pfmea (pankaj nalwa)

8/13/2019 PFMEA (Pankaj Nalwa)

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Process Failure Mode Effect Analysis (PFMEA)

Uniparts India Limited By: Pankaj Nalwa


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Our product or process is established, it doesnt have any failure modes.

Every product or process has modes of failure, which can arise eventhough your product or process is established and you are producing orperforming it for years.


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FMEA takes lot of time and resources, also it does not provide any benefit. It

can be done by one person instead.

FMEA do take time and people resources as it is a team based activity.Effective FMEAs cannot be done by one person sitting alone and fillingout FMEA forms.FMEA do not require complicated statistics, still it can yield significantsavings for organization by reducing cost liabilities due to process orproduct that does not performed as required.


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Current Paradigm

FMEA

-Taken lightly

Selective products / processes chosen.

Based on opinion.

All magically below the RPN cut-off.

-Too late

Error / Mistake proofing window long gone.

Rarely validated with field results.

Paper exercise done when pushed


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New Paradigm

FMEA

Error / Mistake

Proofing

Process Control

Plans

Maintenance

Plans

-Taken Seriously All critical and new products / processes.

Data driven.

Roll-up RPN values.

-Early

Completed while design is still fluid.

Living document.

Ensures our products and processes are

robust


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The objective of a FMEA is to look for all of the ways a process orproduct can fail.

A product failure occurs when the product does not function as it

should or when it malfunctions in some way.

Failures are not limited to problems with the product. Because

failures also can occur when the user makes a mistake, those types

of failures should also be included in the FMEA.

Anything that can be done to ensure the product works correctly,

regardless of how the user operates it, will move the product closerto 100% total customer satisfaction.


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Process FMEA is an effort to prevent failures (due to process)before they happen, to assess the risk associated with those failuremodes, to rank the issues in terms of importance and to identify andcarry out corrective actions to address the serious concerns.

Process FMEAs uncover process problems related to the manufacture of

the product.

It is helpful when conducting a process FMEA to think in terms of the five

elements of a process: People, Materials, Equipment, Methods and

Environment. With these five elements in mind, ask: How can process

failure affect the product, processing efficiency or safety?


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FMEA Core Team

It is helpful to have people in team who have different levels of familiarity

with the product or process.

Those who are most familiar with it will have valuable insights, but may

overlook some of the most obvious potential problems. Those who are lessfamiliar with the process or product will bring unbiased, objective ideas into

the FMEA process.

A point is often debated with FMEAs is what role the process expert plays

on the FMEA team. A person with expertise in the process can bring

tremendous insight to the team and can help speed the process.


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Ten Steps for an Process FMEA

1) Review the process.

2) Brainstorm potential failure modes.

3) List potential effects of each failure mode.

4) Assign a Severity ranking for each effect.

5) Assign an Occurrence ranking for each failure mode.

6) Assign a Detection ranking for each failure mode and /or effect.

7) Calculate the Risk Priority Number for each effect.

8) Prioritize the failure modes for action.

9) Take action to eliminate or reduce the high-risk failure modes.

10) Calculate the resulting RPN as the failure modes are reduced or

eliminated.


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Ways in which a product or process can fail are called FAILUREMODES.

Each failure modes has a potential effect, and some effects are more

likely to occur than others. In addition, each potential effect has a

relative risk associated with it.

The FMEA process is a way to identify the failures effects and riskswithin a process or product and then eliminating or reduce them.


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Evaluating the Risk of FailureThe relative risk of a failure and its effects is determined by three

factors:

SeverityThe consequence of the failure should it occur.

OccurrenceThe probability or frequency of the failure occurring.

DetectionThe probability of the failure being detected before the

impact of the effect is realized.


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Using the data and knowledge of the process or product, each potential

failure mode and effect is rated in each of these three factors on a scale

ranging from 1 to 10, low to high.

By multiplying the ranking for the three factors (Severity x Occurrence x

Detection), a risk priority number (RPN) will be determined for each potential

failure mode and effect.

The risk priority number (which will range from 1 to 1,000 for each failure

mode) is used to rank the need for corrective actions to eliminate or reduce

the potential failure modes.

Once corrective action has been taken, a new RPN for the failure is

determined by reevaluating the Severity, Occurrence and Detectionrankings. This new RPN is called Resulting RPN.

Improvement and corrective action must continue until the resulting RPN is

at acceptable level for all potential failure modes.


