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Track 1 Session 3
1:00 to 2:00 p.m. Wednesday,
October 22, 2008
Trapped by MTBF - A Study of Alternate Reliability Metrics
MTBF is probably the most common metric used to describe the reliability of a product, but it is perhaps the least understood and most misleading metric as well. What do we really mean by MTBF and how much information does it really give us? We find that it is very difficult to write reliability plans with only MTBF as the metric. It is difficult to allocate down to subassemblies, and it is difficult to measure where we are against our goals.
When we use MTBF, we make generalized assumptions such as constant failure rate, and these assumptions are not only rarely true, but also cause us to miss meaningful information relative to the design attributes of our product, especially in what happens in the early life portion and in the wear out portion of our product life. For us to perform a robust Design for Reliability
(DFR) process, we must include all areas of our product life, not just the steady state portion of our product life.
In this presentation, we shall study a number of other more descriptive and useful metrics, including Reliability, DOA, AFR, Life, and others to help describe product reliability in a more rich context.
Key Words: Reliability, MTBF, MTTF, Non-repairable, AFR, DOA, Exponential, Weibull
Fred Schenkelberg and Mike Silverman
Ops A La Carte |
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