Main spindle failure detection device for machine tool and method of detecting main spindle failure

A main spindle failure detection device for a machine tool, comprising:

• a spindle rotation speed detector;
• a first computer-readable medium having computer-executable components that estimate a reach time in which the rotation speed of the main spindle reaches a predetermined rotation speed threshold using a non-linear model, the estimation being performed based on a rotation speed of the main spindle at a start of an inertia operation detected by the rotation speed detection unit and a rotation speed of the main spindle detected by the rotation speed detection unit after an elapse of preset measurement time from the start of the inertia operation;
• and
• computer-executable components, on said first computer-readable medium or on a second computer-readable medium, that compare the reach time estimated by the reach time estimation unit with a preset reach time in which the rotation speed reaches the rotation speed threshold, so as to determine a failure in the main spindle based on a result of the comparison.