Numerical control unit

Abstract

A numerical control unit having a load monitoring function for monitoring a load on a tool drive source during a machining operation. The numerical control unit includes a load monitoring section for monitoring the load on an electric motor; a wear recognizing section for recognizing the current extent of tool wear; a storing section for storing a plurality of preset limit load values corresponding individually to predetermined various extents of tool wear; a calculating section for calculating the current limit load value corresponding to the current extent of tool wear recognized in the wear recognizing section, based on the plurality of preset limit load values stored in the storing section; and a comparing section for comparing the load on the electric motor, monitored in the load monitoring section, to the current limit load value calculated in the calculating section, and for judging on the abnormality of the load. The wear recognizing section recognizes the current extent of tool wear by using one parameter selected from a group consisting of the number of times of use of a tool, the duration of cutting by a tool, the distance of cutting by a tool and the number of times of execution of machining program. The load monitoring section monitors at least one of maximum value, average value and minimum value of the load in a certain procedure of a machining program.

Description

technical field [0001] The present invention relates generally to numerical control units for machine tools, and more particularly to numerical control units having a load monitoring function for monitoring the load on a tool drive source during machining operations. Background technique [0002] In the field of machine tools, it has been proposed to detect the cutting resistance acting on the machine tool as the load applied to the spindle for rotating the tool or the feed shaft for feeding the tool during machining operations, and according to the magnitude of the load Various methods of controlling the operation of the spindle or feed axis in order to prevent tool breakage. Generally speaking, due to continuous use, the cutting edge of the knife will wear down and eventually will break off. In the event that the edge of the tool is worn, the load applied to the respective tool spindle or tool feed axis will increase during cutting of the workpiece by the tool. Therefore...

AI Technical Summary

Problems solved by technology

In such a low-wear state, when cutting abnormalities occur, the temporarily increased load acting on the spindle or feed shaft will rarely reach the predetermined reference value for preventing tool breakage, therefore, it is difficult to detect locally Cutting abnormalities that reduce machining accuracy

In other words, the continuous use of the tool leads to the development of wear and the gradual increase of the cutting resistance acting on the tool, so that if the judgment standard is fixed, it is difficult to judge the normal cutting state by the magnitude of the load acting on the spindle or feed shaft and abnormal cutting conditions

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