FMEA Process Flow – Failure Mode and Effect of Failure Mode

Potential Failure Mode of the Function

* The ways in which the part could fail to perform its intended design function.. it should be described in a “negative” way.
* Stress how the part could fail, not whether it will fail, to conform to the design specification
* Try asking what could happen to cause a loss of function:
– “How could this part fail?”, or
– “Could it break, deform, wear, corrode, bind, leak, short, open, etc.?”

FMEA-Process-Flow

* Examples of failure modes:
– Isolate electrical data signals → loss of dielectric
– Provide mating surface to part B → worn mating surface
– Provide dielectric material for impedance →  loss of signal transmission integrity
– Provide engaging tab for cam →  bent tab
– Corrosion – Cannot assemble   – Over-deflection

Assume
that the failure could occur for now. Later we will deal with the likelihood of its occurrence. Refer back to the list of functions when asking the What If questions. Also refer back to the FTA to help ensure completeness here.

List each potential failure mode for the part. Note that for these examples, the failure modes are shown following the part’s basic functions (optional).

Other possible failure modes could be a part oxidizing, fracturing, sticking, loosening, not transferring a force, not assembling readily with a mating part, drift, disengaging during operation, etc.

FMEA Process Flow – Effect of Failure Mode

FMEA-Process-Flow-Effect-Of-Failure-Mode

Potential Effect(s) of the Potential Failure Mode

* The outcome of the occurrence of the failure mode on the part or assembly (system).
* Describe the effect of the failure specifically, and in terms of customer reaction: “What does the customer (external or internal) experience as a result of the failure mode of…” or  “Will the component or assembly be inoperative, intermittently operative, noisy, not durable, etc.?”
* Consider whether the effect can also impact other functions or parts.

Examples of effects:

* Loss of dielectric →  low withstanding voltage → assembly shorts out
* Bent tab →  cannot assemble mating part
* Worn mating surface → mating part does not engage
* Loss of signal transmission integrity → incorrect data transmission
* Tab edge does not engage cam → auxiliary bolt sticks
* Cannot assemble → lost time and wasted costs in Final Assembly
* Corrosion → part loses yield strength, with a lower MTBF

<<< DFMEA – Function of the PartDFMEA – Chain of events >>>
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