Multi-Vari Analysis课件.ppt

Multi-Vari Analysis Acknowledgement The examples quoted in this module are from 1) Six Sigma Project # 47-01 “PCCA Head Pad Solder Deposition” by Chan, Foong Yow (Far East Drive Operations) Module Objectives At the end of this module the student will be able to: 1) Describe different sources of variability 2) Create and interpret Multi-Vari Charts Types of Variation Inherent or Natural Variation Due to the cumulative effect of many small, unavoidable causes A process operating with only chance cause of variation present is said to be “in statistical control” Special or Assignable Variation Due to a specific, irregular cause a) improperly adjusted machine b) operator error c) defective raw material A process operating in the presence of assignable causes of variation is said to be “out-of-control” Quality Breakthrough Sources of Variation Variation Process Variation Measurement Variation within unit within instrument between units between instruments between lots between calibrations between operators between operators between machines across time between set-ups across time Multi-Vari Charts The Multi-Vari Chart shows variability due to several sources. It is very useful for comparison of within-unit variation to other families of variation. The term Multi-Vari was given to this form of analysis by L.A. Sedar in his paper “Diagnosis with Diagrams”, published in Industrial Quality Control (Jan-Mar 1950). The Multi-Vari technique had previously been employed by Joseph M Juran, and possibly others, who derived it from the method used by financial editors for showing stock market prices. Multi-Vari Charts (1) The basic Multi-Vari Chart uses a vertical line to show the range of variation within a single product unit. Rw : within unit variation Rb: between units variation Rt : across time variation (between lots variation) Within-Unit Variability Between-Units