design fmea
DESCRIPTION
Design FMEATRANSCRIPT
DFMEA
Purpose
To deepen understanding and refine your current approach to Design FMEA’s.
Definition of FMEA
A Failure Mode and Effect Analysis uses a disciplined technique to identify and help eliminate product and process potential failure modes.
o By ID of potential failures o Assessing the risks caused by failure modes and Identify
corrective actions o Prioritizing corrective actions o Carry out corrective actions
Design FMEA's
Current practices/concerns?
DFMEA/PFMEA Information Interrelationships
DFMEA Design FMEA
Process Flow Diagram
PFMEA Process FMEA
Boundary (Block) Diagram, P- Diagram,
Etc.
Design Verification Plan & Report
(DVP&R)
Process Control Plan
Potential Key Product Characteristics Development
DetectPrevent
RPN
DET
OCC
SEV
ActionTaken
Action ResultsResponse &
TargetComplete
Date
RecommendedActions
RPN
Detec
Current
Controls
Occur
PotentialCause(s)/
Mechanism(s)Of Failure
Class
Sev
PotentialEffect(s) of
Failure
Potential FailureMode
Item / Process Step
DetectPrevent
RPN
DET
OCC
SEV
ActionTaken
Action ResultsResponse &
TargetComplete
Date
RecommendedActions
RPN
Detec
CurrentDesign
Controls
Occur
PotentialCause(s)/
Mechanism(s)Of Failure
Class
Sev
PotentialEffect(s) of
Failure
Potential FailureMode
Item / Process Step
Function
DFMEA
Requirements Documents !•Regulatory •Dimensional •Cosmetic !Req. Spec. Document Drawings Warranty History
Robustness Tools !Boundary Diagram P-Diagram Interface Matrix
10987654321
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SEVERITY
O C C U R R E N C E
POTENTIAL CRITICAL CHARACTERISTICS
Safety/Regulatory
POTENTIAL SIGNIFICANT
CHARACTERISTICSCustomer Dissatisfaction
Special Characteristics Matrix
ANOYANCE ZONE
ALL OTHER CHARACTERISTICSAppropriate actions /
controls already in place
Cascade Technical Requirements Into Special Product Characteristics
Example analysis
Pencil Assembly
Block-Diagram
Step 2 P-diagram
Step 2 P-diagram
P-Diagram (Parameter diagram)
Example of a P-DIAGRAM
Interface matrix
Interface matrix
Functional requirements
Function and Mode
Function and Mode
Function and Mode
Effects and severity
Effects and severity
Severity Column
DetectPrevent
RPN
DET
OCC
SEV
ActionTaken
Action ResultsResponse &
TragetComplete
Date
RecommendedActions
RPN
Detec
CurrentProcessControls
Occur
PotentialCause(s)/
Mechanism(s)Of Failure
Class
Sev
PotentialEffect(s) of
Failure
Potential FailureMode
Item / Process Step
DetectPrevent
RPN
DET
OCC
SEV
ActionTaken
Action ResultsResponse &
TragetComplete
Date
RecommendedActions
RPN
Detec
CurrentProcessControls
Occur
PotentialCause(s)/
Mechanism(s)Of Failure
Class
Sev
PotentialEffect(s) of
Failure
Potential FailureMode
Item / Process Step
Function
Severity Column
AUTOMOTIVE EXAMPLE SEVERITY EVALUATION CRITERIA
Hazardous- with warning
Very High
High
Very high severity ranking when a potential failure mode affects safe vehicle operation and/or involves noncompliance with government regulation without warning
Low
Very Low
Minor
Very Minor
None
Very high severity ranking when a potential failure mode affects safe vehicle operation and/or involves noncompliance with government regulation with warning
Vehicle/item inoperable (loss of primary function).
Vehicle/item operable but at a reduced level of performance. Customer very dissatisfied.
Vehicle/item operable but Comfort/Convenience item(s) inoperable. Customer dissatisfied.
