Failure Mode and Effects Analysis by Bosch

Edition 08.1998

Work group booklet 14

K1/EQS Viehmann*

K3/QSG Länder

K5/QSG Kaczynski

UC/WAY Gatter**

ZQF Eilers

* moderation

** at times

We are also very grateful for the work of those employees who have contributed to this bookletwith their ideas and their constructive criticism.

1998 Robert Bosch GmbH

H14 (43-08/98)

Contents

1 Introduction 6FMEA Objectives .......................................................................................................... 6FMEA History................................................................................................................ 6Possibilities of and limits to the FMEA......................................................................... 6FMEA-types - methodological differences.................................................................... 7

2 Description of Method 8Deadlines for doing the FMEA...................................................................................... 8FMEA-Team .................................................................................................................. 9FMEA-sequence plan................................................................................................... 10Systematic Preparations ............................................................................................... 10Special Characteristics................................................................................................. 11FMEA-Documents ....................................................................................................... 11Updating....................................................................................................................... 11

3 System FMEA 13Structuring.................................................................................................................... 14Functional Analysis ..................................................................................................... 14Risk evaluation............................................................................................................. 16Optimizing ................................................................................................................... 19

4 Design FMEA 20Structuring.................................................................................................................... 21Functional analysis....................................................................................................... 22Failure analysis ............................................................................................................ 22Risk evaluation............................................................................................................. 23Optimizing ................................................................................................................... 25

5 Process FMEA 27Structuring.................................................................................................................... 28Functional analysis....................................................................................................... 29Failure analysis ............................................................................................................ 29Risk assessment............................................................................................................ 30Optimizing ................................................................................................................... 33

6 Cooperation with customers 34FMEA presentation for customers ............................................................................... 34System or interface FMEA in cooperation with the customer..................................... 34

7 Cooperation with suppliers 35

8 Further FMEA-applications 36Interface FMEA ........................................................................................................... 36Logistics FMEA........................................................................................................... 36FMEA for software ...................................................................................................... 37FMEA for control units................................................................................................ 37

9 Selection/Prioritizing for FMEA 38Selection according to application criteria .................................................................. 38Selection with QFD...................................................................................................... 38Further possibilities for selection................................................................................. 38

4 Contents

10 Relation to other methods 39FMEA and Quality Function Deployment (QFD) ....................................................... 39FMEA and value analysis ............................................................................................ 39FMEA and Team Oriented Problem Solving (TOPS) ................................................. 40FMEA and review procedures ..................................................................................... 40

11 Computer assistance 41IQ FMEA ..................................................................................................................... 41Sibylle for windows ..................................................................................................... 41

12 Bibliography 42

13 Appendix 43Appendix 1: Forms....................................................................................................... 43Appendix 2: Short description ..................................................................................... 46Appendix 3: Questions on the columns of the form .................................................... 48

Index 49

Foreword 5

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ForewordIn this booklet, the Failure Mode and Effects Analysis (FMEA) is described as method for riskevaluation. The method used at Bosch is oriented on the successful procedures of theautomobile industry. The objective of this manual is a methodological description(introduction) of a RB-uniform FMEA procedure. The already existing training material ‘BasicSeminar for System-, Construction-and Process-FMEA‘‚2. Edition (2/95) has been integrated inits contents. QSP0305 ‘FMEA and the existing FMEA procedures in the division have alsobeen taken into consideration.

In this booklet, some of the terms specifically used at RB have been substituted by morecommon terms. The expert is already familiar with these terms; those who have just started toget into this subject should be aware of the fact that within the period of change, they will stillfind outdated terms like ‘failure effect‘, ‘severity‘, ‘scope‘ and ‘RZ‘ in the existing documents.

With the publication of this booklet, there is also a change of software. The programs used sofar are no longer up-to-date and are not further developed. With the now available IQ-FMEAprogram, we have the possibility to efficiently support the FMEA. You will find moreinformation in chapter ‘Computer assistance‘.

The efficiency of the FMEA is dependent on its timely implementation, on the cooperation ofcompetent employees and the concentration on relevant aspects.

The FMEA-documentation and its contents are together with other documents, for exampledrawings, production- and inspection notes a know-how which is worth protecting and shouldonly be handed on under defined circumstances (see chapter ‘Cooperation with customers’).

The FMEA is organizationally tied up in existing design and production planning sequences. Itis also successfully used in new areas of employment, for example in the SW-development orlogistics-planning.

Please use the FMEA in view of the fact that systematic analyses in regard to potential failuresand their documentation help to prevent failure causes with means of the FMEA. In the longrun, the early and thus preventive usage of FMEA helps securing the success of theorganization.

6 Introduction

� ,QWURGXFWLRQ

)0($�2EMHFWLYHVThe Failure Mode and Effects Analysis (FMEA) is an analytical method of the preventivequality assurance. It serves to find the potential failure of a product/process, to recognize andevaluate its importance and to identify appropriate actions to prevent the potential failure or todiscover it in time. The systematic analysis and removal of weak points leads to theminimization of risks, to the reduction of failure costs and to an improved reliability.

)0($�+LVWRU\In the mid-1960s, this method was developed within the Apollo-project in the USA. It has firstbeen used by the aerospace industry and the nuclear technology and later by the automobileindustry and also in other sections. Today, FMEA is an important part of the Bosch-qualitysystem.

3RVVLELOLWLHV�RI�DQG�OLPLWV�WR�WKH�)0($A FMEA is a good means to analyze risks caused by individual failures. The individual risksare weight against each other to recognize priorities. A FMEA does not provide a statement onthe total failure risk. For the analysis of failure combinations, the fault-tree analysis is moreappropriate.

The advantages of a FMEA prove that the effort to prevent failures from the beginning of thedevelopment process of a product are justified because the very much higher resulting costs areeliminated later. Advantages are, e.g.:

• Prevention of failures in design and development• Less subsequent product changes and thus reduction of costs• Prevention of repeated failures through systematic consideration of expert/failure

knowledge on the product or process.

An argument which is often used against FMEA is its high expenditure. The following topicsplay an important role:

• Complexity of the product• Level of analysis/type of FMEA• methodological experience of moderator/team• Quality of preparations• Terms of reference/scope of analysis

Especially the two last topics offer big saving potentials. Important things to note with asystematic preparation are described in chapter 2.

The scope of analyses can be reduced in co-ordination with the client and the team. Approachesfor savings are:

• Priority system and selection of analyses (compare chapter 9)• a decision analysis that shows the critical component groups• the use of existing products/processes with similar FMEA• the use of a ‘Basis-FMEA‘ with parts / products / processes which are repeatedly

analyzed

Introduction 7

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Whereas the expenditure of a FMEA can be easily determined, the savings can often not bedirectly measured. The implementation of a FMEA is necessary when products are newlydeveloped, when there are changes on the product or procedures, products with safetyregulations or customer requirements (see [QSP0305]). Besides all that, the FMEAimplementation shows the following positive aspects, for example.:

• all project participants are ready for team work at an early stage• better understanding of the system for all participants• early detection of problem areas• consequent taking of actions up to implementation

The biggest benefit is gained when the FMEA is made at an early stage simultaneous to thedevelopment and planning of the production. It is important that the results can be used in theproduct development process and so unnecessary recurrences are avoided.

)0($�W\SHV��PHWKRGRORJLFDO�GLIIHUHQFHVThere are different types of FMEA depending on the time, the depth and the object of theanalysis. Basically, all FMEA types are identical in their procedure; the useage of the sameform proves this.

System FMEA

The system FMEA analyzes the correct functional interrelation of the system components andtheir connections. The goal is to avoid defects in system selection and layout and field risks.The system requirements are the basis for the analysis.

The system development department is responsible for the system FMEA .

Design FMEA

The design FMEA analyzes the design and layout of products/components according to thespecification to avoid design errors and process defects influenced by the design.

The product/component design department is responsible for the design FMEA.

Process FMEA

The process FMEA analyzes process planning and performance for products/componentsaccording to the drawing specifications to avoid planning errors and manufacturing defects.

The product planning department is responsible for the process FMEA.

8 Description of Method

2 'HVFULSWLRQ of 0HWKRG

'HDGOLQHV�IRU�GRLQJ�WKH�)0($As soon as possible, a FMEA is prepared in a team. The knowledge and experience of expertsfrom all affected areas are taken into consideration. The FMEA analyzes the state of a projectand is to be continually updated as changes occur.

