FMEA

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FMEA

• Intelligent use of FMEA

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Potential Failure Mode and Effects
Analysis (Design FMEA)
__ System __ Subsystem __ Component Model
Year/Vehicle(s) Core Team
FMEA Number Page 1 or 1 Prepared by Lee
Dawson FMEA Date (Orig.)
Design Responsibility Key Date
Potential Cause(s)/ Mechanism(s) Of Failure
Current Design Controls Prevention
Current Design Controls Detection
Item
Action Results
Responsibility Target Completion Date
O C C U R
D E T E C
C L A S S
Potential Failure Mode
Potential Effect(s) of Failure
S E V
R. P. N.
Recommended Action(s)
R. P. N.
S E V
O C C
D E T
Actions Taken
Function
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What Is An FMEA?

• Opportunity to Defeat Murphys Law
• Focus on Prevention
• Failure Mode And Effects Analysis is
• An assessment of Risk
• Safety
• Regulatory
• Customer Satisfaction
• Program
• Coordinated/Documented team effort
• To determine what can go wrong
• A method to determine the need and priority of
  actions

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Requirements Cascade

• How Fmea fits into Product and Process Development

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Potential KPC Development

• Requirements Documents
• Regulatory
• Dimensional
• Cosmetic
• Req. Spec. Document
• Drawings
• Warranty History

Robustness Tools Boundary Diagram P-Diagram Inter
face Matrix
Cascade Technical Requirements Into Special
Product Characteristics
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Characteristics Matrix Development
Process Flow

• Special Characteristics Sources
• DFMEA (Potential KPCs Significant and Critical
  Characteristics)
• Drawings
• Regulations

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Characteristics Matrix
Characteristics Ranked in order of Importance
Potential Significant and Critical
Characteristics from DFMEA Other Sources
Process Operation from Process Flow
High/Medium Interactions are causes/failure modes
in PFMEA
Prioritized ranking of process steps relative to
risk
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FMEA Deployment

• A layered approach is highly recommended as
  FMEAs can get complex.
• FMEAs are like ONIONS/LAYERS.
• Each layer is closer to the root cause
• Each layer is more detailed
• The closer to core the more detail
• Core gets to the root cause
• Do too many and you will cry.

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System Boundary Diagram
Cylinder Head
Compression Brake
Vibration

• Arm Group Assembly
• Intake rocker assembly
• Exhaust rocker assembly
• Stand(s) W W/o oil supply
• Shaft Assembly
• Mounting Bolt
• Spring/Spacer

• Shaft Assembly
• Shaft
• Cup
• Pin

• Additional Clearances
• Injector Spring
• Injector Spring Base
• Injector retainer
• Injector Bridge
• Injector injector clamp

Vibration

• Intake Rocker Assembly
• Exhaust Rocker Assembly
• Body
• Insert
• Roller
• Pin
• Clip

Clearance
Valve Cover
Bridge
Floating

• Pushrod
• Rod
• Cup
• Ball

Lube Oil

• Valve
• Injector oil

• Spring Group
• Inner Outer Springs
• Spring Base
• Retainer/Rotator
• Valve Keeper

Load
Cylinder Head

• Lifter Assembly
• Body
• Insert
• Roller
• Pin
• Clip
• wire

• Valve Group
• Intake Valve
• Exhaust Valve
• Intake Seat
• Exhaust Seat
• Valve Guide
• Valve Guide Seal

Valve Stem Seal
Clear at full stroke

• Oscillating Lifter
• Pressure Lube
• OR
• Bore in Block
• Pressure Lube

Lube Oil
CAM Shaft
Cylinder Head
CAM Bearings
Valve Seat
Seat Insert
Thrust Plate
Cylinder Head
Cylinder Block
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P-Diagram
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FMEA Preparation Vertical Approach

• Key Elements of Efficient Development
• Identify all functions/process steps
• Boundary Diagram
• P Diagram
• Identify all failure modes via
  brainstorming/data/warranty/COQ
• Identify all effects via brainstorming/data
• Customer focus
• Develop data pools for
• Failure Modes, Effects and Causes for future/
  faster FMEA development

