Rainbow Charts

Last Revised: 1/6/03           By: REW

Keywords: rainbow, color, graph, cart, region, feature, zone control, rainbow chart, B4

Summary

DataLyzer® Spectrum software with the registration code B4 offers Rainbow Chart data graphing.  Rainbow charts allow users to get an initial estimate of data values, runs, and trends within three different zones with just a glance.  There are two types of rainbow charts.  One chart is based on control limits, and the other is based on specification limits.  Below is an example rainbow chart.

NOTE: Rainbow charts are currently available for variable control charts.  Attribute and Incoming Inspection characteristics do not currently have the rainbow chart feature.

Control Limit Color Zones

Rainbow charts are divided into three zones: the green zone, the yellow zone, and the red zone. 

• The green zone is defined as plus or minus 1 sigma from the average x-value.  In the picture below, this area is the area in Zone C.
• The yellow zone is defined as the area between 1 and three sigmas.  This area is shown as Zone A and Zone B in the example below.
• The red zone is defined as the area outside the control limits.  The Upper Control Limit and Lower Control Limit are located 3 sigmas away from the average x value. 

For more information on control limit zones, refer to the Western Electric book, item 2 of Appendix E.   

Specification Limit Color Zones

Specification Limit control charts are also colored in red, yellow, and green. 

• The area in Red is located outside of the specification limits.
• The area in Yellow is located between the control limits and specification limits.
• The area in Green is located within the control limits and the specification limits.

NOTE: when using a specification limit control chart, the Rainbow chart is automatically turned off if the cPk is less than 1.

Activating Rainbow Chart Feature

Rainbow charts can be activated by characteristic, or they may be applied globally to apply to all features.  However, a characteristic’s individual preferences always override the global preferences.

To apply rainbow charts globally, select Setup/Preferences/Statistical Preferences from the main DataLyzer® Spectrum window.  Applying rainbow charts globally will have no affect on attribute or incoming inspection characteristics.

To apply a rainbow chart to a characteristic, open the characteristic from the main DataLyzer® screen by pressing File/Open Characteristic.  Select the part and characteristic file.  Once the selected characteristic is open, select Preferences/Set Preferences.

Click the “Control Chart Presentation” tab.  In the “Chart Style” area, click “Rainbow – CLs” to activate rainbow charts based on control limits, and click “Rainbow – Specs” to activate rainbow charts based on specification limits.  Press “Save” and “Exit” to save your changes and return to the program.

DataLyzer® Spectrum Application Note

Compliments of DataLyzer International, Inc.

Control Number: 149