Cost optimization on warning threshold and non-fixed periodic inspection intervals for machine degradation monitoring

A cost-optimal monitoring and maintenance strategy could not only reduce the operation hazards, but also save the overall costs in industry. In this paper, a novel non-fixed periodic inspection strategy with a warning degradation threshold will be proposed and optimized, whose optimization objectives are warning threshold and inspection interval applied. In our proposed strategy, above warning threshold will divide a degradation process into two parts, namely, normal and warning areas, where two different inspection intervals can be used, accordingly. To calculate their optimal solutions, an overall maintenance cost-based model should be mathematically constructed on account of existing cost factors in reality. Next, the effectiveness of our proposed inspection strategy is tested with an industrial tool wear experiment of the high speed milling machine, which can achieve acceptable results of an overall maintenance cost less than $6237.5 and the monitoring performance of R2 above 0.970.