A numerical control device that controls a machine tool that machines work by moving a tool relatively to the work on the basis of a machining program includes a analyzing unit that analyzes the machining program and generates movement command data, a detecting unit that detects abnormality during the machining, a retract control unit that supplies, when abnormality is detected, an operation command for a retract operation for retracting the tool from the work, and an integrating unit that integrates a movement amount of the tool based on the supplied operation command. The analyzing unit executes a tool retraction program for moving the tool or the work to a predetermined position after adding the movement amount of the tool integrated by the integrating unit to a coordinate value of the tool on the machining program to update the coordinate value at a point in time when the retract operation ends.

In a method for controlling a milling machine, a milling operation is able to be monitored on the basis of a temporally variable parameter of a numerical control in that the parameter is monitored for the exceeding or undershooting of a limit value during the milling operation. The method includes filtering out the tooth-meshing frequency in the time characteristic of the parameter (Iqnom).

A method for operating a monitoring unit (100), configured to monitor a manipulation of at least one object (40, 45) by a user, the method comprising: receiving, via a cellular network (60), actual user position data comprising an actual position of at least one portion of user used to manipulate the at least one object, and actual object position data comprising an actual position of the at least one object, matching the actual user position data to predefined user position data provided at the monitoring unit (100), the predefined user position data indicating a correct position of the at least one portion of the user for manipulating the at least one object, and matching the actual object position data to predefined object position data provided at the monitoring unit, the predefined object position data indicating a correct position of the at least one object, determining, based on the matching, whether the manipulation of the at least one object by the at least one portion of the user is correct or not.