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DFMEA MANUAL

Document DEM102Version 1

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COMPANY X Document #: DEM102 of 16 Electronic Original

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TABLE OF CONTENTS

SECTION DESCRIPTION PAGE

Title Page......................................................................................................................... 1Change Record................................................................................................................. 2Table of Contents............................................................................................................. 3

COMPANY X Document #: DEM102Version 1 of 16

1. INTRODUCTION................................................................................................................ 41.1 Purpose............................................................................................................................... 41.2 Referenced Documents....................................................................................................... 5

2. COMPLETING THE HEADER (SEE CIRCLED NUMBERS 1-5).....................................5

3. COMPLETING THE FOOTER (SEE CIRCLED NUMBERS 6-8)......................................6

4. FUNCTIONS (SEE CIRCLED NUMBER 9).......................................................................6

5. ITEMS (SEE CIRCLED NUMBER 10)...............................................................................7

6. POTENTIAL FAILURE MODES (SEE CIRCLED NUMBER 11)......................................7

7. POTENTIAL FAILURE EFFECTS (SEE CIRCLED NUMBER 12)...................................8

8. SEVERITY CRITERIA (SEE CIRCLED NUMBER 13).....................................................9

9. CLASSIFICATION (SEE CIRCLED NUMBER 14)..........................................................10

10. POTENTIAL CAUSES (SEE CIRCLED NUMBER 15)....................................................12

11. OCCURRENCE (SEE CIRCLED NUMBER 16)...............................................................13

12. CURRENT DESIGN CONTROLS (SEE CIRCLED NUMBER 17)..................................13

13. DETECTION (SEE CIRCLED NUMBER 18)...................................................................14

14. RISK PRIORITY NUMBER (RPN) (SEE CIRCLED NUMBER 19).................................15

15. RECOMMENDED ACTION(S) (SEE CIRCLED NUMBER 20)......................................15

16. RESPONSIBILITY (FOR RECOMMENDED ACTIONS) (SEE CIRCLED # 21)............16

17. ACTIONS TAKEN (SEE CIRCLED NUMBER 22)..........................................................16

18. RESULTING RPN (SEE CIRCLED NUMBER 23)...........................................................16

19. FOLLOW-UP..................................................................................................................... 16


DFMEA MANUALFOR COMPANY X AUTOMOTIVE SAFETY PRODUCTS

1. INTRODUCTION

1.1 Purpose

a) “In its most rigorous form, a FMEA is a summary of an engineer’s and the team’s thoughts (including an analysis of items that could go wrong based on experience and past concerns) as a component, subsystem, or system is designed. This systematic ap-proach parallels, formalizes and documents the mental disciplines that an engineer nor-mally goes through in any design process.” (from the Introduction of the AIAG FMEA Manual). As indicated in the quotation from the AIAG manual above, a DFMEA is a tool intended to help an engineer quantify and organize design issues identified during the normal course of the design process. The objective of a FMEA is to provide an “impartial” analysis of the design process so that the most “critical” design issues are addressed first, and the least critical last. Properly applied, this technique should in-crease the efficiency of the design process. The generic FMEA process defined in the AIAG Manual may work well for traditional automotive items, such as springs and bumpers, where there is an extensive design and experience base. However, it is not in-tuitively obvious how to apply such a technique to unique, one-shot, high-reliability safety devices such as airbag inflators. The purpose of this document is to clarify the AIAG manual’s guidelines and provide examples of how the technique can and should be efficiently used at COMPANY X to aid the design process. The FMEA discipline requires a Design FMEA for all new parts, changed parts, and carryover parts used in new applications or environments. It should be initiated by an engineer from the de-sign-responsible team, but should directly and actively involve representatives from all affected areas of COMPANY X.

b) Effective use of this tool requires a commitment to the technique, as well as a thorough understanding of the functional operation of the design being analyzed. The result of the DFMEA will be directly proportional to the quality of the technical input included in the analysis. Every new DFMEA should be a stand-alone document and should not reference a previous document. The DFMEA is a living document and should be initi-ated before or at design concept finalization, be continually updated as changes occur or additional information is obtained throughout the phases of product development, and be fundamentally completed before the production drawings are released for tooling. All open items should be closed out prior to release of a document. At the beginning of a new design program, it is recommended that the DFMEA be approached from a “top-down” perspective and conducted initially on the “full-up” design. As the design ma-tures, the DFMEA should be approached from a “bottom-up” perspective, beginning at the piece part level, and carried out through all the subassemblies to the top assembly.

c) The DFMEA should be prepared per the AIAG FMEA manual and this document, us-ing COMPANY X Form F-DEM101-3. This document has also drawn extensively


from the Delphi DFMEA Guidelines, which may be a useful reference tool in the preparation of a DFMEA. This manual will follow a step-by-step approach to complet-ing the DFMEA form to minimize its completion time and insure commonality of ap-proach at COMPANY X.

