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Failure Mode and Effects Analysis (FMEA)

FMEA is a structured analysis for identifying ways &

methods in which the product or processes can fail and

then plan to prevent those failures. FMEA is a proactive

tool for reducing defects and non-conformities.

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Failure Mode and Effects Analysis (FMEA)

FMEA is a structured approach in :-

• Identifying ways in which a product / process can fail to

meet critical customer requirements.

• Estimating the risk of causes with regard to these failures.

• Evaluating control plan for preventing these failures.

• Prioritizing the actions for improving the process.

FMEA is an extremely important tool for each phase of Six

Sigma strategy viz. Measure, Analyze, Improve, Control.

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Advantages of FMEA

• For improving the reliability and safety of the

products.

• For improving customer satisfaction.

• Tracking actions to reduce non-conformities.

• New product development.

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Definition of terms

Failure Mode : It is a manner in which a part or a process

can fail to meet specifications. It is usually associated with

defect or non-conformities.

Examples : Missing part, Oversized, Undersized, Incorrect

price, Offspec parts.

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Definition of terms

Cause : Causes are sources of variation which are

associated with key process inputs. Cause can be best

defined as a deficiency which results in a failure mode.

Examples : Instructions not followed, Lack of experience,

Incorrect documentation, Poor handling etc.

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Definition of terms

Effect : Effect is the impact on the customer (both internal

& external) if the failure mode is not prevented or

corrected.

Examples : Customer dissatisfaction, Frequent product

breakdowns, Customer downtime.

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Relationship of cause, failure mode & effect

Cause Failure

Mode Effect

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Failure

Mode

Causes Causes Causes

Causes Causes Causes

Effect

Prevent

or Detect

FMEA through Cause & Effect Diagram

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Steps in FMEA process

1. Develop a process map and identify process steps.

2. List key process outputs for satisfying internal and

external customer requirements.

3. List key process inputs for each process steps.

4. List ways the process inputs can vary (causes) and

identify associated failure modes and effects.

5. Assign severity occurrence and detection rating for each

cause.

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6. Calculate risk priority number ( RPN) for each potential

failure mode.

7. Determine recommended actions to reduce RPN’s.

8. Establish time frame for corrective actions.

9. Take corrective actions.

10. Put all controls in place.

Steps in FMEA process

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Ranking terms used in FMEA calculations Scale:1(Best) to 10 ( Worst)

• Severity (SEV) : Severity indicates how severe is the impact of the effect

on the customer.

• Occurrence (OCC) : This indicates the likelihood of the cause of the

failure mode to occur.

• Detection (DET) : This indicates the likelihood of the current system to

detect the cause or failure mode if it occurs.

• Risk priority number : This number is used to place priority to items for

better quality planning.

RPN = SEV X OCC X DET

See next slides for specimen best to worst ratings on a 10 point scale.

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Best to Worst ratings for FMEA calculations

Rating Degree of Severity Likelihood of Occurrence Ability to detect

1 Customer will not at all observe Very remote possibility Sure that the potential failure

the adverse effect will be detected & prevented

before reaching the next

customer

2 Customer will experience Low failure with supporting Almost sure that the potential

slight discomfort documents failure will be detected before

reachig the next customer

3 Customer will experience Low failure without supporting Less chances that the

annoyance because of slight documents potential failure will reach the

degradation of performance next customer undetected

4 Customer dissatisfied due to Occasional failures Some controls may detect

reduced performance the potential from reaching the

next customer

5 Customer is uncomfortable Moderate failure rate with Moderate chances that the

supporting documents potential failure will reach the

next customer

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Rating Degree of Severity Likelihood of Occurrence Ability to detect

6 Warranty repairs Modearate failure rate without Controls are not likely to detect

supporting documents or prevent the potential failure

from reaching the next

customer

7 High degree of customer High failure rate with supporting Less chances that the potential

dissatisfaction documents failure will be detected or

prevented before reaching

the next customer

8 Vey high degree of customer High failure rate with supporting Very less chances that the

dissatisfaction documents potential failure will be detected

or prevented before reaching

the next customer

9 Negative impact on the Failure is almost certain Existing controls will not detect

customer the potential failure

10 Negative impact on the Assured failure Existing controls will not detect

customer, people & society the potential failure

Best to Worst ratings for FMEA calculations

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1 2 3 4 5 6 7 8 9

Process Potential failure mode Potential failure effect SEV Potential causes OCC Current Controls DET RPN

Part No.

1

2

3

4

5

List failure

modes for each

step

List effects

of each

failure mode

List causes

for each failure

mode

Rank severity

on 1 to 10

scale

Rank occurrence

on a 1 to 10

scale

List how the cause

is presently

being controlled

Rank how well

cause/failure

can be detected

on 1 to 10 scale

RPN=

SEV*OCC*DET

FMEA Form: ( Column 1 to 9 )

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10 11 12 13 14 15

Actions Recommended Responsibility SEV OCC DET RPN

List actions

recommended

on RPN pareto

Designates people

responsible for

corrective action

FMEA Form contd: ( column 10 to 15 )

RPN is recalculated

on completion of

corrective action