Electricity: motive power systems – Positional servo systems – Program- or pattern-controlled systems
Patent
1990-04-02
1992-01-14
Ip, Paul
Electricity: motive power systems
Positional servo systems
Program- or pattern-controlled systems
318569, 318572, 318618, 318603, 36447434, G05B 1918
Patent
active
050814079
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Technical Field
This invention relates to a numerical control apparatus in which an operation for returning the spindle of a spindle motor to a reference point is improved. More particularly, this invention relates to a numerical control apparatus adapted in such a manner that a spindle is returned to a reference point merely by executing a single-step reference-point return command.
2. Background Art
Generally, in a numerically controlled machine tool, such as a machining center or a numerically controlled lathe, an orientation function is required for stopping a spindle at a predetermined machine reference point as when automatically changing tools. Methods of commanding return to a reference point for the purpose of implementing an orientation function of this kind include a method in which a servomotor or the like is provided separately of a spindle motor, and a method in which a spindle amplifier is provided with a spindle reference-point restoration function and a command necessary for orientation is supplied by an NC apparatus.
However, the method in which a servomotor is separately provided has economical disadvantages. Specifically, a more complicated mechanical structure cannot be avoided, and a motor for returning the spindle to the reference point must be installed. In the arrangement wherein a spindle amplifier is internally provided with a spindle reference-point return function, the signal system for commands from the NC apparatus and for reference-point setting commands is complicated, and control for positioning the spindle cannot be carried out with a single-step reference-point return command. Accordingly, in order to run the NC apparatus, the command program steps must be modified depending upon the type of machine tool to be numerically controlled.
SUMMARY OF THE INVENTION
The present invention has been devised in order to solve the foregoing problems. An important object of the present invention is to provide a numerical control apparatus in which the distance from a one-revolution signal to a machine reference point is set beforehand on the side of a spindle amplifier, and return to the reference point can be commanded in simple fashion merely by commanding the distance from the machine reference point to a stopping position.
In accordance with the present invention, there can be provided a numerical control apparatus having a function for controlling, for return to a reference point, a spindle motor capable of positionally controlling a controlled object by a position signal, comprising setting means for setting a driving amplifier of the spindle motor to a grid-shift quantity of the controlled object, command means for commanding a distance to a stopping target position during a positional control operation by a positioning control mode command, and monitoring means for monitoring the status of positional control by the spindle motor.
In the numerical control apparatus of the present invention, a grid-shift quantity decided by the relationship between the spindle motor and the controlled object is set on the side of the spindle amplifier before numerical control unit operation of a machine tool or the like, and the grid-shift quantity is added to position data, which corresponds to a machining starting point, transferred before a fixed-position stopping command. Therefore, when a reference-point return command is outputted to the side of the spindle amplifier, a transition is made automatically to positional control to start a reference-point return operation with respect to the target position so that the spindle can be positioned at the machining starting point. Accordingly, when the spindle is controlled to be positioned at a machining starting point of C-axis machining, it will suffice merely to execute a single-step reference-point return command.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a block diagram illustrating an embodiment of the present invention,
FIG. 2 is a diagram for describing an operation for returning a spindle to a refer
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patent: 4855657 (1989-08-01), Isobe et al.
Kono Shinichi
Takahashi Hironobu
Fanuc Ltd.
Ip Paul
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