PURPOSE: To attain to enhance the detection reliability of the breakage of a tool, by automatically setting the sensitivity of an AE sensor corresponding to a tool to be used on the basis of the processing position of an object to be processed.
CONSTITUTION: The work 1 fixed to the base 2 of a ball disc is drilled by the drill 3 controlled by a numerical value control apparatus 4. A dummy breakage signal generator 5 is attached to the work 1 and driven by a drive circuit 6. The output of an AE sensor 7 is applied to an AE signal pressing part 8 which, in turn, gradually amplifies the signal of the sensor 7 from the point of time when the drill 3 was contracted with the work 1 and detects the signal of the breakage of the tool to apply the same to CPU10 through an input/output IF (interface) 9. ROM11, the apparatus 4, RAM12 and an input/output IF13 are connected to CPU10 which, in turn, applies the predetermined drive level of the generator 5 to the circuit 6 on the basis of the inputs of said connected elements and controls the AE sensor to optimum sensitivity on the basis of the AE signal level obtained by the processing part 8 corresponding to the position of the tool.
NAKAMURA HIDEAKI
YAMADA TAKESHI