System FMEA

For base projects, the system FMEA is implemented after the drafting of system concepts or theproposing of. For specific individual projects, the system FMEA is done after the description ofthe function scope including project sheet, if possible before the component design accounts areissued and before the design FMEA for new concepts is made.

Design FMEA

First draft is done before the start of B-sample manufacturing and testing. Corrective actionsshould be completed before product release.

Process-FMEA

First draft is concurrent with preparations of the production sequence plan and the planning ofoperational supplies, to the release of the product. Corrective actions should be completedbefore the start of production.

System development

Component development

Concept Design Testing

Production Engineering Department

Planning Procurement

Pre-Series

Series

System FMEA

First draft Completion of corrective actions further updating

Design FMEA

First draft Completion of corrective actions further updating

Process FMEA

First draft Completion of correctiveactions

furtherupdating

uProposal for specialcharacteristics, QB1

uDefinition of specialcharacteristics, QB2

uRealization of special

characteristics e.g. Cpk, QB3

Systemdevelopmentorder

Componentdevelopment order

Start ofB(C)-sampleproduction/testing

Planning order./product pre-release

Product release Start of series(product -delivery-release)

Fig.1: Chronological integration of the FMEA (example)

Description of Method 9

H14 (43-08/98)

)0($�7HDPTo improve efficiency, the FMEA is performed by a team of experts from all responsible andaffected areas.

Team work should lead to• parallel instead of serial work at an early stage• the benefit of a greater potential of knowledge and experience• an open way of dealing with existing information• increased creativity• quicker harmonized decisions• consensus building and improved acceptance of results• the promotion of cooperation within different departments.

For an efficient FMEA implementation, core teams are created (approx. 3 to 5 members). Ifnecessary, additional experts are included.

System FMEA Design FMEA Process FMEA

Core team • System development(responsible)

• Application

• Moderator

• Design(responsible)

• Testing

• Plant (productionengineering department orquality assurance)

• Moderator

• Production engineeringdepartment(responsible)

• Quality assurance

• Manufacturing operationsdepartment

• Moderator

Supplementalmembers

• Componentdevelopment

• Sales

• Department

• Purchase department

• Application/System development

• Endurance testings

• Departments

• Sales department

• Plant


• Development (design and/ortestings)

• Departments


Table 1: FMEA team members (example)


)0($�VHTXHQFH�SODQ

The following table shows the individual criteria and sub-criteria which are important for aFMEA.

0. Preparation and Planning • determine problem, problem definition and objective • team, sequential planning of action • materials for team • functional description

1. System structuring • numbering • component or working operations

2. Functional analysis • functions/characteristics

3. Failure analysis • potential types of failures • failure effects and failure causes

4. Risk assessment • failure prevention and failure detection • significance of failure effect (S) • occurance probability (O) • detection probability (D) • risk priority number RPN = S x O x D

5. Optimizing / Quality improvement • chose priority order of risks (analyze S, O, D and RPN) • determination of actions for improvement with R: and I: • introduction of actions for improvement • assess improvements (O,D)

Table 2: FMEA-sequence plan

6\VWHPDWLF�3UHSDUDWLRQVBefore beginning with a FMEA, you have to do the following:

• define scope (type of FMEA)• define objective• select team members• determine need for training, if necessary organize training• prepare tables and diagrams• plan topics which have to be dealt with• estimate expense• do organizational preparations

A systematic preparation of the FMEA can reduce the expenditure of the actual FMEA, i.e. thetime spend on team work. Involved in the preparations are the moderator of the FMEA, ifnecessary also the FMEA-coordinator, the representative of the FMEA team (the expert) andsometimes the client. The representative of the team is an important contact person forproducing departments (production area, plant) and thus an important contact person for themoderator and he/she advises him with his expert knowledge.

When planning and preparing a FMEA, scope and objectives have to be clearly defined. At thisstage, you have to decide which parts of a system or a process have to be analyzed. If severalFMEA are planned, set the priorities according to urgency and required time which has to bespend.

Description of Method 11

H14 (43-08/98)

The employees needed for a FMEA are to be exempt from their usual work, i.e. they should beavailable during team work. Precondition for the cooperation in a FMEA team is the knowledgeof the FMEA method. If no training of this method takes place, there are unnecessarymethodological discussions when working in a team.

After the definition of the topics which have to be dealt with, the moderator estimates theexpense and coordinates this with the client.

Before the actual team work starts, all necessary documents have to be prepared. At thebeginning of the FMEA team-work, the team is supported by a functional description with thehelp of drawings and sample parts. Is the product a successor product, the already existing data(failure data, change applications, improvement proposals, field failures) can be additionallyused to support the team.

Important influence factors for the quality of FMEA are:− time of the FMEA/start in time− composition of team− ability of employees of working in a team− knowledge of the FMEA-method− in a process-FMEA : knowledge on the possibility of translating the measures

through MA into action in the production− willingness to hand on information

6SHFLDO�&KDUDFWHULVWLFVWhen determining and dealing with special characteristics (critical/significant/ R/D/ SPC) youhave to take note of the following:

• special characteristics which result from customer requirements have to be merked inthe FMEA.

• The special characteristics (critical/significant/ R/D/ SPC) are deduced from theFMEA and the marking is done according to the stipulations of the division.

)0($�'RFXPHQWVThe following documents are recommended for the publication of the FMEA as provided onthe FMEA- cover sheet:

− cover sheet with general information and a summary− description of product which is to be analyzed (drawings, sketches,...)− list of used documents (used rating chart)− FMEA-forms− evaluation (time schedule, FMEA-summary,...)

8SGDWLQJFMEA updating includes entering product and process changes and changed operatingconditions; information on manufacturing, zero-mileage and field experiences are entered andthe measures are reviewed. A redistribution follows the revision.

The associate responsible for updating of the FMEA (see cover sheet) must be informed by theassociate responsible for introducing quality improvement measures when these are introduced.The effectiveness of these measures must be checked and the ratings reviewed, if necessary.The old ratings are put in brackets - [ ] or < > -. The new and valid ratings do not have anybrackets.


The updating of the FMEA has to be guaranteed in documenting the development andproduction of a product. When updating, especially the latest actions have to be taken intoconsideration. It is recommended to update the FMEA every six months to every year.

System-FMEA 13

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� 6\VWHP�)0($The system FMEA analyzes the correct functional interrelation of the system components andtheir connections. The goal is to avoid defects in system selection and layout and field risks.The system requirements are the basis for the analysis. The system development department isresponsible for the system FMEA.

<ggf. Vertraulichkeitshinweis>

System-FMEA Page:Department:

Quality Assurance Product:Number:

FMEA-Number:Date:

No. Componentor Process

Function Failuremodes

Failureeffects

C Failurecauses

Failureprevention

Failuredetection

S O D RPN ActionsR:/I:

(1) (2) (3) (4) (5) (6) (7) (8) (9) (10) (11) (12) (13) (14)

This document is the exclusive property of Robert Bosch GmbH. Without their consent it may not be reproduced or given to third parties.

Fig. 2: The FMEA-form

Preparations

The following documents should be prepared for the first team meeting:

(also see chapter 2 - systematic preparations)− system-requirements, e.g. system target specification, machine list and block

diagram with detailed functional description.− field failure statistics and failure rates of comparable products− failure lists− prepared structuring and functional analysis

Base data

The base data are entered in the form (see following table).

Field System FMEA contents Notes

RB-Logo Additional customer-logo with jointFMEA

FMEA type System FMEA Product The system or sub-system which is analyzed in the FMEA Article number The identity number of the analyzed system or the project

number (as far as it exists)

Confidence note if necessary note on how to treat the FMEA Here, a conficence note can beentered

Page Page number of the FMEA-forms Is generated automatically throughSW

Department The department responsible for the realization of the FMEA FMEA-NR. Numbering according to BOSCH-standard N12A or N10 another numbering can be

determined

Date Date of the corresponding FMEA-edition Footnote Includes copyright and if necessary an explanation to the

appreviations used in the FMEA Is generated automatically throughSW

Tabelle 3: Base data

14 System-FMEA

The following description of the system FMEA procedure is oriented on the FMEA-sequenceplan (see page 10) and on the FMEA-form.

