fmea presentation

Dr. Edgardo J. Escalante.

FMEA: A Problem Prevention Tool


(*) Missile Defense Agency


We have designed a 5-floor commercial aircraft that has-tennis courts-restaurants-boutiques

The only problem is that we haven’t verified if it can fly!!!

A story…


Quality “Control”

RELIABILITY-fmea


The production elements

1.- Men2.- Materials 3.- Machines and equipment 4.- Methods 5.- Information

NKS/Factory Magazine (1988)


Information Materials Machines

MenMethods

An important missing element. What is it?


CONTROLCONTROL

Information Materials Machines

MenMethods

…right!


What does Control mean?

To take actions to keepa situation in a certain

desired state


A systemized group of activities designed to 1. RECOGNIZE and EVALUATE the POTENTIAL FAILURE of a PRODUCT/PROCESS and its EFFECTS 2. IDENTIFY ACTIONS WHICH COULD ELIMINATE or REDUCE the CHANCE of POTENTIAL FAILURE OCURRING

3. DOCUMENT the PROCESS

(D,F,GM. FMEA, 2001)

Definition of FMEA Failure Mode and Effects Analysis


Two types of FMEA

-Design FMEA or DFMEA

-Process FMEA or PFMEA


Characteristics of FMEA

-It looks to minimizeminimize the probabilityprobability of a failure, or tominimizeminimize its effects

-Should be initiated before or at design concept finalization (DFMEA), or before production starts(PFMEA)

-It is an endless iterative process

-It is a way to document processes and designs


The DFMEA evaluates what can go wrongwith the product during its use andits use and

during its manufacturingduring its manufacturing as a consequenceof design weaknesses

(Aldridge, Taylor 1991)

The PFMEA focuses on the reasons ofpotential failures during manufacturingduring manufacturing as a result

of not complying with the original design or failing to meet the design’s specifications



History of FMEA

Originally used by NASA during the 60s. Ford Motor Co. started using it

during the 70s

(Gilchrist, 1993)


FMEA benefits

-Reduction of internal cost due to re-work for notdoing things right the first time -Reduction of the number of complaints and warranty costs

-Increase of customer satisfaction

-Confidence that a company’s products are based in reliable and robust production methods



Potential Failure Mode and Effects Analysis

Item Potential Potential

Sev

Class

Occur

Current

Detec

RPN

ResponsibilityActions Results

Failure Effect(s) of Recommended & TargetFunction Mode Failure

Potential Causes/Mechanisms(s)

FailureControls

Action(s) Completion DateDet

Occ

RPN

ActionsTaken

Sev

What are the functions, featuresor requirements?

What can go wrong?

- No Function

- Partial/ Over/ Degraded Function

- Intermittent Function

- Unintended Function

What are the

Effect(s)?

How bad is it?

What are the Cause(s)?

Howoften does

ithappen?

How can this be preventedand detected?

How good is

this method

atdetecting

it?

What can be done?

- Design changes

- Process changes

- Special controls

- Changes to standards, procedures, or guides

Prevention/Detection

(D,F,GM. FMEA, 2001)Summary of DFMEA/PFMEA

Who is goingto do it andwhen?

What did theydo and what

are theoutcomes


Definitions

Failure Mode:Failure Mode: is the way in which the failure is manifested

Failure effect:Failure effect: is the consequence of the failure

Failure cause:Failure cause: is what induces the failure


Example (Ford, 1991; D,F,GM. FMEA,2001) PFMEA

Manual application ofwax inside door

Insufficiente waxcoverage overspecified surface

7 Manually insertedspray head notinserted far enough

To cover inner doorlower surfaces at min.wax thickness toretard corrosion

Process/ Op.description and purpose

Potentialfailure mode

Potentialfailure effects

C Potential causes/

mechanismof failures

lSev

as

Deteriorated life ofdoor leading to:

Unsatisfactory appea-rance due to rust through paint overtime


O D R

c e Pu t Nr er c8 Visual inspection

every hour. Verify thick-ness and coverage with gauge once per shift.(D).Test spray pattern atstart-up and after idleperiods. (P).

