FMEA new

FMEA

Introduction

What is FMEA ?

• Means to assure that potential failure modes and their

associated cause and mechanism, have been addressed

though earlier detection.

• A tool for design and process engineers.

• “Before-the-event” action NOT an “After-the-fact”

exercise.

FMEA Application Case 1 : New designs, new technology, or new process.

Case 2 : Modification to existing design or process.

Case 3 : Use of an existing design or process in a new

environment, location or application.

Do not forget “Rule of Ten”

Design

FMEA

SPC

PPM

At

Supplier

end

Proces

s

FMEA

Design

and

developm

ent

Advanced

product

quality

planning

Purchasing Use

Manufac

turing

Manufacture Customer

Rs.1/- Rs. 10/- Rs. 100/- Rs. 1000/-

SPC

PPM

At

prodn

Rs. 10,000/- Prevention cost Internal failure cost External failure

Potential

defect

Internal

defect

External

defect

CO

ST

O

F Q

UA

LIT

Y

Nature of cost

Ratio of cost

Defect Stage

Defect report

point

Product flow

stage

Evaluation

mechanism

FMEA Stage

Process

Flow

Design

Product

Brief

Product

Concept

Product

Proto

Design

Product

Proto Build

System,

Sub system,

Part Design

Product

PILOT Build

Product

Start of

Production

+ Review

Of issues

At Proto

+ Review

Of issues

At Pilot

Potential Failure Mode & Effects Analysis Sequence

PFMEA - SEQUENCE

PFMEA SEQUENCE.xlsx

PFMEA SEQUENCE.xlsx

PFMEA SEQUENCE.xlsx

PFMEA SEQUENCE.xlsx

Slide 17 (1).xlsx

Application

Application Design

FMEA

Process

FMEA

Purpose Meeting specification /

Customer & Legal

requirements.

Production in compliance with

drawing

Responsibility Design and development Production / Mfg Engg.

Objective Avoiding design failures Avoiding failures during process

planning, production implementation

Timing for

commencement

Before or at design concept

finalization

Before or at feasibility stage or prior

to looking for production

Period of review Prior to the first trial run Prior to any investment

FMEA first

completion

Prior to production drawing

release for tooling

Prior to bulk production

Step # Step details

1 Define Project Scope

2 Brainstorm all potential failure modes

3 Identify the potential effects of failures

4 Determine severity rankings

5 Identify the causes of failures

6 Determine Occurrence rankings

7 Identify the current controls

8 Determine the detection rankings

9 Evaluate Risk Priority Numbers(RPN)

10 Prioritise corrective actions.

FMEA STEPS

• Formulate cross functional team

• Understand customer/process requirements.

• Define start and end of process

• All team members walk and observe the process.

• Get the „process worker‟ to explain the

operation/process under review.

• Make notes/observations.

Defining Scope of FMEA is CRITICAL!

1. PFMEA Process Scope

1. Design FMEA Block Diagram Example

Switch on/off

C

Housing

A

Bulb

Assembly

D

Plate

E

+

Attaching Method

1. Skip Fit 4. Snap Fit

2. Rivets 5. Compressive Fit

3. Thread

2

3

4

Spring

F

--

Batteries

B

4

5 5

5

System Level

Subsystem Level Component Frame

Bicycle Frame Upper Frame Design Objectives: 1. Minimum 3000 hours of riding without need for maintenance and 10000 hours of riding for design life . 2. Accommodates male adults comfortably to the 99.5th percentile 3. ...etc.... Function1: * Ease of use Potential failure model(s): * Difficult to steer * difficult to pedal Function2: * Provide reliable transportation Potential failure model(s): * Chain break frequently * Tire require frequent maintenance Function3: * Provide comfortable transportation Potential failure model(s): * seating position is not comfortable

Function1: * provide stable attachment for seat support Potential failure model(s): * Structural failure of seat support * Excessive deflection of seat support . Function 2: * Provide pleasing appearance. Potential failure model(s): * Finish (Shine ) deteriorates * Paint chips

Function 1: * Provide structural support Potential failure model(s): * Structural Failure * Excessive deflection Function 2: * Provide dimensional control for correct finished fame geometry Potential failure model(s): * Length of frame mounting point too long * Length of frame mounting point too short Function 3: * Support frame assembly production methods (welding) Potential failure model(s):

Handle bar assembly

Front Wheel assembly

Real wheel assembly Lower front tube

Sprocket assembly

Seat assembly Lower rear tube

Chain assembly Sprocket tube

1. PFMEA process scope

Step # Step details











FMEA STEPS

2. Potential Failure Mode

• Potential Failure Mode is defined as the manner in which a

component, subsystem, or system could potentially fail to

meet the design intent.

