A machine tool controlled by a numerical controller, wherein
- the numerical controller has a function to determine a replacement time for a maintenance component used in a movable portion of the machine tool and outputting to the machine tool an operation instruction related to the movable portion,
- an operation completion signal output unit is provided outside the machine tool and outputs, to the numerical controller, an operation completion signal indicating that the operation of the movable portion based on the operation instruction is complete,
- the numerical controller includes:
- a response time calculation unit that calculates, as a response time of operation, a time from a point in time when the numerical controller outputs the operation instruction until a point in time when the numerical control device receives the operation completion signal from the operation completion signal output unit;
- a maintenance component replacement time determination unit that determines that a time has come to replace the maintenance component used in the movable portion when the calculated response time of operation is longer than a preset set time;
- a display unit that displays a result of determination by the maintenance component replacement time determination unit;
- and
- a counter that counts a number of operations of the maintenance component used in the movable portion of the machine tool or an operation duration clocking unit that clocks a duration of operation of the maintenance component or a duration of operation of the machine tool,
- the display unit further displays, when displaying a result of determination by the maintenance component replacement time determination unit, the number or duration of operations of the maintenance component, and
- the response time of operation is a sum of time needed for signal processing in the machine tool plus an actual operating time of a mechanical component of the machine tool.