Abstract

In this study, we establish the relationship model in process capability indices, the coefficient of process shift and quality target utilizing statistical tolerance technology. A new systematic method for concurrent design of process quality, Statistical Tolerance (ST) and control chart is presented. A set of standardized Process Quality Indices (PQIs) for variables is introduced for meeting the measurement and evaluation to process yield, process centering and quality loss. To develop a quality-oriented SPC approach, a standardized interface between process quality indices system and the parameter design of EWMA control charts is needed. The two-dimensional array form ST (C_p*, &delta*) is presented for selecting a set of parameters (&lambda, L) with suitable ARL₀ and ARL1 to realize the optimal control for a process toward a predetermined quality target. The ST (C_p*, k*) will be the guideline to form the restriction of the centerlines of the control charts for assuring the preset PQIs. If the process statistical parameters are unknown, (C_p*, k*) will be converted into the ST form for estimated values based on a required confidence probability. A case study shows the detail procedure of this concurrent design for PQIs, ST and SPC parameters.

Keywords:

Concurrent design, EWMA control chart, process quality, statistical tolerance,

References

Competing interests

The authors have no competing interests.

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Copyright

The authors have no competing interests.