Data processing: generic control systems or specific application – Specific application – apparatus or process – Product assembly or manufacturing
Reexamination Certificate
1999-11-19
2003-08-19
Picard, Leo (Department: 2125)
Data processing: generic control systems or specific application
Specific application, apparatus or process
Product assembly or manufacturing
C700S181000, C700S159000
Reexamination Certificate
active
06609045
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a file conversion apparatus for a machining program for a numerical control system and a computer readable recording medium for storing a program for the computer to execute the file conversion process. More particularly this invention relates to a file conversion apparatus for a machining program including a NURBS interpolation command and a computer readable recording medium for storing a program for the computer to execute the file conversion process.
BACKGROUND ART
In a numerical control system, basic commands for designating the machine travel route include a linear interpolation command (G
01
) and an arcuate interpolation command (G
02
, G
03
).
For designating a travel route corresponding to a free curved shape, a curve is approximated with minuscule line segments and a command is issued according to linear interpolation. In such a linear interpolation of minuscule line segments, a string of points on the curve are connected by straight lines for interpolation. Depending on the accuracy of approximating the curve by minuscule line segments, therefore, the machine travel route may lose the smoothness in the boundary between minuscule line segments.
In view of this, the method of generation of a smooth curved interpolation trace by passing through a string of points formed by spline interpolation instead of by linear interpolation has already been employed in some fields.
FIGS.
17
(
a
) and (
b
) show about a spline interpolation and a command program. In this program, the G code for designating a spline are described. Then, the coordinates of a series of the passing points are described so that the numerical control system controls the machine travel through a smooth designated route passing through the designated string of points.
In FIGS.
17
(
a
) and (
b
), the machine travels up to a point P
0
by linear interpolation according to a command code G
01
, and then the spline interpolation mode with a command code G
06
.
1
is entered, followed by designating the coordinate values of the passing points P
1
, P
2
, . . . , P
n
. In this way, the machine is controlled to travel along a smooth curve passing through the points P
1
, P
2
, . . . , P
n
.
A technique has also been proposed in which a part of the curve is not approximated by minuscule line segments but directly by an arithmetic definition of the curve. This curve definition is directly read by the numerical control system so that the machine travel route is controlled by the curve interpolation. For the curve definition in this case, the NURBS (Non Uniform Rational B-Spline) having a high freedom of curve expression has been proposed.
FIG. 14
shows a command format according to a program for NURBS interpolation described in Japanese Patent Application Laid-Open Publication No. HEI 4-175905. In this command format, the number of steps of NURBS is designated by address M following the code G
70
.
0
, the number of control points of NURBS by address N, the knot vector by address K following the code
70
.
0
, the (X, Y, Z) coordinate of each control point by addresses X, Y, Z following G
70
.
1
, and the weight of each control point by address W.
FIG. 15
shows a command format according to the program for NURBS interpolation described the above mentioned publication HEI 8-305430. In this command format, the number of steps of NURBS is designated by address P following code G
06
.
2
, the knot vector by address K, the (X, Y, Z) coordinate of control points by addresses X, Y, Z, and the weight of each control point by address R.
In any way, the NURBS curve can be uniquely defined by designating the number of steps and the coordinates and the weight of each control point.
In a NC machine tool having the NURBS interpolation function, the machining program including the NURBS interpolation command described in the format described above is directly read and the distance covered along the NURBS curve is distributively controlled at servo interpolation periods thereby to carry out the NURBS interpolation.
The NC machine tool having the NURBS interpolation function, however, has yet to find wide applications, and such a function, if any, is offered as an expensive option.
Further, the NURBS interpolation command lacks a standard format, and different NC system makers employ different formats.
Therefore, there is disadvantage that only a small proportion of specified machines can actually carry out the machining work using a machining program output in a format including the NURBS interpolation command designed according to NURBS having a high degree of shape design freedom.
Another problem is that the machining program prepared in the NURBS interpolation command format of a given company cannot be used for the machining work on the NC machine tool of another company.
The present invention has been developed in view of the problems described above, and the object thereof is to provide a file conversion apparatus in which a machining program including the NURBS interpolation command described in a given format is converted into a machining program having a code system or a format usable with a NC machine tool not equipped with the NURBS interpolation function but supports the linear interpolation, the spline interpolation or the NURBS interpolation command of a different format, and a computer readable recording medium for storing a program for the computer to execute the file conversion process.
DISCLOSURE OF THE INVENTION
According to the present invention, there is provided a computer-operated file conversion apparatus for converting a source file constituting a machining program for a numerical control system including the NURBS interpolation command into a destination file, comprising a conversion unit for inputting the machining program as the source file, sequentially analyzing the input machining program, and leaving portions other than the NURBS interpolation command as they are and converting the NURBS interpolation command into a minuscule line segment interpolation command, wherein the destination file is generated by leaving portions other than the NURBS interpolation command as they are by the conversion unit and converting the NURBS interpolation command into a minuscule line segment interpolation command.
As a result, the NURBS interpolation command of a machining program for a numerical control system including the NURBS interpolation command is converted into a minuscule line segment interpolation command, and an ordinary machining program including no NURBS interpolation command is obtained as a destination file.
Further, according to the present invention, there is provided a computer-operated file conversion apparatus for converting a source file constituting a machining program including the NURBS interpolation command for a numerical control system into a destination file, comprising a conversion unit for inputting the machining program as the source file, sequentially analyzing the input machining program, and leaving portions other than the NURBS interpolation command portion as they are and converting the NURBS interpolation command portion into a spline interpolation command, wherein the destination file is produced by leaving portions other than the NURBS interpolation command as they are and converting the NURBS interpolation command into the spline interpolation command by the conversion unit.
As a result, the NURBS interpolation command of a machining program for a numerical control system including the NURBS interpolation command is converted into the spline interpolation command thereby to produce an ordinary machining program not including any NURBS interpolation command as a destination file.
Further, according to the present invention, there is provided a computer-operated file conversion apparatus for a machining program for a numerical control system, comprising a unit for converting the NURBS interpolation command into a spline interpolation command, wherein a string of points is generated by polygonal approximation in such a manner
Jarrett Ryan
Mitsubishi Denki & Kabushiki Kaisha
Picard Leo
LandOfFree
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