Tool Breakage Monitoring

Another problem often faced is the breakage of tool during cutting, which if not detected in time may lead to various problems associated with spoiled jobs, particularly in unmanned machining shifts. Hence it is necessary to have systems which can detect the breakage of tools through some means and give an alarm to the operator, or automatically replace the tool by a sister tool from the secondary tool storage.

In the plate sensor or any other cutting force measuring system, it is possible to detect a drop in cutting force almost to zero from peak during a breakage. The force drops since the tool may lose contact because of tool breakage. Hence the controller can be given the signal for either sister tool change, or stoppage till the operator attends. This is the most effective system and commercial systems are available from Sandvik and Krupp Widia.

Another method used by a number of machine tool manufacturers is to check the tool length or tool offset at the end or beginning of the cut using the tool probes described earlier. This value is compared with the tool values stored for the new tool. If the difference is more than a certain value (typically 1 mm), it is considered as tool breakage. This type of system is simple, but can detect tool breakages only after a cut. Any tool breakage during cutting remains unnoticed. However this system does reduce the effective damage caused by broken tools.