Fmea handout

FMEA
FAILURE MODE AND EFFECTS ANALYSISFAILURE MODE AND EFFECTS ANALYSIS

OUTLINE
Failure Mode and Effects Analysis
Learning Objectives
What is FMEA?
History
Motivation
Types
FMEA Steps

LEARNING OBJECTIVES
To understand the use of Failure Modes
Effect Analysis (FMEA)
To learn the steps to developing FMEAs
To summarize the different types of FMEAs
3
To summarize the different types of FMEAs
To learn how to link the FMEA to other
Process tools

WHAT IS FMEA?
A Failure Mode and Effects Analysis is a systemized
group of activities intended to:
recognize and evaluate potential failure and its effects
identify actions which will reduce or eliminate the chance of
failure
document analysis findings

• PFMEA = Process Failure Mode and Effects Analysis
• PFMEA is a tool intended to document the entire process
– Recognize and evaluate the potential failures of a process
– Assess the effects of each potential failure (Identify Risk)
– Identify potential process causes and identify process
DEFINITION OF PFMEA
– Identify potential process causes and identify process
variables on which to focus controls
– Identify actions (Control Plan) that could eliminate or reduce
the chance of the failure occurring (Mitigate Risk)
5

HISTORY OF FMEA
First used in the 1960’s in the Aerospace
industry during the Apollo missions
In 1974, the Navy developed MIL-STD-1629
regarding the use of FMEA
Examples
regarding the use of FMEA
In the late 1970’s, the automotive industry
was driven by liability costs to use FMEA
Later, the automotive industry saw the
advantages of using this tool to reduce risks
related to poor quality

MOTIVATION FOR CONDUCTING A FMEA
Improves design by discovering unanticipated
failures
Highlights the impact of the failures
Potentially helpful during legal actions
Provides a method to characterize product safetyProvides a method to characterize product safety
Often required (e.g. FDA and DOD
procurement)

4TH EDITION KEY EMPHASIS POINTS
• Severity, Occurrence, Detection ranking tables
– Improved ranking tables so that they are more meaningful to real
world analysis and usage.
• Role of management and its sanction
– For resources and monitoring
• Incorrect interpretation and reliance on RPN in the evaluation of risk
8
• Incorrect interpretation and reliance on RPN in the evaluation of risk
priorities and improvement actions
– Inappropriate use of RPN to obtain an arbitrary threshold
• Improve the understanding of the role of the FMEA process
throughout the APQP phases
– Including continual improvement during production
– FMEA is more than a static document necessary only for PPAP
approval

• Confusion between cause & effect
• Too few causes identified
• Lack of repeatability in risk assessment
• FMEA done only by the FMEA moderator the night before a
customer
visit, an audit, initial sample presentation…
COMMON MISTAKES OFTEN SEEN
visit, an audit, initial sample presentation…
• Actions not relevant or not validated
• Detection assessed too low for a visual inspection
• Changing the severity index after action on the process
• Confusion between Design, process and machine FMEA
9Source : Joe Yap of GM

• Can’t eliminate all human errors
• Only single event initiators of the problem identified
• Examination of external influences limited
• Results are dependent on the quality of input!
PFMEA assumptions
LIMITATIONS OF PFMEA
PFMEA assumptions
• You have to assume material is to spec
• You have to assume Design is robust
10

TYPES OF FMEAS
Design
Analyzes product design before release to
production, with a focus on product function
Analyzes systems and subsystems in early concept
and design stages
ProcessProcess
Used to analyze manufacturing and assembly
processes after they are implemented
11

Design FMEA
• Main focus is on design of the product and specifications which
enable the product to meet the intended use.
Process FMEA
• Main focus is on the manufacturing process which will allow the
product to be made repeatedly to the print design specifications.
DESIGN VS. PROCESS FMEA
product to be made repeatedly to the print design specifications.
• Utilizes process knowledge and historical process data to identify
and help eliminate potential process failure modes.
The thought pattern for development is identical
12

DESIGN FMEA (DFMEA)
The Design FMEA is used to analyze products
before they are released to production.
It focuses on potential failure modes of
products caused by design
deficiencies.deficiencies.
Design FMEAs are normally done at three
levels – system,
subsystem, and component levels
This type of FMEA is used to analyze hardware,
functions or a
combination
13

PROCESS FMEA (PFMEA)
The Process FMEA is normally used to analyze
manufacturing and assembly processes at the
system, subsystem or component levels.
This type of FMEA focuses on potential failureThis type of FMEA focuses on potential failure
modes of the process that are caused by
manufacturing or assembly process deficiencies.
14

• The risk analysis must be driven by multifunctional teams.
• Is a LIVING document that represents the current process or product.
PROCESS FMEA
If it is correctly used, it WILL eliminate failures on products and
process.
15

• 25% of our Spills were driven by change
-Process
-Product
-New Model Year Launches
-Tool Moves
LESSONS LEARNED
16
All quality spills could have been avoided
if defined processes had been followed

Five significant Failure Modes are responsible for
80% of the Spills:
17

WHY DO FMEA?
Failures: unavoidable? Or are they?
• Manufacturing is a complex environment
• The potential for many things to go wrong, or fail, is high
• A failure is any change or any manufacturing error that renders a
component, assembly, or system incapable of performing its
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component, assembly, or system incapable of performing its
intended function
• Process failures result in defects, defects result in waste
• Undetected defects could result in spills, customer dissatisfaction,
and hence huge cost (REACTIVE)
• Need to recognize risks – work on reduction (PREVENTIVE)

WHY DO FMEA?
• Target oriented, early determination of risks at product development and
process planning.
• Evaluation and minimization of risks
• Increase products reliability and process capability;
• Warranty safety and better ergonomics.
Prevention instead of correction
19
• Warranty safety and better ergonomics.