6WUXFWXULQJA successful possibility to structure the system FMEA is the component/function-matrix of thesystem. The SW IQ-FMEA offers more possibilities for system structuring (e.g. system tree,functions- or failure grid.


(1) (2)

Column (1) No.

The numbering of the component is taken, e.g., from the block diagram or the machine list andsupplemented through a number for the failure cause, e.g. 010.01 or 01.001.

Column (2) Component or Process

In column 2, the system components, component groups to be analyzed are entered according toblock diagram/machine list or component/function-matrix. Software-modules/-functions canalso be analyzed.

)XQFWLRQDO�$QDO\VLV


Function

(3)

Column (3) Function/ Purpose

The system FMEA lists all functions of the system components on the basis of the systemrequirements in view of operating conditions, starting from a black-box analysis.

The scope of the FMEA is determined within a functional analysis.

The more exact the description of the functions and characteristics is, the more exact thepotential failure types can be derived. The functions should be described with a noun, verb.

System-FMEA 15

H14 (43-08/98)

Failure analysis



Failureeffects

C Failurecauses

(4) (5) (6) (7)

Column (4) Failure mode

In the failure mode column, it is described why a required function or characteristic could nothave been fulfilled.

The system FMEA analyzes all potential malfunctions and functional deficits that are inferablefrom the functions of the system components and from their connections.

Column (5) Failure consequence

A failure consequence is a short and precise description of a causal chain from failure mode toeffect on the highest system level (e.g. vehicle) or the environment or the customer (externaland internal). This description should be done in different steps - direct, next, end.

Column (6) Special characteristics

The special characteristics are identified according to the stipulations of the division (see alsochapter special characterlistics, page 11).

Column (7) Failure causes

In this column, those failure causes are to be listed that might lead to the analyzed failure mode(= potential failure causes). The actual cause has to be described in such a way that anynecessary measures for improvement can be directly introduced.

The system FMEA looks at failures of functional groups or components and their connections;for the design as well as for the field.

All operating conditions (lifetime, temperature, time acceleration factors etc.) and operatingconditions (e.g. complete load, partial load, ABS breaking, partial breaking,...) have to beanalyzed.

Failure causes during the system development phase and system testing phase are to be lookedfor in the selection, co-ordination, design and development.

16 System-FMEA

5LVN�HYDOXDWLRQFor the risk evaluation, the already introduced actions are listed in the columns failureprevention and detection.



Failureeffects

C Failurecauses

Failureprevention

Failuredetection

(8) (9)

Column (8) Failure prevention

Failure prevention is a preventive action taken during the system design phase to prevent failurecauses to occur or to complicate their occurrence.

In a system FMEA (field and interpretation), the introduced actions are to be analyzed thatminimize the risk of system interpretation failures, prevent or limit the failure consequences.

Column (9) Failure detection

In a system FMEA , everything from failure detection during system development to system-release (design failures) is analyzed and failure detection through the system even in the field(field failure) are analyzed.

Actions for failure detection during the design are e.g. the system testings, testings in thevehicle, simulations and endurance testings.

Actions for failure detection in the field are e.g. internal diagnosis (together with appropriatesubstitutional functions), warning lamp/display, symptoms (noises etc.)



Failureeffects

C Failurecauses

Failureprevention

Failuredetection

S O D RPN

(10) (11) (12) (13)

Column (10) Relevance of failure consequence (S)

In column 10, the significance of the „end“- or. „distant effect“ of the failure type on the systemand/or the customer is evaluated. The evaluation criteria are covered by the VDA-Evaluationtables (see VDA vol. 4.2) or QS 9000 evaluation tables. The product-specific adaptation of therating charts can be of importance for the individual divisions.

System-FMEA 17

H14 (43-08/98)

System FMEA:S - Severity of failure consequence Rating Extremely serious failure, which affects safety and/or violates legalrequirements, without previous warning.

10

Extremely serious failure, which possibly affects safety and/or violateslegal requirements with previous warning or leads to “breaking down“.

9

Serious failure, failure of primary functions, e.g. vehicle not in running order. 8 Serious failure, reliability of vehicle very restricted, immediate servicingrequired.

7

Moderately serious failure, failure of important operational and comfortsystems; immediate servicing not required.

6

Moderately serious failure, limited functioning of important operational andcomfort systems.

5

Moderately serious failure, little reliability restriction of operational andcomfort systems; detectable by any driver

4

The failure is insignificant. The customer is only slightly bothered, and willprobably only notice slight interference;can be noticed by the average driver.

3

It is unlikely that the failure could have a noticeable effect on the behavior ofthe vehicle; only noticeable by experts or experienced drivers.

2

No effect 1

Table 4: Evaluation criteria for the importance of the failure consequence (B)in system FMEA

Column (11) Occurrence probability (O)

The rating ‘O’ says how probable it is that the failure type occurs at the customer’s/user‘sbecause of a certain failure cause. Actions which have been introduced to avoid the failurecause are analyzed and are assumed to be efficient.

System FMEAO - occurance probability

Possiblefailure rate*

ppm*

Rating points

Very high It is almost certain that the type/cause of failure willoccure very often.

1/10

1/20

100.000

50.000

10

9 High The type/cause of failure occurs repeatedly. Problematic, notperfect system.

1/50

1/100

20.000

10.000

8 7

Moderate The type/cause of failure occurs occationally. Advancedsystem.

1/200

1/1.000

1/2.000

5.000

1.000

500

6 5 4

Low The probability that the type/cause of failure occurs is low.Proven system design.

1/15.000

1/150.000

67

6,7

3 2

Unlikely. The occurence of the type/cause of failure is unlikely. <1/1.500.000 <0,67 1 *pro LD (LD = product lifetime)

Table 5: Rating chart for probability of occurrence (O) in system FMEA

The failure rates (e.g. λ - rates, ppm) in the rating chart are based on the number of failures thatare expected to occur within the required lifetime of a product. The dependencies of operatingtime (h), road performance (km), cycle numbers are to be taken into account. Plant, 0-mileageand field experiences are to be considered.

18 System-FMEA

Column (12) Detection probability (D)

In the system FMEA, there are different “D“ ratings for the detection probability of systemdesign and field failures.

With design failures, ‘D’ assesses the actions taken for inspection and detection of the systemdevelopment phase, e.g. simulation, functional testings, vehicle inspection, endurance testing,customer-initial sample testing according to system target specification and test plan.

With field failures, ‘D’ assesses the detection measures, displays and symptoms that are perfectfor detecting field failures in time, e.g. system-immanent tests (e.g. self-diagnosis), service,diagnosis, driver, warning lamps, changed functions.

System FMEA :D – detection probability

Evaluation criteria ”design” Rating

Unlikely It is impossible or unlikely that a type and/or cause of failure isdetected through test and analysis measures in the development phase.

10

Very low The probability is very low that the type and/or cause of failure isdetected through test and analysis measures in the development phase.

98

Low The probability that the type and/or cause of failure is detected throughtest and analysis measures in the development phase is low.

76

Moderate The probability that the type and/or cause of failure is detectedthrough test and analysis measures in the development phase is moderate.

54

High The probability that the type and/or cause of failure is detected throughtest and analysis measures in the development phase is high.

32

Very high It is certain that the the type and/or cause of failure is detectedthrough test and analysis measures in the development phase.

1

Evaluation criteria ”field“ Rating

It is impossible or improbable that the failure is detected at all or on time. 10

The failure can be detected through, e.g.:- reading of the fault memory during service work, substitue measures of thesystem do not exist- changed secondary function or another symptom (e.g. noise, noticeablesmell)

987

Diagnosis and substitute functions of system are active, warning lights atvehivle have to be turned on (e.g. emission)

6

Clearly noticeable impairement of secondary function (e.g. very loud noise)or slowly increasing impairement of function

5

Diagnosis and substitute function of system are active, light does not have tobe turn on.

432

The failure is definitely detected and ist effect is definitely prevented. 1

Table 6: Rating criteria for probability detection (D) in system FMEA

Column (13) Risk priority number

The risk priority number is the product of S, O and D. It is the standard for the ranking ofexisting risks.

RPN = S x O x D

System-FMEA 19

H14 (43-08/98)

2SWLPL]LQJThe RPN and the individual ratings S, O and D clearly show the system risks. If there is a highRPN or high individual ratings, improvements are required.

