Design fmea

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


TargetComplete

Date

RecommendedActions

RPN

Detec

CurrentDesign

Controls

Occur

PotentialCause(s)/


Class

Sev


Failure


Item / Process Step

Function

DFMEA

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

Robustness Tools !Boundary Diagram P-Diagram Interface Matrix

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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


TragetComplete

Date

RecommendedActions

RPN

Detec

CurrentProcessControls

Occur

PotentialCause(s)/


Class

Sev


Failure


Item / Process Step

DetectPrevent

RPN

DET

OCC

SEV

ActionTaken


TragetComplete

Date

RecommendedActions

RPN

Detec


Occur

PotentialCause(s)/


Class

Sev


Failure


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


TragetComplete

Date

RecommendedActions

RPN

Detec


Occur

PotentialCause(s)/


Class

Sev


Failure


Item / Process Step

DetectPrevent

RPN

DET

OCC

SEV

ActionTaken


TragetComplete

Date

RecommendedActions

RPN

Detec


Occur

PotentialCause(s)/


Class

Sev


Failure


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






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

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SEVERITY

O C C U R R E N C E

POTENTIAL CRITICAL CHARACTERISTICS Safety/Regulatory

POTENTIALSIGNIFICANT


ALL OTHER CHARACTERISTICS

Appropriate actions / controls already in place


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


ALL OTHER CHARACTERISTICS

Appropriate actions / controls already in place


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.

Design fmea

Business

p diagram

id of potential failures

design life ranking

high severity

high high

severity of effect rnk

occurrence evaluation

current approach