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System/Subsystem/ Design FMEA

• Failure Mode Pure anti-function

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System/Subsystem/ Design FMEA

• Effect
• Customer view/customers words
• Regulation violation
• Level of dissatisfaction
• Consider All Customers
• End User
• Engineering Community
• Manufacturing Community
• (Operators/Employees)
• Regulatory Body

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Severity Column
Severity Column
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SEVERITY EVALUATION CRITERIA
EFFECT
CRITERIA Severity of Effect
RNK.
Very high severity ranking when a potential
failure mode affects safe vehicle operation
and/or involves noncompliance with government
regulation without warning
Hazardous- without warning
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Hazardous- with warning
Very high severity ranking when a potential
failure mode affects safe vehicle operation
and/or involves noncompliance with government
regulation with warning
9
Very High
Vehicle/item inoperable (loss of primary
function).
8
Vehicle/item operable but at a reduced level of
performance. Customer very dissatisfied.
High
7
Vehicle/item operable but Comfort/Convenience
item(s) inoperable. Customer dissatisfied.
Moderate
6
Vehicle/item operable but Comfort/Convenience
item(s) operable at a reduced level of
performance. Customer somewhat dissatisfied.
Low
5
Fit Finish/Squeak Rattle item does not
conform. Defect noticed by most customers
(greater than 75).
Very Low
4
Fit Finish/Squeak Rattle item does not
conform. Defect noticed by 50 of customers.
Minor
3
Fit Finish/Squeak Rattle item does not
conform. Defect noticed by discriminating
customers (less than 25).
Very Minor
2
None
No discernable effect.
1
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FMEA General
For High Severity 9/10
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Failure Mode/Cause Relationship In Different
FMEA Levels
Inadequate Electrical Connection
Failure Mode
Cause
Motor Stops
Failure Mode
Inadequate Electrical Connection
Causes
Inadequate Locking Feature
Harness Too Short
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Causes

• Causes from P-Diagram
• Noise factors
• Continue through all failure modes.
• Note that many causes are recurring.

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Occurrence Column
Occurrence Column
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Occurrence Evaluation Criteria
SUGGESTED OCCURRENCE EVALUATION CRITERIA
Probability of
Likely Failure Rates Over Design Life
Ranking Failure
? 100 per thousand vehicles/items
10
Very High Persistent failures
50 per thousand vehicles/items
9
20 per thousand vehicles/items
8
High Frequent failures
10 per thousand vehicles/items
7
5 per thousand vehicles/items
6
Moderate Occasional failures
2 per thousand vehicles/items
5
1 per thousand vehicles/items
4
0.5 per thousand vehicles/items
3
Low Relatively few failures
0.1 per thousand vehicles/items
2
Remote Failure is unlikely
? 0.01 per thousand vehicles/items
1
Note Zero (0) rankings for Severity,
Occurrence or Detection are not allowed
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Occurrence Rating

• If an action would effectively eliminate the
  possibility of the cause occurring, the action is
  listed as described earlier.
• Occurrence of 1 or 2 require proof using a
  surrogate product or mistake proofing.

DATA
HARD FACTS
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Example of Significant/ Critical Threshold
Used by permission of Ford Motor Company
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Classification And Definition Column
C l a s s
O c c u r
D e t e c
Action Results
Item
Potential Cause(s) / Mechanism(s) of Failure
Response Target Complete Date
S e v
R. P. N.
Potential Failure Mode
Potential Effect(s) of Failure
Current Design Controls
Recommended Actions
Actions Taken
O c c
S e v
D e t
R. P. N.
Function
Classification and Definition Column
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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.
• Prevention is specifically related to reduction
  or elimination of a cause.
• Detection is how well the test or series of
  tests may find the design flaw
• Causes
• Failure Mode