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For High Severity 9/10


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Process FMEA document

Process

Control

Plan

Operator

Job

Instructions

Process

Flow

Diagram

Process

Changes

Current or

Expected

quality

performance

Customer

Design

Requirements

Implementation

and verification

RecommendedCorrective actions

i.e.

Error proofing

Continuous Improvement Efforts

And RPN reduction loop

Communication of standard

of work to operators


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EffectCriteria: Severity of Effect

Ranking RemarksThese rankings results when a potential failure mode results 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 two severities.

Customer Effect Manufacturing / Assembly Effect

Hazardous withoutwarning

Very high severity ranking when apotential failure mode affects safe

vehicle operation and/or involves

noncompliance with governmentregulation without warning.

Or may endanger operator (Machine or assembly) without

warning.

10 Criticalcharacteristic

Hazardous with

warning

Very high severity ranking when a

potential failure mode affects safevehicle operation and/or involvesnoncompliance with government

regulation with warning.

Or may endanger operator

(Machine or assembly) withwarning.

9 Criticalcharacteristic

Very High Vehicle / item inoperable (loss of

primary function)

Or 100% of product may have to be

scrapped, or vehicle / item repaired

in repair shop with repair timegreater than one hour.

8 Majorcharacteristic

High Vehicle / item operable but at a

reduced level of performance.Customer very dissatisfied.

Or product may have to be sorted

and a portion (less than 100%)scrapped, or vehicle / item repairedin repair department with a repair

time between hr and an hour.

7Moderate Vehicle/item operable but comfort /

convenience item(s) inoperable.Customer dissatisfied.

Or a portion (less than 100%) of the

product may have to be scrappedwith no sorting, or vehicle / item

repaired in repair shop with a repair

time of less than hr.

6


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Effect

Criteria: Severity of Effect

Ranking RemarksThese rankings results when a potential failure mode results 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 two severities.

Customer Effect Manufacturing / Assembly Effect

Low Vehicle / item operable but comfort /

convenience item(s) operable at areduced level of performance.

Or 100% of product may have to be

reworked, or vehicle / item repairedoff-line but does not go to repair

department.

5Very Low Fit and Finish / Squeak and Rattle

item does not conform. Defectnoticed by most customers (greater

than 75%).

Or the product may have to be

sorted, with no scrap, and a portion(less than 100%) reworked.

4Minor Fit and Finish / Squeak and Rattle

item does not conform. Defectnoticed by 50% of customer.


product may have to be reworked,with no scrap, on-line but out-of-

station.

3Very Minor Fit and Finish / Squeak and Rattle

item does not conform. Defectnoticed by discriminating customers

(less than 25%).


product may have to be reworked,with no scrap, on-line but in-station.

2None No discernible effect. Or slight inconvenience to operation

or operator, or no effect.1


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Probability Likely Failure Rates Ranking RemarksVery High: Persistent Failures

100 per thousand pieces 1050 per thousand pieces 9

High: Frequent Failures 20 per thousand pieces 810 per thousand pieces 7

Moderate: Occasional

Failures

05 per thousand pieces 602 per thousand pieces 501 per thousand pieces 4

Low: Relatively Few Failures 0.5 per thousand pieces 30.1 per thousand pieces 2

Remote: Failure is unlikely 0.01 per thousand pieces 1

Suggested P.F.M.E.A Occurrence Evaluation Criteria.


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Detection Criteria

Inspectio

n Types Suggested Range of Detection Methods Ranking

A B C

AlmostImpossible Absolute certainty of non-detection Cannot detect or is not checked. 10Very

Remote

Control will probably not detect Control is achieved with indirect or random checks only. 9Remote Controls have poor chance of

detectionControl is achieve with visual inspection only. 8

Very Low Control have poor chance of

detection

Control is achieve with double inspection only. 7Low Controls may detect Controls is achieved by charting methods, such as Statistical

Process Control. 6Moderate 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 set up and first-piece check (for set up causes

only).4

High Controls have a good chance to

detect

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 Error detection in-station (automatic gauging with automaticstop feature). Cannot pass discrepant part. 2

Certain Controls certain to detect Discrepant parts cannot be made because item has been error-

proofed by process/product design. 1


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Severity

10 Confirmed Critical Characteristic9

8

Confirmed Significant

Characteristic; Action Required

7

6

5

4 Annoyance

3 Zone

2

1

1 2 3 4 5 6 7 8 9 10

Occurrence

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