JPS61224006A - Positioning device for numerically controlled machine tool - Google Patents

Abstract

PURPOSE:To heighten accuracy of positioning of a feeding shaft by controlling to lock a servomotor after completion of positioning of the feeding shaft and to release lock of the servomotor when starting positioning of the feeding shaft thereafter. CONSTITUTION:A feeding amount signal V2 is inputted form a numerical controller 50 to a deviation counter 53, and a feedback pulse V1 is inputted from an encoder 32 and a waveform shaping circuit 56, and the positioning of the feeding shaft is executed by a servomotor 30. When the positioning of the feeding shaft is completed, a sequence controller 52 outputs a controlling signal V4 to make a braking device 33 to operate the device 33. At the same time, it outputs a controlling signal V5 to turn off power source of the motor 30. When starting positioning of the feeding shaft thereafter, the device 52 makes a switch 58 off by the controlling signal V4 to release operation of the device 33, and at the same time, makes a switch 57 on by the controlling signal V5 to enable a driving circuit 55 to operate. Thus, as the surface of a work can be polished with the feeding shaft in the state of perfect stop, accuracy of polishing can be heightened.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a positioning device that accurately positions a shaft such as a main shaft of a numerically controlled machine tool.

[Prior art] Conventionally, the feed control of the feed axis in numerically controlled machine tools is feedback control in which the position of the feed axis is detected and used as a feedback signal in response to a signal that commands the feed amount. It is done by the system. When the positioning of the feed axis is completed, the feedback system is constantly operating so that the deviation between the command signal and the feedback signal is maintained at zero.
In other words, dynamic positioning control is performed.

[Problems to be solved by the invention] Due to dynamic positioning control, the tracking deviation is not stable at zero due to various internal disturbances and disturbance conditions in the closed loop, so the servo motor is driven and positioning becomes unstable by a small width. becomes. In addition, even after positioning is complete, the servo motor is constantly in operation to ensure that the following deviation is zero due to dynamic control, so it generates heat, which causes thermal expansion, and in addition, reduces the positioning accuracy of the feed axis. It was lowering it. In particular, dynamic instability in positioning control of the feed axis is a major problem in machine tools for polishing surfaces such as silicon wafers.

It is an object of the present invention to overcome these conventional drawbacks and improve the positioning accuracy of the feed axis of a numerically controlled machine tool.

[Technical means for solving the problem] The present invention provides a numerical control device that outputs a feed rate signal that commands the feed rate of a feed axis driven by a servo motor to a deviation counter; and a position detector that detects the detected signal and outputs the detected signal as a feedback signal, and a drive device that drives the servo motor according to a deviation between the feed amount signal and the feedback signal. A positioning device for a machine tool includes a brake device that locks the rotation of the servo motor by a control signal, and a control signal from the numerical control device is input, and the brake device is actuated in accordance with the control signal. , a sequence control unit that performs a sequence of locking the servo motor and stopping power supply to the drive device, and a sequence of unlocking the servo motor and starting power supply to the drive device. The numerical control device outputs a lock control signal for locking the servo motor to the sequence control unit after completing positioning of the feed axis, and locks the servo motor when positioning of the feed axis starts thereafter. This positioning device for a numerically controlled machine tool is characterized in that it outputs a lock release control signal to the sequence control section.

A feature of the present invention is to electromechanically lock the servo motor and stop power supply to the servo motor when positioning of the feed axis is completed, and to release the electromechanical lock of the servo motor when positioning is resumed. However, a device is provided to supply power to the servo motor.

[Operation] After the positioning of the feed axis is completed, the numerical control device outputs a lock control signal for locking the servo motor to the sequence control section. When the sequence control unit receives a lock control signal from the numerical control device.

The brake device is activated to lock the servo motor and stop power supply to the drive device. Through this process, the feed shaft is statically stopped regardless of the inner and outer holes of the control system, so the control accuracy of the feed shaft is improved. Further, when positioning of the feed axis starts after that, the numerical control device outputs an unlock control signal to unlock the servo motor to the sequence control section, and the sequence control section unlocks the servo motor and starts the drive device. Start supplying power to.

