This document provides an overview of process failure mode and effects analysis (PFMEA). It discusses the steps to conduct a PFMEA, including identifying critical process steps and their potential failure modes, effects, causes, controls, and risk priority numbers. The goals of a PFMEA are to proactively identify potential process failures, prioritize issues based on risk, and determine actions to reduce failures and improve process quality, reliability, and customer satisfaction. Conducting a thorough PFMEA requires a cross-functional team approach.
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An FMEA is a systematic method for identifying,
analyzing, and documenting potential failure
modes and their effects on the system, the product
and process performance. The possible causes of
failure can then be prioritized.
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What We Will Learn …
1. As a Team, how to construct an FMEA
and associated Action Plan
2. How the FMEA process ties to
process mapping
3. The relationship between Failure
Mode, Cause and Effect
4. The different types of FMEAs
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Why Use FMEAs?
Identify ...
critical product characteristics and process variables
Prioritize ...
product and process deficiencies in support of downstream
improvement actions
Help focus ...
on prevention of product and process problems
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Benefits of FMEA’s
Improves the quality, reliability and safety of
products.
Helps increase customer satisfaction.
Reduces product development timing and cost.
Reduces the amount of rework, repair and
scrap.
Documents and tracks actions taken.
Prioritizes deficiencies to focus improvement
efforts.
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Process FMEA Steps
Prior to FMEA:
Charter Team
Develop and
Characterize
Process Map
1. Identify “Heavy Hitter” Process Step
2. Identify Associated y’s (Product
Parameters)
3. Failure Mode
4. Identify Failure Effects/Rate
Severity
5. Identify Causes/Rate Occurrence
6. Identify Controls (if any)/Rate
Detection
7. Calculate RPN
8. Prioritize by RPN Order
9. Determine Actions/Plan
10.Recalculate RPN Based on Plan
11.Take Action
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Item : Process Responsibility : FMEA Number:
Model Year(s)Program(s) : Rev. Date : Rev.No :
Core Team : FMEA Date(Orig.) Prepared By :
Processstep/
Function
Requirements
PotentialFailure
Mode
PotentialEffect
(s)offailure
Severity
Classification
PotentialCausesof
failure
Current Process
RPN
RecommendedAction
Responsibility&
TargetCompletion
Date
Actions Results
Controls
Prevention
Occurrence
Controls
Detection
Detection
ActionsTaken
with
CompletionDate
Severity
Occurrence
Detection
Risk
Step 1
Step 2
ID y’s
Step 3
Step 4
Step 5 Step 6
Step 7 & 8
Step 9
Step 10
Step 9
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Step 1: Identify “Heavy Hitter” Process Step
From the Process Map, identify the process step with the
most likelihood of having failure modes with significant
effects.
Use defect data and/or team knowledge about failure
modes when selecting process steps.
Significant impact to the business? (COPQ, cycle time,
fill rate, ...)
Use a Cause and Effect Diagram to capture brainstorming
results.
After completing FMEA Steps #2-7 for all failure modes
associated with this process step, return to this step and
select the next most likely “Heavy Hitter” process step.
Not all process steps will need to be analyzed by the
FMEA.
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Step 2: Identify Associated y’s
From the Process Map, identify the y’s that are
associated with the process step being investigated.
As the y’s are the indications of a successful completion
of the process step, they are crucial as a basis for
determining failure modes.
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Step 3: Identify Failure Mode
Brainstorm failure modes for the selected process step
Identify the ways in which the process could fail to
generate each of the expected “y’s.”
Eliminate “duplicates” from brainstorm list.
Are the failure modes from the same level of the process?
Are the failure modes specific?
Are the failure modes the most likely?
Do the failure modes provide good coverage of the process
step?
Have all y’s been considered?
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Step 4: Identify Failure Effects/Rate Severity
Pick the most likely failure mode and brainstorm the most
important effects:
FAILURE EFFECTS are the outcome of the
occurrence of the failure mode in the process.
The impact on the customer is what the customer
experiences as a result of the Failure Mode.
Identify each effect as being “Attribute” or “Variable.”
Severity doesn’t change unless the design changes.
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Step 5: Identify Causes/Rate Occurrence
Identify the most likely causes for each failure mode using a
Cause and Effect Diagram :
– CAUSES are the conditions that bring about the Failure
Mode.
Transfer the resulting information to the FMEA form.
Assign an occurrence value (1-10) to the likelihood that
each particular cause will happen and result in the failure
mode.
