Patent ID: 8195431

Claim:
A method for evaluating efficacy of prevention maintenance for a tool, comprising the steps of: (a). choosing a tool which has been maintained preventively and choosing a productive parameter of the tool; (b). collecting values of the productive parameter generated from the tool during a time range for building a varying curve of the productive parameter versus time, wherein a starting point of the time range is a first predetermined number of days before the prevention maintenance for the tool and an ending point of the time range is a second predetermined number of days after the prevention maintenance for the tool; (c). modifying the varying curve of the productive parameter versus time with a moving average method; (d). transforming the varying curve of the productive parameter versus time into a Cumulative Sum chart; and (e). judging whether the values of the productive parameter generated from the tool after the prevention maintenance are more stable, compared with the values of the productive parameter generated from the tool before the prevention maintenance, according to the Cumulative Sum chart.