DEVICE AND METHOD OF CONTROLLING MACHINE TOOL, TO CONTROL SYNCHRONIZED OPERATION OF SPINDLE AXIS AND FEED AXIS

• US 20160291580A1
• Filed: 03/29/2016
• Published: 10/06/2016
• Est. Priority Date: 03/30/2015
• Status: Active Grant

• Current Assignee: Fanuc Corporation
• Original Assignee: Fanuc Corporation
• Inventors: Morita, Yuuki, Okita, Tadashi
• Granted Patent: US 9,910,426 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: B23Q 15/007 while the tool acts upon the workpiece
• CPC Class Codes: G05B 19/416 characterised by control of velocity, acceleration or deceleration G05B19/19 takes precedence
• CPC Class Codes: G05B 2219/49108 Spindle speed
• CPC Class Codes: G05B 2219/50216 Synchronize speed and position of several axis, spindles

Abstract

A controller for controlling a synchronized operation of spindle and feed axes. A spindle-axis control section includes a section for making a spindle axis perform an accelerated rotation at maximum capacity from a process start position; sections for respectively detecting a maximum acceleration, a residual rotation amount and a current speed of the spindle axis; a section for making the spindle axis perform a decelerated rotation at maximum capacity to reach a target thread depth after the accelerated rotation; and a section for executing a torque-limiting during the accelerated rotation of the spindle axis, in such a manner that a torque command lower than a maximum torque command is given to the spindle axis at a start of acceleration, and thereafter the torque command is gradually increased so that the maximum torque command is given to the spindle axis when a predetermined time has elapsed.

Claims

1. A controller of a machine tool, configured to control a synchronized operation of a spindle axis and a feed axis, the controller comprising:

a numerical control section configured to prepare a spindle-axis command and a feed-axis command based on a tapping program;

a spindle-axis control section configured to control a rotational motion of the spindle axis in accordance with the spindle-axis command;

a rotation detecting section configured to detect a rotational position of the spindle axis; and

a feed-axis control section configured to control a feed motion of the feed axis in accordance with the feed-axis command, based on the rotational position;

the numerical control section comprising;

a spindle-axis command outputting section configured to obtain, from the tapping program, a total rotation amount and a maximum rotation speed of the spindle axis during a period when the spindle axis operates from a process start position to a target thread depth, and to send the total rotation amount and the maximum rotation speed as the spindle-axis command to the spindle-axis control section;

the spindle-axis control section comprising;

an initial-motion control section configured to make the spindle axis perform an accelerated rotation at maximum capacity, from the process start position toward the target thread depth, with the maximum rotation speed set as a target value;

a torque-limit executing section configured to execute a torque-limiting for the initial-motion control section during a period when the initial-motion control section makes the spindle axis perform the accelerated rotation, in such a manner that, at a start of acceleration, a predetermined torque command lower than a maximum torque command provided for the accelerated rotation at maximum capacity is given to the spindle axis, and during a predetermined time elapsing from the start of acceleration, the predetermined torque command is gradually increased so that the maximum torque command is given to the spindle axis at an instant when the predetermined time has elapsed;

a maximum-acceleration detecting section configured to detect a maximum acceleration of the spindle axis during the accelerated rotation at maximum capacity, based on the rotational position;

a residual rotation-amount detecting section configured to detect a residual rotation amount of the spindle axis during a period when the spindle axis operates from a current position to the target thread depth, based on the total rotation amount and the rotational position;

a current-speed detecting section configured to detect a current speed of the spindle axis based on the rotational position; and

a positioning-motion control section configured to make the spindle axis perform a decelerated rotation at maximum capacity so as to reach the target thread depth, after the accelerated rotation at maximum capacity, based on the maximum acceleration, the residual rotation amount and the current speed.

2. The controller of claim 1, wherein the positioning-motion control section is configured to make the spindle axis reach the target thread depth, after the accelerated rotation at maximum capacity, based on the maximum acceleration, the residual rotation amount, the current speed and a predetermined acceleration-change time, by making the spindle axis perform a decelerated rotation at an acceleration lower than the maximum acceleration and changing at a predetermined rate during the acceleration-change time, while making the spindle axis perform the decelerated rotation at maximum capacity during a time except for the acceleration-change time.

3. The controller of claim 1, wherein the spindle-axis command outputting section is configured to obtain, from the tapping program, a total return-rotation amount and a maximum return-rotation speed of the spindle axis during a period when the spindle axis operates from the target thread depth to a return completion position, and to send the total return-rotation amount and the maximum return-rotation speed as the spindle-axis command to the spindle-axis control section;

wherein the initial-motion control section is configured to make the spindle axis perform an accelerated inverse rotation at maximum capacity, from the target thread depth, or from an initial return position at which the spindle axis has returned by a predetermined rotation number from the target thread depth, toward the return completion position, with the maximum return-rotation speed set as a target value;

wherein the maximum-acceleration detecting section is configured to detect or obtain a maximum acceleration of inverse rotation during a period when the spindle axis performs the accelerated inverse rotation from the target thread depth;

wherein the residual rotation-amount detecting section is configured to detect a residual return-rotation amount of the spindle axis during a period when the spindle axis operates from a current position to the return completion position, based on the total return-rotation amount and the rotational position;

wherein the current-speed detecting section is configured to detect a current speed of inverse rotation of the spindle axis based on the rotational position; and

wherein the positioning-motion control section is configured to make the spindle axis perform a decelerated inverse rotation at an acceleration lower than the maximum acceleration of inverse rotation and changing at a predetermined rate during a predetermined acceleration-change time, and also perform a decelerated inverse rotation at maximum capacity during a time except for the acceleration-change time, so as to make the spindle axis stop at the return completion position, after the accelerated inverse rotation at maximum capacity, based on the maximum acceleration of inverse rotation, the residual return-rotation amount, the current speed of inverse rotation and the acceleration-change time.