1.2 Referenced Documents

All referenced documents are the current, released version/revision.

COMPANY X

F-DEM101-3 Potential Design FMEA Form

AIAG

FMEA Potential Failure Mode And Effects Analysis (FMEA)

2. COMPLETING THE HEADER (SEE CIRCLED NUMBERS 1-5)

NOTE: Refer to the sample FMEA form in the back of this document for correspond-ing circled numbers.

1. Identify the “System:” (Inflator), “Subsystem:” (Subassembly), or “Component:” (Piece Part) being analyzed by PN. Identify the Model Year and Vehicle the inflator will be used in, if known.

2. The “key” date listed in the header is the date the production design is to be released and is also the planned release date of the DFMEA as a controlled document.

3. The FMEA document number is the prefix “DFMEA”, followed by the PN of the item being analyzed.

4. The preparer’s name and extension number should be included for the benefit of some-one who is reviewing the document, and may have questions or comments, but doesn’t know who to contact. It is also a requirement of our quality system to identify the indi-vidual responsible for the document.

5. Record the date the analysis was originated, as well as the date of the last revision.


3. COMPLETING THE FOOTER (SEE CIRCLED NUMBERS 6-8)

1. It is a requirement that the names and functions of the team members who contributed to/reviewed the FMEA be recorded. Recording of job functions provides immediate evidence of the use of cross-functional teams.

2. Identifying the page number is a useful tool for locating the specific item under discus-sion during a review.

3. Recording the reference location of the blank FMEA form, the file location, and the date printed are useful for historical and logistical traceability.

4. FUNCTIONS (SEE CIRCLED NUMBER 9)

The process begins by developing a listing of what the inflator assembly, subassembly, or piece part is expected to do (and what it is expected not to do), i.e., the design intent. This is a very important step in the analysis and can only be performed by an individual inti-mately familiar with the design and the customer’s requirements. The better the definition of the desired functions of the item, the easier it is to identify potential failure modes for corrective action. The function list should be as concrete as possible; minimize speculation and obtain the customer’s input, if possible, as to the function of the inflator in his/her appli-cation. Each function should be listed separately. A block diagram of the functions of the item may be a useful place to start. Some examples of typical inflator assembly functions are:

Provides gas/ pressure to deploy airbag Withstands expected vehicle dynamic environ-ments

Interfaces with customer module Maintains attachment to customer module

Provides structural integrity for the pressure vessel

Interfaces with vehicle/ airbag sensor electrical system

Withstands module loading conditions Provides corrosion protection prior to assem-bly into module

Provides inflator traceability information Maintains pressurant gas load in the inflator prior to actuation

NOTE: Other functions may be identified for various inflator applications.


5. ITEMS (SEE CIRCLED NUMBER 10)

The entries in this column are to be engineering specifications directly off the drawing for the component, subassembly, or top-level assembly, i.e., dimensions, notes, or items from the drawing’s parts list (subassembly & top assembly drawings). All of the dimensions, notes, etc., which affect compliance with a given function should be grouped together next to the entry for that function. Dimensions and notes may be listed more than once if they affect compliance with more than one function or more than one failure mode related to that function.

6. POTENTIAL FAILURE MODES (SEE CIRCLED NUMBER 11)

A potential failure mode is defined as the manner in which a component, subsystem, or in-flator assembly could potentially fail to meet the design intent. The potential failure mode may also be the cause of a potential failure mode in a higher level subsystem, or system, or be the effect of one in a lower level component. Avoid the temptation to focus excessively on the next-level customer application without having adequate information regarding the type of failure or its severity at that level. Obtain as much information from the customer as possible regarding failure modes, effects, and severity rankings related to COMPANY X’s inflator in their system. If this information is not readily available, confine analysis of the design to information provided in customer drawings and specifications. If more than one potential failure mode exists for each function, each mode should be listed as a separate en-try behind the function. The assumption is made that the failure could occur, but may not necessarily occur. Failure modes should be described as directly as possible in terms which define a failure to perform a function, i.e., “physical” or technical terms, not as a symptom noticeable by the customer. Typical, but not all-inclusive, inflator failure modes include:

Inflator does not inflate/fill airbag (or meet closed/open tank performance envelope)

Inflator does not maintain structural integrity prior to/during actuation

Inflator will not interface with/is misoriented to customer module

Inflator does not remain attached to module before/during actuation

Inflator fails to withstand dynamic environ-ments

Inflator does not maintain electrical interface with vehicle

Inflator fails to retain gas pressurant load prior to actuation

Inflator fails to withstand module loading con-ditions

Inflator corrodes excessively prior to module installation

Traceability information missing/illegible

NOTE: Other failure modes will be identified as different functions are identified.


