Exercise Quality Management

Transcription

1 Quality Management Prof Schmitt Exercise 09 Exercise Quality Management 09 Failure Mode and Effects Analysis Dipl-Ing Dipl-Wirt Ing Michael Vorspel-Rüter Dipl-Ing Dipl-Wirt Ing Michael Vorspel-Rüter Group Business Excellence & Development Department Quality Management Chair of Metrology and Quality Management Steinbachstr 25 (ADITEC), D Aachen, Tel: +49 (0) Fax: +49 (0) URL: Failure Mode and Effects Analysis E 09 page 0

2 Quality Management Prof Schmitt Exercise 09 Example - FMEA Design Execution of a design FMEA based on the example of a: corkscrew Seite 1 Failure Mode and Effects Analysis E 09 page 1

3 Quality Management Prof Schmitt Exercise 09 What is FMEA? FMEA = Failure Mode and Effects Analysis or: Fehler-Möglichkeits- und Einfluss-Analyse FMEA is a quality planning technique, ie it is used in INNOVATIVE development and manufacturing processes Targets: To forecast and reveal possible failures and to avoid them by implementing appropriate measures To document know-how (eg What can go wrong at which point in turning process? What parameters are important?) Inter-departmental interface for the exchange of expert knowledge (Personal communication is encouraged) Seite 2 Failure Mode and Effects Analysis E 09 page 2

4 Quality Management Prof Schmitt Exercise 09 Basic Methodology of FMEA Basic Methodology of FMEA Effectiveness of FMEA Definition of Contents Preventive Application Team Work are preconditions for Eg Reducing the cost of quality (source T Pfeifer) Actual status FPC TC Target status FPC Systematic approach FC TC FC Legend: FPC = Failure Prevention Cost FC = Failure Cost TC = Testing Cost Seite 3 Failure Mode and Effects Analysis E 09 page 3

5 Quality Management Prof Schmitt Exercise 09 FMEA Failure Costs FMEA is a preventive approach, ie weaknesses are recognized and eliminated at an early stage System-FMEA Process 100,- Costs per Failure System-FMEA Product -,10 1,- 10,- Planning Idea to product Process planning Demand on stock Final inspection Product in use Seite 4 Failure Mode and Effects Analysis E 09 page 4

6 Quality Management Prof Schmitt Exercise 09 FMEA Teamwork Preparation in centers of competence Used information (eg): Tolerance Analysis, dimensioning process feasibility failure lists techn drawing Task of the moderator: Project planning and - organisation Documentation, evaluation Assure methodological correctness Moderation of conversation Decision finding in team Team selection (example) responsible permanently involved temporarily involved design moderator process planning quality assurance development procurement Seite 5 Failure Mode and Effects Analysis E 09 page 5

7 Quality Management Prof Schmitt Exercise 09 FMEA Process I Organisational preparation Choose processes / products f FMEA Build up teams Specify dates II Description of the object to be analysed What should be included in the analysis? What is the relation between the object and the environment? Clear definition of focus and borders of investigation? III Functional Analysis Functions Malfunctions Interface functions V Evaluation of failures Significance grade Occurrence probability grade Detection evaluation grade VI Measures Identification of weak points Definition of measures Responsibility and schedule VII Updating measures already implemented Estimation of residual risk Field FMEA IV Identification of potential failures Potential failures Potential effects of failures Potential causes for failures Seite 6 Failure Mode and Effects Analysis E 09 page 6

8 Quality Management Prof Schmitt Exercise 09 To Task I: FMEA Checklist (eg) FMEA-criteria: Weighting Evaluation Result Evaluation Result Degree of innovation Technology Legal requirements Innovative development New type of design Use of new materials New manufacturing techniques Other conditions of use No similar product on market Critical process Complex product Statutory regulations Safety part In this example: The corkscrew is more important Cork- screw knife Seite 7 Failure Mode and Effects Analysis E 09 page 7

9 Quality Management Prof Schmitt Exercise 09 To Task II: Description of the object to be analysed II1: Identify the system structure II2: Identify the level of analysis Level of structure A B C D Level of structure A B C D : System elements : System elements Seite 8 Failure Mode and Effects Analysis E 09 page 8

10 Quality Management Prof Schmitt Exercise 09 To Task III, IV: Definition of functions and malfunctions III1: Identify the function of every system element System element III2: Specify potential malfunctions System element IV: Linking of malfunctions to the failure net Level of structure (eg) A B C FE F FC Function 1 Malfct 1 Malfct A1 Malfct C1 Function 2 Function 3 Malfct 2 Malfct 3 Malfct A2 Malfct An Malfct B1 FE : Failure Effect F : Failure FC : Failure Causes Malfct C2 Malfct Cm Seite 9 Failure Mode and Effects Analysis E 09 page 9