WHO PARTICIPATES & WHY?
• Who: A cross functional team of Engineers, Designers, Operators,
Supervisors, and Suppliers.
• Why: Each person has a unique perspective and expertise based on
their job assignment.
21
PE: Product Eng; (Process/Test Eng’g.)
ME: Manufacturing Eng;
QP: Quality Planning Eng; (Quality Eng’g.)
MT: Maintenance;
MF: Manufacturing GL/TL, etc.; (Production)

FMEA: A TEAM TOOL
A team approach is necessary.
Team should be led by the Process Owner who is
the responsible manufacturing engineer or technical
person, or other similar individual familiar with
FMEA.FMEA.
The following should be considered for team
members:
– Design Engineers – Operators
– Process Engineers – Reliability
– Materials Suppliers – Suppliers
– Customers
22

IMPORTANCE OF FLOW DIAGRAMS
• Usually the First “Picture” of a Process
• Provides a logical pictorial which represents the
Flow of the Process
• Used as the Foundation for PFMEAs, Control Plans,
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• Used as the Foundation for PFMEAs, Control Plans,
Tooling Layouts, Work Station Layouts, Etc…
• All Operations should be shown, including Inspection,
Gauging Operations and Rework and Scrap Areas.

FLOW DIAGRAM QUICK CHECKLIST
Recommended Base Requirements of a Process Flow Diagram:
• Manufacturing Process Title
• Numbering/Lettering Scheme – Standard format
• Include ALL Operations
– Gauging & key process control related operations
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– Rework areas
– Scrap areas
– Labeling
– Shipping
• Key for Symbols; consistent use

FLOW DIAGRAM PFMEA & CONTROL PLAN
PROCESS FLOW
PFMEA
25
• They are like Triplets
– They look very similar
– They contain the same major items
– All three are just presented a little different with varying information for different
outcomes
CONTROL PLAN

WHEN TO USE FMEA
FMEA is designed to prevent failures from occurring or
from getting to internal and external customers.
Therefore, FMEA is essential for situations where failures
might occur and the effects of those failures occurring aremight occur and the effects of those failures occurring are
potentially serious.
FMEA can be used on all Six Sigma projects. It serves as
an overall control document for the process.
26

DEVELOPMENT OF A PROCESS FMEA
List the process and
detailed process
steps
Identify all functions
/requirements of
each process step
List all Failure Modes List the effects
List all possible
causes
29
How likely is the
cause to occur? (1-
10)
How serious is the
effect? (1-10)
Current controls
Can failure/cause be
detected?(1-10)
Calculate RPN
Take actions to
reduce the risk
Identify the root
cause

PROCESS FLOW WORKSHEET
EXAMPLE
- Employee Picks Up Cover - Pick-up Cover
- Employee Engages Edge of Cover to Final - Engage Cover
DVD Assembly
Process Step
(List the Process Step to be studied)
Process Function(s)
(Verb-Noun)
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DVD Assembly
- Employee Finishes Placing the Cover on the DVD - Place Cover
- Employee Picks up Two Screws - Pick-up Screw
- Employee Picks up Screw Gun - Pick-up Gun
- Employee Fastens Cover to the Final DVD - Torque Screw
Assembly with the Screws

FMEA STEPS
1.Fill in the header information.
2.Fill in the process steps.
3.For each process step, list requirements.
4.For each requirement, list the failure mode.
5.For each failure mode, list the effect of failure.5.For each failure mode, list the effect of failure.
6.For each effect of failure, estimate the severity.
7.For each failure mode, list causes.
31

FMEA STEPS (CONT.)
8. For each cause of failure, estimate
the likelihood of occurrence.
9. For each cause of failure, list the current process
controls.
10. For each process control, estimate the detection.10. For each process control, estimate the detection.
11. For each cause of failure, calculate the Risk
Priority Number.
12. For high priority causes of failure and/or failure
modes, develop recommended actions.
32

FMEA STEPS (CONT.)
13. For each recommended action,
assign responsibility and
completion dates.
14. For each recommended action, implement the
action and note its effect.action and note its effect.
15. For each implemented action, re-estimate the
severity, occurrence and detection rankings and
recalculate the RPN.
33

THE FMEA FORM
34
Identify failure modes
and their effects
Identify causes of the
failure modes
and controls
Prioritize Determine and
assess actions
34

