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Next: Types Of FMEA: Design FMEA (DFMEA), Process FMEA (PFMEA) | 1 | 2 | 3 | 4 | 5 | FMEA Tutorial Lesson 1: Definition of Failure Mode and Effects Analysis Failure Mode The manner in which the product/part or service does not meet the customer’s expectations Effects Analysis A study of the effects of failure on the function or purpose of the product/part or service The customer could be external to the company, or internal (within the company). It is considered a reliability planning tool, but it has also become a method for prioritizing alternative actions (that do not deal with failure modes), e.g., in the Six Sigma process. FMEA is a systematized group of activities intended to: * Recognize and evaluate the potential failure modes and causes associated with the designing and manufacturing of a product * Identify actions which could eliminate or reduce the chance of the potential failure occurring, and * Document the above process. It increases the likelihood that potential failures, and their effects and causes, will be considered prior to the final design and/or release to production. The key to the actions in this Reliability Analysis method is to plan preventive actions. A completed FMEA, which should be applied in an iterative process, contains a great deal of information about the product or process. It can be used as the starting point for later control plans, trouble-shooting guides, preventive maintenance plans, etc. Key Things To Keep In Mind "One of the most important factors for the successful implementation of an FMEA program is timeliness… Up- front time spent properly completing an FMEA well, when product/process changes can be most easily and inexpensively implemented, will minimize late change crises." AIAG FMEA Instruction Manual (3rd Edition) When going through the FMEA process, it is also important to remember to base your decisions on data, not on hunches! It should occur very early in the planning cycle. FMEA teams will find themselves
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Page 1: FMEA

Next: Types Of FMEA: Design FMEA (DFMEA), Process FMEA (PFMEA) | 1 | 2 | 3 | 4 | 5 |

FMEA Tutorial Lesson 1: Definition of

Failure Mode and Effects Analysis

Failure Mode

The manner in which the product/part or service does not meet the customer’s expectations

Effects Analysis

A study of the effects of failure on the function or

purpose of the product/part or service

The customer could be external to the company, or internal (within the company). It is

considered a reliability planning tool, but it has also become a method for prioritizing alternative

actions (that do not deal with

failure modes), e.g., in the Six Sigma process.

FMEA is a systematized group of activities intended to:

* Recognize and evaluate the potential failure modes

and causes associated with the designing and manufacturing of a product

* Identify actions which could eliminate or reduce the

chance of the potential failure occurring, and

* Document the above process.

It increases the likelihood that potential failures, and their effects and causes, will

be considered prior to the final design and/or release to production. The key to the actions in this

Reliability Analysis method is to plan preventive actions. A completed FMEA, which should be

applied in an iterative process, contains a great deal of information about the product or process.

It can be used as the starting point

for later control plans, trouble-shooting guides, preventive maintenance plans, etc.

Key Things To Keep In Mind

"One of the most important factors for the successful implementation of an FMEA program is

timeliness… Up-

front time spent properly completing an FMEA well, when

product/process changes can be most easily and inexpensively

implemented, will minimize late change crises." AIAG FMEA Instruction Manual (3rd Edition)

When going through the FMEA process, it is also important to remember to base your decisions

on data, not on hunches!

It should occur very early in the planning

cycle. FMEA teams will find themselves

Page 2: FMEA

spending more time than usual early on,

which will lead to leveraged savings later on.

The use of data to verify the relationships between root causes and effects, to establish accurate

rating criteria, and to determine effective preventive actions is one of the critical-to-success

factors in the FMEA process.

Costs vs. Benefits

Lots of Tedious Work → Increased success of implementation, & knowledge well captured by

the cross-functional team.

FMEA Tutorial Lesson 2: FMEA Supporting

Tools: Root Cause Identification, Fault Tree

Analysis (FTA)

Next: 5 Why's Technique - Analyzing For Root Causes in FMEA | 1 | 2 | 3 | 4 |

FMEA Tutorial Lesson 2: FMEA Supporting

Tools: Root Cause Identification, Fault Tree

Analysis (FTA)

In this lesson you will be learn:

- Root Cause Identification

- Fault Tree Analysis (FTA)

Timing For Applying The FMEA Quality Tools

Page 3: FMEA

Legend

D/PFMEA – Design/Process FMEA

FTA – Fault Tree Analysis

DOE – Design of Experiments

SPC – Stat. Process Control

Poka Yoke – Japanese for mistake-proofing

All of the tools, whether they are used in the context of concurrent development or not, should be

applied based on the Voice of the Customer (VOC). The first VOC priority is from the external customer.