In this way, the next positioning control is performed.

[Example] The present invention will be described below based on a specific example.

FIG. 1 is a block diagram showing the configuration of the device of this embodiment. A servo motor 3 is installed vertically above the head 10.
A column 20 is provided which holds a ball screw 31 and a ball screw 31. A servo motor 30 is disposed on the column 20, and rotation of the servo motor 30 causes a ball screw 31 to rotate. The amount of rotation of the ball screw 31 is detected by the encoder 32, and its signal is input to the deviation counter 53 via the waveform shaping circuit 56. Also, ball screw 31
A nut 40 is screwed into the shaft, and the nut 40 is fixed to the spindle head 41. Therefore, the rotation of the ball screw 31 allows the spindle head 41 to move in the Z-axis direction.

Here, the two axes correspond to the above-mentioned feed axes, and in this embodiment, the feed amount of the feed axes is measured by the rotation of the ball screw. or,
The position detector includes an encoder 32 and a waveform shaping circuit 56, and the output v1 of the waveform shaping circuit 56 corresponds to the feedback signal.

A spindle motor 42 is disposed in the spindle head 41.
The main shaft motor 42 rotates a main shaft 43 and rotates a grindstone 44 disposed on the main shaft 43. On the other hand, the head 10 is provided with a workpiece support stand 11, on which a rotary table 12 on which a workpiece 13 is placed is arranged. After the spindle head 41 is positioned at a predetermined position on two axes by the servo motor 30, the wafer-shaped workpiece 13 is polished by mutual rotation of the spindle 43 and the workpiece 13.

In addition, a brake device [33 is attached to the servo motor 30, and a control signal [4] from the sequence control device 152 is attached to the servo motor 30.
As a result, the switch 58 is actuated, and the rotation of the servo motor 30 can be stopped by the electromagnet. A data input device 1f51 is connected to the numerical control device 50, and control data is input thereto.

The feed suspension signal 2 is divided into pulses and outputted to the deviation counter 53. The deviation counter 53 includes an encoder 32;
A feedback pulse V1 is input from the waveform shaping circuit 56, and predetermined positioning is performed.

The output of the a difference counter 53 is amplified by an amplifier 54, and then a drive circuit 55 causes the servo motor 3o to rotate at a predetermined speed. The drive circuit 55 also includes a switch 5 operated by a control signal 5 of the sequence control device 152.
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The control signal V3 of the numerical control device w150 is input to the sequence control device 52, and according to the control signal, the sequence control device 52 controls the brake device 33 and the drive circuit 5.
5 can be controlled.

FIG. 2 is a flowchart showing the processing of the numerical control device i50, FIG. 3 is a flowchart showing the processing of the sequence control device, and FIG. 4 is an example of a numerical control program. The numerical control device 150 starts execution at step 100 and reads one block of numerical control data. Next, proceed to step 102 and if there is a G code,
In other words, if there is a feed code such as rapid feed or cutting feed,
G code processing is performed in step 104 as in a normal machine tool. It is determined whether there is a movement command code in step 108, and if there is, step 110
Then, pulse distribution processing is performed on the deviation counter 53 to perform predetermined feed control. After the power distribution, return to step 100, repeat the same process, and
If there is an M code in step 06, the process moves to step 112 and the type of M code is determined. In the case of the MO2 code, the process ends, and in other cases, the process proceeds to step 114, where the M code control signal v3 is output to the sequence control device 52. .

The sequence control device 52 performs the processing shown in FIG.

