Numerical control device having function of estimating expiration of life of bearing supporting spindle

摘要

A numerical control device determines whether or not a spindle is in a cutting state where it machines a workpiece. If the spindle is in a cutting state, the numerical control device calculates a second rotational speed, which is obtained by multiplying a rotational speed of the spindle by a weight corresponding to a force on the spindle calculated based on a torque of a feed shaft, and integrates the calculated value into an index value. If the spindle is not in the cutting state, the numerical control device integrates the rotational speed of the spindle into the index value. The lifetime of a bearing is estimated based on the index value.

主权项

1. A numerical control device having a function of estimating the lifetime of a bearing which supports a spindle of a machine tool and configured to control the machine tool, the numerical control device comprising:
a physical quantity acquisition unit configured to acquire, for each predetermined period, a rotational speed of the spindle and a torque of a feed shaft from a control unit for controlling drive shafts or detectors mounted on the drive shafts; a cutting signal monitoring unit configured to monitor a cutting signal output from the control unit and indicative of a cutting state; a load calculation unit configured to calculate a force acting on the spindle based on the torque of the spindle acquired by the physical quantity acquisition unit; a weight extraction unit configured to extract a weight corresponding to the force on the spindle calculated by the load calculation unit from a previously given table; an integration unit configured to integrate the rotational speed of the spindle for each predetermined period if the cutting signal indicates a non-cutting state and to integrate, for each predetermined period, a second rotational speed of the spindle obtained by multiplying the rotational speed of the spindle acquired by the physical quantity acquisition unit by the weight extracted by the weight extraction unit if the cutting signal indicates the cutting state; and a storage unit configured to store an integrated value integrated by the integration unit, the lifetime of the bearing being estimated based on the integrated value obtained by the integration unit.