JP2796335B2 - Numerical control unit - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a numerical controller that controls a machine tool, and more particularly to a numerical controller that controls a lathe or the like that processes a workpiece by rotating the workpiece.

[Conventional technology]

The numerical controller that controls a lathe, etc., has a polar coordinate interpolation that converts commands programmed in a rectangular coordinate system into linear axis movement (tool movement) and rotation axis movement (workpiece rotation) to perform contour control. There is a function called. The numerical controller performs linear interpolation on a command programmed in a rectangular coordinate system in a rectangular coordinate system, and converts the interpolation amount into a movement amount in a polar coordinate system. This function is effective when cutting a linear cutout in the outer diameter of a work, or when cutting a camshaft.

Hereinafter, the polar coordinate interpolation will be described with reference to the drawings. FIG. 3 is a diagram showing a program example of polar coordinate interpolation using a linear axis (X axis) and a rotation axis (C axis).

First, the origin of the local coordinate system or the work coordinate system is set as the origin O of the polar coordinate system. Polar coordinate interpolation is performed on a plane (polar coordinate interpolation plane) having a linear axis (X axis) as a first axis on a plane and a virtual axis Cy orthogonal to the linear axis as a second axis on a plane.
Command the orthogonal coordinate values on this polar coordinate interpolation plane,
To the tool 2 so that the tool 2 processes the program path 3. Polar coordinate interpolation is performed on the program path 3. That is, the movement is converted into a movement on the linear axis (X axis) and a movement on the rotation axis (C axis) according to the program path 3. When tool correction is applied to this program command, the same polar coordinate interpolation is performed on the path 4 after tool correction.

[Problems to be solved by the invention]

When performing such polar coordinate interpolation, the rotation axis (C
The local coordinate system or the work coordinate system must be set so that the center of the (axis) coincides with the origin O of the coordinate system. However, when polar coordinate interpolation is performed between the linear axis (X axis) and the rotation axis (C axis), an error occurs when the work is mounted, and the rotation center of the work does not coincide with the center of the rotation axis (C axis). May shift. This error is about 20-30μm
Of the order.

FIG. 4 is a view showing a case where a linear axis passing through the rotation center of the workpiece is shifted by an error P from the linear axis at the time of the program command. In such a case, the error in the direction of the linear axis (X axis) can be easily corrected by moving the tool, but the error in the direction of the virtual axis Cy depends on the movement of the rotation axis (C axis). I can't fix it. Therefore, conventionally, there has been a problem that a tool must be attached so that an error does not occur in the virtual axis direction, and if an error occurs, a measure cannot be taken on the numerical controller side.

The present invention has been made in view of such a point,
It is an object of the present invention to provide a numerical controller capable of correcting an error in a virtual axis direction during polar coordinate interpolation and performing polar coordinate interpolation.

[Means for solving the problem]

In the present invention, in order to solve the above problems, in a numerical control device that controls a numerically controlled machine tool having at least a linear axis and a rotary axis, the numerical control apparatus includes the linear axis on a plane formed by the linear axis and the rotary axis. Interpolating means for interpolating a command instructed in a rectangular coordinate system and outputting an interpolation amount;
Conversion means for converting the amount of error in the direction perpendicular to the linear axis to P, and the amount of interpolation to the amount of movement in a polar coordinate system including the linear axis and the rotation axis by the following equation: (Where X and Cy are commands in a rectangular coordinate system, and Xro and θo are movement amounts in a polar coordinate system).

[Action]

The rotation center of the actual work does not exist on the rotation axis,
In addition, when a linear axis passing through the rotation center of the workpiece has a certain error in a direction perpendicular to the linear axis, the error cannot be corrected only by the orthogonal coordinate values at the time of the program command. However, by including, in the numerical control device, a conversion means for correcting an error that a linear axis passing through the rotation center of the work has in the orthogonal direction thereof, even if there is an error, accurate machining can be performed only by setting the error amount. .

〔Example〕

 Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

FIG. 2 shows a numerical controller (CN) for implementing the present invention.
FIG. 3C is a block diagram of hardware.