• If B ≥ 9, actions that reduce the importance of the failure consequence shouldpossibly be taken. Usually, these are system changes. If this is not possible, A has tobe reduced to such a degree that only a small and warrantable risk remains.

• Other limiting values for S, O, D, and RPZ are set by the team in such a way that thedifferent quality objectives for the product have to be met at the start of production.

In some areas, the following is valid:• Dependend on the degree of FMEA specification (system, subsystem, component),

the limit for introducing quality improvements should have a RPN between 60 and300.



Failureeffects

C Failurecauses

Failureprevention

Failuredetection


(14)

Column (14) Actions R:/I:

After the actions have been written down in the FMEA-form, they have to be completed by theresponsible person (R) and the deadline (I).

The ratings for the planned improvement are entered in the round brackets ().

If there are extreme concept changes, all 5 steps of the system FMEA are retaken for allconcerned sections – from system structuring to optimizing.

The final assessment is done after the action has been taken and after testing its effectiveness.

If a type of failure does not exist any longer because of the proposed action, the assessmentnumbers S, O, D, PRZ are to be put equal zero. If a failure cause does not exist any longerbecause of an action, the assessment number for O and RPN are to be put equal to zero.Alternatively, the cancelled failure type/cause can be documented.

20 Design FMEA

� 'HVLJQ�)0($The design-FMEA analyzes the design and layout of products/components according to thespecification to avoid design errors and process defects influenced by the design.

The product/component design department is responsible for the design FMEA.


Design-FMEA Page:Department:


FMEA-Number:Date:



Failureeffects

C Failurecauses

Failureprevention

Failuredetection


(1) (2) (3) (4) (5) (6) (7) (8) (9) (10) (11) (12) (13) (14)



Preparations

The following documents should be available at the first team meeting (see also chapter 2 -systematic preparations):

− Target specification− Development drafts− Parts lists− prepared FMEA structure

In addition, the following documents are also very helpful:− System FMEA− Functional description− Test sheet, sample− Technical customer documents− Endurance test results− 0-mileage and field failure statistics of comparable products− Failure lists− Uncleared-topics-list− Failure rates of comparable products

Design FMEA 21

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Base data


Field Design FMEA contents Notes

RB-Logo FMEA type Design FMEA Product The product analyzed in the FMEA Article number The identity number of the analyzed product Confidence note if necessary note on how to treat the FMEA Here, a conficence note can be

entered


Department The department responsible for the realization of the FMEA FMEA-NR. Numbering according to BOSCH-standard N12A or N10 Another numbering can be

determined



Table 7: Base dates in design FMEA

The following description of the design FMEA procedure is oriented on the FMEA-sequenceplan (see page 10) and on the column structure of the Bosch FMEA form.

6WUXFWXULQJThe structuring of the design FMEA can be derived from the component-function-matrix.


(1) (2)

Column (1) No.

The number serves the clear identification of the analyzed failure cause. In the design FMEA, itconsists of, e.g., the position numbers of the parts lists and of a serial number for the failurecause.

Column (2) Component or Process

In column 2, the component groups (component parts which are to be analyzed are enteredaccording to parts list.

22 Design FMEA

)XQFWLRQDO�DQDO\VLV


Function

(3)

Column (3) Function

The design FMEA lists all important functions and operating conditions of components; on thebasis of the component target specification and the design characteristics. The total product lifecycle up to the recycling of the product is to be analyzed.

The scope of the FMEA is determined within the functional analysis.

The more exact the description of the functions and characteristics is, the more exact thepotential failure types can be derived. The functions should be described with a noun, verb.

)DLOXUH�DQDO\VLV



Failureeffects

C Failurecauses

(4) (5) (6) (7)


In the failure mode column, it is described why a required function or a characteristic could nothave been fulfilled.

The design FMEA analyzes all potential malfunctions and functional deficits that are inferablefrom the component functions and which are described as physical expression. The designwhich meets the requirements of production is also to be analyzed; however, the process FMEAis not anticipated.


A failure consequence is a short and precise description of a causal chain from failure mode tothe effect on the highest system level (e.g. vehicle) or the environment or the customer (externaland internal). This description should be done in different steps - direct, next, end. The failureconsequence can be derived from the system FMEA.


The special characteristics are identified according to the stipulations of the division (see alsochapter 2 - special characteristics).


In this column, the failure causes are to be listed that might lead to the failure mode underconsideration (= potential failure causes). The actual cause has to be described in such a waythat any necessary measures for improvement can be directly introduced.

The design FMEA looks at failures which result from the design, selection or system as well asproduction and assembly failures which can be constructively influenced.

All operating conditions (lifetime, temperature, time acceleration factors etc.) have to beconsidered.

Design FMEA 23

H14 (43-08/98)

5LVN�HYDOXDWLRQFor the risk evaluation, the already introduced actions are listed in the columns failureprevention and detection.



Failureeffects

C Failurecauses

Failureprevention

Failuredetection

S O D RPN

(8) (9)


Failure prevention is a preventive action taken during the design phase to prevent failure causesto occur or to complicate their occurrence.

Preventive actions are derived from theoretical knowledge and practical experience. DoE(Design of Experiments) prevents failures for the designs and processes (robust design/robustprocess).


Defect detection within the design FMEA are inspections and testings in the development andother detection possibilities up to the product release.

To keep the testing expense as small as possible, actions which prevent failures have to betaken. Testings have to be done to provide security for the design. Through a specific planningof experiments, the expense for the testings is minimized.



Failureeffects

C Failurecauses

Failureprevention

Failuredetection

S O D RPN

(10) (11) (12) (13)


In column 10, the ‘end’ or ‘distant effect’ of the failure mode on the system and/or the customerare evaluated. The evaluation criteria are covered by the VDA-rating charts or QS 9000 ratingcharts (see [VDA4/2(96)], [CFG9000(95)]. It is better to make new rating charts for none K-areas.

24 Design FMEA

Design FMEA:S - Importance of failure consequence

Rating

Extremely serious failure, which affects safety and/or violates legalrequirements, without previous warning.

10


9


7


6


5


4


3


2

No effect 1

Table 8: Evaluation criteria for the importance of the failure consequence (S)in design FMEA


The rating ‘O’ says how probable it is that the failure type occurs at the customers/users –without previous detection - because of a certain failure cause. Actions which have beenintroduced to avoid the failure cause are analyzed and are assumes to be efficient.


Design FMEAO - occurance probability


ppm*

Rating points

Very high It is almost certain that the type/cause of failure willoccure very often.

1/10

1/20

100.000

50.000

10

9 High The type/cause of failure occurs repeatedly. Problematic, not aperfect design.

1/50

1/100

20.000

10.000

8 7

Moderate The type/cause of failure occurs occationally. Advanceddesign.

1/200

1/1.000

1/2.000

5.000

1.000

500

6 5 4

Low The probability that the type/cause of failure occurs is low.Proven design.

1/15.000

1/150.000

67

6,7

3 2

Unlikely. The occurence of the type/cause of failure is unlikely. <1/1.500.000 <0,67 1 *pro LD (LD = product lifetime)

Table 9: Rating chart for probability of occurrence (O) in design FMEA

Design FMEA 25

H14 (43-08/98)


In the design FMEA, ‘E’ assesses the test and detection measurements of the developmentphase, e.g. functional testings,

endurance testings, vehicle testings, customer-initial sample testings according to targetspecification and test plan.

Actions within the design FMEA that make the detection of the failures possible only after theproduct release should be rated with E=9 or 10.

Design FMEA:D – detection probability

Evaluation criteria ”design” Rating

Unlikely It is impossible or unlikely that a type and/or cause of failure isdetected through test and analysis measures in the development phase.

10

Very low The probability is very low that the type and/or cause of failure isdetected through test and analysis measures in the development phase.

98

Low The probability that the type and/or cause of failure is detected throughtest and analysis measures in the development phase is low.

76

Moderate The probability that the type and/or cause of failure is detectedthrough test and analysis measures in the development phase is moderate.

54

High The probability that the type and/or cause of failure is detected throughtest and analysis measures in the development phase is high.

32

Very high It is certain that the the type and/or cause of failure is detectedthrough test and analysis measures in the development phase.

