| 摘要 |
A numerical controlling unit according to the present invention includes: an inputting part into which a machining program for machining a workpiece is inputted; an analyzing part that analyzes the machining program to generate an instructed spindle rotational speed and calculates a spindle load ratio indicating a ratio of a load applied to a spindle under a machining condition according to the machining program, with respect to a spindle load being caused when the workpiece is machined under a machining condition of a certain reference; and a distributing part that generates, based on the machining program, a distribution amount per unit period to be inputted into a feed-axis servo driver for moving a feed axis. A spindle-rotational-amount-command outputting part receives the instructed spindle rotational speed and outputs a spindle-rotational-amount command for commanding a rotational amount per unit period. The spindle-rotational-amount command is inputted into a spindle driver. A cutting-load-for judgment calculating part calculates a reference torque value based on the spindle load ratio outputted by the analyzing part, the distribution amount outputted by the distributing part, and the spindle-rotational-amount command outputted by the spindle-rotational-amount-command outputting part. A spindle-load comparing part compares the reference torque value with a load torque value which is feedback inputted by the spindle driver and outputs a tool-breakage detecting signal when the load torque value is higher than the reference torque value. |
