A - Nc data outputting method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To output highly precise NC data which are much more closer to the shape acquired from the calculated value of a working point coordinate. SOLUTION: An output error allowance (t) in the moving direction of a working point and an output error allowance (n) in a direction orthogonal to the moving direction are inputted, and the coordinate value of the working point and the moving direction of the working point are calculated. An intersection point on the minimum set unit mesh which is not more than the output error allowance (t) in the moving direction and the output error allowance (n) in the orthogonal direction is detected. An intersection coordinate value which is the closest to the calculated point of the working point coordinate value among the detected intersection points is outputted. When any intersection point which is not more than the allowance (n) is absent, an intersection point coordinate value which is not more than the allowance (t) with the minimum error in the orthogonal direction is outputted.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for outputting NC data for a processing machine such as a machine tool.

[0002]

2. Description of the Related Art For example, NC data for a mold processing machine has conventionally been output by a CAM system in a method as shown in a flowchart of FIG. First, step S11
Then, the processing shape is input, and in step S12, the tool shape,
Processing conditions such as a processing method, a pick feed amount, and an allowable processing error amount are input. The processing method includes contour processing, scanning line processing, processing along a surface, and the like. Next, step S13
Then, based on the input processing shape and processing conditions, the coordinate value of the processing point which is a point on the processing shape line or its offset shape line is calculated.

In step S14, the coordinates of the intersection closest to the calculated machining point coordinate value among the intersections on the minimum setting unit mesh are output to the NC unit. This way,
The path connecting the output points with a straight line is the moving path of the tool. The minimum setting unit mesh is obtained by dividing plane coordinates at intervals of the minimum setting unit of the NC data. At present, the minimum setting unit is generally 1 μm.

[0004]

However, in recent years, NC
Improvements in machine tool accuracy have enabled machining of surface roughness close to the minimum setting unit depending on the accuracy of the NC data. According to the conventional NC data output method, the permissible machining error amount approaches the minimum setting unit. In such a case, there is a problem that good surface roughness cannot be obtained. This problem will be described below with reference to the working mode shown in FIG.

FIG. 4 shows an example in which a cylindrical processing surface S is subjected to scanning line processing in the X-axis direction by a tool T such as a ball end mill. S0 is an offset surface obtained by offsetting the processing surface S by the radius of the tool T, and Yi is a surface perpendicular to the Y axis. Li is an intersection line between the vertical plane Yi and the offset plane S0, and indicates an ideal movement path of the tool center.

Here, the NC data output to the NC device is a group of points divided into minute line segments. These points are illustrated in FIG.
, Two adjacent points (Ci, j) and (Ci, j)
j + 1) at any position on the line segment connecting
Is calculated so that the distance from the input is equal to or less than the allowable processing error amount δ.

At this stage, as shown in FIG.
When the next path Li + 1 is projected onto the path Li on the XZ plane, if (Ci, j) and (Ci + 1,
Even if the position is shifted from j), the polygonal line connecting the point groups on each path does not deviate more than the allowable processing error amount δ.

However, as shown in FIG. 7, when the calculated value is adjusted to the minimum setting unit of the NC data by rounding or the like and the intersection coordinate value on the minimum setting unit mesh is output, in some cases, a polygonal line connecting the output points may be obtained. Is larger than the allowable processing error amount δ, and an error of (δ + minimum setting unit × √2) occurs at the maximum.

FIG. 8 shows a plane orthogonal to the moving path of the tool (FIG. 4).
(The YZ plane of FIG. 3) shows the surface roughness of the processed surface. When there is no error in the point cloud data, as shown in (a), the unevenness amount h of the processed surface is approximately obtained from the following equation using the tool radius R and the pick feed amount P. h = P ² ÷ 8R

On the other hand, when an error exceeding (P ² ÷ 2R) occurs in a direction (Z-axis direction) perpendicular to the processing surface,
As shown in (b), the unevenness amount of the processing surface is 4 h, and the path for moving at a high position (the center path) does not remain in the final processing surface, so that the purpose of making the pick feed fine is not achieved, and the surface roughness is not achieved. Degree decreases.

The surface roughness of the machined surface is affected by various errors of the machine and the control system in addition to the accuracy of the NC data.
C data is required to have the highest possible accuracy. However, according to the conventional method, as the allowable processing error amount approaches the minimum setting unit, there is a problem that the influence of the error by the method of outputting the coordinate value closest to the processing point coordinate value increases.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a method capable of outputting high-precision NC data which is closer to a shape obtained from a calculated value of a processing point coordinate.

[0013]

In order to solve the above-mentioned problems, an NC data output method according to the first aspect of the present invention calculates a coordinate value of a machining point and a moving direction of the machining point, and calculates an orthogonal value to the moving direction. The method is characterized in that an allowable value of an output error in a direction to be set is set, and a coordinate value of an intersection closest to the processing point among intersections on the minimum setting unit mesh which is equal to or less than the allowable value is obtained and output.

According to a second aspect of the present invention, there is provided an NC data output method, wherein a coordinate value of a processing point and a moving direction of the processing point are calculated, and an allowable value of an output error in the moving direction and an output error in a direction orthogonal to the moving direction are calculated. And a straight line extending in the same direction as the moving direction passing through the processing point is obtained, and an intersection on the minimum setting unit mesh which is equal to or less than an allowable value of the output error in the moving direction is obtained. Calculate the distance,
It is characterized by outputting the coordinate value of the intersection closest to the processing point among the intersections where the distance is equal to or less than the allowable value of the output error in the direction orthogonal to the moving direction.

