JP2539097B2 - Machining error correction method and machine tool - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a machine tool capable of simultaneously controlling two axes and a method for correcting a machining error thereof.

[0002]

2. Description of the Related Art For example, on the order of nanometers (nm)
An ultra-precision lathe is one of the multi-axis simultaneous control machine tools that requires high machining accuracy.

FIG. 1 shows the basic structure of an ultra-precision lathe.
It The X table 13 and the Z table 14 are stone surface plates 16
They are arranged orthogonally above. The X table 13 is equipped with a tool rest 12 and moves straight in the radial direction of rotation of the spindle.
4 is equipped with a spindle 10 for rotating a workpiece 15 and moves straight in the direction of the spindle rotation axis. Tables 13 and 1 of each
It is possible to perform simultaneous biaxial control of the positions of 4 according to the NC data by the NC device 17 and perform turning of the workpiece 15 into a spherical / aspherical rotational shape.

FIG. 5 shows the X-axis table 53 of this super-precision lathe.
And a laser interference feedback system is used for positioning control of the Z-axis table 54 . Where the blade 5
Spindle spindle that holds the workpiece 55 to be turned by 1.
The handle 50 is mounted on the Z-axis table 54. A laser beam emitted from a laser oscillator 57 installed on the stone surface plate 56 is divided into two laser beams orthogonal to each other by a beam splitter 58, and is incident on a laser interferometer 59 and bent in a straight direction of each table. Reflectors 6 on each table
It is incident on 0. The laser light is reflected by the reflecting mirror 60 and the laser interferometer 5.
It reciprocates between 9 and re-enters the laser interferometer 59 to form interference light. The interference light enters the receiver 61, and the position of each table is detected by the built-in photoelectric element. Each table is positioned by feeding back the obtained photoelectric signal to the position control unit of each table.

Straightness is required for the linear motion of both the X and Z axis tables in such an ultra-precision lathe. However, in reality, there is a straightness error due to the method of the table guide surface, the processing accuracy of the table, and the disturbance to the workpiece or the table. For example, as shown in FIGS. 4 and 6, when the position of the cutting edge is controlled to point P, the X-axis table causes a straightness error of ΔZ in the Z-axis direction, and the Z-axis table causes a straightness error of ΔX in the X-axis direction. If it happens, it is actually from point P

The cutting edge is positioned at point Q, which is separated by only.
If such straightness error is left as it is, the ideal shape (NC command) shown by the dotted line in FIG. 7 is processed into a shape having an error as shown by the solid line. That is, only by improving the positioning accuracy of each table by using a laser interference position feedback system or the like, a positioning error associated with the straightness error of the table remains, so that high precision machining cannot be performed.

[0007]

SUMMARY OF THE INVENTION The present invention comprises a machining error correction method and a method therefor capable of machining an ideal shape by correcting a straightness error during machining of each table of X and Z axes in real time. The purpose is to provide a machine tool that does.

The machining error correcting method of the present invention comprises a spindle having a rotation axis in the Z-axis direction for rotating a workpiece, a Z-axis table mounted with the spindle and moving back and forth in the Z-axis direction, and the Z-axis table. Position to detect the Z-axis table position
A Z-axis table position detector that outputs a feedback signal, an X-axis table that moves back and forth in the X-axis direction orthogonal to the Z-axis,
The position of the X-axis table is detected and the X-axis table position flag is detected.
X-axis table position detector that outputs a feedback signal, a blade mounted on the X-axis table, and the Z- axis table
Z-axis position command signal for commanding the movement position of the cable and the above
X-axis position command signal that commands the movement position of the X-axis table
Z for positioning the output position command section and the Z-axis table at the movement position designated by the Z-axis position command signal.
A shaft table position control unit, the X-axis table; and a X-axis table position controller for positioning the moving position designated by the X-axis position command signal and turning the workpiece by the tool machine In the machining error correction method, the displacement of the Z-axis table in the X-axis direction is measured while performing the turning , and the straightness error of the Z-axis table is measured.
A Z-axis table straightness error measuring step for outputting an X-axis table position correction signal, and a Z indicating the straightness error of the X-axis table by measuring the displacement of the X-axis table in the Z-axis direction while performing the turning. Outputs axis table position correction signal
And X-axis table straightness error measurement process that, the X-axis table
If the position correction signal is superimposed on the X-axis position command signal,
Both X-axis on which the X-axis table position correction signal is superimposed
Position command signal and X-axis table position feedback
The position of the X-axis table is turned based on the signal.
An X-axis table position correcting step of correcting while, the
The Z-axis table position correction signal is superimposed on the Z-axis position command signal.
The Z-axis table position correction signal is superimposed while being folded.
Z-axis position command signal and the Z-axis table position
The Z-axis table position is raised based on the feedback signal.
The Z-axis table position correcting step for correcting while performing turning processing is provided to achieve the above object.

In the machine tool of the present invention, a spindle having a rotation axis in the Z-axis direction for rotating a workpiece, a Z-axis table for mounting the spindle and advancing and retracting in the Z-axis direction, and a position of the Z-axis table. To detect Z-axis table position feedback
A Z-axis table position detector that outputs a signal, an X-axis table that moves back and forth in the X-axis direction that is orthogonal to the Z-axis, and a position of the X-axis table that detects the position of the X-axis table position feeder.
X-axis table position detector that outputs a check signal,
A blade mounted on the axis table for turning the workpiece, and a Z-axis position finger for instructing the movement position of the Z-axis table.
Command signal and X-axis to command the moving position of the X-axis table
A position command section that outputs a position command signal and an X-axis table position compensation that indicates the straightness error of the Z-axis table by measuring the displacement of the Z-axis table in the X-axis direction while performing the turning process.
Z-axis table straightness error measuring means for outputting a positive signal ,
The Z-axis direction of the displacement of the X-axis table and the turning
Z axis showing the straightness error of the above X axis table measured while
X-axis table straightness error measuring means for outputting a table position correction signal, and the X-axis table position correction signal for the X-axis
The Z-axis table described above is superimposed on the axis position command signal.
Position where the position correction signal is superimposed on the Z-axis position command signal
The correction signal superimposing means and the X-axis table position correction signal are
Overlaid X-axis position command signal and the X-axis table position
Turning the above X-axis table based on the feedback signal
X-axis table position control unit for positioning while machining
And the Z-axis position on which the Z-axis table position correction signal is superimposed
Position command signal and the Z-axis table position feedback signal
While turning the Z-axis table based on the
The above-mentioned object is achieved by including a Z-axis table position control unit that is arranged.

[0010]

By adopting such a machining error correction method, the straightness error of the X and Z both-axis tables during machining can be corrected in real time, and therefore the machine tool can machine an ideal shape in response to the NC command. Become.

[0011]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 2 shows an embodiment in which a straightness error detector is installed on the ultra-precision lathe shown in FIG. The tool rest 22 in the X-table 23 the target 26 than the stroke length of the X table 23 is fixed to the longitudinal direction is perpendicular to the Z axis. The straightness error ΔZ during the rectilinear movement of the X-axis table 23 is detected as a displacement from the X-axis by a straightness error detector 27 installed on the tool post 22 so as to face the target 26. Similarly, the Z-axis table 24 has
A target 28 having a length equal to or longer than the stroke is fixed with its longitudinal direction orthogonal to the X-axis, and detected by a straightness error detector 29 installed facing the straightness error ΔX target 28 of the Z-axis table 24. To be done. For example, laser interferometers are used as the straightness error detectors 27 and 29, and if a reflecting mirror is fixed as a target 26 or 28 on each table in parallel with the axis , high accuracy on the order of nanometer (nm) is obtained. Straightness error measurement is possible. These straightness error detectors 27 and 29 have a function of outputting the measured values ΔX and ΔZ in real time during processing.

FIG. 3 is a block diagram of the error correction system of this embodiment. The inside of the broken line is the configuration of the NC device 30 , which is the X-axis table 23 and the Z-axis table from the position command unit 31.
A command for designating the position of the cable 24 is issued to the pulse distributor 32.
As the position command signals NX and NZ, the X-axis table 2
Table drive motors 35a and 35b by distributing to the respective position control units 33 and 34 of the Z-axis table 24.
To drive the, provided so as to simultaneously control the two-axis
It At the same time, the X-axis table 23 and the Z-axis table 2
The position of No. 4 is measured by the position detectors 36a and 36b, and the position detection signals from the position detectors 36a and 36b at this time are detected.
The feedback signals FX and FZ are fed back to the X-axis and Z-axis position control units 33 and 34, and the position command unit is provided.
The position is controlled so as to be positioned at the position designated by 31 . In the present embodiment, however, the X-axis table is further added.
23 and Z-axis table 24 straightness error detectors 27, 2
9, obtained straightness error signal SX, Te based on the SZ
Table position correction signals TX and TZ to position command signals NX and N
Interface 38 as superimposing means for superimposing on Z
Have. Now, when the machining program is given from a paper tape or an internal memory, the position command section 31 outputs position command signals NX and NZ indicating the position command corresponding thereto to the X-axis table.
Position control units 33 and 34 of the Z-axis table 24 and the Z-axis table 24
Is applied. Then, the position control units 33 and 34
The X-axis table 2 by driving the drive motors 35a and 35b.
3 and the Z-axis table 24 are displaced. At the same time, position system
The control parts 33 and 34 are connected to the flaps from the position detectors 36a and 36b.
The position is continuously controlled based on the feedback signals FX and FZ . At this time, the X table measured by the straightness error detector 27 facing the target 26 on the tool rest 22.
The straightness error signal SZ indicating the Z-direction straightness error ΔZ of 23
Is output to the interface 38, and the straightness error signal SX indicating the X-direction straightness error ΔX of the Z-axis table 24 measured by the straightness error detector 29 facing the target 28 on the Z-axis table 24 is interleaved. Fe
Is output to the source 38 . As a result, interface 3
At 8, the correction of -ΔX based on the straightness error signal SX is made.
X-axis table position correction signal TX for performing
Command signal NX, and the superimposed signal is the position control unit 3
3 is applied. Also, in the interface 38,
Based on the straightness error signal SZ, correction of −ΔZ is performed.
Z-axis table position correction signal TZ for position command signal NZ
And the superimposed signal is applied to the position controller 34.
It is.