Also important is the VOC of the internal customer. Note the typical timing for the tool usage. Also see

the Legend at the bottom for a definition of the acronyms. FMEA and FTA (Fault Tree Analysis) will be

covered in this course. Note the use of D/PFMEA as soon as possible in the Product Design and Process

Design phases, respectively. Design of Experiments (DOE) should also be used in both phases. FMEA is

most effective when other tools are applied at the right time in order to provide the best input to

include in the FMEA. This is not a complete list; there are many other tools which can and should be

used throughout the product and product development processes

Page 4: FMEA

Lesson 3

Goal of this Lesson:

Completing the Design FMEA Form:

- Identifying the Product Function

- Identifying Potential Failure Modes

- Identifying Potential Failure Effects

- Determining the Severity of the Effect

- Identifying Potential Cause(s) of the Failure Mode

- Determining the Probability of Occurrence of the Failure Mode

- Identifying Design Verifications for the Causes

- Determining the Probability of Non-Detection of the Failure Mode

Using the Completed DFMEA Form:

- Calculating the Risk Priority Number (RPN)

- Determining Corrective and Preventive Actions

- Prioritizing Actions Based on the RPN

What Is A Design FMEA?

* FMEA is a method for identifying potential or known failure modes and providing corrective

and preventive actions.

* The Design FMEA is a disciplined analysis of the part design with the intent to correct or

prevent the design-based failure modes prior to the first production run.

The FMEA Process:

* Identify potential or known failure modes

* Identify the effects and causes of each failure mode

* Prioritize the identified failure modes based on the frequency of occurrence, the severity of the

failure mode, and the likelihood of detection

* Provide for follow-up corrective and preventive actions

* Follow up

Page 5: FMEA

Prev: FMEA Tutorial Lesson 3: Performing a Design FMEA Next: When Should You Do A

Design FMEA | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 |

Design FMEA Example

For this abbreviated example, there are 4 basic functions of the car door. One way (failure mode)

the door could potentially fail to perform the last 2 basic functions listed is by the interior lower

door panels becoming corroded.

The failure mode could potentially lead to deteriorated door panel life (a failure mode effect of

door panel corrosion), resulting in poor appearance and impaired function of the interior door

hardware. Note: it is acceptable to break down the effect in a chain of events as shown if it better

Page 6: FMEA

describes the problem being worked on. The effect is described from the perspective of the

customer, although the description need not be in the customers’ language. The severity of the

deteriorated door life effect is rated as a 6 here.

There are 4 potential design-based root causes of the door panel corrosion (the failure mode

here) listed. Note that while these causes may show up in fabrication or assembly, they are

design-based, that is, the designers specify their values or settings. Each cause receives its own

probability of occurrence rating score, based on the likelihood of the cause happening and its

resulting in the failure mode.

The only design verifications (DVs) presently in place are the Design group’s phase design

reviews. The ability of the design reviews to prevent the design-based cause (or detect the

potential failure mode) from happening is assessed for each of the causes listed.

Then the RPN is calculated for each cause so that their corrective/preventive actions can be

prioritized. The highest scores become the highest priorities. The fact that none of the scores is

close to the maximum possible score (1000) does not mean anything. Just the relative scores are

meaningful.

Page 7: FMEA

Design FMEA Process Flow

These steps of the FMEA will be discussed and explained later in detail, but it is helpful to see

the overall flow, at this overview level, for now. Try to match the additional following examples

to this flow to give you a feel for how Design FMEAs can be used.

The Design FMEA (DFMEA) needs to be done early in the product design cycle, after the design concept

has been selected since it needs detailed part functions; it should be continually updated as the program

develops.

* FMEA can be applied as a supporting method as part of the Concurrent Engineering development

process.

* Try for some concurrency between the Design and Process FMEAs.

The information developed from the DFMEA will provide excellent input for the earlier phases of the

Concurrent Engineering or Integrated Product Development processes, and vice versa. Having some

Page 8: FMEA

timing overlap (concurrency) between the DFMEA and the PFMEA will further reduce the Time to

Market.