11 Quality Management Prof Schmitt Exercise 09 To Task V: Evaluation Malfct A1 Malfct A2 Malfct An Malfct B1 Malfct C1 Malfct C2 Malfct Cm Failure Chain Failure Effect Failure Failure Causes! Risk numbers R n S R n D R n O Significance Detection evaluation grade Occurrence probab evaluation grade Hint: Evaluation follows the actual implemented measures consider initial measures! Seite 10 Failure Mode and Effects Analysis E 09 page 10

12 Quality Management Prof Schmitt Exercise 09 To Task V: Evaluation of failures Risk Priority Number = R n O x R n S x R n D Measure of existence of a weak point extends from 1 (low risk) to 1000 (high risk) How likely is this failure cause? Probability that the cause of this failure occur from 1 (improbable) to 10 (probable) How severe is this failure effect? The effect of the failure on the customer from 1 (no effect) to 10 (eg endangering safety of the customer) How likely is it that this failure cause will be detected? Probability that the failure cause will be discovered prior to delivery to customer from 1 (probable) to 10 (improbable) Seite 11 Failure Mode and Effects Analysis E 09 page 11

13 Quality Management Prof Schmitt Exercise 09 To Task VI: Risk minimisation procedure Risk analysis based on implemented measures No Risk? Specify Introduce Review Yes Risk minimisation Measures with date and competence Effect limiting Remedial Detection End Seite 12 Failure Mode and Effects Analysis E 09 page 12

14 Quality Management Prof Schmitt Exercise 09 To Task VI: Risk identification I Risk-Identification is based on classified, partly subjective evaluations Risk Identification cannot be done on the basis of fixed rules or limits Risks can only be prioritised relatively to each other The following methods of risk-identification and determination of appropriate measures must therefore be verified from the engineers point of view Seite 13 Failure Mode and Effects Analysis E 09 page 13

15 Quality Management Prof Schmitt Exercise 09 To Task VI: Risk identification II Identify necessity for measures Specify limit values for the risk Eg: RPN > 124 and RN 'significance' > 8 & RN occurrence > Pareto- Analysis (cover 80%) ID 1 ID 2 ID 3 ID 4 ID 5 % Sum(%) Risk evaluation Failure causes Measures O S D Ideal condition (target) no measures (nm) insignificance, rare failure nm Failure does not reach user nm Failure reaches user yes frequent failure, identifiable, expensive yes frequent failure, reaches user yes serious, frequent failure yes difficulties yes, yes, yes!!! Seite 14 Failure Mode and Effects Analysis E 09 page 14

16 Quality Management Prof Schmitt Exercise 09 To Task VI: Pareto Chart (eg) ID 1 RPN 460 % 63,3 Sum (%) 63, % ,2 11,2 80,5 91, Chart of RPN- % % Sum(%) ,5 97, , ID 1 ID 2 ID 3 ID 4 ID 5 Total Chart of absolute RPN (combined with %) abs Sum(%) 80% 50 0 ID 1 ID 2 ID 3 ID 4 ID 5 Seite 15 Failure Mode and Effects Analysis E 09 page 15

17 Quality Management Prof Schmitt Exercise 09 To Task VI: Determination of measures Basis: The RPN- priorised chains of failures For each single risk number (R N S, R N D, R N O) specific measures can be determined (see below) For the reduction of Total- RPN it usually makes sense, first to reduce the single R N with highest scores by appropriate measures Note measures always with the responsible person and date! Failure chain Failure effect Failure cause Risk numbers R N S R N D R N O Significance Detection evaluation grade Occurrence probab evaluation grade Measures Effect limiting Detection Remedial Seite 16 Failure Mode and Effects Analysis E 09 page 16

18 Quality Management Prof Schmitt Exercise 09 Example Corkscrew Rivets Casing Spiral shaft Levers Seite 17 Failure Mode and Effects Analysis E 09 page 17

19 Quality Management Prof Schmitt Exercise 09 Step II 1 (and II 2) Identification of system structure Level of structure A Level of structure B Level of structure C Gear rod Spiral shaft Cork thread Bore- hole Corkscrew Lever Casing Thread Rivet hole Guidance Rivet Construction Cases Seite 18 Failure Mode and Effects Analysis E 09 page 18

20 Quality Management Prof Schmitt Exercise 09 Step III 1 Identify functions of every system element Level of structure A Level of structure B Level of structure C Spiral shaft to center to transmit tractive force Gear rod Form closure with lever enable rotation to the lever transmit tractive force to lever Cork thread Corkscrew to pull cork as a whole Casing Positioning on bottles to center spiral shaft to bring up counter moment screwing in form closure with cork (transmit tractive f to the cork) Rivet hole to retain rivets Guidance to allow vertical movement and rotation to prevent tilting Seite 19 Failure Mode and Effects Analysis E 09 page 19

