Concurrent Engineering

Eng. K.C Wickramasinghe

BSc(Hon’s), AMIESL

Dept. of Mechanical & Manufacturing

Engineering,

Faculty of Engineering,

University of Ruhuna.

Lecture Session 03

01

Rule base method :- Failure Mode and Effect Analysis

FMEA is a procedure for analysis of potential failure modes within

a system for the classification by severity or determination of the

failure's effect upon the system.

Introduction

02

Why FMEA

03

To identify potential failure modes

To determine their effect on the operation

of the product

To identify actions to mitigate the failures.

The early and consistent use of FMEAs in the design process

allows the engineer to design out failures and produce reliable,

safe, and customer pleasing products.

FMEA Types

04

System - focuses on global system functions

Design - focuses on components and subsystems

Process - focuses on manufacturing and assembly processes

Service - focuses on service functions

05

FMEA Usage

Develop product or process requirements that minimize the likelihood of those

failures.

Evaluate the requirements obtained from the customer or other participants in

the design process to ensure that those requirements do not introduce potential

failures.

Identify design characteristics that contribute to failures and design them out of

the system or at least minimize the resulting effects.

Develop methods and procedures to develop and test the product/process to

ensure that the failures have been successfully eliminated.

Track and manage potential risks in the design.

Ensure that any failures that could occur will not injure or seriously impact the

customer of the product/process.

FMEA Benefits

06

Improve product/process reliability and quality

Increase customer satisfaction

Early identification and elimination of potential product/process

failure modes

Prioritize product/process deficiencies

Emphasizes problem prevention

Documents risk and actions taken to reduce risk

Provide focus for improved testing and development

Minimizes late changes and associated cost

Catalyst for teamwork and idea exchange between functions

07

Failure modes and effects analysis (FMEA)

Project: Date:

FMEA

Team:

Prepared

by:

SEV = How severe is effect on the customer?

OCC = How frequent is the cause likely to occur?

DET = How probable is detection of cause?

RPN = Risk priority number in order to rank concerns; calculated as SEV x OCC x DET

Process

step

Potential

failure

mode

Potential

failure

effects

S

E

V

Potential

causes

O

C

C

Current

process

controls

D

E

T

R

P

N

Actions

recomm

ended

Responsi

bility

(target

date)

Actions

taken

N

e

w

S

E

V

N

e

w

O

C

C

N

e

w

D

E

T

N

e

w

R

P

N

What is

the step?

In what

ways can

the step

go wrong?

What is

the

impact on

the

customer

if the

failure

mode is

not

prevented

or

corrected

?

10

What

causes

the step

to go

wrong?

(i.e., How

could the

failure

mode

occur?)

10

What are

the

existing

controls

that either

prevent

the failure

mode

from

occurring

or detect

it should

it occur?

10 1000

What are

the

actions

for

reducing

the

occurrenc

e of the

cause or

for

improving

its

detection

? You

should

provide

actions

on all high

RPNs and

on

severity

ratings of

9 or 10.

Who is

responsibl

e for the

recomme

nded

action?

What

date

should it

be

complete

d by?

What

were the

actions

implemen

ted?

Include

completio

n

month/ye

ar (then

recalculat

e

resulting

RPN).

10 10 10 1000

0 0

08

FMEA Procedure

Describe the product/process and its function. - Column 1

Create a Block Diagram of the product or process. This

diagram shows major components or process steps as blocks

connected together by lines that indicate how the components

or steps are related.

If items are components, list them in a logical manner under

their subsystem/assembly based on the block diagram.

09

FMEA Procedure

10

Identify Failure Modes. A failure mode is defined as the

manner in which a component, subsystem, system, process,

etc. could potentially fail to meet the design intent. - Column 2

Examples of potential failure modes include:

• Corrosion

• Hydrogen embrittlement

• Electrical Short or Open

• Torque Fatigue

• Deformation

• Cracking

FMEA Procedure

11

For each failure mode - determine what the ultimate effect will be.

A failure effect is defined as the result of a failure mode on the function of

the product/process as perceived by the customer. They should be described

in terms of what the customer might see or experience should the identified

failure mode occur. Examples of failure effects include:

• Injury to the user

• Inoperability of the product or process

• Improper appearance of the product or process

• Odors

• Degraded performance

FMEA Procedure

12

Establish a numerical ranking for the severity of the effect -

Column 4

Identify the causes for each failure mode – Column 5

Examples of potential causes include:

• Improper torque applied

• Improper operating conditions

• Contamination

• Erroneous algorithms

• Improper alignment

• Excessive loading

• Excessive voltage

13

FMEA Procedure

Enter the Probability factor-Column 6

A numerical weight should be assigned to each cause that

indicates how likely that cause is (probability of the cause

occurring). A common industry standard scale uses 1 to

represent not likely and 10 to indicate inevitable.

Identify Current Controls (design or process) –Column7

These are the mechanisms that prevent the cause of the failure

mode from occurring or which detect the failure before it

reaches the Customer.

Determine the likelihood of Detection - Column 8

FMEA Procedure

14

Column 9 - Review Risk Priority Numbers (RPN).

The Risk Priority Number is a mathematical product of the numerical

Severity, Probability, and Detection ratings:

RPN = (Severity) x (Probability) x (Detection)

Determine Recommended Action(s) to address potential failures that have a

high RPN - Column 10

Assign Responsibility and a Target Completion Date for these actions –

Column 11

Column 12- Indicate Actions Taken. After these actions have been taken, re-

assess the severity, probability and detection and review the revised RPN's.

Are any further actions required?

FMEA Procedure

15

Update the FMEA as the design or process changes, the assessment

changes or new information becomes known