1

Table 10: Rating criteria for probability detection (D) in design FMEA


The risk priority number is the product of S, O and D. This number shows the risk connected tothe failure cause and allows a rating of the failure causes.

2SWLPL]LQJThe RPN and the individual ratings S, O, and D clearly show the system risks. If there is a highRPN or high individual ratings, improvements are required.

• If S ≥ 9, actions that reduce the meaning of the failure consequence should possiblybe taken. Usually, these are system changes. If this is not possible, O has to bereduced to such a degree that only a small and warrantable risk remains.

• For high O-ratings, actions have to be taken that guarantee the set quality objectivefor the product at the beginning of the production. That means that normally O=2 to 3should be reached. If there is safety relevance, the objective should be O=1.

To make sure that the quality objectives will be met, action for detection have to betaken.

In some areas, the following is valid:• If RPN exceeds a limit which is to be set (e.g. 125), actions for quality improvement

have to be taken.• If RPN are close to the set limit (e.g. between 50 and 125) actions for continuos

improvement have to be taken to reach the quality objective at the production-start.

26 Design FMEA



Failureeffects

C Failurecauses

Failureprevention

Failuredetection


(14)




If there are extreme concept changes, all steps of the FMEA are retaken for all concernedsections – from system structuring to optimizing.

The final assessment is done after the action has been taken and after testing its effectiveness.

If a type of failure does not exist any longer because of the proposed action, the assessmentnumbers S, O, D, PRZ are to be put equal zero. If a failure cause does not exist any longerbecause of an action, the assessment number for O and RPN are to be put equal to zero.Alternatively, the cancelled failure type/cause can be documented.

If an action is taken (e.g. change of the design draft or change of the production procedure), ithas to be examined which new risks arise. If actions are found which lead to the canceling of afailure type/cause, the new actual state is to be analyzed. The old and new actual state have tobe weight up.

Process FMEA 27

H14 (43-08/98)

� 3URFHVV�)0($Definition: The process FMEA analyzes process planning and performance for products/com-ponents according to the drawing specifications to avoid planning errors and manufacturingdefects.


System-FMEA Page:Department:


FMEA-Number:Date:



Failureeffects

C Failurecauses

Failureprevention

Failuredetection


(1) (2) (3) (4) (5) (6) (7) (8) (9) (10) (11) (12) (13) (14)

This document is the exclusive property of Robert Bosch GmbH. Without their consent it may not be reproduced or given to third parties..


Preparation

The following documents should be available at the first team meeting (see also chapter 2 –Systematic preparations, Page 10):

− Design FMEA− Parts lists− Production sequence plans− Production drafts− Functional description− Sample− Technical customer documents− 0-mileage and field failure statistics of comparable products− Failure lists− Failure rates of comparable products− Machine and process capability data− prepared FMEA structure

28 Process FMEA

Base data


Field Process FMEA contents Notes

RB-Logo Additional customer-logo with jointFMEA

FMEA type Process FMEA Product The product under consideration in the FMEA Article number The identity number of the product under consideration Confidence note if necessary note on how to treat the FMEA Here, a conficence note can be

entered


Department The department responsible for the realization of the FMEA FMEA-NR. Numbering according to BOSCH-standard N12A or N10 Another numbering can be

determined



Table 11: Base dates in process FMEA

The following description of the design FMEA procedure is oriented on the FMEA-sequenceplan (see page 10) and on the column structure of the Bosch FMEA form.

6WUXFWXULQJThe structuring of the process FMEA results from the process sequence plan or the productquality assurance plan (PQP).


(1) (2)

Column (1) No.

The number serves the clear identification of the failure cause and the assignment of theindividual process in the FMEA to the product quality assurance plan (PQP). In the processFMEA, the first part of the number is the operation number of the sequence plan and the secondpart is, e.g. a serial number for the failure cause.

Column (2) Component/Process

In column 2, the working operations/steps which have to be analyzed are entered in the workingplan.

Process FMEA 29

H14 (43-08/98)

)XQFWLRQDO�DQDO\VLV


Function

(3)

Column (3) Function

The process FMEA lists all important process functions (working plan) and parts characteristics(drawing).

The size of the FMEA is determined within the functional analysis.

The more detailed the description of the functions and characteristics is, the more accurate thepotential failure types can be derived. The functions should be described with substantive, verband the criteria for compliance (target values, tolerances, ...).

)DLOXUH�DQDO\VLV



Failureeffects

C Failurecauses

(4) (5) (6) (7)


The process FMEA analyzes all potential process failures that can be deducted from therequired process functions and parts characteristics and that can be described as deviation.


A failure consequence is a short and precise description of a causal chain from failure mode toeffect on the highest system level (e.g. vehicle) or the environment or the customer (externaland internal). This description should be done in different steps - direct, next, end. It can bededucted from the design or system FMEA .


The special characteristics are identified according to the stipulations of the division (see alsochapter 2.5).


In this column, the failure causes are to be listed that might lead to the analyzed failure mode(= potential failure causes). The actual cause has to be described in such a way that anynecessary measures for improvement can be directly introduced.

Basically, all process-oriented failure causes are to be listed here. The term process includes allprocess sections, from supplying the material to transport, the actual production, cleaning,assembly, packaging, storing to the delivery to the customer.

The commitment of the product to a certain design should no longer be questioned.

30 Process FMEA

5LVN�DVVHVVPHQWFor the risk evaluation, the already introduced actions are listed in the columns failureprevention and detection.

It is important to note that double-evaluations should be avoided. Double evaluations existwhen the efficiency of a preventive or detective action are presupposed in an evaluation atsome other place. Examples for a non-permissible argumentation: a) „The detection is verygood, i.e. D=1, the failure does not reach the customer, he/she does not notice the failure;therefore S=1“, b) „The detection is very good, i.e. D1, therefore the occurrence probability isO=1.“



Failureeffects

C Failurecauses

Failureprevention

Failuredetection

(8) (9)


Failure prevention is a preventive action taken during production preparations to prevent failurecauses to occur or to complicate their occurrence.

SPC is an action within the process FMEA to prevent failures (process capability)

DoE (Design of Experiments) prevents failures of design and processes (robust design/robustprocess).


Actions which lead to the detection of failures make an early detection of the failure in theprocess possible and prevent products with failures to get to the customer. Processes in controlprevent failures and are thus preferred to inspections.

Only established or obligatory testings and detections within the process (e.g. next workingoperation not possible) should be taken into consideration.

In the process FMEA, it is distinguished between random and systematic failures. The SPC-sampling inspection is a detective action for systematic but not for random failures (samplinginspection). Random failures can be detected with a 100% inspection; or if a working operationat some later time can not be realized (e.g. .....)

Process FMEA 31

H14 (43-08/98)



Failureeffects

C Failurecauses

Failureprevention

Failuredetection

S O D RPN

(10) (11) (12) (13)


In column 10, the ‘end’ or ‘distant effect’ of the failure mode on the system and/or the customerare evaluated. The evaluation criteria are covered by the VDA-rating charts or QS 9000 ratingcharts (see [VDA4/2(96)],[CFG9000(95)]). It is better to make new rating charts for none K-areas.

Process FMEA:S - Importance of failure consequence

Rating

Extremely serious failure, which affects safety and/or violates legalrequirements, without previous warning.

10


9


7


6


5


4


3


2

No effect 1

Table 12:Evaluation criteria for the importance of the failure consequence (S)in process FMEA


The rating ‘O’ reflects the probability with which the failure type occurs as a consequence of acertain failure cause - without previous detection. Actions which have been introduced to avoidthe failure cause are analyzed and are assumed to be efficient.

32 Process FMEA

Process FMEAO - occurance probability


ppm*

Cpk Rating points

Very high It is almost certain that the type/cause offailure will occure very often.

1/10

1/20

100.000

50.000

- *

- *

10

9

High The type/cause of failure occurs repeatedly.Problematic, not a perfect design.

1/50

1/100

20.000

10.000

- *

- *

8 7

Moderate The type/cause of failure occurs occationally.Advanced design.

1/200

1/1000

1/2000

5.000

1.000

500

0,94

1,10

1,17

6 5 4

Low The probability that the type/cause of failure occursis low. Proven design.

1/15000

1/150.000

67

6,7

1,33

1,50

3 2

Unlikely. The occurence of the type/cause of failure isunlikely.

