Patent ID: 7092786

Claim:
A detecting device for determining tool defect in which indexes, each index indicative of a load exerted on a tool for machining a workpiece, are acquired for a plurality of machining cycles, an index acquired in a present machining cycle is compared with an average of indexes acquired in machining cycles preceding the present machining cycle to acquire a comparison value indicative of a result of the comparison in each machining cycle, and determining damage and/or abnormality of the tool when the comparison value deviates from an allowable range defined by set values of thresholds, said detecting device comprising means for determining the set values of the thresholds, including: detecting means for detecting the indexes for a plurality of machining cycles; comparing means for comparing an index in a selected machining cycle with an average of indexes for a plurality of machining cycles preceding the selected machining cycle to acquire a comparison value indicative of a result of the comparison; first storage means for storing values of the thresholds; writing means for writing initial values of the thresholds in said first storage means; updating means for updating the stored values of the thresholds to revised values according to a comparison value that deviates from an allowable range defined by the stored values of the thresholds when the comparison value acquired in the selected machining cycle deviates from the allowable range; means for discontinuing the updating of the stored values of the thresholds in response to a command to discontinue the updating of the thresholds; and determining means for determining the set values of the thresholds based on the stored values of the thresholds when the update of the values of the thresholds is discontinued.