The occurrence score for each cause should be related to
the likelihood of that cause resulting in the failure mode and
producing the specific associated effect.
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Organize Brainstorming Ideas
Copy Process Fishbone
What other causes
should we add?
Copy Misaligned
Out of cal Wrong size
paper
Select wrong
orientation
Humidity Doc moved
when
lid closed
Align marking
not clear
Environment Methods Machines
Measurements Materials Personnel
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Step 6: Identify Controls (if any)/Rate Detection
Identify the current mechanisms in place which prevent
the cause from occurring, or detect it before the product
reaches the customer. Some examples of controls are
SPC, training, maintenance, inspection, SOP etc.
Assign a detection value (1-10) based on an assessment
of the likelihood that the current control mechanisms will
detect the cause of the failure mode before it reaches the
customer.
Don’t agonize over detectability.
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Step 7: Calculate Risk Priority Number (RPN)
The product of the estimates of severity
occurrence and
detection.
The RPN provides a relative priority for taking action;
the bigger the RPN, the more important to address.
RPN = SEVERITY x OCCURRENCE x DETECTION
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Steps 8 & 9: Prioritize by RPN Order
& Determine Actions/Plan
STEP 8: Prioritize by RPN Order
Use the “Sort” command in Excel to order the
spreadsheet in descending order of Risk Priority
Number (RPN).
STEP 9: Determine Actions/Plan
Based on the causes found, determine actions that will
minimize the effect of each cause, in priority order.
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Steps 10 & 11: Recalculate RPN Based on Plan
& Take Action
STEP 10: Recalculate RPN Based on Plan
Assuming the actions are carried out successfully, reassign
severity, occurrence and detectability.
Place these new ratings in the “predicted” columns (ps, po
& pd).
Assign a rating from 1 to 5 for each action that will show the
“risk” associated with each action (5 being the greatest risk).
Place the rating in the “risk” column.
STEP 11: Take Action
Based on the risk mitigation column (Risk * rpn), take the
actions indicated or reassign actions.
Complete the actions indicated by the times stated!
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Helps analyze manufacturing and assembly processes to
reduce the occurrence and improve detection of defects.
Assists in the development of process control plans.
Establishes a priority for improvement activities.
Documents the rationale behind process changes and
helps guide future process improvement plans.
IS PROACTIVE! Should be started when new processes
are designed or when old processes are changed.
Process FMEA
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Design/Product FMEA
Helps to identify potential product failure modes early in
the product development cycle.
Increases the likelihood that all potential failure modes
and their effects on assemblies will be considered.
Assists in evaluating product design requirements and test
methods.
Establishes a priority for design improvement.
Documents the rationale behind design changes and
helps guide future development projects.
IS PROACTIVE! Should be done when new products are
designed or existing products are changed.
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Defect FMEA
Helps identify the root causes of defects.
Establishes a priority for improvement activities.
Documents plan of action.
Provides methodology to battle initial ground swell of
defects.
Focuses effort on defects with highest $ impact.
IS NOT PROACTIVE!
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When to Update an FMEA?
An FMEA should be updated whenever a change is being
considered to a product’s:
design
application
environment
material
product’s manufacturing or
assembly process
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Summary of Product/Process FMEA’s
What is the tool? - Spreadsheet
What will the tool identify/ show?
All product/process failure modes, related
effects, causes, & methods of control.
Risk Priority Number (RPN) for action
based on failure severity, probability of
occurrence and detection capability.
Actions/plans to reduce elements of RPN.
When to apply this tool?
When evaluating product for
robustness (functionality,
produceability, reliability).
During early stages of
defect reduction efforts to
identify causes.
When identifying key
process/product parameters
and evaluating methods for
control.
What results can you expect?
Learn to identify critical product/
process parameters.
Achieve consensus on solutions and
methods of implementation.
Detailed product/process understanding.
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Keys to Success
Identify purpose...BE SPECIFIC!
Understand effects...INVOLVE CUSTOMERS & SUPPLIERS!
Link to the process map.
Use to prioritize efforts, allocate resources.
Use as a risk assessment/prioritization tool based on predicted
impact.
Use to build consensus on prioritization.
Encourage creativity...TEAMWORK!
PLAN!
ASK QUESTIONS!