< 1/1500000 < 0,67 >1,67

1

*data not sensible

Table 13: Rating chart for probability of occurrence (O) in process FMEA



In the process FMEA, ‘D’ assesses the test and detection measurements of the production andassembly. The rating is oriented on verbal criteria or on the portion of non-detected parts inrelation to the portion of nonconforming items in the lot.

Actions within the process FMEA that make the detection of the failures possible only after theproduct release should be rated with D=10.

Process FMEA:E – detection probability

Certainty ofthe testingprocesses

Rating

UnlikelyThe failure is not detected or cannot be detected.

10

Very lowThe probability that the failure is detected is very low.

90% 9

LowThe probability of detecting the failure is low.

98% 87

ModerateThe probability of detecting the failure is moderate..

99,70% 654

HighThe probability of detecting the failure is high.

99,90% 32

Very highThe probability of detecting the failure is certain.

99,99% 1

Table 14: Rating criteria for probability detection (D) in process FMEA

Process FMEA 33

H14 (43-08/98)


The risk priority number is the product of S, O and D. This number shows the risk connected tothe failure cause and allows a rating of the failure causes.

2SWLPL]LQJThe RPN and the individual evaluations B, A and E show the risks. If there are high RPN orhigh individual ratings, improvement measures are necessary.

• The objective for safety relevance is O = 1. If this is not possible, you have to makesure with suitable detection measurements that no nonconforming products get to thecustomer.

• If there is a high probability of failures to occur, actions have to be taken whichensure the reaching of the quality objective. In general, this means that processes incontrol coincide with Cpk > 1,33 - 1,67 or A = 1 or 2.

In some areas, the following is valid:• If RPZ exceed a limit which is to be set (e.g. 125), actions for quality improvement

have to be taken.• If RPZ are close to the set limit (e.g. between 50 and 125) actions for continuos

improvement have to be taken to reach the quality objective at the production-start.



Failureeffects

C Failurecauses

Failureprevention

Failuredetection


(14)




If there are extreme concept changes, all steps of the FMEA are retaken for all concernedsections – from system structuring to optimizing.

The final assessment is done after the action has been taken and after the testing of itseffectiveness.

If a type of failure does not exist any longer because of the proposed action, the assessmentnumbers S, O, D, RPN are to be put equal zero. If a failure cause does not exist any longerbecause of an action, the assessment number for O and RPN are to be put equal to zero.Alternatively, the cancelled failure type/cause can be documented.

34 Cooperation with customer

6 Cooperation with customersCustomer contacts for FMEA are regulated by the K/VKK directive ‘Submittal of FMEA’s tocustomers’, dated 1/26/1995. Cooperation with customers takes place when the customerwhishes so on sight or after the FMEA is handed over or after a cooperaqtive preparation of asystem or interface FMEA.

FMEA presentation for customersThe FMEA presentation is usually performed and organized by the sales department togetherwith other responsible departments.

On the first presentation of a FMEA, the RB-FMEA-method and the used rating charts shouldbe explained.

The FMEA with regard to its contents should be presented by an employee of the responsibledepartment. System and design FMEA are usually done by the development department,process FMEA by the plant. The FMEA resume (enclosure...) can be handed over to thecustomer, if requested.

Details should be regulated specific to the division.

System or interface FMEA in cooperation with the customerA system or interface FMEA in cooperation with the customer investigates the functionallycorrect interaction of the input and output functions on the interface between RB and customercomponents of a system. This can be software or hardware components.

This can be conducted by FMEA moderators of RB or by the customer. The FMEA incooperation with the customer should be well prepared and structured by RB. First, ratingcharts have to be determined which are accepted by both parties.

Working on a system or interface FMEA in cooperation with the customer has to be approvedof by the responsible division.

Cooperation with supplier 35

H14 (43-08/98)

� &RRSHUDWLRQ�ZLWK�VXSSOLHUVBasis for the cooperation with the supplier is the guideline for suppliers. To guarantee thequality of fabricating parts, Bosch demands of its suppliers, among others, that they make a andpresent FMEA (supplier FMEA).

Procedure with (sub-) system or design FMEA

After the draft has been made by the supplier, the Bosch development department wants toinspect the (sub-)system of design FMEA through RN-MA (development and purchasedepartment) and wants to discuss the draft with the supplier.

Process FMEA procedure

After the production process has been planned by the supplier, the Bosch purchase departmentwants to inspect the process FMEA through RB-MA (production, quality assurance, purchasedepartment) and wants to discuss the production process with the supplier.

Representation of a FMEA-request− Product, component, drafts and article numbers− RB-specification, target specification or lists of functionally important measures

and characteristics.− Notes on the significance of failure consequences and their rating, specific to the

application of products.− Date of FMEA and discussion− Form for FMEA-summary

Criteria for FMEA discussion at supplier• Submittal of FMEA-summary• The FMEA of the supplier is comparable to the RB-FMEA-methodics• Assessment of the significance (S), occurrence probability (O) and detection

probability (D)• Introduction of actions with responsible persons and deadline• Scope of FMEA

36 Further FMEA-applications

� )XUWKHU�)0($�DSSOLFDWLRQV

,QWHUIDFH�)0($The interfaces between different systems, subsystems or components are analyzed in this typeof FMEA. The interface FMEA can be part of a system or design FMEA and is methodically asystem or design FMEA. It is done if required. The system development or product/componentdevelopment department is responsible for the internal interface FMEA. Initiation andpreparation of the external (with customer) interface FMEA by the RB system development orproduct/component department is preferred. The FMEA is done by RB in cooperation with thecustomer.

/RJLVWLFV�)0($The methodology of the logistics FMEA is comparable to that of the process FMEA. Thelogistics FMEA analyzes the logistical flow of products from receiving at Bosch until deliveryto the customer.

Logistics errors comprise a large portion of the customer complaints statistics. It is advisable toanalyze and evaluate these customer complaints with logistics FMEA.

Logistics procedure of a product• from packing at the end of the production line (usually end of process FMEA of the

assembly) to the delivery to the customer• from delivery of parts or materials to the receiving goods department at Bosch to the

delivery to the production line.

For the evaluation and assessment of the significance, the occurrence probability and thedetection probability, the rating charts of a process FMEA are used for the logistics FMEA aswell.

For the evaluation of the significance, the occurrence probability and the detection probability,the rating charts of the process FMEA are used.

FMEA for software 37

H14 (43-08/98)

)0($�IRU�VRIWZDUHBasic is the functional approach of the system FMEA . Analyzed can be, e.g.:

• the functional requirements and effects of their non-fulfillment• Failures on interfaces• Failures of individual software parts

The following premises are valid for the use of FMEA for software− For reasons of efficiency, this method is only used in the early development phases

before coding− Documents are required that are described on an abstract level (e.g. HW and SW

block diagram or SW architecture model).− Failures which occur during coding are not individually analyzed.− Procedure and form are adopted without a change− In some cases, the rating charts have to be adapted.

With a FMEA for software, a risk evaluation concerning quality characteristics reliability andsafety is made. This method can be used in various software improvement/refinement levels.So, in a top-down procedure, results of a higher level of the FMEA can be used again for thelevel which is momentarily analyzed.

Software can also be seen as part of the system of a system FMEA

)0($�IRU�FRQWURO�XQLWVSystem FMEA

Within the system FMEA of the whole system, the control units are regarded as black box. Insome cases, the main actions or in the system FMEA for electronic the component-level areinspected.

Function, redundancies and their functional failures and effects on the whole system areanalyzed. In case of analyzing SW-functions, their intersections to the outside are analyzed. Fora detailed analysis, other test techniques have proved to be good in the software development,e.g. reviews.

Apart from the system FMEA there are also failure simulations.

Design FMEA – mechanic proportion

The procedure of the mechanic proportion corresponds to the known design FMEA.

Design FMEA – electronic proportion

If the design of the electronic proportion is analyzed with FMEA, it has been succesful to buildthe wiring plan corresponding to the functional groups and to treat the functional groups likecomponents.

In the electronic development, procedures like design-rules, tolerance analyses, checklists anddesign-reviews have been also succesful.

