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- Title
The economic performance of the Shewhart t chart.
- Authors
Celano, Giovanni; Castagliola, Philippe; Trovato, Enrico; Fichera, Sergio
- Abstract
In the production of small batches of customized parts, high flexibility and frequent switching of production from one product variant to another could not allow for the implementation of a control chart to monitor the process. In fact, when a short-run production should be started, the distribution parameters of the quality characteristics to be monitored are frequentlytextitunknown and the production run is too short to get sufficient Phase I samples. To overcome this problem, the statistical properties of Shewhart t charts monitoring a short production run have been recently discussed in literature. In this paper, we investigate their economic performance: the SPC inspection cost optimization is constrained by the manufacturing and the inspection activities configuration. The decision variables of the problem include the chart design parameters and the size of batches of parts to be worked and released to the local inspection area. A numerical analysis aimed at evaluating the economic performance of the Shewhart t chart vs the Shewhart chart with known parameters has been performed. The expected economic loss associated with the implementation of the Shewhart t chart is acceptable with respect to the 'ideal' condition of the control chart with known parameters when the cost optimization is achieved without a statistical constraint limiting the number of expected false alarms. Finally, the effect of an erroneous initial set-up on the correctness of the inspection cost estimation has been investigated. Copyright © 2011 John Wiley & Sons, Ltd.
- Subjects
QUALITY control charts; PRODUCTION control; PROCESS control systems; NUMERICAL analysis; GRAPHIC methods
- Publication
Quality & Reliability Engineering International, 2012, Vol 28, Issue 2, p159
- ISSN
0748-8017
- Publication type
Article
- DOI
10.1002/qre.1222