FMEA STEP 1
1. Fill in the header information.
Failure Mode & Effects Analysis (FMEA)
Process Description: FMEA Number:
Black Belt: Page: of
Team Members: Prepared by:
FMEA Date:
Revision Number & Date:
Process
Step
Requirements
Potential
Failure
Mode
Potential
Effect(s)
of Failure
Severity
Potential
Cause(s)/
Mechanism(s)
of Failure
Occurrence
Current
Process
Controls
Detection
RPN
Recommended
Action(s)
Responsibility
& Target
Completion Date
Actions
Taken
Sev
Occ
Det
RPN
Action Results
A. Describe the process B. Number the FMEA
C. Identify the Black Belt D. Identify page numbers
E. List team members F. Name the preparer
G. Enter the FMEA date H. Enter the revision data
35

FMEA - STEP 2
2. Fill in the process steps.
Add all value added process steps
from the process map to the FMEA
form.
Start
End
Step 2A Step 2B Step 2C
Step 1
Weld Nut to
Pedestal
Good?Rework
YesNo
VA
NVA
NVA
EndGood?Rework
Process
Step
Requirements
Weld Nut to Pedestal
36

- A simple description of the process or operation being analyzed.
- Purpose or intent of a particular process.
- All functions are written in verb-noun (action-object) format.
PFMEA TERMS AND DESCRIPTION
FUNCTION
37

FMEA - STEP 3
3.For each process step, list requirements.
Requirements can be
specifications, if available, or
statements of what the process
Process
Step
statements of what the process
step should accomplish.
Requirements
Nut Present
Nut Welded Securely
Internal Threads in
good condition 38

- Inputs to the process specified to meet the design intent and
other customer requirements.
- Outputs of each operation/step and relate to the requirements
for the product.
- Provide a description of what should be achieved at each
operation/step.
REQUIREMENTS
- Provide the team with a basis to identify potential failure
modes.
39

FMEA - STEP 4
Process
Step
Requirements
Potential
Failure
Mode
Weld Nut to PedestalWeld Nut to Pedestal
Nut Present Nut not present
Nut Welded Securely Nut welded
insecurely
Internal Threads in Internal threads
good condition damaged
40

FMEA TIPS ABOUT STEP 4
Tips about Step 4:
Failure modes are negative statements of requirements.
Failure modes are not causes. “Operator fails to load weld nut” is not a
failure mode. It is a cause of the failure mode, “Nut not present.”failure mode. It is a cause of the failure mode, “Nut not present.”
This column is easy - if you avoid discussing causes! Just wait.
Everyone can discuss causes in step 7.
41

- The manner in which the process could potentially fail to meet the
process requirement.
There are 7 kinds of failure modes (by GM):
1. Omission = No action, Did not do the action
2. Excessive = Too much/many, Did action too much/ too many
3. Incomplete = Too little/few, Did action too little
4. Erratic = Mis-position inconsistent
FAILURE MODE
4. Erratic = Mis-position inconsistent
5. Uneven = Mis-position consistent
6. Too quickly = fast, Did action too quickly
7. Too slowly = slow, Did action too slowly
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Note : The assumption is made that the failure could occur, but may not necessarily occur.
Potential failure modes should be specific and should be written as a negative outcome of “Requirements”.

Failure Mode is the event which comes between the Cause and the
Effect.
LINKING FAILURE MODE TO CAUSE & EFFECT
Cause
Failure
Mode
Effect
43
Cause
Mode
Effect

FMEA - STEP 5
5.For each failure mode, list the effect of failure.
Process
Step
Requirements
Potential
Failure
Mode
Potential
Effect(s)
of Failure
Nut Present Nut not present Cannot assemble seat
belt restraint to
pedestal
Nut Welded Securely
(110 lbs. min. Tensile
test)
Nut welded Bolt breaks weld nut
insecurely loose when seat belt
restraint is assembled
Internal Threads in Internal threads Seat belt restraint is
good condition damaged assembled, but threads
are stripped. 44

5.For each failure mode, list the effect of failure.
Tips about Step 5:
List only “worst case” effects of failure (that’s all you need to
estimate severity).
Capture what actually happens when the failure mode occurs.
Avoid general statements like, “Part is rejected” or “Customer
complaint.”
By being specific in this column, later steps (estimating severity &
listing causes) will go much easier.
45

- It is the impact or downstream consequence of the failure
mode on the customer.
• Describe the effect of the failure mode in terms of what the
customer will notice or experience.
• Customer may be an internal customer as well as the
ultimate end user. Each must be considered when assessing
EFFECT
ultimate end user. Each must be considered when assessing
the potential effect of a failure.
46

FMEA - STEP 6
6.For each effect of failure, estimate the severity
Process
Step
Requirements
Potential
Failure
Mode
Potential
Effect(s)
of Failure
Severity
Weld Nut to PedestalWeld Nut to Pedestal
Nut Present Nut not present Cannot assemble seat 5
belt restraint to
pedestal
Nut Welded Securely Nut welded Bolt breaks weld nut 6
insecurely loose when seat belt
restraint is assembled
Internal Threads in Internal threads Seat belt restraint is 9
good condition damaged assembled, but threads
are stripped.
Assembly is weak.
47