• The assumption is made that the failure could occur, but

may not necessarily occur. A recommended starting point

is a review of past things-gone-wrong, concern reports, and

group “brainstorming”.

• Typical failure modes could be, cracked leaking,

fractured, oxidized, no signal, drift, etc. ( Described in

physical or technical terms, not as symptom noticed by the

customer).

2. Potential Failure Mode - examples

• Bent

• Cracked

• Contaminated

• Loosened

• Leakage

• Damaged

• Deformed

• Gouged

• Misaligned

• Corroded

• Broken Tooling

• Wrong Tooling

• Wrinkled

• Scratched

• Humidity

• Handling Damage

Step # Step details











FMEA STEPS

3. Potential Effect(s) of Failure

• Effect of failure mode on the customer (s).

• Describe effects of failure in terms of what customer(s) might

notice or experience.

Customer Effect

End user In terms of product / system

performance e.g. noise,

inoperative, poor appearance.

Next operation/ In terms of process/ operation

subsequent performance e.g. fitment problem,

damage

Operation/

location

3. Potential Effect(s) of Failure

• Example could be :

- For end user : Noise, rough, inoperative, leaks,

unstable, erratic operation, etc.

- For next/ subsequent operations: does not fit, can not

mount, damages equipment, excessive tool wear, etc.

Step # Step details











FMEA STEPS

4. Determining Severity

Severity is an assessment of the seriousness of the effect of

the potential failure mode to the next component, subsystem,

system or customer if it occurs. Severity applies to the effect

only. A reduction in Severity Ranking index can be effected

only through a design change. Severity should be estimated

on a “ to “ scale.

4. Suggested PFMEA Severity Ranking

Effect Criteria : Severity of effect

This ranking result when a potential

Failure mode result in a final customer

and/or a manufacturing/assembly plant

defect .The final customer should always

be considered first if both occur, use the

higher of the two severities.

(Customer Effect)

Criteria : Severity of effect

This ranking result when a potential Failure

mode result in a final customer and/or a

manufacturing/assembly plant defect .The

final customer should always be

considered first. if both occur, use the

higher of the two severities .

(Manufacturing/ Assembly Effect)

Rankin

g

Hazardous

Without

warning

Very high Severity ranking when a potential

failure mode affect safe vehicle operation

and/or involves noncompliance with

government regulation without warning

Or may endanger operator(machine or

assembly without a warning

10

Hazardous

With

warning

Very high Severity ranking when a potential

failure mode affect safe vehicle operation

and/or involves noncompliance with

government regulation with warning

Or may endanger operator(machine or

assembly with a warning

9

Very High Vehicle/item inoperable (loss of primary

Function)

Or 100% of product may have to be scrapped

or vehicle item repaired in department with a

repair time greater than one hour

8

High Vehicle/item operable but at reduce level of

performance customer very dissatisfied

Or product may have to be a stored and a

portion(less than 100% )of scrapped or

vehicle item repaired in department with a

repair time greater than one hour.

7

Moderate Vehicle? Item operable but Comfort/

convenience item(s) inoperable.

Customer dissatisfied.

Or a portion (less than 100%) of the product may

have to scrapped with no sorting, or vehicle/item

repaired in repair department with a repair time less

than a half- hour.

6

Low Vehicle/item operable but comfort/

convenience item(s) operable at a

reduced level of performance.

Or 100% of product may have to be reworked, or

vehicle/item repair off-line but does not go to repair

department.

5

Very low Fit and finish/squeak and rattle item

does not conform. Defect noticed by

most customers. (greater than 75%)

Or 100% of product may have to 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 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

4. Suggested PFMEA Severity Ranking

Step # Step details











FMEA STEPS

5. Potential Causes(S)/ Mechanism(s)

of Failure ( Design) • Potential Cause of Failure is defined as an indication of a design weakness, the consequence of which is the failure mode.

