Electricity: motive power systems – Positional servo systems – Program- or pattern-controlled systems
Patent
1990-07-30
1992-09-01
Ip, Paul
Electricity: motive power systems
Positional servo systems
Program- or pattern-controlled systems
318571, 318593, G05B 1918
Patent
active
051442132
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a gravity axis control method of a computerized numerically controlled machine tool, and more specifically, to a gravity axis brake control method of preventing an accidental detaching of a tool mounted on a gravity axis.
2. Description of the Related Art
In general, the Z axis of a vertical type machining center and the Y axis of a horizontal type machining center are referred to as a gravity axis and a tool mounted thereon becomes detached when a power supply is turned off or the excitation of a servo motor of the gravity axis is stopped. This unwanted detaching can be prevented by providing a mechanical brake which is actuated when the power supply is turned off. This brake is generally arranged to clamp the servomotor of the gravity axis when a current supplied to the brake is turned off.
In case of an emergency stop, a programmable controller (hereinafter, referred to as a PC) is notified that the control of the servo motor will be interrupted, whereupon the control of the servo motor is immediately interrupted and an exciting current supplied to the servo motor is turned off. At this time, the PC outputs a signal turning off the current to the brake, to cause the brake to lock the gravity axis.
Nevertheless, since the time at which a computerized numerical control (hereinafter referred to as CNC), interrupts the control of the servo motor and turns off the exciting current supplied to the servo motor of the gravity axis is not synchronized with the time at which the current supplied to the brake is turned off in response to the signal from the PC, thereby locking the gravity axis the tool on the gravity axis may be detached therefrom or the gravity axis may be subjected to shock.
SUMMARY OF THE INVENTION
It is an object of the present invention is to provide a gravity axis brake control method of preventing an unwanted detaching of a tool mounted on a gravity axis.
The present invention achieves the above object by providing a gravity axis brake control method of controlling the brake of the gravity axis of a CNC machine tool, comprising the steps of outputting a signal from the CNC to the PC to notify that the control of the gravity axis will be interrupted, outputting a signal from the PC to the machine tool for actuating the brake, and causing the CNC to turn off an exciting current of the servo motor after a preset brake operation completion time has passed.
First, the CNC notifies the PC that the control of the servo motor will be interrupted and the exciting current supplied to the servo motor will be turned off. The PC receives the signal and turns off a current supplied to the brake, and accordingly, the brake locks the gravity axis. Further, the CNC turns off the exciting current supplied to the servo motor after a preset time has elapsed. This preset time is slightly longer than the time from that at which the CNC notifies the PC to interrupt the control of the servo motor as compared to the time at which the brake locks the gravity axis.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is an execution flows diagram of a gravity axis brake control method according to the present invention; and
FIG. 2 is a diagram of a hardware arrangement for carrying out the present invention.
DESCRIPTION OF THE PREFERRED EMBODIMENT
An embodiment of the present invention will be described below with reference to drawings.
FIG. 1 is a conceptual view of a gravity axis brake control method according to the present invention. The control flow will be described with respect to respective steps. In the figure, numerals prefixed with an "S" indicate the numbers of the steps of the process.
At step S1, the CNC receives an emergency stop signal or the like and notifies a programmable machine controller (hereinafter, referred to as a PMC) that the control of the servo motor of a gravity axis will be interrupted, i.e., an exciting current supplied to the servo motor will be turned off, and at step S2, the PMC receives a signal f
REFERENCES:
patent: 3806788 (1974-04-01), Ullmann et al.
patent: 4506321 (1985-03-01), Comstock et al.
patent: 4514677 (1985-04-01), Kaufman III et al.
patent: 4602195 (1986-07-01), Eberle et al.
patent: 4794311 (1988-12-01), Kiya et al.
patent: 4928047 (1990-05-01), Arai et al.
Hosokawa Masahiko
Murakami Kunihiko
Sasaki Takao
Fanuc Ltd
Ip Paul
LandOfFree
Brake control method of gravity axis does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Brake control method of gravity axis, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Brake control method of gravity axis will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-769912