5 280 Add positive depth stopto sprayer

R. López

0X 10 15

Automatic spraying R. López

0X 12 15

Example (Ford, 1991; D,F,GM. FMEA,2001) PFMEA (cont)

Currentprocesscontrol

Recommendedactions

Responsibility& target

completiondate


A C T I O N R E S U L T SActions S O D Rtaken e c e P

v u t Nr c

Stop added, sprayer checked on line

Rejected due to complexity ofdifferent doors on same line

7 2 5 70

Example (Ford, 1991; D,F,GM. FMEA,2001) PFMEA


General Recommendations (Palady 1995)

1. To determine the effects it’s important to capture the finalcustomer experiences. Try to experiment what the customerwould feel. Otherwise severity may be underestimated.

2. To define severity, take into consideration safety issues as wellas costs.

3. The recommendations must be justified based on its cost-benefitrelationship, and must have a high degree of permanence.


Aldridge J., Taylor J.(1991) “The Application of Failure Mode and Effects Analysis at an Automotive Components Manufacturer”. International Journal of Quality and Reliability Management, Vol. 8 No. 3.

Chrysler Corp., Ford Motor Co., General Motors Corp.(1995). Potential Failure Mode and Effects Analysis. 2d. ed. A.I.A.G.

DaimlerChrysler Corp., Ford Motor Co., General Motors Corp.(2001). Potential Failure Mode and Effects Analysis. 3rd. ed. A.I.A.G.

Gilchrist W. (1993) “Modelling Failure Modes and Effects Analysis”. International Journal of Quality and Reliability Management, Vol. 10 No. 5.

NKS/Factory Magazine (1988). Poka Yoke. Improving Quality by Preventing Defects. Productivity.Palady P. (1995) Failure Modes And Effects Analysis. PT Publications, Inc.

Palady P. (1995) Failure Modes And Effects Analysis. PT Publications, Inc.

References


APPENDIX


Hazardous-withwarning

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 discernible effect.

10

8

7

6

3

2

1

Hazardous-withoutwarning

Moderate

4

5

EFFECT CRITERIA: Severity of Effect RANK

DFMEA SEVERITY EVALUATION CRITERIA

9

(D,F

,GM

. FM

EA

, 200

1)


Probability of Failure

Likely Failure Rates Over Design Life

Ranking

Very High: Persistent failures

100 per thousand vehicles/items 10

50 per thousand vehicles/items

9

High: Frequent failures



7

Moderate: Occasional failures



5


4

Low: Relatively few failures

0.5 per thousand vehicles/items 3

0.1 per thousand vehicles/items

2

Remote: Failure is unlikely

0.01 per thousand vehicles/items

1

(D,F

,GM

. FM

EA

, 200

1)

DE

SIG

N O

CC

UR

RE

NC

E E

VA

LU

AT

ION


Detection

Criteria: Likelihood of DETECTION by Design

Control

Ranking

Absolute Uncertainty

Design Control will not and/or can not detect a potential cause/mechanism and subsequent failure mode; or there is no Design Control.

10

Very Remote

Very remote chance the Design Control will detect a potential cause/mechanism and subsequent failure mode.

9

Remote

Remote chance the Design Control will detect a potential cause/mechanism and subsequent failure mode.

8

Very Low

Very low chance the Design Control will detect a potential cause/mechanism and subsequent failure mode.

7

Low

Low chance the Design Control will detect a potential cause/mechanism and subsequent failure mode.

6



Moderate

Moderate chance the Design Control will detect a potential cause/mechanism and subsequent failure mode.

5

Moderately High

Moderately high chance the Design Control will detect a potential cause/mechanism and subsequent failure mode.

4

High

High chance the Design Control will detect a potential cause/mechanism and subsequent failure mode.

3

Very High

Very high chance the Design Control will detect a potential cause/mechanism and subsequent failure mode.

2

Almost Certain

Design Control will almost certainly detect a potential cause/mechanism and subsequent failure mode.