- An assessment of the seriousness of the effect of a failure mode.
• Severity applies to the effect only. It is associated with the most
serious effect of a given failure mode.
• Severity rankings should be identical for identical Potential
Effects.
• A reduction in the severity ranking can be effected through a
SEVERITY (S)
• A reduction in the severity ranking can be effected through a
design change to the system, subsystem or component, or a
design of the process.
48

FMEA - STEP 6: AIAG* SEVERITY GUIDELINES
SEVERITY
SCALE
Criteria : This ranking results when a potential failure
mode results in a final customer and/or a
manufacturing/assembly plant defect. The final
customer should always be considered first. If both
occur, use the higher of the two severities.
10 Hazardous - w/o warning Very high severity ranking when a potential failure mode
affects safe vehicle operation and/or involves
noncompliance with government regulation without
warning
9 Hazardous - w/ warning Very high severity ranking when a potential failure mode
affects safe vehicle operation and/or involves
noncompliance with government regulation with warning
8 Very High Vehicle/item inoperable, with loss of primary function.
7 High Vehicle/item inoperable, but at a reduced level of
performance. Customer very dissatisfied.
Or product may have to be sorted and a portion, (less than 100%)
repaired in repair department with a repair time between a half-hour
Criteria : This ranking results when a potential failure mode results
in a final customer and/or a manufacturing/assembly plant defect.
The final customer should always be considered first. If both occur,
use the higher of the two severities.
Or may endanger operator (machinery assembly) without warning.
Or may endanger operator (machinery assembly) with warning.
Or 100% of product may have to be scrapped, or vehicle/item
repaired in repair department with a repair time greater than one
hour.
* Note: AIAG is the Automotive Industry Action Group, which currently
compiles the FMEA standards for the North American Auto Industry.
6 Moderate Vehicle/item operable, but comfort/convenience
inoperable. Customer dissatisfied.
5 Low Vehicle/item operable, but comfort/convenience operable
at a reduced level of performance. Customer somewhat
dissatisfied.
4 Very Low Fit and Finish/Squeaks and Rattle item does not
conform. Defect noticed by most Customers. (greater
than 75%)
3 Minor Fit and Finish/Squeaks and Rattle item does not
conform. Defect noticed by 50% Customers.
2 Very Minor Fit and Finish/Squeaks and Rattle item does not
conform. Defect noticed by discriminating Customers.
(less than 25%)
1 None No discernible effect
and an hour.
Or a portion (less than 100%) of the product may have to be
scrapped with no sorting, or vehicle/item repaired in the repair
department with a repair time less than a half-hour.
Or 100% of product may have to be reworked, or vehicle/item
repaired off-line but does not go to repair department.
Or the product may have to be sorted, with no scrap, and a portion
(less than 100%) reworked.
Or a portion (less than 100%) of the product may have, with no
scrap, on-line but out-of-station.
Or a portion (less than 100%) of the product may have, with no
scrap, on-line but in-station.
Or slight inconvenience to operation or operator, or no effect.
49

6.For each effect of failure, estimate the severity
Tips about Step 6:
The auto industry uses the AIAG guidelines as a standard.
Whatever guidelines are used…
Keep a copy with your FMEA.
Always make the highest number most severe, the lowest least
severe.
50

THE AIAG FMEA FORM - “CLASS”
COLUMN
On the AIAG FMEA form there is a column labeled,
“Class” (short for Classification).
This column is used to indicate a failure mode that
directly affects a customer’s safety, critical, major or
minor item.
Symbols such as an inverted delta, a safety badge, and
diamonds frequently appear in this column.
In most Six Sigma Projects this column is not needed. If
a FMEA is used for presentation to automotive
customers, then this column should be used.
51

- Used to highlight high priority failure modes or causes that may
require additional engineering assessment.
- Classify any special product or process characteristic (e.g., critical,
key, major, significant) for components, subsystems, or systems
that may require additional process controls.
• Customer specific requirements may identify special product or
process characteristic symbols and their usage.
•
CLASSIFICATION (CLASS)
• The following internal characteristics are considered:
* W – an important product or process characteristic whose
execution to specification is of special importance to the
operation of the product or its further processing.
* D – indicate a product or process characteristics, which requires
archived documentation.
52

FMEAFMEA -- Step 7Step 7
Process
Step
Requirements
Potential
Failure
Mode
Potential
Effect(s)
of Failure
Severity
Potential
Cause(s)/
Mechanism(s)
of Failure
Nut Present Nut not present Cannot assemble seat 5 Welder cyles without
belt restraint to nut present
pedestal Operator fails to load
nut into welder
Nut is loaded but falls
out before weld cycle
Nut Welded Securely Nut welded Bolt breaks weld nut 6 Variation in pedestal
insecurely loose when seat belt raw material
restraint is assembled Weld strength variation
is too large
Variation in weld nut
raw material
Grease, contamination
on weld surfaces
Variation in welder
power circuit
Incorrect welder
set-up
53

Tips about Step 7:
Use Cause and Effect Diagrams to do a thorough investigation of
causes for tough failure modes.
Sometimes hypothesis testing can be useful in demonstrating a cause
54
Sometimes hypothesis testing can be useful in demonstrating a cause
is strong.
Try to verify that the listed causes are important to avoid too long a list
of causes.
If you list causes everyone already knows about, you may not be able
to reduce risk.
54