38 Selection / prioritizing for FMEA

� 6HOHFWLRQ�3ULRULWL]LQJ�IRU�)0($To reach a possibly high effectiveness, i.e. to recognize and prevent failure possibilities as faras possible, a high level of specification is necessary for the functional analysis/systemstructuring. To keep up effectiveness and efficiency during implementation, the use of selectionand tightening approaches is useful.

6HOHFWLRQ�DFFRUGLQJ�WR�DSSOLFDWLRQ�FULWHULDA possibility for prioritizing /selection are application criteria. The more criteria listed aboveapply to a component/process, the more important is a FMEA:

• Customer requirements (FMEA)• Potential risk• Changed conditions for product usage• High depreciation in value when failure occurs• Basic new development of a product• Essential change• Parts important for functioning• Change of parts with correlation• Use of new materials, procedures• Recycling of problematic parts• Critical objective• Production transfer (new production line)

6HOHFWLRQ�ZLWK�4)'Quality Function Deployment (QFD) is a method for quality planning and communication.Above everything else, it serves a better and consistent planning of the individual qualitycharacteristics, from customer and development to production.

If a QFD is done for a product, it can be used for selection. Important and difficultcharacteristics should have priority.

)XUWKHU�SRVVLELOLWLHV�IRU�VHOHFWLRQCritical paths for critical failures of a system, component or process result from a system,functional and failure analysis according to the top-down principle (functional and fault treeanalysis). The critical failures which are part of subsystems, components, characteristics or sub-processes should have priority.

Relation to other methods 39

H14 (43-08/98)

�� 5HODWLRQ�WR�RWKHU�PHWKRGV

)0($�DQG�4XDOLW\�)XQFWLRQ�'HSOR\PHQW��4)'�Chronologically, the QFD method (Quality Function Deployment) comes before the applicationof a FMEA. QFD aims at converting customer demands on a product into technicalcharacteristics necessary for development and production.

Core of QFD is the ‘House of Quality’. In this document, the customer requirements are putopposite to the technical characteristics. And opposing requirements on the product are listed(e.g. small case seize, loss of power). Also possible in the House of Quality is the comparisonto products of competitors. The level of meeting the individual characteristics results in aproduct profile.

QFD should be used in the market analysis phases and conceptional phases. Apart from thedevelopment and sales departments, the product planning and marketing department should alsobe involved when applying this method.

QFD can lead to aspects important for following FMEA projects.

)0($�DQG�YDOXH�DQDO\VLVThe time of applying the value analysis (value engineering) mainly corresponds with the timeof starting the FMEA: from finishing the concept to the production-start. Both methods arebased on a systematic functional analysis but differ in their goals:

− FMEA failure prevention− Value analysis minimizing costs

However, minimizing costs should not have a negative impact on quality. The actions of aFMEA to prevent failures have an influence on the costs but do not always reduce costs.Preventing potential failures often includes investments in advance.

To prevent unnecessary work, the use of both methods has to be coordinated.

40 Relation to other mathods

)0($�DQG�7HDP�2ULHQWHG�3UREOHP�6ROYLQJ��7236�Whereas the FMEA methodically ‘looks into the future’ and analyzes the occurrence ofpotential failures, the TOPS method (Team Oriented Problem Solving) analyzes real problemswhose cause is unknown. For such an analysis, it is necessary to ‘look back into the past’ tofind out the reasons for the problems.

TOPS is based on a problem analysis just like Kepner-Tregoe. It was further developed in theautomobile industry (compare Ford “8D“=eight disciplines). With the systematic procedure ofTOPS, the problem is described, potential causes are found out, the actual cause is identifiedand certain actions are taken.

FMEA and TOPS complement one another:− To find out the reasons for a problem, a finished FMEA can be of help.− The basis for creating a new FMEA are the findings of problems with similar

products.

)0($�DQG�UHYLHZ�SURFHGXUHVReview procedures are mainly used for software development, but they can also be used inother areas (e.g. layout – review ).

Just like a FMEA, reviews are done according to a fixed order of sequence.

Other than that, FMEA and review have the following in common:• Main objective is the early failure detection and thus the prevention of failures in the

course of the system development.• Interdisciplinary team work with moderator• The result of the working group is dependent on the competence (system knowledge

and experience) and creativity of the team members.

The following are the differences of review procedures and FMEA:• Time

Reviews can already take place during concept finding/selection. The making of aFMEA makes sense if a system concept is at hand.

• Analyzed characteristicsWith a review, different quality characteristics like, e.g. usability or completeness (ofdemands) are tested, dependent on the selected technique.

• SequenceDifferent review procedures are used dependent on the test object, the objective andthe planned test expense. The FMEA is done according to a defined sequential plan ofevents whose main elements are risk analysis and risk evaluation.

Computer assistance 41

H14 (43-08/98)

�� &RPSXWHU�DVVLVWDQFH

,4�)0($IQ FMEA has been on the market since 1992 and is being continually developed further incooperation with users.

The five FMEA steps are supported by IQ FMEA through several editors who visualize the dataand guarantee an optimal access. IQ FMEA supports the Bosch form, and also the formsaccording to VDA and QS-9000. It is possible to switch between the different forms.

Databases can be installed and administered in several languages. The language of the programinterface can be dynamically switched; at the moment, German, English, French and Spanish.

IQ-FMEA can export complete databases as SGML, forms can be stored in HTML-format.Other export possibilities are (RTF, CSV, TXT, WMF, MPX).

• Prerequisites:− Sibylle for Windows requires an IBM-compatible PC (Processor 486 or higher).− Hard-Disk with 10 MB space− VGA (800 x 600 or more)− 12 MB memory for Win 3.x, 16 MB for Win 95, 24 MB for Win NT− MS-DOS Version 5.0 or higher (only for Win 3.x)− MS-Windows 3.1 or MS-Windows for Workgroups or Win 95 or NT

IQ-FMEA is available via the Intranet (at ZQF). Via the exchange-distribution list “IQ-FMEAUser“, information on IQ-FMEA are distributed. The news-group bosch.fmea.iqfmea isavailable for exchanging information.

The seminar TQ012 offers information on the making of a FMEA with IQ-FMEA.

6LE\OOH�IRU�ZLQGRZVSibylle for Windows is a program to prepare RB-standard documents for FMEA.

The RB-self-development can be received from your contact person or from the FTP-server inFrankfurt.

Sibylle is a transitional solution until IQ-FMEA is introduced and it substitutes the MS-DOSvariant of the program.

• Prerequisites:− Sibylle for Windows requires an IBM-compatible PC (Processor 486 or higher, at

least 4 MB memory). To print the FMEA, a postscript printer is recommended,other printers are also possible.

− For a graphical operating system, Microsoft Windows is required, at least Version3.1. The typeface Courier New has to be installed as True Type Face (TTF).

• Compatibility:− Sybille for Windows has command of the storage format of the MS-DOS variant.

So, FMEA between both programs can be exchanged.

42 Bibliography

�� %LEOLRJUDSK\References:

[CFG9000 (95)] Chrysler, Ford, General Motors (QS9000): Potential Failure Mode andEffects Analysis (FMEA). 2. Auflage 1995, Carwin Continuous Ltd.

[K/VKK (95)] RB: K/VKK-Vertriebshinweis - FMEA-Übergabe an Kunden. Stand:26.1.1995.

[QFDa] RB: QFD - Quality Function Deployment - Mit besseren Produktenschneller am Markt. (RB interne Unterlage - kann bei ZQF angefordertwerden).

[SWFMEA (96)] RB: Leitfaden für die Durchführung von FMEA für Software. Ausgabe 1.2(15.2.1996) (RB interne Unterlage - kann bei ZQF angefordert werden).

[TOPS (89)] RB: T.O.P.S. / 8 D - Leitfaden zur Problemlösung in der Projektgruppe.Ausgabe 8903/E5 (RB interne Unterlage - kann bei ZQF angefordertwerden)

[VDA4/2 (96)] VDA: Sicherung der Qualität vor Serieneinsatz - Band IV/2 - System-FMEA. 1. Auflage 1996, VDA.

Intranet:

[WWWzqf] ZQF: Web-Seite der Zentralabteilung Qualitätssicherung (ZQ) -Zentralstelle Qualitätsförderung (ZQF) - Methoden der Qualitätstechnik -FMEA - Software für FMEA (Einstieg:http://www.intranet.bosch.de/zq/zqf/index.htm).

