Machining apparatus and cutting method

A machining apparatus comprising:

• a rotation mechanism configured to rotate a spindle to which a cutting tool or workpiece is attached;
• a rotation controller configured to alternately control an acceleration of the rotation of the spindle by the rotation mechanism and control a deceleration of the rotation of the spindle by the rotation mechanism;
• and
• a feed mechanism configured to move the cutting tool relative to the workpiece,
• wherein the rotation controller continuously increases acceleration of the rotation of the spindle in a period of accelerating the rotation of the spindle to make a speed fluctuation ratio between a current cutting speed and a cutting speed one rotation before at the same rotation position equal to or greater than a first value that is greater than 1, and continuously decreases deceleration of the rotation of the spindle in a period of decelerating the rotation of the spindle to make the speed fluctuation ratio equal to or less than a second value that is less than 1.

A machining apparatus comprising:

• a rotation mechanism configured to rotate a spindle to which a cutting tool or workpiece is attached;
• a rotation controller configured to control the rotation of the spindle by the rotation mechanism;
• and
• a feed mechanism configured to move the cutting tool relative to the workpiece,
• wherein, when a speed fluctuation ratio between a current cutting speed and a cutting speed one rotation before at the same rotation position is equal to or less than a first threshold that is greater than 1 and is equal to or greater than a second threshold that is less than 1, chatter vibration possibly occur, and
• wherein the rotation controller alternately controls an acceleration control of the spindle to make the speed fluctuation ratio equal to or greater than a first value that is greater than the first threshold and a deceleration of the rotation of the spindle to make the speed fluctuation ratio equal to or less than a second value that is less than the second threshold.