- Refers to how the failure mode could occur, and is described
in terms of something that can be corrected or can be
controlled.
• Only specific error or malfunctions (e.g. Operator fails to
install) should be listed. Ambiguous phrases (i.e. operator
error, machine malfunction) should not be used.
CAUSE
55

USE THE C & E DIAGRAM
Process Step/
Requirements
Potential
Failure Mode
Potential
Effects of
Failure Severity
Potential
Causes of
Failure
FMEA
Causes
Effect
56

8.For each cause of failure, estimate the
likelihood of occurrence.
Process
Step
Requirements
Potential
Failure
Mode
Potential
Effect(s)
of Failure
Severity
Potential
Cause(s)/
Mechanism(s)
of Failure
Occurrence
Nut Present Nut not present Cannot assemble seat 5 Welder cyles without 8
57
Nut Present Nut not present Cannot assemble seat 5 Welder cyles without 8
belt restraint to nut present
pedestal Operator fails to load 2
nut into welder
Nut is loaded but falls 1
out before weld cycle
Nut Welded Securely Nut welded Bolt breaks weld nut 6 Variation in pedestal 2
insecurely loose when seat belt raw material
restraint is assembled Weld strength variation 6
is too large
Variation in weld nut 2
raw material
Grease, contamination 2
on weld surfaces
Variation in welder 3
power circuit
Incorrect welder 2
set-up

FMEA - STEP 8: AIAG* OCCURRENCE
GUIDELINES
OCCURENCE
SCALE OCCURENCE SCALE
10 > or = 100/1,000 vehicles
9 50/1,000 vehicles
8 20/1,000 vehicles
7 10/1,000 vehicles
Very High: Failure is almost
inevitable
High: Repeated failure
7 10/1,000 vehicles
6 5/1,000 vehicles
5 2/1,000 vehicles
4 1/1,000 vehicles
3 0.5/1,000 vehicles
2 0.1/1,000 vehicles
Remote: Failure is unlikely 1 < or = 0.010/1,000 vehicles
Moderate:Occasional failures
Low: Relatively few failures
58

8.For each cause of failure, estimate the likelihood of
occurrence.
Tips about Step 8:
The auto industry uses the AIAG as a standard.
Whatever guidelines are used…
Keep a copy with your FMEA.
Always make the highest number most severe, the lowest least
severe.
59

- How frequently the specific failure cause is projected to occur.
- Is the likelihood that a specific cause/mechanism of failure will
occur.
• If statistical data are available, these should be used to
determine occurrence ranking.
• One occurrence ranking for each cause (e.g., “worn/broken
OCCURRENCE (O)
• One occurrence ranking for each cause (e.g., “worn/broken
tool”) must have two separate rankings.
60

- Are controls that prevent to the extent possible the cause of the
failure or the failure mode from occurring, or reduce its rate of
occurrence.
• Controls are adequately explained and do not just reference a
document number.
PREVENTIVE ACTIONS
61

9.For each cause of failure, list the current process
controls.
Process
Function
Requirements
Potential
Failure
Mode
Potential
Effect(s)
of Failure
Severity
Potential
Cause(s)/
Mechanism(s)
of Failure
Occurrence
Current
Process
Controls
Spot weld nut to
pedestal
Nut present Nut not present Cannot assemble seat belt 5 Welder cycles without nut 8 100% Visual Inspection by
62
Nut present Nut not present Cannot assemble seat belt
restraint to pedestal
5 Welder cycles without nut
present
8 100% Visual Inspection by
operator after cycle
Operator fails to load nut
into welder
Nut is loaded but falls out
before weld cycle
Nut welded
securely
Nut welded
insecurely
Bolt breaks weld nut loose
when seat belt restraint is
assembled
6 Variation in pedestal raw
material
2 Supplier Certifications and
SPC information of
metallurgy
Weld strength variability is
too high
6 Welder is calibrated every
shift, maintained every
Variation in nut raw
material
SPC information of
metallurgy
Grease, contamination on
weld surfaces
2 Standard handling
procedures
Variation in the welder
power circuit
Welder incorrectly set up 2 1st piece weld strength

9.For each cause of failure, list the current process controls.
Tips about Step 9:
Make sure you list the actual controls.
Don’t list “wannabe” controls.
Be brutally honest, if there is no control, just say it.
Frequently, there is no control for the cause of the failure mode; but
there is a control to detect the failure mode itself (see the next slide).
63

PROCESS CONTROL EXAMPLE
In an injection molding process, injection pressure of
over 6895 pieze (kilo-pascals) leads to a small
dimension. At a later stage, this makes assembly
difficult.
A process control on the cause (injection pressure)
might be a high pressure alarm on the hydraulic
circuit.circuit.
A process control on the failure mode (small
dimension) might be a
dimensional inspection
of each part.
64

- Identify the cause of the failure or the failure mode,
leading to the development of associated corrective
action(s) or counter-measures.
DETECTION ACTION
65