In the figure, reference numeral 10 denotes a numerical controller (CNC). The processor 11 is a processor which is a central control unit of the numerical control device (CNC) 10 and reads out a system program stored in the ROM 12 via the bus 21 and controls the entire numerical control device (CNC) according to the system program. Execute The RAM 13 stores temporary calculation data, display data, and the like. The DRAM 13 is a DRAM. The CMOS 14 stores a tool correction amount, a pitch error correction amount, a machining program, parameters, and the like. In the case of the present embodiment, the error amount P in the virtual axis direction is stored here as a parameter. cm
The OS 14 is backed up by a battery (not shown) and is a non-volatile memory even when the power of the numerical controller (CNC) 10 is turned off.

The interface 15 is an interface for an external device, and is connected to an external device such as a paper tape reader, a paper tape puncher, and a paper tape reader / puncher. A processing program (rectangular coordinate values on a polar coordinate interpolation plane) is read from a paper tape reader, and a numerical controller (CNC) 10
The processing program edited inside can be output to the paper tape puncher.

PMC (Programmable Machine Controller) 16 is C
The machine is controlled by a sequence program built in NC10 and created in ladder format. That is, according to the M function, S function and T function commanded by the machining program,
These are converted into necessary signals on the machine side by a sequence program, and output from the I / O unit 17 to the machine side. This output signal drives the magnet on the machine side, and the hydraulic valve,
Activate the pneumatic valve and electric actuator. The processor 11 also receives signals from limit switches on the machine side and switches on the machine operation panel, performs necessary processing, and performs
Pass to.

The graphic control circuit 18 provides a current position of each axis, an alarm,
Digital data such as parameters and image data is converted into an image signal and output. This image signal is sent to the display device 26 of the CRT / MDI unit 25 and displayed on the display device 26.
Interface 19 is keyboard 2 in CRT / MDI unit 25
It receives the data from 7 and passes it to the processor 11.

The interface 20 is connected to a manual pulse generator 32,
It receives a pulse from the manual pulse generator 32. The manual pulse generator 32 is mounted on the machine operation panel and is used for manually moving the machine operation part precisely.

The axis control circuits 41, 42, and 43 receive the movement command of each axis from the processor 11, and output the command of each axis to the servo amplifiers 51, 52, and 53. The servo amplifiers 51, 52 and 53 receive the movement command and drive the servo motors 61, 62 and 63 of each axis. The servo motor 61 is a motor for the linear axis (X axis), the servo motor 62 is a motor for the Z axis, and the servo motor 63 is a motor for the rotary axis (C axis). The servomotors 61, 62 and 63 have a built-in pulse coder for position detection, and the position signal is fed back as a pulse train from the pulse coder. In some cases, a linear scale is used as the position detector. This pulse train is converted to F / V (frequency / speed)
By performing the conversion, a speed signal can be generated. Furthermore, a tacho generator may be used for speed detection. In the figure, the position signal feedback line and velocity feedback are omitted.

The spindle control circuits 71 and 74 receive a spindle rotation command and a command such as spindle orientation,
A spindle speed signal is output to the spindle amplifiers 72 and 75. The spindle amplifiers 72 and 75 receive the spindle speed signal and rotate the spindle motors 73 and 76 at the commanded rotation speed. In addition, the spindle is positioned at a predetermined position by an orientation command.

The spindle motor 73 is a motor for rotating the work, and can be alternately switched with the servo motor 63 according to the type of machining. Spindle motor 76
Is a motor for rotating the tool, and is used when performing contour control or the like. A position coder 82 is connected to the spindle motor 73 by a gear or a belt. Accordingly, the position coder 82 rotates in synchronization with the spindle 73 and outputs a feedback pulse, which is read by the processor 11 via the interface 81. This feedback pulse is used to move another axis in synchronization with the spindle motor 73 to perform processing such as thread cutting.

Next, the operation of polar coordinate interpolation will be described with reference to FIG. FIG. 1 is a diagram for explaining the operation of the embodiment of the present invention. This figure shows a case where the linear axis passing through the rotation center of the workpiece is shifted from the linear axis at the time of the program command by an error P, similarly to FIG.

