Purpose of dfmea design failure mode effects analysis
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PURPOSE OF DFMEA (DESIGN FAILURE MODE EFFECTS ANALYSIS). Identify , quantify , and reduce design risk (especially for critical systems) Provide a traceable document for making design decisions Prioritize which design activities to pursue next

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Purpose of dfmea design failure mode effects analysis
PURPOSE OF DFMEA(DESIGN FAILURE MODE EFFECTS ANALYSIS)

  • Identify, quantify, and reduce design risk(especially for critical systems)

  • Provide a traceable document for making design decisions

  • Prioritize which design activities to pursue next

  • NOTE: A DFMEA is not a one meeting activity(It needs to evolve with the product)


Dfmea inputs
DFMEA INPUTS

  • Product Design Requirements

    • Design requirement document (if available from customer)

    • Legal and technical regulations

  • Bill of Materials (BOM) and Specific Hardware

    • List of components

    • Components and/or samples as supplied by the customer

  • Product Definition

    • Drawings, sketches, animations, and simulations

    • Description of systems and components

  • Previous Experience (Lessons Learned from Others)

    • Experience with similar concepts, designs, and DFMEA

    • Customer and supplier inputs

    • Design guides and design standards (for example ASME codes)


Dfmea outputs
DFMEA OUTPUTS

  • RAN: Risk Assessment Number

    • RAN = (Severity) x (Occurrence) x (Detection)

    • Identification of both systems and components with high RAN values represents a summary of high risk items.

  • Identification of Critical and Significant Characteristics

    (This is also normally required by a customer)


Dfmea methodology
DFMEA METHODOLOGY

  • (1.) Complete the top of the form

    • Project, year, team members, date, and DFMEA iteration

  • (2.) List items and functions

    • Start with the system, then subsystems, and finally components

  • (3.) Document potential failure modes

    • How could the design potentially fail to meet the design intent

    • Note: this might be the cause of failure at a higher level (i.e. component to subsystem) or the effect of a failure at a lower level.

    • Consider all types of failure

  • (4.) Document the potential effects of failure

    • How would the design potentially fail to meet the design intent.


Dfmea methodology continued
DFMEA METHODOLOGY: (CONTINUED)

  • (5.) Rate the severity of the failure effect

    (linked to the effect of the failure)1 = device operable with minor loss of functionality 2 = device operable with significant loss of functionality 3 = device damaged and inoperable, but repair is possible 4 = device damaged beyond repair 5 = failure causes moderate to severe operator injury

  • (6.) Document potential causes and mechanisms of failure

    • Failure causes and mechanisms are an indication of design weaknesses

    • Potential failure modes are the consequences of the failure causes

    • A single failure mode may have multiple failure mechanisms

    • Don’t be afraid to identify as many potential causes as you can


Dfmea methodology continued1
DFMEA METHODOLOGY: (CONTINUED)

  • (7.) Rate the occurrence of the failure1 = likely to occur at some point in product testing2 = likely to occur periodically across multiple test sessions3 = likely to occur during almost every test session

  • (8.) List the design controls

    • Design controls are intended to:

      • Prevent the cause of the failure mode (1st choice solution)

      • Detect the cause of the failure mode (2nd choice solution)

      • Detect the failure mode directly (3rd choice solution)

    • Applicable design controls include

      • Predictive code analysis, simulation, and modeling

      • Tolerance “stack-up” studies

      • Prototype test results (acceptance tests, DOE’s, limit tests)

      • Proven designs, parts, and materials


Dfmea methodology continued2
DFMEA METHODOLOGY: (CONTINUED)

  • (9.) Rate the detectability of the failure1 = uses sensors and active controls to avoid upset condition2 = uses operator training/procedures to spot imminent failure3 = fails without warning

  • (10.) Calculate the RAN of each potential failure effect

    • RAN = (Severity) x (Occurrence) x (Detection)

    • What are the highest RAN items?

  • (11.) Define recommended actions

    • These could be design changes, tests, or revised operation procedures


Dfmea methodology continued3
DFMEA METHODOLOGY: (CONTINUED)

  • (12.) Assign action items

  • (13.) Complete “Action Results” Section of DFMEA

    • Change ratings if action results justify adjustment, but the rules are:

      • Severity: May only be reduced through elimination of the failure effect

      • Occurrence: May only be reduced through a design change

      • Detection: My only be reduced through improvement and additions in design control (i.e. a new detection method, better test methodology, better codes)

  • (14.) Repeat: undertake the next revision of the DFMEA

    Revise your DFMEA frequently!

    Include documentation of your results!


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