4. The controller of claim 3, wherein the numerical control section is configured to monitor the residual rotation amount and to judge that a tapping process reaches the target thread depth when the residual rotation amount becomes equal to or less than a first predetermined value;

wherein the positioning-motion control section is configured to make the spindle axis stop at the target thread depth;

wherein the initial-motion control section is configured to make the spindle axis perform the accelerated inverse rotation at maximum capacity, from the target thread depth toward the return completion position, with the maximum return-rotation speed set as a target value;

wherein the torque-limit executing section is configured to execute a torque limiting for the initial-motion control section during a period when the initial-motion control section makes the spindle axis perform the accelerated inverse rotation, in such a manner that, at a start of acceleration, a predetermined torque command lower than a maximum torque command provided for the accelerated inverse rotation at maximum capacity is given to the spindle axis, and during a predetermined time elapsing from the start of acceleration, the predetermined torque command is gradually increased so that the maximum torque command is given to the spindle axis at an instant when the predetermined time has elapsed; and

wherein the maximum-acceleration detecting section is configured to detect the maximum acceleration of inverse rotation during the accelerated inverse rotation at maximum capacity, based on the rotational position.

5. The controller of claim 3, wherein the numerical control section is configured to monitor the residual rotation amount and to judge that a tapping process reaches the target thread depth when the residual rotation amount becomes equal to or less than a first predetermined value;

wherein the positioning-motion control section is configured not to make the spindle axis stop at the target thread depth but to make the spindle axis perform an accelerated inverse rotation at the maximum acceleration of inverse rotation, which is identical to a maximum deceleration during the decelerated rotation at maximum capacity, to the initial return position, after the spindle axis reaches the target thread depth;

wherein the initial-motion control section is configured to make the spindle axis perform the accelerated inverse rotation at maximum capacity, from the initial return position toward the return completion position, with the maximum return-rotation speed set as a target value; and

wherein the maximum-acceleration detecting section is configured to obtain the maximum deceleration in the decelerated rotation at maximum capacity as the maximum acceleration of inverse rotation.

6. The controller of claim 4, wherein the numerical control section is configured to monitor the residual return-rotation amount and to judge that a return motion is completed when the residual return-rotation amount becomes equal to or less than a second predetermined value.

7. The controller of claim 1, further comprising a feed detecting section configured to detect a feed position of the feed axis;

wherein the numerical control section comprises;

a feed-axis command outputting section configured to obtain, from the tapping program, a total feed amount and a thread pitch of the feed axis during a period when the feed axis operates from the process start position to the target thread depth, and to send the total feed amount and the thread pitch as the feed-axis command to the feed-axis control section; and

wherein the feed-axis control section comprises;

a feed-motion control section configured to control the feed motion of the feed axis, based on the thread pitch and the rotational position; and

a residual feed-amount detecting section configured to detect a residual feed amount of the feed axis during a period when the feed axis operates from a current position to the target thread depth, based on the total feed amount and the feed position.

8. The controller of claim 7, wherein the numerical control section comprises a position recognizing section configured to recognize the current position of the spindle axis based on the residual rotation amount, and also recognize the current position of the feed axis based on the residual feed amount.

9. The controller of claim 7, wherein the numerical control section comprises a synchronization-error calculating section configured to calculate a synchronization error in the synchronized operation, based on the residual rotation amount, the residual feed amount and the thread pitch.

10. The controller of claim 3, further comprising a feed detecting section configured to detect a feed position of the feed axis;

wherein the numerical control section comprises;

a feed-axis command outputting section configured to obtain, from the tapping program, a total return-feed amount and a thread pitch of the feed axis during a period when the feed axis operates from the target thread depth to the return completion position, and to send the total return-feed amount and the thread pitch as the feed-axis command to the feed-axis control section, when the numerical control section judges that the tapping process reaches the target thread depth; and

wherein the feed-axis control section comprises;

a feed-motion control section configured to control a return-feed motion of the feed axis, based on the thread pitch and the rotational position; and

a residual feed-amount detecting section configured to detect a residual return-feed amount of the feed axis during a period when the feed axis operates from a current position to the return completion position, based on the total return-feed amount and the feed position.

11. The controller of claim 10, wherein the numerical control section comprises a position recognizing section configured to recognize the current position of the spindle axis based on the residual return-rotation amount, and also recognize the current position of the feed axis based on the residual return-feed amount.