FIG. 4 is a diagram showing the locus of the cutting edge according to this embodiment. Position command signals NX, NZ from the position command unit 31
Transmits the command of the ideal surface indicated by the broken line to the position control units 33 and 34. Since the X-axis table 23 and the Z-axis table 24 have the straightness error as described above, the cutting edge draws the error indicated by the solid line only by performing the NC control of the X-axis table 23 and the Z-axis table 24. Therefore, in the present embodiment , the straightness is set by the interface 38 during turning.
X for correcting -ΔX based on the error signal SX
Axis table position correction signal TX is superimposed on position command signal NX
The superimposed signal is applied to the position controller 33.
Further, in the interface 38, the straightness error signal S
Z-axis table for correcting -ΔZ based on Z
The position correction signal TZ is superimposed on the position command signal NZ,
The generated signal is applied to the position controller 34. as a result,
Position command for X-axis table 23 and Z-axis table 24
The straightness error (-ΔX, -ΔZ) is superimposed on (X, Z).
It Next, in the position control unit 33, the X-axis table position
The position command signal NX on which the correction signal TX is superimposed and the position detection signal NX
Based on the feedback signal FX output from the output device 36a,
Then, the X-axis table 23 is positioned. Furthermore, the position
In the control unit 34, the Z-axis table position correction signal TZ is overwritten.
The folded position command signal NZ and the position detector 36b output
Z-axis table based on the applied feedback signal FZ
24 positioning is performed. This allows the position of the cutting edge to
Can be compensated in real time. As a result, not only static straightness error such as straightness error generated in the manufacturing process of the table or straightness error caused by assembly error, but also random random dynamic error caused by uncertain factors during turning. The straightness error can also be corrected accurately, and for example, ultra-precision turning processing on the order of nanometer (nm) is possible.

Although this embodiment relates to a method for correcting a machining error of an ultra-precision lathe with simultaneous two-axis control, the same effect can be obtained with a machine tool that simultaneously controls two orthogonal axis tables (column heads). can get.

Further, a laser interference position feedback system is used as a detector of table positioning error.
As long as it is a measuring device capable of highly accurate measurement, it can be applied to both contact and non-contact types. For example, a capacitance type, a differential transformer type, or an eddy current type displacement meter may be used.

[0017]

The present invention has the following special effects. That is, the straightness error of each of the X-axis table and the Z-axis table generated during turning can be corrected in real time with high accuracy. Especially, the X-axis table
Bullet position correction signal and X-axis position command signal and X
Axis table position feedback signal and Z-axis table
Bullet position correction signal and Z-axis position command signal and Z
Position control based on axis table position feedback signal
By doing so, not only static straightness error such as straightness error generated in the manufacturing process of the table or straightness error caused by assembly error, but also accidental due to uncertain factors during turning. It is also possible to accurately correct a random dynamic straightness error that occurs. By enabling high-precision straightness error correction of the X-axis table and the Z-axis table in real time, for example, ultra-precision turning processing on the order of nanometer (nm) is possible.

[Brief description of drawings]

FIG. 1 is a schematic view (perspective view) of an ultra-precision lathe.

FIG. 2 is a diagram showing a processing error detection system according to an embodiment of the present invention.

FIG. 3 is a block diagram of an error correction system according to an embodiment of the present invention.

FIG. 4 is a diagram showing X and Z components of a processing error vector and their combined vector.

FIG. 5 is a schematic view (top view) in which a laser interference position feedback system is installed on an ultra-precision lathe.

FIG. 6 is a diagram showing occurrence of straightness error of the X and Z axis tables.

FIG. 7 is a diagram showing a machining error of a workpiece caused by a straightness error.

