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Case Study
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The Multi-Vari Chart: An Underutilized Quality Tool

Publication:
Quality Progress
Date:
October 1995
Issue:
Volume 28 Issue 10
Pages:
pp. 81-83
Author(s):
Zaciewski, Robert D.; N'meth, Lou
Organization(s):
General Motors Powertrain, Ypsilanti, MI

Abstract

The multi-vari chart is a key to identifying root causes of excessive variation. It is especially useful for inside and outside diameters, runout, and taper. It is applicable in service and manufacturing sectors. In a case study, a grinding operation had been producing parts with unacceptable variation in outside diameter and taper that was out of specification. A multi-vari chart was constructed to display four readings for eight different runs, each consisting of six consecutive pieces. The chart showed the taper variation to be nonrandom and pointed to a problem in the dressing process. Corrective actions in this process decreased the taper and the variation in outside diameter.

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