Control device for a tool driving unit

A control device for a tool driving unit wherein a tool mounted at a front end of a spindle is controlled to be rotated around a central axis of the spindle and longitudinally fed along the central axis of the spindle by said control device, said control device being controlled by a microcomputer which outputs a spindle current command for driving a spindle servo motor to rotate the tool and a feed shaft current command for driving a feed shaft servo motor to longitudinally feed the tool, said microcomputer comprising:

• NC control means for reading an NC program and outputting a spindle command for controlling said spindle servo motor when performing a tapping operation, and for outputting said spindle command and a first feed shaft command for said feed shaft servo motor when performing a drilling operation;
• thread pitch control means for controlling a thread pitch by outputting a second feed shaft command for said feed shaft servo motor when a tapping operation is performed;
• feed shaft command selecting means for receiving said first feed shaft command when performing a drilling operation and for receiving said second feed shaft command when performing a tapping operation and for selectively outputting one of said feed shaft commands as a selected feed shaft command;
• spindle position control means for detecting a first angular position of said spindle servo motor, determining a first positional difference between said first angular position and said spindle command, and outputting a spindle speed command for said spindle servo motor based on said first positional difference;
• spindle speed control means for detecting a first rotational speed of said spindle servo motor, determining a first speed difference between said first rotational speed and said spindle speed command, and outputting said spindle current command based on said first speed difference;
• feed shaft position control means for detecting a second angular position of said feed shaft servo motor, determining a second positional difference between said second angular position and said selected feed shaft command, and outputting a feed shaft speed command for said feed shaft servo motor based on said second positional difference;
• and
• feed shaft speed control means for detecting a second rotational speed of said feed shaft servo motor, determining a second speed difference between said second rotational speed and said feed shaft speed command, and outputting said feed shaft current command based on said second speed difference.

A control device for controlling a tool driving unit, the tool driving unit having a spindle servo motor, responsive to a spindle current command, for rotating a tool, and a feed shaft servo motor, responsive to a feed shaft servo command, for feeding the tool along a longitudinal axis thereof, said control device comprising:

• spindle position control means for receiving a spindle command, for detecting a first angular position of the spindle servo motor, for determining a first positional difference between said first angular position and the spindle command, and for outputting a spindle speed command based on said first positional difference;
• spindle speed control means for detecting a first rotational speed of said spindle servo motor, for determining a first speed difference between said first rotational speed and said spindle speed command, and for outputting the spindle current command based on said first speed difference;
• feed shaft command selecting means for receiving a first and a second feed shaft command and for selectively outputting one of said first and second feed shaft commands as a selected feed shaft command based on a tooling operation being performed by said tool driving unit;
• feed shaft position control means for detecting a second angular position of the feed shaft servo motor, for determining a second positional difference between said second angular position and said selected feed shaft command, and for outputting a feed shaft speed command based on said second positional difference;
• and
• feed shaft speed control means for detecting a second rotational speed of said feed shaft servo motor, for determining a second speed difference between said second rotational speed and said feed shaft speed command, and for outputting the feed shaft current command based on said second speed difference.