If an existing design, on which there is already a DFMEA, is applied in a different environment or usage,

then the FMEA should be focused on the impact of the new environment or application.

The DFMEA process will be explained and demonstrated using the numbering scheme shown on the

preceding blank DFMEA form. You may want to periodically refer back to this blank form as each step

and column of the process is described. There will also be a flowchart that progressively develops in

sequence with the numbered steps.

Prev: When Should You Do A Design FMEA Next: FMEA Process Flow - Failure Mode and

Effect of Failure Mode | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 |

DFMEA Definitions

Function of the Part

* The function of the part is the task that it must perform to meet

its design intent. it should be described in a way that is:

Page 9: FMEA

- Concise

- Exact

- Clear to all participants and users

* Use a verb-noun format

Examples:

- Isolate electrical data signals

- Provide mating surface to part B

- Provide dielectric material for impedance

- Provide engaging tab for cam

- Last for 40,000 cycles

- Operate within specified environmental

conditions

- Be manufactured at specified productivity

and quality rates

Right about now in the FMEA process would be a good time to perform the Fault Tree Analysis

FTA. Then you would transfer the information to the FMEA form as you go through the steps.

Note that

you will likely adding to that information, but it is an excellent way to make the FMEA more

thorough.

Although the DFMEA assumes the part

will be manufactured to the design intent,

it should still take into account realistic limitations of the manufacturing and assembly processes,

e.g., clearances for tooling, achievable tolerance capabilities, realistic parts/hour rates, etc.

Design FMEA - Use this blank form to develop your own example.

Page 10: FMEA

Prev: DFMEA Definitions Next: Severity of the Failure Mode Effect - FMEA Process Flow | 1 | 2 | 3 | 4

| 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 |

FMEA Process Flow - Failure Mode and

Effect of Failure Mode

Potential Failure Mode of the Function

* The ways in which the part could fail to perform its intended design function.. it should be described in

a "negative" way.

* Stress how the part could fail, not whether it will fail, to conform to the design specification

* Try asking what could happen to cause a loss of function:

- "How could this part fail?", or

- "Could it

break, deform, wear, corrode, bind, leak, short,

open, etc.?"

Page 11: FMEA

* Examples of failure modes:

- Isolate electrical data signals → loss of dielectric

- Provide mating surface to part B → worn mating surface

- Provide dielectric material for impedance → loss of signal transmission integrity

- Provide engaging tab for cam → bent tab

- Corrosion - Cannot assemble - Over-deflection

Assume that the failure could occur for now. Later we will deal with the likelihood of its occurrence.

Refer back to the list of functions when asking the What If questions. Also refer back to the FTA to help

ensure completeness here.

List each potential failure mode for the part. Note that for these examples, the failure modes are shown

following the part’s basic functions (optional).

Other possible failure modes could be a part oxidizing, fracturing,

sticking, loosening, not transferring a force, not assembling readily with a mating part, drift, disengaging

during operation, etc.

FMEA Process Flow - Effect of Failure Mode

Potential Effect(s) of the Potential Failure Mode

Page 12: FMEA

* The outcome of the occurrence of the failure mode on the part or assembly (system).

* Describe the effect of the failure specifically, and in terms

of customer reaction: "What does the customer (external

or internal) experience as a result of the failure mode of..."

or "Will the component or assembly be inoperative, intermittently operative, noisy, not durable, etc.?"

* Consider whether the effect can also impact other functions

or parts.

Examples of effects:

* Loss of dielectric → low withstanding voltage → assembly shorts out

* Bent tab → cannot assemble mating part

* Worn mating surface → mating part does not engage

* Loss of signal transmission integrity → incorrect data transmission

* Tab edge does not engage cam → auxiliary bolt sticks

* Cannot assemble → lost time and wasted costs in Final Assembly

* Corrosion → part loses yield strength, with a lower MTBF

The loss of dielectric is an example of a failure mode resulting in a low withstanding voltage, which in

turn results in the assembly shorting out (the effect). Using a chain of events is a good technique if it

helps you better explain the failure modes and their effects.

Look for the outcomes or consequences of the failure mode on the part, assembly, other parts, end

user, etc. You should also include safety or regulatory non-compliance outcomes.

