Method for controlling a manufacturing process utilizing control charts with specified confidence intervals
AssigneeInternational Business Machines Corporation
InventorsJerome M. Kurtzberg, Menachem Levanoni
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Abstract
The invention discloses methodology for qualitatively extending and exploiting the utility of presently known manufacturing control charts. The method introduces a separate control mechanism comprising establishing confidence intervals to already existing control limits. The confidence intervals, in turn, can be used in presently known control charts to take into account an otherwise uncertainty in a generation of the control limits themselves, thereby increasing the accuracy and robustness of decisions based on the use of the control charts.
Claims12
A computer-implemented method for monitoring state of manufacturing control process, said method comprising the steps of:
- constructing a control chart, said control chart comprising:
- a time series of a variable of interest measurement for said manufacturing control process, and an upper control limit, a lower control limit and a target control limit;
- computing an upper confidence interval for said upper control limit and a lower confidence interval for said lower control limit at a confidence level;
- comparing latest manufacturing process data values with said computed upper and lower confidence intervals;
- generating a warning signal when said data values are outside of said computed upper and lower confidence intervals;
- and
- maintaining said confidence level when said data values are within said computed upper and lower confidence intervals.
A computer program device readable by a machine, tangibly embodying a program of instructions executable by a machine to perform method steps for monitoring state of manufacturing control process, said method comprising the steps of:
- constructing a control chart, said control chart comprising:
- a time series of a variable of interest measurement for said manufacturing control process, and an upper control limit, a lower control limit and a target control limit;
- computing an upper confidence interval for said upper control limit and a lower confidence interval for said lower control limit at a confidence level;
- comparing latest manufacturing process data values with said computed upper and lower confidence intervals;
- generating a warning signal when said data values are outside of said computed upper and lower confidence intervals;
- and
- maintaining said confidence level when said data values are within said computed upper and lower confidence intervals.
Dependencies are inferred from the claim text.