[0015]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a flowchart showing a method of outputting NC data in a machine tool, and FIG. 2 is a schematic diagram illustrating a method of determining an output point using a minimum setting unit mesh of a two-dimensional shape portion. However, the present invention does not
The following method is not limited to the three-dimensional shape part, and can be applied to the three-dimensional shape part.

In FIG. 1, first, a processing shape is input in step S1, and processing conditions are input in step S2. The processing conditions include a tool shape, a processing method, a pick feed amount, an allowable processing error amount, an output error allowable value t in the moving direction, an output error allowable value n in a direction orthogonal to the moving direction, and the like.
The processing method includes contour processing, scanning line processing, processing along a surface, and the like.

Next, in step S3, a coordinate value (x, x) of a processing point which is a point on the processing shape line or its offset shape line.
y) and the moving direction α of the machining point are calculated, and these values are stored in the memory. The coordinate value and the moving direction are calculated by the CAM based on the input processing shape and processing conditions.

Subsequently, in step S4, an intersection point on the minimum setting unit mesh which is equal to or smaller than the output error allowable value t in the moving direction and the output error allowable value n in the direction orthogonal to the moving direction is detected. If there are a plurality of intersections that are equal to or less than the allowable values t and n, in step S5, the coordinate value of the intersection closest to the calculation point of the machining point coordinate value is output. If there is no intersection that is less than or equal to the permissible value t, n, the coordinate value of the intersection at which the error in the direction orthogonal to the moving direction is smaller than the permissible output value t in the moving direction is output in step S6.

The processing of steps S4 to S6 will be described in detail with reference to FIG. 2. The minimum setting unit mesh M is the minimum setting unit Ux, Uy (for example, U
(x, Uy = 1 μm). Here, first, a calculation formula of a straight line L passing through the coordinate value calculation point C (x, y) and extending in the same direction as the moving direction α y = f
(X) is obtained. Next, the intersection points P0, P1, P-1, P2, P2,
P-2 ... Pi ... is specified.

P0 is an intersection on the mesh M closest to the calculation point C (x, y) of the coordinate value, and is represented by a rounded value (x0, y0) of the calculation point C. P1 is a straight line L at a position x1 away from x0 by the minimum setting unit Ux in the X-axis direction in the positive direction.
, And is represented by the rounded value (x1, y1) of the point on the straight line L at x1. y
1 = f (x1).

P-1 is an intersection point on the mesh M closest to the straight line L at a position x-1 that is separated from x0 by the minimum setting unit Ux in the negative direction, and the rounded value of the point on the straight line L at x-1 (X-1, y-1). y-1 = f (x-1). Hereinafter, the allowable error value t in both the positive and negative directions from (x0, y0)
Intersections P2, P-2 ... Pi.
Is defined similarly.

Then, the distances D0, D1, D-1,... To the straight line L are calculated for each of the intersections P0, P1, P-1,.
An intersection Pi where i is equal to or smaller than an error allowance n in the orthogonal direction is detected. When a plurality of intersections Pi are detected, the coordinate value of the intersection Pi closest to the calculation point C is output.
If no intersection that is less than or equal to the error allowable value n is not detected, the coordinate value of the intersection at which the error in the orthogonal direction is smaller than the output error allowable value t in the moving direction, that is, the intersection Pi at which the distance Di is the shortest is calculated. Output. In the illustrated example, D-2
>N>D3> D-3 and d-3> d3, the intersection P
The coordinate value (x3, y3) of 3 is output.

[0023]

As described in detail above, according to the NC data output method of the present invention, a point having a small error is selected and output from a plurality of points included in the error tolerance in the moving direction. The allowable error value in the direction orthogonal to the direction can be set to be equal to or less than the minimum setting unit, thereby providing an excellent effect that it is possible to output high-precision NC data closer to the shape obtained from the calculated values of the processing point coordinates.

[Brief description of the drawings]

FIG. 1 is a flowchart illustrating an NC data output method according to an embodiment of the present invention.

FIG. 2 is a schematic diagram showing a method of determining an output point using a minimum setting unit mesh.

FIG. 3 is a flowchart showing a conventional NC data output method.

FIG. 4 is a perspective view illustrating a processing mode.

FIG. 5 is a schematic diagram illustrating an allowable processing error amount.

FIG. 6 is a schematic diagram illustrating a processing error in a plurality of paths.

FIG. 7 is a schematic view showing a conventional problem.

FIG. 8 is a schematic diagram illustrating a surface roughness of a processed surface.

[Explanation of symbols]

t · · · error tolerance in the moving direction, n · · · error tolerance in the orthogonal direction, C · · · calculation point of coordinate value, M · · · minimum setting unit mesh, P · · · intersection on the mesh, L · · · straight line, D: The distance between the intersection and the straight line.

Claims (2)

[Claims] 1. A coordinate value of a processing point and a moving direction of the processing point are calculated, and an allowable value of an output error in a direction orthogonal to the moving direction is set. NC data output method, wherein a coordinate value of an intersection point closest to a processing point is obtained and output. And calculating a coordinate value of the processing point and a moving direction of the processing point, and setting an allowable value of an output error in the moving direction and an allowable value of an output error in a direction orthogonal to the moving direction. Is obtained, a straight line extending in the same direction as the moving direction is obtained, an intersection on the minimum setting unit mesh which is equal to or less than an allowable value of the output error in the moving direction is obtained, a distance from the straight line is calculated for each intersection, and the distance is determined as the moving direction. An NC data output method comprising: outputting a coordinate value of an intersection closest to a processing point among intersections which are equal to or less than an allowable value of an output error in an orthogonal direction.