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Unformatted text preview: Chapter 9 Capability and Rolled Throughput Yield What is capability analysis? And what can it tell us? Measuring Capability • Measure the true quality levels of products and services. • Report the relationship between what is acceptable to the customer and what the process can naturally deliver. • Process Capability – is defined as the spread within which almost all of the values of a data distribution will fall. (Generally described as 6 σ or ± 3 σ ) – The main objective of 6 σ is to have no more than 3.4 defects per million opportunities (DPMO). – The process must be brought into statistical control so that performance becomes predictable and capable of consistently meeting customer expectations. What is a normal distribution? www.barringer1.com/jan98f1.gif6 σ5 σ4 σ3 σ2 σ1 σ 1 σ 2 σ 3 σ 4 σ 5 σ 6 σ μ So what is Capability? • The proportion of output that will be within product specification tolerances. Specification Range Usually set by customer LSL Lower Specification Limit USL Upper Specification Limit Process Range How is capability measured? C p >=1 process capable C p <1 process not capable C p = 1.33 minimum value for process to be considered capable*. *Most organizations use 1.33 as the minimum due to the shift that occurs over time We have a lower sigma for longterm than short term since longterm process capability is expected to shift over time by 1.5 σ. 6 σ1 .5 σ = 4 .5 σ 3 .4 DPMO answer to HW #1 ST σ 6 or capability Process tolerance ion Specificat C index Capability p = = Indices of Capability  C p LSL Lower Specification Limit USL Upper Specification Limit C p <1 C p = 1 C p = 1.5 C p = 2.0 Improvement Improvement Capability Example Example 9.1 • CALCULATE the C p – Process has a mean = .738 – σ= .0 7 2 5 – LSL=.500, USL=.900 Is this process capable? Why?...
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This note was uploaded on 12/03/2011 for the course EIN 5226 taught by Professor Staff during the Fall '11 term at FIU.
 Fall '11
 STAFF

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