Vehicle/item operable but Comfort/Convenience item(s) operable at a reduced level of performance. Customer somewhat dissatisfied.
Fit & Finish/Squeak & Rattle item does not conform. Defect noticed by most customers (greater than 75%).
Fit & Finish/Squeak & Rattle item does not conform. Defect noticed by 50% of customers.
Fit & Finish/Squeak & Rattle item does not conform. Defect noticed by discriminating customers (less than 25%).
No discernable effect.
10
8
7
6
3
2
1
Hazardous- without warning
Moderate
4
5
EFFECT CRITERIA: Severity of Effect RNK.
SEVERITY EVALUATION CRITERIA
9
FMEA General● For High Severity 9/10
Occurrence Column
DetectPrevent
RPN
DET
OCC
SEV
ActionTaken
Action ResultsResponse &
TragetComplete
Date
RecommendedActions
RPN
Detec
CurrentProcessControls
Occur
PotentialCause(s)/
Mechanism(s)Of Failure
Class
Sev
PotentialEffect(s) of
Failure
Potential FailureMode
Item / Process Step
DetectPrevent
RPN
DET
OCC
SEV
ActionTaken
Action ResultsResponse &
TragetComplete
Date
RecommendedActions
RPN
Detec
CurrentProcessControls
Occur
PotentialCause(s)/
Mechanism(s)Of Failure
Class
Sev
PotentialEffect(s) of
Failure
Potential FailureMode
Item / Process Step
Function
Occurrence Column
Occurrence Evaluation Criteria
*Note: Zero (0) rankings for Severity, Occurrence or Detection are not allowed
Probability of Likely Failure Rates Over Design Life Ranking Failure
SUGGESTED OCCURRENCE EVALUATION CRITERIA
Very High: Persistent failures
High: Frequent failures
Moderate: Occasional failures
Low: Relatively few failures
Remote: Failure is unlikely
≥ 100 per thousand vehicles/items
50 per thousand vehicles/items
20 per thousand vehicles/items
10 per thousand vehicles/items
5 per thousand vehicles/items
2 per thousand vehicles/items
1 per thousand vehicles/items
0.5 per thousand vehicles/items
0.1 per thousand vehicles/items
≤ 0.01 per thousand vehicles/items
10
9
8
7
6
5
4
3
2
1
Example of Significant/ Critical Threshold
*Used by permission of Ford Motor Company
10987654321
1 2 3 4 5 6 7 8 9 10
SEVERITY
O C C U R R E N C E
POTENTIAL CRITICAL CHARACTERISTICS Safety/Regulatory
POTENTIALSIGNIFICANT
CHARACTERISTICSCustomer Dissatisfaction
ALL OTHER CHARACTERISTICS
Appropriate actions / controls already in place
Special Characteristics Matrix
ANOYANCE ZONE
Design Verification (Current Design Controls)
▪ Think of Design Control in two ways; Prevention and Detection. List them separately. ▪ To save time, add any new (untried) prevention/
detection ideas to the document under Recommended Actions column.
o Prevention is specifically related to reduction or elimination of a cause.
o Detection is how well the test or series of tests may find the design flaw – Causes – Failure Mode
Detection Rating
Absolute Uncertainty
Very Remote
Remote
Very Low
Low
Moderate
Moderately High
High
Very High
Almost Certain
10
9
8
7
6
5
4
3
2
1
Design Control will not and/or cannot detect a potential cause/ mechanism and subsequent failure mode; or there is no Design Control.
Very Remote chance the Design Control will detect a potential cause/mechanism and subsequent failure mode.
Remote chance the Design Control will detect a potential cause/ mechanism and subsequent failure mode.
Very Low chance the Design Control will detect a potential cause/mechanism and subsequent failure mode.
Low chance the Design Control will detect a potential cause/mechanism and subsequent failure mode.
Moderate chance the Design Control will detect a potential cause/ mechanism and subsequent failure mode.
Moderately High chance the Design Control will detect a potential cause/mechanism and subsequent failure mode.
