Failure Modes and Effects Analysis

(FMEA)

What is FMEA?

A method to define, identify, prioritize and eliminate known and potential failure of the system, design, or manufacturing process before they reach the customer.

· Identify failure modes

· Determine effect and severity

· Find causes of failures

· Develop action plans

· Facilitate dialog and documentation

FMEA Steps

1. Determine product or process functions.

· Active verb + measurable noun

· “What does this product/process do?”

· “How does it do that?”

· “If it is deleted, then what functions disappear?”

2. For each function note the acceptable operating limits and its sensitivity to aging, environment and manufacturing variability.

FMEA Steps

3. Determine failure mode of each function

· Ask, “What if this function fails to occur?”

· Extend the basic question with the clauses:

· …. at the right time (too soon or too late)?”

· …. in the right sequence?”

· …. to occur completely?”

· …. in the right amount (too much or too little)?”

· Also look for “Surprise” failure modes.

· Consider all use conditions. Brainstorm for unusual use conditions.

FMEA Steps

4. Identify the potential effect of each failure.

· If this failure occurs, what effect, consequences or ramifications will it have?

· If this failure occurs, what else might happen?

· Consider the effect to all customers. What exactly might they notice.

FMEA Steps

5. For each effect consider a severity or hazard.

FMEA Steps

6. Determine the cause(s) of the Failure mode.

· Types

· Design errors (errors in work already done)

· Manufacturing errors (errors in work already done)

· Operational errors (impossible??)

· Look for causes not symptoms

· Use Fishbone diagram, Fault tree of experiments

FMEA Steps

7. Identify corrective actions

· Mechanisms, methods, tests procedures, or controls to prevent the cause of the failure mode in the product.

· Prevention is better than shielding, which is better than controlling, which is better than warning.

· Want to detect potential failure modes early in design process.

· Use tests and analyses to study failure modes

· Include FMEA as part of process to evolve concepts into products

FMEA Steps

8. Develop action plan

· Increase probability of detection (reactive, not advised)

· Make failure mode easier to perceive

· Change maintenance procedure

· Reduce probability of occurrence

· Eliminate function

· Change design to eliminate cause

· Change design to decouple cause from effect

· Reduce severity of consequence

· Reduce severity of effect