Page 429 - Design for Six Sigma a Roadmap for Product Development

Failure Mode–Effect Analysis 393

occur. A potential failure mode may be studied from a previous base-
line and current data, tests, fleet tests, and current FMEAs.
3. Potential failure effects(s). A potential effect is the consequence of
the failure on other physical entities as experienced by the customer.
4. Severity. Severity is a subjective measure of “how bad” or “seri-
ous” the effect of the failure mode is. Usually severity is rated on a dis-
crete scale from 1 (no effect) to 10 (hazardous effect). Severity ratings
of 9 or higher indicate a potential special effect that needs more atten-
tion, and this typically is a safety or government regulation issue
(Table 11.1). Severe effects are usually classified as “critical,” “signifi-
cant,” or “control.” “Critical” effects are usually a safety issue and

TABLE 11.1 Automotive Industry Action Group (AIAG) Severity Rating
Effect Severity of effect defined Rating
None No effect 1
Very minor Minor disruption to production line; a portion ( 100%) 2
of the product may have to be reworked on line but in
station; fit/finish/squeak/rattle item does not
conform; defect noticed by discriminating customers
Minor Minor disruption to production line; a portion ( 100%) of 3
the product may have to be reworked on line but out
of station; fit/finish/squeak/rattle item does not conform;
defect noticed by average customers
Very low Minor disruption to production line; product may have 4
to be sorted and a portion ( 100%) reworked; fit/finish/
squeak/rattle item does not conform; defect noticed by
most customers
Low Minor disruption to production line; 100% of product 5
may have to be reworked; vehicle/item operable, but
some comfort/convenience item(s) operable at reduced
level of performance; customer experiences some
dissatisfaction
Moderate Minor disruption to production line; a portion ( 100%) 6
may have to be scrapped (no sorting); vehicle/item
operable, but some comfort/convenience item(s)
inoperable; customers experience discomfort
High Minor disruption to production line; product may have 7
to be sorted and a portion ( 100%) scrapped; vehicle
operable, but at a reduced level of performance; customer
dissatisfied
Very high Major disruption to production line; 100% of product 8
may have to be scrapped; vehicle/item inoperable, loss
of primary function; customer very dissatisfied
Hazardous: with May endanger operator; failure mode affects safe vehicle 9
warning operation and/or involves noncompliance with govern-
ment regulation; failure will occur with warning
Hazardous: May endanger operator; failure mode affects safe vehicle 10
without warning operation and/or involves noncompliance with govern-
ment regulation; failure will occur without warning