Very High chance the Design Control will detect a potential cause/ mechanism and subsequent failure mode.
High chance the Design Control will detect a potential cause/ mechanism and subsequent failure mode.
Design Controls will almost certainly detect a potential cause/ mechanism and subsequent failure mode.
DETECTION
SUGGESTED DETECTION EVALATION CRITERIACRITERIA RNK.
Analysis Of Risk
▪ RPN / RISK PRIORITY NUMBER ▪ What Is Risk? ▪ Probability of danger ▪ Severity/Occurrence/Cause
Evaluation by RPN Only
▪ Case 1 o S=5 O=5 D=2 RPN = 50
▪ Case 2 o S=3 O=3 D=6 RPN = 54
▪ Case 3 o S=2 O=10, D=10 = 200
▪ Case 4 o S=9 O=2 D=3 = 54
WHICH ONE IS WORSE?
Example
▪ Extreme Safety/Regulatory Risk o =9 & 10 Severity
▪ High Risk to Customer Satisfaction o Sev. > or = to 5 and Occ > or = 4
▪ Consider Detection only as a measure of Test Capability.
Example of Significant/ Critical Threshold
*Used by permission of Ford Motor Company
10987654321
1 2 3 4 5 6 7 8 9 10
SEVERITY
O C C U R R E N C E
POTENTIAL CRITICAL CHARACTERISTICS Safety/Regulatory
POTENTIALSIGNIFICANT
CHARACTERISTICSCustomer Dissatisfaction
ALL OTHER CHARACTERISTICS
Appropriate actions / controls already in place
Special Characteristics Matrix
ANOYANCE ZONE
Actions
Item
Function
System Subsystem Component:
Model Year/Vehicle (s):
Core Team:
Your Company Name Here Potential Failure Mode and Effects Analysis
(Design FMEA)
Design Responsibility: Key Date:
FMEA Number: Page of Prepared by: FMEA Date (Orig.): (Rev.):
Potential Failure Mode
Potential Effect (s) of
Failure
s e v
c l a s s
Potential Cause (s)/
Mechanism (s) Failure
o c c u r
Current Design
Controls
D e t e c
R. P. N.
Recommended Action(s)
Responsibility & Target
Completion Date
Actions Taken
s e v
o c c
D e t
R. P. N.
A c t i o n R e s u l t s
Actions
EXAMPLE:
Project: Date OfMeeting:
IssueNumber
Issue Status/Open Date
IssueChampion
ActionNumber
ActionDate
Action Person Resp.Team
CompletionDate
143
Re-rating RPN After Actions Have Occurred
Item
Function
System Subsystem Component:
Model Year/Vehicle (s):
Core Team:
Your Company Name Here Potential Failure Mode and Effects Analysis
(Design FMEA)
Design Responsibility: Key Date:
FMEA Number: Page of Prepared by: FMEA Date (Orig.): (Rev.):
Potential Failure Mode
Potential Effect (s) of
Failure
S e v
C l a s s
Potential Cause (s)/
Mechanism (s) Failure
O c c u r
Current Design
Controls
D e t e c
R. P. N.
Recommended Action(s)
Responsibility & Target
Completion Date
Actions Taken
S e v
O c c
D e t
R. P. N.
A c t i o n R e s u l t s
Re-rating RPN After Actions Have Occurred
▪ Severity typically stays the same. ▪ Occurrence is the primary item to reduce / focus on. ▪ Detection is reduced only as a last resort. ▪ Do not plan to REDUCE RPN with detection actions!!!
o 100% inspection is only 80% effective! o Reducing RPN with detection does not eliminate failure mode,
or reduce probability of causes o Detection of 10 is not bad if occurrence is 1
FMEA in a continuous flow process ●Steel Making example: !▪Design FMEA was performed on a Crankshaft to
determine the best material for the product being considered. This was a critical application. !▪Key features such as Geometry, Strength, Duty Cycle,
were described to the Steel producer.