Pre-control is a simple alternative to traditional control charts that is very effective in shop floor environments. Pre-control is unique for two reasons: (1) it incorporates the specification limits into the control chart, which most control charts do not, and (2) it uses color-coded zones (green, yellow, and red) to make control chart interpretation very easy for operators. Pre-control limits are established based on the following –
- the middle 50% of the chart is the Green Zone, which makes up 50% of the specification tolerance for the feature being measured
- there is a Yellow Zone on either side of the Green Zone that makes up the remaining 50% of the specification tolerance (25% for each yellow zone)
- the Red zone is everything outside of the specification limits
There are a few guidelines for building and reacting to pre-control charts, but overall they are quite simple to use.
Information and downloads on this website are for general educational purposes only, provided as-is, to be used at your own risk, with no warranties of any kind. While we strive to develop highly relevant content, the information and files provided on this site are not guaranteed to be completely relevant or up to date.