Typical failure causes may include: - Incorrect Material Specified.

- Inadequate Design Life Assumption

- Over-stressing.

- Insufficient Lubrication Capability.

- Poor Environment Protection.

- Incorrect algorithm.

- In progress tolerance specified.

• Typical failure mechanisms may include:

Creep Fatigue Wear Corrosion

5. Potential Cause(s) of Failure

• Every conceivable failure cause assignable to each

potential failure mode.

• Specific causes where remedial efforts can be aimed.

• Examples

- Part missing or mis-located,

- Improper torque,

- Improper welding,

- Inaccurate gauging, etc.

- Inadequate lubrication,

- Chip on located, etc.

Step # Step details











FMEA STEPS

6. Occurrence(O)

• Occurrence is the likelihood that a specific cause/ mechanism

will occur.

• Removing or controlling one or more of the causes/mechanism of the failure mode through a design change is the only way a reduction in the occurrence ranking can be effected.

• Estimate the likelihood of occurrence of potential failure cause mechanism on a “1” to “10” scale. Questions such as the following should be considered:

- What is the service history/field experience with similar components or subsystems?

- Is component carryover or similar to a previous level component or subsystem?

Contd…

6. Occurrence(O) (contd…)

- How significant are changes from a previous level component or subsystem?

- Is component radically different from a previous level component ?

- Is component completely new ?

- Has the component application changed?

- What are the environmental changes?

- Has an engineering analysis been used to estimate the expected comparable occurrence rate for the application?

6. Determine Occurrence Rating

Suggested Evaluation Criteria: Design

Probability of failures Possible Failure Rates Ranking

Very High: persistent failures ≥ 100 per thousand vehicles/ item. 10

50 per thousand vehicles/ item. 9

High : Frequent failures 20 per thousand vehicles/ item. 8


Moderate :occasional failures 5 per thousand vehicles/ item. 6



Low : Relatively few failure 0.5 per thousand vehicles/ item. 3

0.1 per thousand vehicles/ item. 2

Remote : Failures is Unlikely ≤ 0.010per thousand vehicles/ item. 1

Process FMEA Suggested PFMEA occurrence evaluation criteria with Ppk values

Probability Likely Failure Rates * Ppk Ranking

Very High: Persistent Failure ≥ 100 per thousand pieces < 0.55 10

50 per thousand pieces. ≥ 0.55 9

High : Frequent Failures 20 per thousand pieces. ≥ 0.78 8


Moderate : Occasional Failures 5 per thousand pieces. ≥ 0.94 6



Low : Relatively Few Failures 0.5 per thousand pieces. ≥ 1.20 3

0.1 per thousand pieces. ≥ 1.30 2

Remote : Failure us unlikely ≤ 0.01 per thousand pieces. ≥ 1.67 1

6. Determine Occurrence Rating

Step # Step details











FMEA STEPS

7. Current Controls (Design)

• List the preventing, design validation/verification (DV), or

other activities which will assure the design adequacy for

the failure mode and/or cause/ mechanism under

consideration.

• Current controls are those that have been or are

being used with the same or similar designs.

Three types of Design Controls:

- prevent the cause/mechanism of failure mode effect

from occurring, or reduce their rate of occurrence.

- detect the cause/mechanism and lead to corrective

actions, and

- detect the failure mode.

7. Current Design Controls (contd…)

Prevention (P) e.g. building redundancy,

Design oriented failsafe arrangement, Pokayoke,

• control

Detection (D) e.g. lab test, design

oriented verification, road test, inspection

etc

• Specify „P‟ & „D‟ controls in separate columns. If one column is used

for current design control, specify „P‟ or „D‟ before each control.

Types of Process Controls Affects

Prevent the cause / mechanism or

failure mode / effect from occurring

or reduce their rate of occurrence.

Occurrence Ranking

Detect the cause / mechanism &

lead to Corrective Actions.

Detection Ranking

Detect the failure mode. Detection Ranking.

