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Process Capability: ExamplesThe Quality Toolbook > Process Capability > Examples When to use it | How to understand it | Example | How to use it | Practical variations
ExampleA company producing kitchen worktops, specified the length of one range at 120 cm ± 0.25 cm. As a normal part of production monitoring, Control Charts were kept for such specified measures and all output was inspected against specification limits. A request from the sales team for tighter limits prompted the question of whether the limits could be reduced to ± 0.1cm, as this could result in significant orders from a new customer who preferred not to shave worktops to fit. The production supervisor used the Control Chart data to draw a Histogram and check for Normal distribution, then calculate Cpk, across samples from a week's work, as in the figure below . This showed that the process was currently so capable that inspection could be dropped and the new limits still met. This turned out to be as a result of old specification limits coupled with several recent process improvements. As a result, the new orders were achieved and savings were also made on inspection costs.
Fig. 1. Process Capability example
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