10. For each process control, estimate the
detection.
Process
Function
Requirements
Potential
Failure
Mode
Potential
Effect(s)
of Failure
Severity
Potential
Cause(s)/
Mechanism(s)
of Failure
Occurrence
Current
Process
Controls
Detection
Spot weld nut to
pedestal
Nut present Nut not present Cannot assemble seat belt 5 Welder cycles without nut 8 100% Visual Inspection by 4
66
present
4
into welder
4
before weld cycle
4
Nut welded
securely
Nut welded
insecurely
assembled
material
SPC information of
metallurgy
2
too high
5
material
SPC information of
metallurgy
2
weld surfaces
2 Standard handling
procedures
2
power circuit
2
Welder incorrectly set up 2 1st piece weld strength 2

FMEA - STEP 10: AIAG* DETECTION GUIDELINES
DETECTION
SCALE Criteria A B C Suggested Range of Detection Methods
10 Almost Impossible Absolute certainly of non-detection X Cannot detect
9 Very Remote
Controls will probably not detect
X
Control is achieved with indirect or random checks only
8 Remote Controls have poor chance of detection X Control is achieved with visual inspection only
7 Very Low
Controls have a poor chance of detection
X
Control is achieved with double inspection only.
6 Low
Controls may detect
X X
Control is achieved with charting methods, such as
SPC (Statistical Process Control)
5 Moderate
Controls may detect
X
Control is based on variable gauging after parts have
left the station, or Go/No/Go gauging performed on
100% of parts after parts have left the station.
Controls have a good chance to detect
X X
Error detection in subsequent operations, OR gauging
performed on setup and first-piece check (for setup
Inspection
Type
4 Moderately High
X X
causes only)
3 High
Controls have a good chance to detect
X X
Error detection in-station, or error detection in
subsequent operations by multiple layers of
acceptance: supply, select, install, verify. Cannot
accept discrepant part.
2 Very High
Controls almost certain to detect
X X
Error detection in-station (automatic gauging with
automatic stop feature) . Cannot pass discrepant part.
1 Very High
Controls almost certain to detect
X
Discrepant parts cannot be made because item has
been error-proofed by process/product design.
Inspection Types:
A - Error Proofed
B - Gauging
C - Manual Inspection
67

11. For each cause of failure, calculate the Risk
Priority Number.
Process
Function
Requirements
Potential
Failure
Mode
Potential
Effect(s)
of Failure
Severity
Potential
Cause(s)/
Mechanism(s)
of Failure
Occurrence
Current
Process
Controls
Detection
RPN
Spot weld nut to
pedestal
Nut present Nut not present Cannot assemble seat belt 5 Welder cycles without nut 8 100% Visual Inspection by 4 160
68
present
4 160
into welder
4 40
before weld cycle
4 20
Nut welded
securely
Nut welded
insecurely
assembled
material
SPC information of
metallurgy
2 24
too high
5 180
material
SPC information of
metallurgy
2 24
weld surfaces
2 Standard handling
procedures
2 24
power circuit
2 36
Welder incorrectly set up 2 1st piece weld strength 2 24

- An assessment of the probability that the current process
control detect the cause or the failure mode.
• Do not automatically presume that the detection ranking is
low because the occurrence is low, but do assess the
ability of the process controls to detect low frequency
failure modes or prevent them from going further in the
DETECTION (D)
failure modes or prevent them from going further in the
process.
• One Detection ranking for each Occurrence ranking.
Record the lowest ranking value in the Detection column.
69

RISK PRIORITY NUMBER (RPN)
The RPN number is calculated from the team’s
estimates of Severity, Occurrence and Detection.
RPN = S x O x D
If you are using a 1 - 10 scale for Severity,
Occurrence and Detection, the worst RPN = 1000Occurrence and Detection, the worst RPN = 1000
(10 x 10 x 10), while the best would be RPN = 1 (1
x 1 x 1).
Use RPN numbers to prioritize failure modes and/or
causes of failures in order to work on the highest
priority issues.
70

11. For each cause of failure, calculate the Risk Priority Number.
Tips about Step 11:
Any failure mode with a severity of 9 or 10 must be identified as high
priority regardless of the RPN.priority regardless of the RPN.
Addressing the highest RPNs is more important than setting an actual
target (all RPNs < 150, for example).
Teams are all different, so different teams will obtain different RPNs.
Use the high RPNs to identify critical issues (failure modes, causes of
failures, key process inputs).
71

FMEA TREE STRUCTURE
.
.
.
Failure
Mode 1
Cause 2
Cause 1
Cause 3
Cause n
CurrentMeasures1
(PreventionandDetection)
CurrentMeasures2
CurrentMeasures3
CurrentMeasuresn
72
.
.
.
.
.
.
Function/
Process
Failure
Mode 1
Cause 2
Cause 1
Cause n
CurrentMeasures1
CurrentMeasures2
CurrentMeasuresn

- RPN is the product of the Severity (S), Occurrence (O)
and Detection (D) rankings.
RPN = S x O x D
• The use of an RPN threshold is NOT a recommended
practice for determining the need for actions.
• Order of Importance
RISK PRIORITY NUMBER (RPN)
• Order of Importance
1st Severity
2nd Occurrence
3rd Detection
73