7. POTENTIAL FAILURE EFFECTS (SEE CIRCLED NUMBER 12)

Potential Effects of Failure are defined as the effects of the failure mode on the function, as defined by the customer. It should be remembered that the “customer” may be internal, such as a member of the COMPANY X production department who may have to deal with the effects of a given failure, i.e., a failure of a hybrid inflator to hold pressure during the assembly process. Also, the effect of a failure in a component or low-level subassembly may be limited to the next level assembly and may not reach the top-level assembly at all. Functional failures which could impact safety or noncompliance to regulations should be identified. Speculative failure effects should be avoided. Some common inflator failure ef-fects are:

Inflator fails to deploy when actuated Ballistic performance compromised

Customer dissatisfaction Customer “No-Build”

Inflator traceability lost/ returned to COM-PANY X

Premature module deployment

Potential module/ airbag damage Inflator structural integrity compromised

Inflator deploys/ partially deploys prematurely Customer returns inflator to COMPANY X

Pressurant gas leaks prior to actuation Inflator functions in high-output mode when low-output mode is desired (dual-output infla-tors)

NOTE: Other failure effects may be identified.

8. SEVERITY CRITERIA (SEE CIRCLED NUMBER 13)

a) Severity is an assessment of the seriousness of the effect (listed in the previous column) of the potential failure mode to the next component, subassembly, full-up inflator, next-level or OEM customer, or the final consumer level, if it occurs. Customer input, if available, is extremely valuable in making severity determinations. Severity applies to the “effect” only. The DFMEA defines the minimum severity ranking for each failure mode. Severity numbers reflect the worst-case potential effect without regard to its oc-currence or detection probabilities.

b) The AIAG FMEA manual provides a list of generic severity criteria related to the auto-motive field. The AIAG information has been adapted to apply specifically to airbag inflators as detailed in the following list. Please note there is an attempt here to nar-rowly define severity rankings in quantifiable terms which are not subject to interpreta-tion. This is done to minimize debate over the number chosen for a particular effect.


The ranking system for Severity (and Occurrence and Detection numbers which follow) should be permanently attached to the DFMEA and published as a preamble of each re-vision.

Ranking Severity of Effect

12 Additional harm imparted to user of product or system (i.e., the inflator fails to maintain structural integrity when activated).

10 May affect performance of the vehicle’s safety system, compliance to governmen-tal regulations, and/or occupant safety issues without warning (i.e., the inflator does not fire due to a defective initiator, leakage of pressurant gas (hybrid infla-tors), degraded or “dudded” propellant, or some other defect which registers the in-flator nonfunctional).

9 Same as above, except the condition is recognized with warning.

8 High degree of customer (Tier 1 or OEM) dissatisfaction (i.e., inflator must be re-moved from module and replaced due to defect discovered after installation (re-call), etc.)

7 High degree of customer dissatisfaction (i.e., customer’s assembly plant shutdown due to entire inflator inventory determined to be non-usable (prior to module instal-lation), inflator cannot be assembled into module due to defective geometry or out-of-approved-configuration condition (no-build), orientation features misaligned (module plate, flange, end plug, stud), etc.).

6 Moderate degree of customer dissatisfaction (the inflator is operable, but at a re-duced performance level, i.e., inflates the airbag but with a pressure vs. time curve outside the specified requirement, inflator can be installed in module only with great difficulty due to out-of-approved-configuration condition, inflator can be in-stalled only with additional modification to the inflator or the module on the cus-tomer’s part, illegible or missing labels, etc.)

5 Moderate degree of customer dissatisfaction. Customer detects deterioration of perceived quality standards (i.e., workmanship and cosmetic appearance of inflator, weld blemishes which do not affect inflator structural integrity, variability in crimp appearance or other visible features despite demonstrated functional capability, propellant rattle, out-of-position or damaged, but legible, labels, etc.).

4 Moderate degree of customer dissatisfaction. Vehicle customer does not detect de-fect, but perceives standard for quality is low (i.e., corrosion on exterior of infla-tor, variation/inconsistencies in inflator finish or appearance, etc.).