1


Effect

PROCESS ------------------------------------------------------ Criteria: SEVERITY of Effect

Ranking

Hazardous-withoutwarning

Very high severity ranking when a potential failure mode affects safe operation and/or involves noncompliance with regulations without warning.Or may endanger operator without warning.

10

Hazardous-with warning

Very high severity ranking when a potential failure mode affects safe operation and/or involves noncompliance with regulations with warning.Or may endanger operator with warning.

9

Very high

Product/item inoperable, with loss of primary function. Or 100% of product may have to be scrapped or repair time >1h.

8

High

Product/item operable, but at reduced level of performance. Customer dissatisfied. Or product may have to be sorted and less than 100% scrapped. Repair time between 0.5 and 1h.

7

Moderate

Product/item operable, but comfort/convenience inoperable. Customer dissatisfied. Or a portion (less than 100%) of the product may have to be scrapped with no sorting. Repair time less than 0.5h

6

In th

e th

ird e

ditio

n th

is ta

ble

is pr

esen

ted

in tw

o co

lum

ns b

ut th

e in

form

atio

n is

the

sam

e(c

usto

mer

effe

ct a

nd m

anuf

actu

ring/

asse

mbl

y ef

fect

).

(D,F

,GM

. FM

EA

, 200

1)


Low

Product/item operable, but comfort/convenience operable at a reduced level. Or than 100% of the product may have to be reworked with no sorting. Repairing off-line.

5

Very Low

Fit and finish/squeak and rattle item does not conform. Defect noticed by most customers (greater than 75%). Or product may have to be sorted with no scrap, and a portion (less than 100% reworked.

4

Minor

Fit and finish/squeak and rattle item does not conform. Defect noticed by 50% of the customers. Or a portion (less than 100%) of the product may have to be reworked with no scrap. On-line but out-of-station.

3

Very Minor

Fit and finish/squeak and rattle item does not conform. Defect noticed by discriminating customers (less than 25%). Or a portion (less than 100%) of the product may have to be reworked with no scrap. On-line but in-station.

2

None

No discernible effect. Or slight inconvenience to operation or operator, or no effect.

1



Probability of Failure

Likely Failure Rates Ranking

Very High: Persistent failures

100 per thousand pieces 10

50 per thousand pieces

9

High: Frequent failures



7

Moderate: Occasional failures



5


4

Low: Relatively few failures

0.5 per thousand pieces 3

0.1 per thousand pieces 2

Remote: Failure is unlikely

0.01 per thousand pieces

1

PR

OC

ES

S O

CC

UR

RE

NC

E R

AN

KIN

G

(D,F

,GM

. FM

EA

, 200

1)


Detection Criteria A B C Suggested Range of Detection Methods Ranking

Almost Impossible

Absolute certainty of non-detection.

Cannot detect or is not checked. 10 Very Remote Controls will

probably not detect.

Control is achieved with indirect or random checks only. 9

Remote Controls have poor chance of detection.

Control is achieved with visual inspection only. 8

Very Low Controls have poor chance of detection.

Control is achieved with double visual inspection only. 7

Low Controls may detect.

Control is achieved with charting methods , such as SPC {Statistical Process Control}.

6

Moderate Controls may detect.

Control is based on variable gauging after parts have left the station, OR Go/No Go gauging performed on 100% of

the parts after parts have left the station.

5

Moderately High

Controls have a good chance to detect.

Error detection in subsequent operations, OR gauging performed on setup and first- piece check.

4

High Controls have a good chance to detect.

Error detection in- station, OR error detection in subsequent operat ions by multiple layers of acceptance: supply, select, install, verify. Can not accept discrepant part.

3

Very High Controls almost certain to detect.

Error detection in- station (automatic gauging with automatic stop feature). Can not pass discrepant part.

2

Almost certain Controls certain to detect.

Discrepant parts can not be made because item has been error proofed by process/product design.

1

Inspection types: A=Mistake-proofed, B=Gauging, C=Manual inspection

DETECTION CRITERIA FOR PFMEA(D,F,GM. FMEA, 2001)

fmea presentation

Documents

failure failure cause

design fmea

types of fmea

history of fmea

characteristics of fmea

dfmea process fmea

process d

effects analysiss e