JohnsonControls,Inc.©
January2006
W2FMEAforSixSigma.ppt
12. For high priority causes of failure and/or failure
Process
Function
Requirements
Potential
Failure
Mode
Potential
Effect(s)
of Failure
Severity
Potential
Cause(s)/
Mechanism(s)
of Failure
Occurrence
Current
Process
Controls
Detection
RPN
Recommended
Action(s)
Spot weld nut to
74
Spot weld nut to
pedestal
present
4 160 Design, test &
install a nut
presence
sensing circuit.
Welder will not
cycle w/o weld
nut
a
into welder
4 40 See Note a
before weld cycle
4 20 See Note a

12.For high priority causes of failure and/or failure
Tips about Step 12:
Recommended actions should be low cost and effective.
Use ideas from all team members to improve the existing or planned
project.
Try to think of low cost actions that will reduce the occurrence.
Reducing the occurrence is the most cost effective way to reduce risk.
75

13. For each recommended action, assign
responsibility and completion dates.
Process
Function
Requirements
Potential
Failure
Mode
Potential
Effect(s)
of Failure
Severity
Potential
Cause(s)/
Mechanism(s)
of Failure
Occurrence
Current
Process
Controls
Detection
RPN
Recommended
Action(s)
Responsibility
& Target
Completion Date
Spot weld nut to
pedestal
Nut present Nut not present Cannot assemble seat belt 5 Welder cycles without nut 8 100% Visual Inspection by 4 160 Design, test & Mark, 4/15/96
c
76
present
install a nut
presence
sensing circuit.
Welder will not
cycle w/o weld
nut
a
Mark, 4/15/96
c
into welder
4 40 See Note a See above,
note c
before weld cycle
note c

14. For each recommended action, implement the
action and note its effect.
Process
Function
Requirements
Potential
Failure
Mode
Potential
Effect(s)
of Failure
Severity
Potential
Cause(s)/
Mechanism(s)
of Failure
Occurrence
Current
Process
Controls
Detection
RPN
Recommended
Action(s)
Responsibility
& Target
Completion Date
Actions
Taken
Spot weld nut to
pedestal
Nut presentNut not present Cannot assemble seat belt 5 Welder cycles without nut 8 100% Visual Inspection by 4 160 Design, test & Mark, 4/15/96
c
Circuit installed
Action Results
77
Nut presentNut not present Cannot assemble seat belt
present
install a nut
presence
sensing circuit.
Welder will not
cycle w/o weld
nut
a
Mark, 4/15/96
c
Circuit installed
on 4/12/96.
10,000 welds-
no problem.
Circuit added to
welder design
e
into welder
note c
See above,
note e
before weld cycle
note c
See above,
note e

• The intent of any recommended action is to reduce rankings
in the following order: severity occurrence and detection.
RECOMMENDED ACTION(S)
RESPONSIBILITY & TARGET COMPLETION DATE
78
RESPONSIBILITY & TARGET COMPLETION DATE
• Name of the individual and organization responsible for
completing each recommended action including the target
completion date.

• How can we reduce the occurrence?
• How can we improve the detection?
• Use process improvement skills.
• Where possible apply error proofing techniques.
• Standardization across all products or processes.
• Introduce any change in a controlled manner
PRIORITIZE CORRECTIVE ACTIONS
Note :
Error proofing (poka yoke) the process will result in
either
• Lower occurrence
• Lower detection rankings
Severity rankings will always remain the same. 79

SUMMARY OF POSSIBLE ACTIONS
High RPNs
Severe
?
Frequent
?
Frequent
?
Detection
?
No
No
No
Yes
Yes
Yes
Look for the causes
and carry out
None
80
?
Detection
?
EASY HARD
HARDEASY
Rethink the design
and carry out
preventive actions
The validation plan
is effective but is it
sufficient?
Don’t hesitate in
Spending if not the
Final cost will be
much higher
Expensive but there
Is no alternative
Rethink the design
and carry out
preventive actions
Look for the causes
and carry out
preventive action
Expensive but is there
A choice?
and carry out
preventive action
Cost of the action?
Cost of inaction?

14.For each recommended action, implement the
action and note its effect.
Tips about Step 14:
It is essential that the team not only verify that the recommended action
was implemented, but that they also determine how effective it was.
Was it implemented? Yes or No.
How effective was it? Get data.
81

15. For each implemented action, re-estimate the
Process
Function Potential
Failure
Potential
Effect(s)
Severity
Potential
Cause(s)/
Occurrence
Current
Process
Detection
Recommended
Responsibility
& Target Actions
Action ResultsAction ResultsAction Results
82
Requirements
Failure
Mode
Effect(s)
of Failure
Severity
Cause(s)/
Mechanism(s)
of Failure
Occurrence
Process
Controls
Detection
RPN
Recommended
Action(s)
& Target
Completion Date
Actions
Taken
Sev
Occ
Det
RPN
Spot weld nut to
pedestal
present
install a nut
presence
sensing circuit.
Welder will not
cycle w/o weld
nut
a
Mark, 4/15/96
c Circuit installed
on 4/12/96.
10,000 welds-
no problem.
Circuit added to
welder design
e
5 1 1 5
into welder
note c
See above,
note e
5 1 1 5
before weld cycle
note c
See above,
note e
5 1 1 5