7. Current Process Controls

Step # Step details











FMEA STEPS

8. Detection (d)

• Detection is an assessment of the ability of the

current design controls, to detect a potential cause

/mechanism (design weakness), or

• The ability of the current design controls to detect

the subsequent failure mode, before the component,

subsystem Or system is released for production.

• In order to achieve a lower ranking generally the

planned design control has to be improved.

8. Detection Ranking Suggested Evaluation Criteria: For Design detection

Detection Criteria : Likelihood of Detection by Design Control Ranking

Absolute uncertainty Design Control will not and/or can not detect a potential causes /mechanism an

subsequent failure mode ; or there is no design control

10

Very Remote Very remote chance the Design Control will detect a potential causes /mechanism and

subsequent failure mode .

9

Remote Remote chance the Design Control will detect a potential causes /mechanism and


8

Very low Very low chance the Design Control will detect a potential causes /mechanism and


7

Low Low chance the Design Control will detect a potential causes /mechanism and


6

Moderate Moderate chance the Design Control will detect a potential causes /mechanism and


5

Moderate High Moderate High chance the Design Control will detect a potential causes /mechanism and


4

High High chance the Design Control will detect a potential causes /mechanism and


3

Very High Very high chance the Design Control will detect a potential causes /mechanism and


2

Almost Certain Design Control will almost certainly detect a potential causes /mechanism an subsequent

failure mode .

1

Suggested PFMEA Detection Evaluation Criteria

Detection Criteria Inspection

Types

Suggested Range of Detection Method Rank

A B C

Almost

Impossible

Absolute certainty of non detection X Cannot detect or is not checked 10

Very remote Control will probably not detect X Control is achieved with indirect or Random check only 9

Remote Control have poor chance of

detection

X Control is achieved with Visual inspection only 8

Very low Control have poor chance of

detection

X Control is achieved with double visual inspection only. 7

Low Control may detect X Control is achieved with charting methods, such as SPC. 6

Moderate Controls may detect X 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

Moderate

High

Controls have a good chance to

detect

X X Error detection in subsequent operation, or gauging

performed on setup and first-piece check( for set-up

causes only).

4

High Controls have a good chance to

detect

X X Error detection in-station, or error detection in subsequent

operations by multiple layers of acceptance : supply, select,

install, verify. Cannot accept discrepant part.

3

Very high Controls almost certain to detect. X X Error detection in station ( automatic gauging with

automatic stop feature). Cannot pass discrepant part.

2

Very high Controls certain to detect. X Discrepant parts cannot be made because item has

been error proofed by process/product design.

1

Inspection Types: A. Error-proofed B. Gauging C. Manual Inspection

8. Detection Ranking

Step # Step details











FMEA STEPS

9. Determine Risk Priority Number (RPN)

- Risk Priority Number (RPN)

= Severity x Occurrence x Detection

- To be used for prioritization of corrective actions.

- Ranges between 1 and 1000.

- Regardless of RPN value, special attention should be

given when severity is high.

FMEA Model

Potential Failure

Mode Cause of Failure

Current

Design/Process

Control

Effect of

failure

Frequency of

Failure

Possibility of finding

failure or Cause of

failure

Severity

Rating Occurrence

Rating

Detection

Rating

Step # Step details











FMEA STEPS

10. Recommend Action(s)

• The intent of any recommended action is to reduce any

one or all of the occurrence, severity, and/or detection

rankings.

• An increase in design validation/verification action will

result in a reduction in the detection ranking only.

• A reduction in the occurrence ranking can be effected

only by removing or controlling one or more of the cause

mechanisms of the failure mode through a design change.

• Only a design revision can bring about a reduction in the

severity ranking

• Examples include revised design geometry, and /or

tolerance, revised material specifications, modify the mfg

process

10. Prioritise & implement action(s)

• Enter a brief description of the actual action and effective date.

Resulting RPN

• Estimate & record resulting S,O,D and RPN rankings.

• Resulting RPNs should be reviewed and new set of actions

should be decided accordingly till the desired RPN is not

achieved.

• This ensures FMEA is a Living Document,

• FMEA can also be updated as and when new failure modes

are discovered.

FMEA new

Documents

potential failure modes

design product

potential effects of

typical failure modes

scope of fmea

new process

existing design

fmea applicationcase