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Detection Rating
SUGGESTED DETECTION EVALATION CRITERIA
CRITERIA
RNK.
DETECTION
Design Control will not and/or cannot detect a
potential cause/ mechanism and subsequent failure
mode or there is no Design Control.
Absolute Uncertainty
10
Very Remote chance the Design Control will detect
a potential cause/mechanism and subsequent
failure mode.
Very Remote
9
Remote chance the Design Control will detect a
potential cause/ mechanism and subsequent
failure mode.
Remote
8
Very Low chance the Design Control will detect a
potential cause/mechanism and subsequent failure
mode.
Very Low
7
Low chance the Design Control will detect a
potential cause/mechanism and subsequent failure
mode.
Low
6
Moderate chance the Design Control will detect a
potential cause/ mechanism and subsequent failure
mode.
Moderate
5
Moderately High
Moderately High chance the Design Control will
detect a potential cause/mechanism and subsequent
failure mode.
4
High chance the Design Control will detect a
potential cause/ mechanism and subsequent failure
mode.
High
3
Very High chance the Design Control will detect a
potential cause/ mechanism and subsequent
failure mode.
Very High
2
Almost Certain
Design Controls will almost certainly detect a
potential cause/ mechanism and subsequent failure
mode.
1
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Analysis Of Risk

• RPN / RISK PRIORITY NUMBER
• What Is Risk?
• Probability of danger
• Severity/Occurrence/Cause

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RPN / Risk Priority Number
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Evaluation by RPN Only

• Case 1
• S5 O5 D2 RPN 50
• Case 2
• S3 O3 D6 RPN 54
• Case 3
• S2 O10, D10 200
• Case 4
• S9 O2 D3 54

WHICH ONE IS WORSE?
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Example

• Extreme Safety/Regulatory Risk
• 9 10 Severity
• High Risk to Customer Satisfaction
• Sev. gt or to 5 and Occ gt or 4
  
• Consider Detection only as a measure of Test
  Capability.

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Example of Significant/ Critical Threshold
Used by permission of Ford Motor Company
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Actions
Potential Failure Mode and Effects
Analysis (Design FMEA)
Your Company Name Here
FMEA Number Page of Prepared
by FMEA Date (Orig.) (Rev.)
System Subsystem Component
Design Responsibility Key Date
Model Year/Vehicle (s) Core Team
Item
A c t i o n R e s u l t s
c l a s s
Potential Cause (s)/ Mechanism (s) Failure
Responsibility Target Completion Date
Potential Failure Mode
Potential Effect (s) of Failure
o c c u r
Current Design Controls
s e v
D e t e c
R. P. N.
Recommended Action(s)
Actions Taken
s e v
o c c
D e t
R. P. N.
Function
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Actions
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Re-rating RPN After Actions Have Occurred
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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!!!
• 100 inspection is only 80 effective!
• Reducing RPN with detection does not eliminate
  failure mode, or reduce probability of causes
• Detection of 10 is not bad if occurrence is 1

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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.

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• The key product requirements were mapped against
  the required customer features. E.g. chemistry
  and microstructure, Internal stress at ingot
  level,
• Product Grade and requirements documents created.
  
• Key characteristics mapped against processes
• Process FMEA was performed on processes that
  affected customer wants based on priority.

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Phase I QFD
Product Specifications
Phase Progression
Systems / Sub-Systems / Components
Phase II QFD
Customer Wants (Marketing Information)
DFMEA Failure Modes
Product Specifications
System DFMEA
Sub-System DFMEA
Component DFMEA
QFD Phase Progression
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The Completed Characteristics Matrix
Characteristics Ranked in order of Importance
Process Operation from Process Flow
Potential Significant and Critical
Characteristics from DFMEA
High/Medium Interactions are causes/failure modes
in PFMEA
Prioritized ranking of process steps relative to
risk
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Phase III QFD
Process Operations
System DFMEA
Sub-System DFMEA
Phase IV QFD
Component DFMEA
Process Parameters / Variables
High Priority Process Operations
SCs CCs
Classification of Characteristics
Causes from DFMEAs
SCs CCs
Process Related SCs CCs From all DFMEAs
Causes on PFMEA
Failure Modes on PFMEA
Key Control Characteristics
Process FMEA
Control Plan
QFD Phase Progression
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Summary

• FMEA can be used creatively in continuous
  processing.
• Linking key customer requirements to process
  outputs instead of standard product grade is
  valuable.
• Future customer requirements will drive new and
  modified processes to achieve specialty results
  as a normal practice

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QA