12. The controller of claim 10, wherein the numerical control section comprises a synchronization-error calculating section configured to calculate a synchronization error in the synchronized operation, based on the residual return-rotation amount, the residual return-feed amount and the thread pitch.

13. A controller of a machine tool, configured to control a synchronized operation of a spindle axis and a feed axis, the controller comprising:

a numerical control section configured to prepare a spindle-axis command and a feed-axis command based on a tapping program;

a spindle-axis control section configured to control a rotational motion of the spindle axis in accordance with the spindle-axis command;

a rotation detecting section configured to detect a rotational position of the spindle axis; and

a feed-axis control section configured to control a feed motion of the feed axis in accordance with the feed-axis command, based on the rotational position;

the numerical control section comprising;

a spindle-axis command outputting section configured to obtain, from the tapping program, a total return-rotation amount and a maximum return-rotation speed of the spindle axis during a period when the spindle axis operates from a target thread depth to a return completion position, and to send the total return-rotation amount and the maximum return-rotation speed as the spindle-axis command to the spindle-axis control section;

the spindle-axis control section comprising;

an initial-motion control section configured to make the spindle axis perform an accelerated inverse rotation at maximum capacity, from the target thread depth, or from an initial return position at which the spindle axis has returned by a predetermined rotation number from the target thread depth, toward the return completion position, with the maximum return-rotation speed set as a target value;

a maximum-acceleration detecting section configured to detect or obtain a maximum acceleration of inverse rotation during a period when the spindle axis performs the accelerated inverse rotation from the target thread depth;

a residual rotation-amount detecting section configured to detect a residual return-rotation amount of the spindle axis during a period when the spindle axis operates from a current position to the return completion position, based on the total return-rotation amount and the rotational position;

a current-speed detecting section configured to detect a current speed of inverse rotation of the spindle axis based on the rotational position; and

a positioning-motion control section configured to make the spindle axis perform a decelerated inverse rotation at an acceleration lower than the maximum acceleration of inverse rotation and changing at a predetermined rate during a predetermined acceleration-change time, and also perform a decelerated inverse rotation at maximum capacity during a time except for the acceleration-change time, so as to make the spindle axis stop at the return completion position, after the accelerated inverse rotation at maximum capacity, based on the maximum acceleration of inverse rotation, the residual return-rotation amount, the current speed of inverse rotation and the acceleration-change time.

14. A method of controlling a machine tool, configured to control a synchronized operation of a spindle axis and a feed axis, the method comprising the acts, executed by a controller, of:

obtaining, from a tapping program, a total rotation amount and a maximum rotation speed of the spindle axis during a period when the spindle axis operates from a process start position to a target thread depth;

making the spindle axis perform an accelerated rotation at maximum capacity, from the process start position toward the target thread depth, with the maximum rotation speed set as a target value, while executing a torque-limiting in such a manner that, at a start of acceleration, a predetermined torque command lower than a maximum torque command provided for the accelerated rotation at maximum capacity is given to the spindle axis, and during a predetermined time elapsing from the start of acceleration, the predetermined torque command is gradually increased so that the maximum torque command is given to the spindle axis at an instant when the predetermined time has elapsed;

detecting a maximum acceleration during the accelerated rotation at maximum capacity, based on a rotational position feedback of the spindle axis;

detecting a residual rotation amount of the spindle axis during a period when the spindle axis operates from a current position to the target thread depth, based on the total rotation amount and the rotational position feedback;

detecting a current speed of the spindle axis based on the rotational position feedback; and

making the spindle axis perform a decelerated rotation at maximum capacity so as to reach the target thread depth, after the accelerated rotation at maximum capacity, based on the maximum acceleration, the residual rotation amount and the current speed.

15. A method of controlling a machine tool, configured to control a synchronized operation of a spindle axis and a feed axis, the method comprising the acts, executed by a controller, of:

obtaining, from a tapping program, a total return-rotation amount and a maximum return-rotation speed of the spindle axis during a period when the spindle axis operates from a target thread depth to a return completion position;

making the spindle axis perform an accelerated inverse rotation at maximum capacity, from the target thread depth, or from an initial return position at which the spindle axis has returned by a predetermined rotation number from the target thread depth, toward the return completion position, with the maximum return-rotation speed set as a target value;

detecting or obtaining a maximum acceleration of inverse rotation during a period when the spindle axis performs the accelerated inverse rotation from the target thread depth;

detecting a residual return-rotation amount of the spindle axis during a period when the spindle axis operates from a current position to the return completion position, based on the total return-rotation amount and a rotational position feedback of the spindle axis;

detecting a current speed of inverse rotation of the spindle axis based on the rotational position feedback; and

making the spindle axis perform a decelerated inverse rotation at an acceleration lower than the maximum acceleration of inverse rotation and changing at a predetermined rate during a predetermined acceleration-change time, and also perform a decelerated inverse rotation at maximum capacity during a time except for the acceleration-change time, so as to make the spindle axis stop at the return completion position, after the accelerated inverse rotation at maximum capacity, based on the maximum acceleration of inverse rotation, the residual return-rotation amount, the current speed of inverse rotation and the acceleration-change time.