First, when the origin O of the coordinate system coincides with the center of the rotation axis (C axis), polar coordinate interpolation may be performed on the linear axis (X axis) and the rotation axis (C axis). Therefore, the linear axis (X axis)
Since the point Q of the rectangular coordinates (X, Cy) is programmed on the polar coordinate interpolation plane composed of the virtual axis Cy orthogonal to the linear axis (X axis), the position on the polar coordinates is represented by the polar coordinates (Xr,
θ), Becomes

However, when an error P occurs when the work is mounted and the actual rotation center of the work is shifted from the origin O to the point O1, it cannot be represented by the above-mentioned polar coordinates (Xr, θ). Therefore, when polar coordinate interpolation is performed in consideration of the error P, the point Q
Rotate in the axial direction, find the point Qo that intersects the actual linear axis (Xp axis), and calculate the point from the point Xo and the point Q on the linear axis (Xp axis) of the point Qo.
The rotation angle θo up to Qo is obtained. Therefore, the moving position of the point Q on the polar coordinates is represented by polar coordinates (Xro, θo). Becomes

The error amount P at this time is set in advance by using a parameter.

That is, the command given in the rectangular coordinate system (X, Cy) is
Interpolation may be performed in the orthogonal coordinate system, and the amount of interpolation may be converted into the amount of movement in the polar coordinate system by the above equation.

In this way, the command of the orthogonal coordinate system is interpolated in the numerical controller, and the operation of converting the interpolation amount into the movement amount of the polar coordinate system is performed. Even if a linear axis passing through the rotation center has a certain error in the virtual axis direction, the error can be corrected and polar coordinate interpolation can be performed.

〔The invention's effect〕

As described above, according to the present invention, the conversion means that can correct the error amount in the direction orthogonal to the linear axis at the time of the polar coordinate interpolation is provided. Therefore, even if an error occurs in the orthogonal direction, the error amount can be set only by setting the error amount. Interpolation processing can be performed.

[Brief description of the drawings]

FIG. 1 is a diagram for explaining the operation of an embodiment of the present invention, and FIG. 2 is a numerical controller (CNC) for implementing the present invention.
FIG. 3 is a diagram showing an example of a program for polar coordinate interpolation using a linear axis (X axis) and a rotation axis (C axis). FIG. 4 is a program command for a linear axis passing through the rotation center of the workpiece. It is a figure showing the case where it shifted by error P with respect to the linear axis at the time. 1 Work 2 Tool 3 Program path 4 Path after tool diameter correction Cy Virtual axis P Error in virtual axis direction 11 Processor 12 ROM 13 RAM 14 CMOS 15 Interface 16 PMC (Programmable Machine Controller) 17 I / O unit 18 Graphic control circuit 19 Interface 20 Interface 21 Bus 41 to 43 Axis control circuit 51 ... 53 Servo amplifier 61-63 Servo motor 71,74 Spindle control circuit 72,75 Spindle amplifier 73,76 Spindle motor 81 Interface 82 Position coder

────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Kiyoji Ishii 3580 Kobaba, Oshino-za, Oshino-mura, Minamitsuru-gun, Yamanashi Prefecture FANUC CORPORATION Product Development Laboratory (58) Field surveyed (Int.Cl. ⁶ , DB name) G05B 19/4103

Claims (1)

(57) [Claims] 1. A numerical control apparatus for controlling a numerically controlled machine tool having at least a linear axis and a rotary axis, wherein the numerical control is commanded in a rectangular coordinate system including the linear axis on a plane formed by the linear axis and the rotary axis. Interpolating means for interpolating the given command and outputting an interpolation amount; and letting P be an error amount in a direction perpendicular to the linear axis, and the interpolation amount be a movement amount of a polar coordinate system consisting of the linear axis and the rotation axis. Conversion means for converting by an expression; (Where X and Cy are commands in a rectangular coordinate system, and Xro and θo are movement amounts in a polar coordinate system).