3 Low customer annoyance if detected (i.e., discoloration in inflator appearance, poor paint or coating finish, etc.).


2 Low customer annoyance (i.e., occasional minor scratches and nicks on inflator surface, nonstructural shipping damage, etc.).

1 Customer cannot detect condition or results of failure (internal, non-degrading cor-rosion, pre-sheared shear ring (Gen II PSIR), etc.

9. CLASSIFICATION (SEE CIRCLED NUMBER 14)

This column should be used to highlight any ‘Special Characteristics’, as defined in QSP104, that have been identified for components, subassemblies, or full-up inflators that require additional process controls. In addition, if the DFMEA identifies any failure modes which fall under one of the following conditions, the failure mode must be identified as a Special Characteristic until the Special Characteristics Index (SCI) analysis, as specified in DEM101, can be conducted on the condition and a final decision made as to whether the Special Characteristic symbol must continue to be applied:

a) 6-2-1 Rule: If the Severity ranking of a particular failure cause/mechanism is greater than or equal to six (S≥6), and the Occurrence ranking is greater than or equal to two (O≥2), the Detection ranking must be a one (D=1). Conversely, if Detection in a spe-cific example can never be less than a 2 (D=2), then Occurrence must be a one (O=1). If neither of these conditions is met by the initial DFMEA analysis, the SCI analysis must be performed.

b) O≥4 Rule: If the Occurrence ranking is greater than or equal to 4, then Severity must be less than or equal to 5 (S≤5). If this condition is not met by the initial DFMEA analy-sis, the SCI analysis must be performed.


10. POTENTIAL CAUSES (SEE CIRCLED NUMBER 15)

The potential cause or mechanism for a failure is an indication of a design weakness, the consequence of which is the failure mode. List, to the extent possible, every conceivable failure cause and/or failure mechanism for each failure mode. The cause/mechanism should be listed as concisely and completely as possible so that remedial efforts can be aimed at pertinent causes. In a Design FMEA, all failure causes/ mechanisms should be limited to design-related issues. Process-related failure causes/mechanisms will be covered in the PFMEA. Typical design-related causes/mechanisms at COMPANY X include, but are not limited to:

Incorrect Material/Properties/Process Specified Part Overstressed (not designed to handle load)

Incorrect Algorithm Improper Drawing Dimensions/Tolerances Specified

Inadequate Weld Size/Chemistry/Geometry Specified

Improper Joint Design

Improper Booster/Propellant/Gas Quantity Specified

Improper Gap/Fit/Seal Between Mating Parts Specified

Inadequate Fatigue Resistance Specified Excessive/Inadequate Flow Area


11. OCCURRENCE (SEE CIRCLED NUMBER 16)

“Occurrence” is the likelihood that a specific cause/mechanism (listed in the previous col-umn) will occur. Occurrence should be based on actual statistical data for the condition based on similar designs, if available. By definition, the failure mode “occurs” when a ven-dor/COMPANY X internal/customer source identifies an out-of-tolerance condition. Once an “occurrence” number is assigned, removing or controlling one or more of the causes/mechanisms of the failure mode through a design change is the only way a reduction in the occurrence ranking can be effected. The following is a suggested ranking system for occur-rences:

Ranking Incidents*

10 60,0009 30,0008 15,0007 1,5006 1505 804 153 82 21 0

*Based upon actual supplier or COMPANY X internally-identified incidents and customer returns for the identified failure mode per 1,000,000 units (PRRo/PPMo) containing a similar design function and failure mode.

12. CURRENT DESIGN CONTROLS (SEE CIRCLED NUMBER 17)

a) List the prevention, design verification/validation (DV), detection, and other activities which will assure the design’s adequacy for the failure mode and/ or cause/ mechanism under consideration. Current controls (e.g., inspection and test programs, design re-views, mechanical analyses, mathematical & statistical studies, sample testing, feasibil-ity reviews, prototype tests, field (fleet) testing) are those that have been or are being used with the same or similar designs. There are three types of Design Controls/Fea-tures to consider; those that:

1. Prevent the cause/mechanism or failure mode/effect from occurring, or reduce its rate of occurrence.

2. Detect the cause/ mechanism and lead to corrective actions, and

3. Detect the failure mode.


b) The preferred approach is to use Type 1) controls first, if possible. Type 2) controls would be the second choice. Type 3) controls are the final choice. Type 1) controls de-termine the initial occurrence ranking, provided they are integrated as part of the design intent. The initial detection rankings will be based on the Type 2) or 3) current con-trols, provided the prototypes and models being used are representative of the design in-tent.

