DESIGN FAILURE MODE EFFECTS ANALYSIS (DFMEA) PURPOSE OF DFMEA 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 Product Design Requirements –List of Specifications –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 –Experience with similar concepts, designs, and DFMEA –Customer and supplier inputs –Design guides and design standards (for example ASME codes)

DFMEA OUTPUTS Risk Priority Number (RPN) –RPN = (Severity) x (Occurrence) –Systems/components with high RPNs represent high risk items. Select/Define Remedial Actions based on design risk (where to focus additional development/implementation work)

DFMEA METHODOLOGY (1.) List components, subsystems, and/or functions –Start with the system, then subsystems, and finally components (2.) Document symptoms of failure –How could the design potentially fail to meet the design intent –Consider all types of failure (normal operation, start up, shut down, maintenance, user experience) (3.) Document the potential effects of failure –How would the design potentially fail to meet the design intent. –Some symptoms may have multiple effects (make an entry for each)

DFMEA METHODOLOGY: (CONTINUED) (4.) 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 (5.) Rate the severity of the failure effect (linked to the effects) 4 = Catastropic – failure causes substantial damage to the product itself or related items (including people), requiring remanufacturing 3 = Critical – failure causes significant damage to the product itself or related items, requiring repair of existing components 2 = Marginal – failure causes some damage to the product itself or related items, but limited operation is still possible 1 = Negligible – failure causes no significant damage but could be a nuisance to the operator/user

DFMEA METHODOLOGY: (CONTINUED) (6.) Rate the occurrence of the failure 5 = Very Probable – observed every time 4 = Probable – observed most times 3 = Occasional – observed multiple times during the project 2 = Remote – observed once or twice during the project 1 = Improbable – could be predicted to occur after hand-off (7.) Calculate the RPN of each potential failure effect –RPN = (Severity) x (Occurrence) –What are the highest RPN items? (8.) Classify failures by RPN (9.) Select and describe remedial actions –These could be design changes, tests, or revised operation procedures

DFMEA METHODOLOGY: (CONTINUED) (10.) Assign remedial actions (11.) Reassess severity/occurrence of anticipated failures and update RPN values Notes: Revise your DFMEA frequently! Make your DFMEA an ongoing instructor/team meeting item. Document your design changes and the rationale behind them.