21 Quality Management Prof Schmitt Exercise 09 Step III 2 Specify potential malfunctions Level of structure A Level of structure B Level of structure C Corkscrew Spiral shaft Difficult to turn/ impossible slanty spiral shaft no tractive force transmittable Gear rod no form closure with lever incompatible with lever Cork thread difficult to turn no form closure Cork breaks Bottle gets damaged Cork gets stuck Casing slips down from bottle Spiral shaft tilted difficult to turn spiral shaft Rivet hole Rivets can not be assembled Rivets fall out Shaft- Guidance too much play Guidance is clamping Seite 20 Failure Mode and Effects Analysis E 09 page 20

22 Quality Management Prof Schmitt Exercise 09 Corkscrew: Step IV Linking of malfunctions to the failure net I II Example: Cork gets stuck Cork gets stuck No tractive force transmittable Difficult to turn spiral shaft Malfct A1 Malfct A2 Malfct An Malfct B1 No form closure with lever possible Tooth profile incomp with lever Malfct C1 Malfct C2 Malfct Cm III IV Cork breaks Bottle gets damaged Spiral shaft tilted Shaft- Guidance has too much play V VI Cork breaks Bottle gets damaged Slanty spiral shaft Cork thread without form closure Seite 21 Failure Mode and Effects Analysis E 09 page 21

23 Quality Management Prof Schmitt Exercise 09 Corkscrew: Step V Valuation Failure chain Failure Effect Failure Failure Causes! Risk numbers Measures R n S R n D R n O Significance Effect limiting measures Detection evaluation grade Suggested detection measures Occurrence prob evaluation grade Suggested remedial measures This part will be processed in the exercise Type/model /m anufacture/batch: System no/system element: Function/Task: No Poss S Conseq Control no Failure Mode and Effects Analysis System-FMEA Product System-FMEA Process Page 1of 1 Subject no Responsibility: Dept : Status: Company: Date: Subject no: Responsibility: Dept : Status Company: Date: Poss Poss Remedial D Identific O RPN Responsibility/ f ailures Causes measures Measures Due date S= evaluation grade Si gnifi cance D= Detectio n evalutation grade O = Occurance evaluation grad e Risk Priority Number RPN = S*D*O Seite 22 Failure Mode and Effects Analysis E 09 page 22

24 Quality Management Prof Schmitt Exercise 09 Blank VDA Form (1996) Type/Model/ manufacture/batch: Corkscrew System- No/System- element: Failure Mode and effects analysis System FMEA Product System FMEA Process Subject No: 90 HF AA Status: A/ /KC Guarantor: J Student Firma: FMEA No: Page: Dept: MQ Date: No Possible Failure effect S Poss Failure Poss Failure Remedial O Detection D RPN R/D causes measures measures Seite 23 Failure Mode and Effects Analysis E 09 page 23

25 Quality Management Prof Schmitt Exercise 09 Corkscrew: Pareto Chart ID RPN % Sum (%) Total % 10 0 ID 1 ID 2 ID 3 ID 4 ID 5 ID 6 ID 7 Seite 24 Failure Mode and Effects Analysis E 09 page 24

26 Quality Management Prof Schmitt Exercise 09 Attachment: Criteria for the evaluation grade of the System-FMEA Product Severity evaluation grade S Very high 10 Safety risk, violation of legal regulations 9 High 8 7 Moderate 6 Operability of the vehicle is restricted, immediate stay in the garage is not obligatory, 4 disturbance of fundamental control elements Low 3 2 Operability of the vehicle is constricted, immediate stay in the garage is obligatory, disturbance of the system Low disturbance of the system, remedy of defects near the next regular stay in the garage, disturbance of fundamental control elements Unlikely 1 Unlikely that the failure will have any perceptible consequences, customer will probably not perceive the failure Seite 25 Failure Mode and Effects Analysis E 09 page 25

27 Quality Management Prof Schmitt Exercise 09 Attachment: Criteria for the evaluation grade of the System-FMEA Product Detection grade D Unlikely 10 9 Detection of failure causes is unlikely; the reliability of design could not be proved Low 8 7 Detection of failure causes is less probable; the reliability of the design cannot be proved Testing methods are quiet reliable Moderate 6 Detection of the occurred failure cause is probable; the reliability of the design cannot be 5 proved; testing methods are quiet reliable 4 High 3 Detection of the occurred failure cause is very probable and can be proved using different 2 testing methods Very High 1 The occurred failure cause will be surely detected Seite 26 Failure Mode and Effects Analysis E 09 page 26

28 Quality Management Prof Schmitt Exercise 09 Attachment: Criteria for the evaluation grade of the System-FMEA Product Occurrence evaluation grade O Very high 10 The failure cause occurs very often Inadequate and unsuitable design 9 High 8 7 The failure cause occurs redundantly; problematic, immature design Moderate 6 Failure cause occurs intermittently; suitable, pretty mature design 5 4 Low 3 2 The probability of occurrence of the failure cause is low; reliable design Unlikely 1 The occurrence of the failure cause is unlikely Seite 27 Failure Mode and Effects Analysis E 09 page 27