13. DETECTION (SEE CIRCLED NUMBER 18)

“Detection” is an assessment of the ability of the proposed current design controls (listed in the previous column) to detect a potential cause/mechanism (design weakness) or the subse-quent failure mode during a verification, validation, or preventative process. The ideal would be to identify the failure cause/mechanism, however, sometimes this is not possible. Sometimes only the failure mode can be detected, which is technically an indirect method since any given failure mode may have more than one potential cause or mechanism. (For example, a leak is a failure mode, but it may come from one of several locations and have one of several causes/mechanisms within an inflator.) Ranking numbers for probability of detection are defined in terms of the percent of the defective population which will be iden-tified by the specified design controls. In order to achieve a lower ranking, generally the planned design control activities have to be improved.

Ranking Likelihood of Detection by Specified Design Controls Percent**

10 Design Control will not and/or cannot detect a potential cause/mecha-nism and subsequent failure mode; or there is no Design Control.

0

9 Very remote chance the Design Control will detect a potential cause/mechanism and subsequent failure mode.

20

8 Remote chance the Design Control will detect a potential cause/mecha-nism and subsequent failure mode.

30

7 Very low chance the Design Control will detect a potential cause/mecha-nism and subsequent failure mode.

40

6 Low chance the Design Control will detect a potential cause/mechanism and subsequent failure mode.

60

5 Moderate chance the Design Control will detect a potential cause/mecha-nism and subsequent failure mode.

75

4 Moderately high chance the Design Control will detect a potential cause/mechanism and subsequent failure mode.

90

3 High chance the Design Control will detect a potential cause/mechanism and subsequent failure mode.

95

2 Very high chance the Design Control will detect a potential cause/mech-anism and subsequent failure mode.

99

1 Design Control will almost certainly detect a potential cause/mechanism and subsequent failure mode.

99.9999


** This number represents the percentage of defective units that will be detected by the inspec-tion/test techniques which are being used to identify defects or distinguish between acceptable and unacceptable items. (It does not refer to the percentage of the total population which is de-fective.)

14. RISK PRIORITY NUMBER (RPN) (SEE CIRCLED NUMBER 19)

a) The Risk Priority Number is the product of the Severity (S), Occurrence (O), and De-tection (D) rankings:

RPN = S x O x D

b) The Risk Priority Number is a measure of design risk. This value should be used to “rank” the order of concerns in a design, e.g., in Pareto fashion. The RPN will be be-tween “1” and “1200”. For higher RPN’s, the team must undertake efforts to reduce the calculated risk through corrective action(s). In general practice, regardless of the resultant RPN, special attention should be given when severity is high.

NOTE: See Section 9.0 herein (circled number 14) regarding the RPN number of items identified as potential “Special Characteristics”.

15. RECOMMENDED ACTION(S) (SEE CIRCLED NUMBER 20)

When the failure modes have been “ranked” by RPN, corrective action should be directed first at the highest ranked concerns and critical items. The intent of any recommended ac-tion is to reduce any one or all of the occurrence, severity, and/ or detection rankings. An increase in design verification/ validation actions will result in a reduction in the Detection ranking only. Only a design change which results in the removal or greater control of one or more of the causes of a failure mode can bring about a reduction in either the Severity or Occurrence rankings. Recommended actions can include Design of Experiments (DOE), margin test programs, design/ material changes, additional design verification and validation test programs, analyses or studies. If no actions are recommended for a specific cause, indi-cate this by entering a “None” in this column.

16. RESPONSIBILITY (FOR RECOMMENDED ACTIONS) (SEE CIRCLED # 21)

Enter the Individual(s)/Department(s) responsible for the recommended action and the tar-get completion date.


17. ACTIONS TAKEN (SEE CIRCLED NUMBER 22)

After an action has been completed and implemented, enter a brief description of the com-pleted activity and the completion date.

18. RESULTING RPN (SEE CIRCLED NUMBER 23)

After a corrective action has been implemented, estimate and record the resulting Severity, Occurrence, and Detection rankings. Calculate and record the resulting RPN. The “Result-ing RPN” and related ranking columns should be left blank until the identified action(s) have been completed. All Resulting RPN(s) should be reviewed and , if further action is considered necessary, repeat Sections 15.0 through 18.0 herein (circled numbers 20-23).

19. FOLLOW-UP

The assigned Core Engineer or Program Manager is responsible for assuring that all recom-mended actions have been implemented or adequately addressed. The FMEA is a living document and should always reflect the latest design level, as well as the latest relevant ac-tions, including those occurring after start of production.
