Progress of tool condition monitoring in drilling

The capability of drill status monitoring has a strong economic potential, since large benefits can be obtained when exploiting tools up to their real end-of-life; this can be done once the decay mechanism is clearly defined and understood. A large amount of research activities has been devoted so far in the last decades, particularly for drilling operations, since tool management, usually, relies on a conservative evaluation of tool-life, because of the empirical approach in evaluating the effects of failure mechanisms bringing to sudden failures or decay; this fact leads to an unnecessarily high number of changes and to increase of cost impacts. For this reasons, particularly in automated production systems, efforts in research should be devoted on the measurement of drill-status, which reflects directly on surface features and indirectly on the quality of the holes manufactured. This paper presents a benchmark of a large number of existing drill-decay measurement techniques (DDMT) proposed so far in scientific papers and contributions, providing an up-to-date analysis of main factors which characterized the applicability of DDMT to automated production systems as well as the pro and cons of principal technologies available. The outcome of the work is thus a technical requirement specification useful to provide new hints for realising a reliable wear monitoring system for drilling operations, potentially applicable to automated production system