Other examples include unpleasant odor, unstable, regulatory non- compliance, intermittent operation,

or poor appearance.

Assuming that the failures have occurred, give specific descriptions of the ways in which customers

could observe each failure. Use the perspective of the external or internal customer, but it isn’t

necessary to use the customer’s terminology here.

Note that there could be more than one effect for a given failure mode, or, an effect could be the result

of several failure modes. Don’t forget to refer back to your FTA.

Note: MTBF stands for mean time between failures.

The severity or estimated consequence of the effect

on a 1 to 10 scale, where a 1 is a minor nuisance

and a 10 indicates a severe total failure of the system.

When weighing the consequence (effect) of the failure,

ask "How serious would the effect of this failure be to

the customer, assuming it has happened?"

To reduce the severity of the effect of a product failure

mode, a part design action is usually required.

Page 13: FMEA

The part design action to reduce a high rating may include design additions or revisions that

mitigate the resultant severity of the failure, e.g., seat belts in a car.

Severity is the first of the 3 Risk Priority Numbers (RPN) rating criteria. Think of the estimated

consequence or seriousness of the effect, assuming it does exist*, on the external and/or internal

customer. If the effect is critical, the severity is probably high. *Do not consider the likelihood

that the defect will occur in scoring this criterion; this will be evaluated in the second criterion

(Occurrence).

A sample of a Severity ranking scale is shown here:

Severity Ranking

Ranking Description

1

The effect of the failure is of such a minor nature as to be

undetectable by the customer. For example, the part may be

out of specification on a non-key quality characteristic but not

have any noticeable effect on the system.

2-3

The failure's effect is of a minor nature, although it is detectable by the customer, it

causes only slight annoyance without any noticeable degradation in the system

performance.

4-6 The failure's effect causes some customer dissatisfaction and some system degradation.

7-9 The failure's effect causes major customer dissatisfaction and major system

degradation. serious safety/legal implications.

10 Sudden, catastrophic failure without any prior warning. very serious legal implications.

The company should adapt these sample ratings to

what is appropriate to their industry.

This table of a Severity ranking scale provides guidance for assigning criteria values to the

failure mode effects on a consistent basis. It is only a sample and should not be used without

adaptation to the industry and company.

It is an indication of a design weakness, the consequence

of which is the failure mode. Consider the possible design

mechanisms and/or causes of each failure mode. Analyze

what conditions can help bring about the failure modes.

Page 14: FMEA

Make sure the list of causes is thorough. This helps

point the way toward preventive/corrective actions for

all pertinent causes. Consider the difference between effects, contributing causes, and root

causes.

Examples of causes:

* Wrong polymer specified → moisture absorption → loss of dielectric

* Excess annealing → malleable base material alloy → bent tab

* Maximum material condition stack-up → worn mating surface

* Insufficient gold plating specified → loss of signal transmission integrity

* Least material condition stack-up → gap → Tab edge does not engage cam

Here you are looking for the potential design-based root causes of the potential failure modes.

This includes causes that occur in production but are due to the design. Do not include causes

that are due strictly to errors or flaws in the production process – save these for the PFMEA.

Again, refer to the completed FTA to help ensure the list of causes is as thorough as possible,

and that the root causes are identified.

Other possible causes could include improper material specified for process or end-use operating

environment, incorrect algorithm, incorrect software specification, insufficient re-lubrication

capability, incorrect cam path, etc. Other possible failure mechanisms could include creep,

fatigue, wear, galvanic action, EMI (electromagnetic interference), etc.

Page 15: FMEA

FMEA Tutorial Lesson 4: Performing a

Process FMEA

You will learn:

Completing the Process FMEA Form:

- Identifying the Process Purpose

- Identifying Potential Failure Modes

- Identifying Potential Failure Effects

- Determining the Severity of the Effect

- Identifying Potential Cause(s) of the Failure Mode

- Determining the Probability of Occurrence of the Failure Mode

- Identifying Process Controls for the Causes

- Determining the Probability of Non-Detection of the Failure Mode

Using the Completed PFMEA Form:

- Calculating the Risk Priority Number (RPN)

- Determining Corrective and Preventive Actions

- Prioritizing Actions Based on the RPN

- Using the Maintenance FMEA