Failure Mode and Effects Analysis ? FMEA is a technique utilized to define, identify, and eliminate known or potential failures or errors from a syste...
Failure Mode and Effects Analysis ? FMEA is a technique utilized to define, identify, and eliminate known or potential failures or errors from a system during all phases of a product life cycle ? FMEA has been used extensively in safety-oriented and aerospace businesses. It has become popular in the automotive industry due to requirements of QS 9000 ? FMEA Benefits: - Reduce development cost - Early risk identification - Documented evaluation
- Minimize product failures - Track process improvements - Develop efficient test plans
Process FMEA Severity Ranking Scale EFFECT H azardousw i th o u t w arning H azardousw i th w arning V ery H igh
H igh
M o d e r a te
EFFECT L O W
V ery Low
M in o r
V ery M in o r
N one
Source:Potential Failure Mode and Effects Analysis, AIAG, 1995
C R IT E R IA : S E V E R IT Y O F E F F E C T E n d a n g e rs m a c h i n e o r o p e r a tor. F a i l u r e w i l l o c c u r w ith o u t w a rn in g .
R A N K IN G 10
E n d a n g e rs m a c h i n e o r o p e r a tor. F a i l u r e w i l l o c c u r w ith w a rn i n g .
9
M a j o r d i s r u p ti o n t o p r o c e s s . 1 0 0 % m a y h a v e t o b e s c r a p p e d . In o p e r a b l e , l o s s o f p r i m a r y f u n c tion . C u stom er very dissatisfied. M i n o r d i s r u p t i o n t o p r o c e s s . P r o d u c t m a y h a v e to b e s o r te d ( g o o d o r s c r a p ) . O p e r a b l e b u t a t r e d u c e d p e rform ance level. D issatisfied custom er. M i n o r d i s r u p t i o n t o p r o c e s s . P o r t i o n m a y h a v e to b e s c r a p p e d . O p e r a b l e b u t w i t h o u t a l l o f th e c o n v e n i e n c e s . C u s tom e r experiences discom fort.
Causes of Failure Modes Identify the basic cause or mechanism of the Failure Mode (Be specific) ? Use Quality Improvement tools - Historical Data - Correlation Analysis - Cause and Effect - Brain Storming ? List the cause of each Failure Mode in the FMEA Process 1. Spray Paint Process
Failure Mode Incorrect Paint Thickness
2. Oven Drying Process
Incorrect Oven Temperature Incorrect Oven Humidity
Failure Effect Rework Voids in Paint Surface Scrap Burned Parts
Cause High Paint Solids Paint Surface Failed Temp. Switch Moisture in Temp. Switch Housing
Occurrence of Failure Modes Assign an occurrence score to each failure mode ? Estimation of the frequency of occurrences from each failure mode ? Typical scales used are 1-10 or 1-5 ? Good method of establishing a scale is to define a metric representing the failure rate ? ie. Ford, GM and Crysler corporations rate on 1-10 scale: ? 3 = Relatively few failures = “1 failure per 15,000 operations” ? 8 = Repeated failures = “1 failure per 8 operations” ? List the occurrence score of each failure mode in the FMEA P R O B A B IL IT Y O F F A IL U R E V e r y H ig h : F a ilu r e a lm o s t i n e v i t a b l e V e r y H ig h : F a ilu r e a lm o s t i n e v i t a b l e H ig h : G e n e r a l ly a s s o c ia t e d w i t h p r o c e s s sim ila r t o p r e v io u s p r o c e s s e s t h a t h a v e o f t e n fa ile d “ M o d e r a t e : A s s o c i a t e d w ith p r o c e s s e s s im ila r to p r e v io u s p r o c e s s e s w h ic h h a v e e x p e r ie n c e d o c c a s io n a l fa ilu r e s b u t n o t in m a j o r p r o p o r tio n s “ “ L o w : I s o l a t e d f a i l u r e s a s s o c i a t e d w ith sim ila r processes V e r y L o w : O n ly i s o l a t e d f a i l u r e s a s s o c ia t e d w ith a lm o s t i d e n t i c a l p r o c e s s e s R e m o t e : F a ilu r e is u n lik e l y . N o fa ilu r e s e v e r a s s o c ia t e d w ith a lm o s t i d e n t i c a l p r o c e s s e s
Source:Potential Failure Mode and Effects Analysis, AIAG, 1995
Failure Mode Controls Identify current controls that prevent or detect the failure mode ? Types of controls typically used - Monitors, SPC Charts - Equipment Preventative Maintenance - Inspections/Checks - Standard Operating Procedures ? List the current controls/corrective actions for each failure mode in the FMEA
Detection of Failure Modes Assign a detection score to each failure mode ? Estimation of the probability that the control will detect the failure mode ? Typical scales used are 1-10 or 1-5 ? Good method of establishing a scale is to define levels of likelihood that a failure will be detected ? i.e. Ford, GM and Chrysler corporations rate on 1-10 scale: ? 3 = High = “High likelihood that a failure will be detected” ? 8 = Remote = “Remote likelihood that a failure will be detected”
? List the detection score of each failure mode in the FMEA
Almost Impossible Very Remote Remote Very Low Low Moderate Moderately High High Very High Almost Certain
CRITERIA: LIKELIHOOD THAT THE EXISTENCE OF A DEFECT WILL BE DETECTED BY PROCESS CONTROLS BEFORE NEXT PROCESS OR BEFORE PART OR COMPONENT LEAVES THE MANAUFACTURING OR ASSEMBLY LOCATION No known control(s) available to detect failure mode
RANKING
Very remote chance current control(s) will detect failure mode Remote chance current control(s) will detect failure mode Very low chance current control(s) will detect failure mode Low likelihood current control(s) will detect failure mode Moderate chance current control(s) will detect failure mode Moderately high likelihood current control(s) will detect failure mode High likelihood current control(s) will detect failure mode Very High likelihood current control(s) will detect failure mode Current control(s) almost certain to detect the failure mode. Reliable detection controls are known with similar processes.
