Machine tool having inspection function for deteriorated state of spindle

A machine tool having an inspection function for a deteriorated state of a spindle, the machine tool comprising:

• a spindle configured to hold a tool for machining work, the spindle being rotatably supported by a bearing,
• a motor configured to drive the spindle,
• an encoder configured to measure a rotation angle position of the spindle or the motor, and
• a processor configured to calculate rotating speed of the spindle or the motor from an output of the encoder,
• wherein
• during tool replacement where the tool is detached from the spindle and before a new tool is attached to the spindle, the processor is configured to
• rotate the spindle or the motor at predetermined speed and thereafter interrupt power of the motor to rotate the spindle with inertia,
• clock a set predetermined time after the power of the motor is interrupted,
• detect the calculated rotating speed when the set predetermined time is clocked,
• calculate a value for comparison with a threshold set in advance, on the basis of the predetermined speed, the rotating speed detected when the set predetermined time is clocked, and the set predetermined time,
• determine whether the calculated value for comparison is equal to or smaller than the threshold, and
• output an alarm when the calculated value for comparison is larger than the threshold.

A machine tool having an inspection function for a deteriorated state of a spindle, the machine tool comprising:

• a spindle configured to hold a tool for machining work, the spindle being rotatably supported by a bearing,
• a motor configured to drive the spindle,
• an encoder configured to measure a rotation angle position of the spindle or the motor, and
• a processor configured to
• calculate rotating speed of the spindle or the motor from an output of the encoder,
• rotate the spindle or the motor at predetermined speed and thereafter interrupt power of the motor to rotate the spindle with inertia,
• calculate a value for comparison with a threshold set in advance, from the output of the encoder during inertial rotation of the spindle,
• determine whether the calculated value for comparison is equal to or smaller than the threshold, and
• output an alarm when the calculated value for comparison is larger than the threshold.

A machine tool having an inspection function for a deteriorated state of a spindle, the machine tool comprising:

• a spindle configured to hold a tool for machining work, the spindle being rotatably supported by a bearing,
• a motor configured to drive the spindle,
• an encoder configured to measure a rotation angle position of the spindle or the motor,
• a processor configured to
• calculate rotating speed of the spindle or the motor from an output of the encoder;
• rotate the spindle or the motor at predetermined speed and thereafter interrupt power of the motor to rotate the spindle with inertia;
• and
• calculate deceleration on the basis of the output of the encoder read at every predetermined cycle during inertial rotation of the spindle, and
• a memory configured to store at the every predetermined cycle, the rotation angle position read from the encoder and the calculated acceleration
• wherein the processor is configured to further
• determine whether the calculated acceleration equal to or larger than a predetermined threshold occurs in every same rotation angle amount, and
• output an alarm when it is determined that the calculated acceleration equal to or larger than the predetermined threshold occurs in the every same rotation angle amount.