15.For each implemented action, re-estimate the
Tips about Step 15:
Never recalculate an RPN without implementing an
improvement! Guessing is not allowed!
Usually, it is difficult to reduce the severity of a failure mode.
However, sometimes a failure mode can be eliminated.
The most effective RPN reduction is reducing the likelihood
of occurrence.
The least effective RPN reduction is increasing inspection
(reducing the detection ranking). Although, Poka-Yoke can
reduce the detection ranking and reduce cost! 83

- Identifies the results of any completed actions and their
effect on S, O, D rankings and RPN.
ACTION RESULTS
84

FMEA “TIPS”
Make it a “team effort.”
Analyze new processes to avoid problems before they
happen.
Analyze existing processes to find and fix problems.
Analyze existing processes to discover the high priorityAnalyze existing processes to discover the high priority
(“key”) process input variables.
Work down the columns, not across.
Keep it moving! Avoid paralysis by analysis.
85

WHAT TO DO
Function comes from Functional Analysis,
Functional Decomposition
Potential Failure Mode comes from things that have
gone wrong in the past, concerns of designers, and
brainstorming. Possible considerations are partialbrainstorming. Possible considerations are partial
function, intermittent function, excess function.
Potential Effects are consequences to the design,
the user, and the environment. Safety and
regulation noncompliance are critical issues.
86

WHAT TO DO
Potential Causes of failure should be engineering
related such as incorrect material, corrosion, wear
and human related such as inexperience, misuse,
etc.
Current Design Controls are things like inspections,Current Design Controls are things like inspections,
testing, poke yoke, and other design checks that
are intended to prevent the problem.
87

WHAT TO DO
Assign values to Severity, Occurrence, and
Detection using the tables on the next three pages.
Determine the Risk Priority Number (Severity*
Occurrence * Detection)
Develop an action planDevelop an action plan
Implement an action plan
88

MAINTAINING PFMEAS
• PFMEA must be a LIVING document.
• Review regularly. (Annual review)
• Reassess rankings whenever changes are made to the product
and/or process. (Release of CRB)
• Add any new defects or potential problems when found. (8D Report,
89
• Add any new defects or potential problems when found. (8D Report,
Lessons Learned)
• All revised ratings should be reviewed and if further action is
considered necessary, repeat the analysis.
• The focus should always be on continuous improvement

RISK GUIDELINES
Effect Rank Criteria
None 1 No effect
Very Slight 2 Negligible effect on Performance. Some users may notice.
Slight 3 Slight effect on performance. Non vital faults will be noticed
by many users
Minor 4 Minor effect on performance. User is slightly dissatisfied.
Moderate 5 Reduced performance with gradual performance
degradation. User dissatisfied.
Severe 6 Degraded performance, but safe and usable. UserSevere 6 Degraded performance, but safe and usable. User
dissatisfied.
High Severity 7 Very poor performance. Very dissatisfied user.
Very High Severity 8 Inoperable but safe.
Extreme Severity 9 Probable failure with hazardous effects. Compliance with
regulation is unlikely.
Maximum Severity 10 Unpredictable failure with hazardous effects almost certain.
Non-compliant with regulations.
90

OCCURRENCE RANKING
Occurrence Rank Criteria
Extremely Unlikely 1 Less than 0.01 per thousand
Remote Likelihood 2 ≈0.1 per thousand rate of occurrence
Very Low
Likelihood
3 ≈0.5 per thousand rate of occurrence
Low Likelihood 4 ≈1 per thousand rate of occurrence
Moderately Low 5 ≈2 per thousand rate of occurrenceModerately Low
Likelihood
5 ≈2 per thousand rate of occurrence
Medium Likelihood 6 ≈5 per thousand rate of occurrence
Moderately High
Likelihood
7 ≈10 per thousand rate of occurrence
Very High Severity 8 ≈20 per thousand rate of occurrence
Extreme Severity 9 ≈50 per thousand rate of occurrence
Maximum Severity 10 ≈100 per thousand rate of occurrence
91

DETECTION RANKING
Detection Rank Criteria
Extremely Likely 1 Can be corrected prior to prototype/ Controls will
almost certainly detect
Very High
Likelihood
2 Can be corrected prior to design release/Very High
probability of detection
High Likelihood 3 Likely to be corrected/High probability of detection
Moderately High
Likelihood
4 Design controls are moderately effective
Medium Likelihood 5 Design controls have an even chance of workingMedium Likelihood 5 Design controls have an even chance of working
Moderately Low
Likelihood
6 Design controls may miss the problem
Low Likelihood 7 Design controls are likely to miss the problem
Very Low
Likelihood
8 Design controls have a poor chance of detection
Remote Likelihood 9 Unproven, unreliable design/poor chance for
detection
Extremely Unlikely 10 No design technique available/Controls will not
detect
92

Thank you for your attention
93

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