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Effect
Criteria: Severity of Effect on Product
(Customer Effect)
Rank Effect
Criteria: Severity of Effect on Process
(Manufacturing / Assembly Effect)
Failure to
meet Safety
and/or
Regulatory
Requirements
Potential failure mode affects safe vehicle
operation and/or involves noncompliance
with government regulation without warning
10
Failure to
meet Safety
and/or
Regulatory
Requirements
May endanger operation (machine or
assembly) without warning.
Potential failure mode affects safe vehicle
operation and/or involves noncompliance
with government regulation with warning
9
May endanger operation (machine or
assembly) with warning.
Loss or
Degradation of
Primary
Function
Loss of primary function (vehicle inoperable,
does not affect safe vehicle operation).
8
Major
Disruption
100% of product may have to be
scrapped. Line shutdown or stop ship.
Degradation of primary function (vehicle
operable ,but at reduced level of
performance).
7
Significant
Disruption
A portion of the production run may have
to be scrapped. Deviation from primary
process including decreased line speed
or added manpower.
Loss or
Degradation of
Secondary
Function
Loss of secondary function (vehicle
operable, but comfort/convenience functions
inoperable).
6
Moderate
Disruption
100% of production run may have to be
reworked offline and accepted.
Degradation of secondary function (vehicle
operable, but comfort/convenience functions
at reduced level of performance).
5
A portion of the production run may have
to be reworked offline and accepted.
Annoyance
Apperance or Audible Noise,vehicle
operable,item does not conform and noticed
by most customers (>75%).
4
Moderate
Disruption
100% of production run may have to be
reworked in station before it is
processed.
Apperance or Audible Noise,vehicle
operable,item does not conform and noticed
by many customers (50%).
3
A portion of the production run may have
to be reworked in station before it is
processed.
Apperance or Audible Noise,vehicle
operable,item does not conform and noticed
by discriminating customers (<25%).
2
Minor
Disruption
Slight inconvenience to
process,operation,or operator.
No Effect No discernible effect. 1 No Effect No discernible effect.
PFMEA Severity Table
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Likelihood of Failure
Criteria: Occurrence of Cause - PFMEA
(incidents per items / vehicles)
Rank
Very High
≥ 100 per thousand
≥ 1 in 10 10
High
50 per thousand
1 in 20 9
20 per thousand
1 in 50 8
10 per thousand
1 in 100 7
Moderate
2 per thousand
1 in 500 6
0.5 per thousand
1 in 2000 5
0.1 per thousand
1 in 10,000 4
Low
0.01 per thousand
1 in 100,000 3
≤0.001 per thousand
1 in 1000,000 2
Very Low Failure is elimated through preventive control 1
PFMEA Occurrence Table
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Opportunity for Detection Criteria: Likelihood of Detection by process control Rank
Likelihood of
Detection
No detection opportunity No current process control; Cannot detect or is not analyzed. 10
Almost
impossible
Not Likely to detect at any
stage
Failure Mode and/or Error (Cause) is not easily detected (e.g.,random
audits). 9 Very Remote
Problem Detection Post
Processing
Failure Mode detection post-processing by operator through
visual/tactile/audible means. 8 Remote
Problem Detection at
Source
Failure Mode detection in-station by operator through
visual/tactile/audible means or post-processing through use of attribute
gauging (go/no-go, manual torque check/clicker wrench,etc.)
7 Very Low
Problem Detection Post
Processing
Failure Mode detection post-processing by operator through use of
variable gauging or in-station by operator through use of attribute
gauging (go/no-go, manual torque check/clicker wrench,etc.)
6 Low
Problem Detection at
Source
Failure Mode or Error (Cause) detection in-station by operator through
variable gauging or by automated controls in-station will detect discrepant
part and notify operator (light,buzzer,etc.) Gauging performed on setup
and first piece check (for set-up causes only).
5 Moderate
Problem Detection Post
Processing
Failure Mode detection post-processing by automated controls that will
detect discrepant part and lock part to prevent further processing. 4 Moderately High
Problem Detection at
Source
Failure Mode detection in-station by automated controls that will detect
discrepant part and automatically lock part in station to prevent further
processing.
3 High
Error Detection and/or
Problem Prevention
Error ( Cause) detection in-station by automated controls that will detect
error and prevent discrepant part from being made. 2 Very High
Detection Not Applicable;
Error Prevention
Error (Cause) prevention as a result of fixture design, machine design or
part design. Discrepant parts cannot be made because item has been
error-proofed by product/process design.
1 Almost Certain
PFMEA Detection Table