If the code is not M2O in step 200, the process moves to step 202 and it is determined whether the code is MB2. If the result is YES, the process moves to step 204, where a control signal v4 for turning on the brake system W133 is output, and the brake system V! 133, outputs the control signal V5, turns off the switch 57, stops the output of the drive circuit 55, and turns off the power to the servo motor 3o. If the code is not MB2 in step 202, the process moves to step 206 and other M code processing is performed. When the code is determined to be M2O in step 200, the process moves to step 208, and the control signal v4 turns off the switch 58 to release the brake device 33, and the control signal v5 turns off the switch 58.
is turned on to put the drive circuit 55 in an operable state.

With the above processing, in the case of the M81 code, that is, the lock control signal, when positioning is completed, the brake device can be operated and the power of the servo motor can be turned off, and the feed axis can be stopped statically. Since the surface of the wafer-shaped workpiece can be polished while the feed shaft is completely stopped, polishing accuracy can be improved. Even in such a stopped state, the position detector is operating, so the displacement of the feed axis is input to the deviation counter 53, so this value is used as the correction amount during the next feed control. It can be considered as

Next, when the feed shaft is to be moved by a predetermined amount, it is sufficient to use the M80 code, that is, the lock release control signal, to release the brake device and input power to the servo motor at the start of positioning control. By repeating such feed control, static stop, polishing, and feed control, surface polishing can be continued with high accuracy. Note that the sequence control unit 50 may be provided inside the numerical control device 50, and the operations performed by the sequence control device 52 may be performed inside the numerical control device f[50.

[Effects of the Invention] The present invention includes a brake device that locks the rotation of a servo motor by a control signal, and a control signal from a numerical control device that is inputted and operates the brake device in accordance with the control signal. The present invention is characterized by being provided with a sequence control unit that performs a sequence of locking the servo motor and stopping power supply to the drive device, and a sequence of unlocking the servo motor and starting power supply to the drive device. . After the positioning of the feed axis is completed, the numerical control device outputs a lock control signal for locking the servo motor to the sequence control section,
When the positioning of the feed shaft is started thereafter, a lock release control signal for releasing the lock of the servo motor is output to the sequence control section.

Therefore, unlike dynamic positioning control in which the deviation between the command signal and the feedback signal is maintained at zero using a conventional feedback control system, the feed axis can be statically stopped regardless of various internal disturbances and external disturbances in a closed loop. This improves positioning accuracy.

Furthermore, since heat generation of the servo motor can be prevented, positioning deviation due to thermal expansion can be reduced. Furthermore, since the position detector is activated, it is possible to continue the next feed control.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the configuration of an apparatus according to an embodiment of the present invention. FIG. 2 is a flowchart showing the processing of the numerical control device of the embodiment device, FIG. 3 is a flowchart showing the processing of the sequence control device of the same embodiment device, and FIG. 4 is an example of the numerical control program. FIG. 10... Bed 11... Workpiece support stand 12
... Rotary table 13 ... Workpiece 20 ... Column 30 ... Servo motor 32 ... Encoder 31 ... Ball screw, 40 ... Nut
41...Spindle head 42...Spindle motor 4
3...Main shaft 44...Whetstone

Claims (1)

[Scope of Claims] A numerical control device that outputs a feed rate signal that commands the feed rate of a feed axis driven by a servo motor, a system that detects the feed rate of the feed axis, and uses the detected signal as a feedback signal. A positioning device for a numerically controlled machine tool, comprising: a position detector that outputs a position sensor; and a drive device that drives the servo motor according to a deviation between the feed amount signal and the feedback signal. a brake device that locks rotation by a control signal; and a control signal from the numerical control device is input, and according to the control signal, the brake device is operated to lock the servo motor and control the drive device. The numerical control device includes a sequence control unit that performs a sequence for stopping power supply and a sequence for unlocking the servo motor and starting power supply to the drive device, and the numerical control device is configured to complete positioning of the feed axis. After that, a lock control signal for locking the servo motor is output to the sequence control unit, and when positioning of the feed shaft starts thereafter, an unlock control signal for unlocking the servo motor is output to the sequence control unit. A positioning device for a numerically controlled machine tool, which is characterized by: