11. faliure mode & effect analysis

QUALITY TOOLS & TECHNIQUES

1

TQ TFALIURE MODE & EFFECT ANALYSIS

By: -Hakeem–Ur–Rehman

Certified Six Sigma Black Belt (SQII – Singapore)IRCA (UK) Lead Auditor ISO 9001

MS–Total Quality Management (P.U.)MSc (Information & Operations Management) (P.U.)

IQTM–PU

An Advance Quality Planning Tool used to evaluate Potential Failure Modes and theirCauses.

An FMEA (Failure Mode and Effect Analysis) is a systematic method of identifyingand preventing product and process problems before they occur. FMEAs are focusedon preventing defects, enhancing safety, quality and increasing customersatisfaction.

A technique…

To improve system performance or

To design systems that would resist failure

Prioritizes Potential Failures according to their risk and drives action toeliminate or reduce their likelihood of occurrence

Serves as a disciplined methodology for documenting this analysis for future useand continuous process improvement

Is NOT a problem solver but is used in combination with other problem solvingtools.

“The FMEA presents the opportunity but does not solve the problem”

WHAT IS AN FMEA?

FAILURE MODE & EFFECT ANALYSIS (FMEA): DEFINITION

“FMEA is a systematic and analytical qualityplanning technique at the product, design,process and service stages assessing whatpotentially could go wrong and therebyaiding faulty diagnosis. The objective is toclassify all possible failures according to theireffect measured in terms of severity,occurrence and detection and then findsolutions to eliminate or minimize them.”

Process or

Product Name:Prepared by: Page ____ of ____

Responsible: FMEA Date (Orig) ______________ (Rev) _____________

Process

Step/Part

Number Potential Failure Mode Potential Failure Effects

S

E

V Potential Causes

O

C

C Current Controls

D

E

T

R

P

N

Actions

Recommended Resp.

What are the

process steps?

In what ways can the

process step go wrong?

What is the impact of the

Failure Mode on the

customer?

How

severe

is the e

ffect

on the c

usto

mer? What are the causes of the

Failure Mode?

How

often d

oes the C

ause

or

Failu

re M

ode o

ccur? What are the existing controls

and procedures that prevent the

Cause or Failure Mode?

How

well

can y

ou d

ete

ct

the C

ause o

r F

ailu

re

Mode?

Calc

ula

ted

What are the actions

for reducing the

occurrence,

decreasing severity or

improving detection?

Who is

responsible for

the

recommended

action?

0

0

0

0

0

0

0

0

0

0

0

(FMEA)WHAT IS AN FMEA?

FAILURE MODE & EFFECT ANALYSIS (FMEA): TYPES OF FMEA

There are five types of FMEA as given below:

1. System: focuses on global system function

2. Design: focuses on components and subsystems

3. Process: focuses on manufacturing & assembly processes

4. Service: focuses on service functions

5. Software: focuses on software function

Same Strategy… Different Tactics

STEP1: Determine the process / design component to beconsidered

The use of process flow diagrams provide a processoverview at a glance and shows process functions/behaviors

The conduct of FMEA is limited to the current level ofunderstanding of process behaviors. Anything beyond thelevel of comprehension at a time of drafting should not beincluded.

FAILURE MODE & EFFECT ANALYSIS

When defining failure modes - assume prior steps and incoming materialsare perfect.

STEP 2: Brainstorm potential failure modes generated by the process

/ product design


An effect of a failure is the consequence(s) of a failure modethat would be noticed or experienced at the next station, or asubsequent operation, by a downstream user or by theultimate customer.

Customers are defined as next-in-line customer or the end-user.

Look at effects from within, up to the next immediateprocess. If the particular failure mode has experiences ofending up at the customer, indicate a note to properly effectthe severity rating.

Consider: next user, downstream user, ultimate customer,product operation, safety, government regulations

STEP 3: Identify potential effects of each failure mode


MAN

METHODS

MACHINE

ULTIMATECUSTOMER

MATERIALSFAILURE

MODE

DOWNSTREAM USER

NEXT OPERATION

POTENTIAL EFFECTSCAUSE & EFFECT DIAGRAM

MEASUREMENTSYSTEM


RATING DEGREE OF SEVERITY LIKELIHOOD OF OCCURRENCE

ABILITY TO DETECT

1 Customer will not notice the adverse effect or it is insignificant.

Likelihood of occurrence is remote.

Sure that the potential failure will be found or prevented before reaching the next customer.

2 Customer will probably experience slight annoyance.

Low failure rate with supporting documentation.

Almost certain that the potential failure will be found or prevented before reaching the next customer.

3 Customer will experience annoyance due to slight degradation of performance.

Low failure rate without supporting documentation.

Low likelihood that the potential failure will reach the next customer undetected.

4 Customer dissatisfaction due to reduced performance.

Occasional failures. Controls may not detect or prevent the potential failure from reaching the next customer.

5 Customer is made uncomfortable or their productivity is reduced by the continued degradation of the effect.

Relatively moderate failure rate with supporting documentation.

Moderate likelihood that the potential failure will reach the next customer.

6 Warranty repair or significant manufacturing or assembly complaint.

Moderate failure rate without supporting documentation.

Controls are unlikely to detect or prevent the potential failure from reaching the next customer.

7 High degree of customer dissatisfaction due to component failure without complete loss of function. Productivity impacted by high scrap or rework levels.

Relatively high failure rate with supporting documentation.

Poor likelihood that the potential failure will be detected or prevented before reaching the next customer.

8 Very high degree of dissatisfaction due to the loss of function without a negative impact on safety or governmental regulations.

High failure rate without supporting documentation.

Very poor likelihood that the potential failure will be detected or prevented before reaching the next customer.

9 Customer endangered due to the adverse effect on safe system performance with warning before failure or violation of governmental regulations.

Failure is almost certain based on warranty data or significant DV testing.

Current controls probably will not even detect the potential failure.

10 Customer endangered due to the adverse effect on safe system performance without warning before failure or violation of governmental regulations.

Assured of failure based on warranty data or significant DV testing

Absolute certainty that the current controls will not detect the potential failure.

Severity is a rating corresponding to the seriousness of an effect of a potential failure mode.

Step 4: Determine the SEVERITY of the effect


Cause

A deficiency that results in a failure mode. It is descriptionof how the process could result in a failure.

Be specific! General statements such as “equipmentmalfunction” must not be used

Use only first level causes for this analysis

Step 5: Determine potential cause for each failure mode


Occurrence

The number of times the cause has resulted in the failure modebefore any additional process control are applied.

The rating should be based on actual records such as machinedowntime report, process yield and defects report, SPC log ofactivities, extent of reworks, production reports, etc.

The occurrence rating of each cause should reflect the relativeoccurrence of both the failure and cause.

Step 6: Rank the Occurrence of each Cause


Detection

Detection is rating corresponding to the likelihood thatcurrent process will detect the failure mode before it getsto the customer

Step 7: Identify process / design controls currently used to DETECT

the failure mode or PREVENT the cause


For RPN calculation purpose, the following must be observed:

The largest severity score will be used from among the severity score

The largest occurrence rating will be applied for calculation

However, for detection score - the lowest score is utilized

RPN = S X O X D

Step 8: Calculate RPN


Corrective action measures must be taken to reduce the risk for the following conditions:

It belongs to the top 3 RPN’s (but not necessary)

RPN >100.

The purpose of any action is to reduce the occurrence and/or detection ranking. The action

plan should include

Recommended action: must be defined to reduce the risk associated

Responsibility - the organization and/or individual responsible for the action and the

target date of completion

Action taken - a brief description of the actual completed action and the effective date

Resulting RPN - after C/A has been taken, the occurrence and detection ranking must be

defined and the RPN recalculated

STEP 9: Plan appropriate Corrective Action based on RPN


QUESTIONS

11. faliure mode & effect analysis

Engineering