Other literature:

[Mas (88)] Masing (Hrsg.), Handbuch der Qualitätssicherung, 2. Auflage, München1988

[MIL1629A (84)] Military Standard: MIL 1629A - Procedures for Performing a Failure Mode,Effects and Critically Analysis. Notice 2, November 1984.

[IEC812 (85)] IEC: Publication 812 - Analysis techniques for system reliability -Procedures for failure mode and effects analysis (FMEA). CEI 1985.

[BS5760 (91)] BSI: BS5760 - Reliability of systems, equipment and components - Part 5 -Guide to failure modes, effects and criticality analysis (FMEA andFMECA). Britisch Standard, 1991.

[DIN25448 (90)] DIN 25448 - Ausfalleffektanalyse (Fehler-Möglichkeits- und -Einfluß-Analyse). Mai 1990, DIN.

[DIN25424/1 (81)]DIN 25424 Teil 1 - Fehlerbaumanalyse - Methode und Bildzeichen.September 1981, DIN.

[DIN25424/2 (81)]DIN 25424 Teil 2 - Fehlerbaumanalyse - Handrechenverfahren zurAuswertung eines Fehlerbaums. April 19990, DIN.

[DIN25419 (85)] DIN 25419 - Ereignisablaufanalyse - Verfahren, graphische Symbole undAuswertung. November 1985, DIN.

[QFDb] RB: QFD - Quality Function Deployment - Mit besseren Produktenschneller am Markt - Information für Fach- und Führungskräfte. (RB interneUnterlage - kann bei ZQF angefordert werden).

Appendix 43

H14 (43-08/98)

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- Form English

44 Appendix

Appendix 45

H14 (43-08/98)

46 Appendix

$SSHQGL[��6KRUW�GHVFULSWLRQWhat does FMEA stand for?

‘FMEA’ is short for ‘Failure Mode and Effects Analysis’.

What are the objectives of FMEA?

FMEA is a method to qualitatively assess the failure of individual components in systems,products or processes. Objective of the FMEA is a systematic safety and reliability analysis.

Before the FMEA was introduced, it was only experiences of the past which were used when anew product was developed, i.e. failures which had occurred during or after the productionwere considered. The FMEA aims at the detection of potential failures before the production-start, i.e. during planning, development and design.

Potential failures are prevented by an early detection of weak points and the introduction ofappropriate actions. Thus, the safety and reliability of the products is improved.

When is the FMEA used?

The FMEA is used for• New developments• Changes on the product or procedure• Products with requirements concerning the safety technique• New usage conditions for existing products• Processes and services

Characteristics of the FMEA

The following characteristics are typical for the FMEA method:• systematic procedure with working plan and form• functional oriented approach• interdisciplinary work group – team work leads to creativity• preventive usage

The three FMEA types

Depending on the task or the unit, it is distinguished between system, process and designFMEA.

The system FMEA analyzes the correct functional interrelation of the system components andtheir connections. The goal is to avoid defects in system selection and layout and field risks.The system requirements are the basis for the analysis. The system development department isresponsible for the system FMEA. Note: The system FMEA can also be used in softwaredevelopment.

The design FMEA analyzes the design and layout of products/components according to thespecification to avoid design failures and process failures influenced by the design.

The process FMEA analyzes the process planning and performance for products/componentsaccording to the drawing specifications to avoid planning errors and manufacturing defects.Note: General processes like, e.g. services can also be analyzed with a process FMEA

Appendix 47

H14 (43-08/98)

What is done in the FMEA?

The individual steps in the FMEA are described in the FMEA-sequence plan (here shown asexcerpt):

0. Preparation and Planning • determine problem, problem definition and objective • team, sequential planning of action • materials for team • functional description

1. System structuring • numbering • component or working operations

2. Functional analysis • functions/characteristics

3. Failure analysis • potential types of failures • failure effects and failure causes

4. Risk assessment • failure prevention and failure detection • significance of failure effect (S) • occurance probability (O) • detection probability (D) • risk priority number RPN = S x O x D

5. Optimizing / Quality improvement • chose priority order of risks (analyze S, O, D and RPN) • determination of actions for improvement with R: and I: • introduction of actions for improvement • assess improvements (O,D)

When finishing a FMEA, it is important to give the members a feedback, to distribute thedocumentation and, if necessary, to present the findings. For current products, actualizing theFMEA on a regular basis is important.

Expense and prerequisites of a FMEA

A FMEA only fulfils its purpose if the requirements for completeness and correctness aregenerally met.

The correctness of the analysis is, e.g. guaranteed by a systematic procedure, clear evaluationcriteria, critical assessments (worst case) and an extensive exchange of information within thework team.

The completeness is reached by the analysis of all components or processes in order torecognize all possible failure modes. To shorten the FMEA, individual components can be leftout if they are uncritical despite worst-case inspection.

A frequent argument against a FMEA is its expense. Whereas the expense can be easilydetermined ‘if the books are well kept’, the savings cannot be exactly represented becausefailures which were not made and prevented changes can hardly be calculated.

The advantages of the FMEA, e.g.• Prevention of failures in design and development• Reduction of costs for later product changes• systematic recording of expert knowledge to

prevent repeated failures shows that the prevention of failures at the beginning of the life of aproduct can prevent higher costs at a later point in time.

48 Appendix

$SSHQGL[��4XHVWLRQV�RQ�WKH�FROXPQV�RI�WKH�IRUP


... -FMEA Page:Department:


FMEA-Number:Date:



Failureeffects

C Failurecauses

Failureprevention

Failuredetection


(1) (2) (3) (4) (5) (6) (7) (8) (9) (10) (11) (12) (13) (14)


Fig 4: The FMEA-form

Structuring

(2) Which components/processes are to be analyzed?

Functional analysis

(3) Which functions have to be fulfilled?

Failure analysis

(4) How could the function be negatively affected?

(5) Which are the consequences of the failure mode?

(7) Which failure causes are possible?

Risk assessment

(8a) Which actions are introduced to reduce consequences? (BM)

(10) How important is the consequence?

(8b) Which actions are introduced to prevent failures? (VM)

(11) How probable is the occurrence of the failure?

(9) Which actions to detect failures are taken?

(12) How probable is the detection of the failure?

(13) RPN = S x O x D (RPN)

Optimizing

(10 to 13) Where a high risks? (via S, O, D, RPN)

(14) Which actions are taken to reduce the risk?

(14) Who is responsible?

(14) Which deadline is planned?

Appendix 49

H14 (43-08/98)

,QGH[8D 40

Analyses 6

Base data 21, 28

Design FMEA 7, 8, 20, 21, 22, 23, 24, 25,27, 28, 34, 35, 36, 37, 46

Detection probability 18, 36, 47

DoE 23

Failure analysis 29, 47

FMEA

Chronological integration of the FMEA8

Functional analysis 47

Interface FMEA 34, 36

IQ-FMEA 14, 41

Kepner-Tregoe 40

Logistics-FMEA 36

Preparation 10, 20, 27, 34, 36, 47

Prioritizing 38

Process FMEA 7, 8, 11, 22, 27, 28, 29, 30,31, 32, 34, 35, 36, 46

QFD 38, 39, 42

Rating charts 36

Relevance of failure consequence 16, 17,23, 24, 31

Review 40

Risk evaluation 16, 23, 30, 40

Risk evalution 47

RPN 10, 18, 19, 23, 25, 26, 31, 33, 47, 49

Selection 38

Sequence plan 10, 14, 21, 28

Sibylle 41

Significance of failure consequence 47

Software

FMEA for software 37

Special characteristics 11, 15, 22, 29

Structuring 14, 21, 26, 28, 33, 34

System FMEA 7, 8, 13, 14, 15, 16, 18, 19,20, 29, 37

Team work 9, 11, 46

TOPS 40

Updating 11

Value analysis 39

Robert Bosch GmbHZentralstelleQualitätsförderung (ZQF)Responsible: Eilers

Telephone (07 11) 8 11-4 47 88Telefax (07 11) 8 11-4 51 55

Edition 08.1998

Robert Bosch GmbHZentralstelleQualitätsförderung (ZQF)Postfach 30 02 20D-70442 Stuttgart

Telefon (07 11) 8 11-4 47 88Telefax (07 11) 8 11-4 51 55

Stand 08.1998