[Explanation of symbols]

10 ... Spindle spindle, 11 ... Tool, 12 ... Tool rest, 1
3 ... X-axis table, 14 ... Z-axis table, 15 ... Workpiece, 16 ... Stone surface plate, 17 ... NC device, 18 ... Vibration isolation table, 2
0 ... Spindle spindle, 21 ... Blade, 23 ... X-axis table, 24 ... Z-axis table, 25 ... Workpiece, 26 ... Target, 27 ... Straightness error detector, 28 ... Target, 2
9 ... Straightness error detector, 30 ... NC device, 31 ... Position command unit, 32 ... Pulse distribution unit, 33 ... X-axis position control unit, 3
4 ... Z-axis position control unit, 35 ... Table drive motor, 36
... Position detector, 37 ... Straightness error detector, 38 ... Interface, 50 ... Spindle spindle, 51 ... Blade, 53
... X-axis table, 54 ... Z-axis table, 55 ... Workpiece,
56 ... Stone surface plate, 57 ... Laser oscillator, 58 ... Beam splitter, 59 ... Laser interferometer, 60 ... Reflector, 61 ... Receiver.

Claims (2)

(57) [Claims] 1. A rotation axis and the spindle for rotating the provided workpiece in the Z-axis direction, and the Z-axis table for forward and backward in the Z-axis direction by mounting the spindle, to detect the position of the Z-axis table
A Z-axis table position detector that outputs a Z-axis table position feedback signal, an X-axis table that moves back and forth in the X-axis direction orthogonal to the Z-axis, and a position of the X-axis table are detected.
X to output the X- axis table position feedback signal
Axis table position detector, blade mounted on the X-axis table, Z axis for commanding the moving position of the Z axis table
Position command signal and command the moving position of the X-axis table
Position command section for outputting an X-axis position command signal, and the Z-axis
And Z-axis table position controller that positions the table moving position designated by the Z-axis position command signal, the X
Axis table comprises an X-axis table position controller for positioning the moving position designated by the X-axis position command signal, the workpiece in the machining error correction method for a machine tool for turning by the tool, the Z The displacement of the X-axis table in the X-axis direction is measured while performing the turning process , and an X-axis table position correction signal indicating the straightness error of the Z-axis table is obtained.
Z-axis table showing the Z-axis table straightness error measuring step of outputting, the Z-axis direction of the displacement of the X-axis table straightness error of measurement <br/> boss the X-axis table with the turning
An X-axis table straightness error measuring step of outputting a position correction signal, and the X-axis table position correction signal are transmitted to the X-axis position finger.
Command signal and X-axis table position correction
X-axis position command signal with the signal superimposed and the X-axis table
The X-axis table based on the position feedback signal
The X-axis table position correction step for correcting the position of No. 1 while performing the turning process, and the Z-axis table position correction signal
The Z-axis table is superposed on the Z-axis position command signal.
The Z-axis position command signal on which the position correction signal is superimposed, and
Based on the Z-axis table position feedback signal, the above Z
Z to correct the position of the axis table while performing the above turning
An axis table position correction step is provided, and a machining error correction method is provided. Wherein the axis of rotation and the spindle for rotating the provided workpiece in the Z-axis direction, and the Z-axis table for forward and backward in the Z-axis direction by mounting the spindle, to detect the position of the Z-axis table
A Z-axis table position detector that outputs a Z-axis table position feedback signal, an X-axis table that moves back and forth in the X-axis direction orthogonal to the Z-axis, and a position of the X-axis table are detected.
X to output the X- axis table position feedback signal
Axis table position detector, blade mounted on the X-axis table for turning the workpiece, Z-axis table
Z-axis position command signal for commanding the moving position of the
Position command unit that outputs an X-axis position command signal that commands the movement position of the table, and the displacement in the X-axis direction of the Z-axis table is measured while performing the turning , and the Z-axis table straightness Z-axis table straightness error measuring means for outputting an X-axis table position correction signal indicating a degree error, and Z of the X-axis table.
A Z-axis table position correction signal that indicates the straightness error of the X-axis table by measuring the axial displacement while performing the turning process.
And X-axis table straightness error measuring means for outputting, the X
Superimpose the axis table position correction signal on the X-axis position command signal
The Z-axis table position correction signal
Position correction signal superposition means for superposing on the axis position command signal,
X-axis position finger on which the X-axis table position correction signal is superimposed
Command signal and the above X-axis table position feedback signal
Positioning while turning the above X-axis table based on
X-axis table position control unit and the Z-axis table position
Z-axis position command signal on which the position correction signal is superimposed and the Z-axis
Based on the table position feedback signal, the Z-axis
Z-axis table for positioning the table while turning
A machine tool characterized by comprising a position controller .