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What is a Failure Mode and Effect Analysis (FMEA)?
Failure Mode and Effect Analysis (FMEA), also known as “Potential Failure Modes and Effects
Analysis” as well as “Failure Modes, Effects and Criticality Analysis (FMECA)” is a systematic
method for identifying possible failures that pose the greatest overall risk for a process,
product, or service which could include failures in design, manufacturing or assembly lines. A
process analysis tool, it depends on identifying:
1. Failure mode: One of the ways in which a product can fail; one of its possible deficiencies
or defects
2. Effect of failure: The consequences of a particular mode of failure
3. Cause of failure: One of the possible causes of an observed mode of failure
4. Analysis of the failure mode: Its frequency, severity, and chance of detection
An FMEA can be used when designing or improving a process.
Types of FMEA
There are currently two types of FMEA: Design FMEA (DFMEA) and Process FMEA (PFMEA).
Design FMEA
Design FMEA (DFMEA) is a methodology used to analyze risks associated with a new, updated
or modified product design and explores the possibility of product/design malfunctions,
reduced product life, and safety and regulatory concerns/effects on the customer derived from:
Material Properties (Strength, Lubricity, Viscosity, Elasticity, Plasticity, Malleability,
Machinability etc.)
The Geometry of the Product (Shape, Position, Flatness, Parallelism,
Tolerances/Stack-Ups
Interfaces with other Components and/or Systems (Physical Attachment/Clearance;
Energy Transfers; Material Exchange or Flow i.e. Gas/Liquid; Data Exchanges – Commands,
Signals, Timings)
Engineering Noise including User Profile, Environments, Systems Interactions &
Degradation
Process FMEA
Process FMEA (PFMEA) is a methodology used to discovers risks associated with process
changes including failure that impacts product quality, reduced reliability of the process,
customer dissatisfaction, and safety or environmental hazards derived from the 6Ms:
Man: Human Factors / Human Error
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Methods: Methods involved in processes of product/service including assembly lines,
supply chains and communications standards
Materials: Materials used in the process
Machinery: Machines utilized to do the work
Measurement: Measurement systems and impact on acceptance
Mother Earth: Environment Factors on process performance
Example: FMEA
The process is very straightforward, and begins by identifying all of the probable failure modes.
This analysis is based on experience, review, and brainstorming, and should use actual data if
possible.
New designs or processes may not have actual historical data to draw from, but "proxy" data
may be available from similar designs or processes. The next step is to assign a value on a 1-10
scale for the each of failure modes:
1. Severity, 2. Probability of occurrence, 3. Probability of Detection
After assigning a value, the three numbers for each failure mode are multiplied together to
yield a
Risk Priority Number = Severity x Occurrence x Detection
Severity: The severity of the failure mode is rated on a scale from 1 to 10. A high severity rating
indicates severe risk.
Occurrence (or Probability): The potential of failure occurrence is rated on a scale from 1 to 10.
A high occurrence rating reflects high failure occurrence potential.
Detection: The capability of failure detection is rated on a scale from 1 to 10. A high detection
rating reflects low detection capability.
The RPN becomes a priority value to rank the failure modes, with the highest number
demanding the most urgent improvement activity.
FMEA Example:
Here is an example of a simplified FMEA for a seat belt installation process at an automobile
assembly plant.
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As you can see, three potential failure modes have been identified. Failure mode number two
has an RPN of 144, and is therefore the highest priority for process improvement.
FMEA's are often completed as part of a new product launch process. RPN minimum targets
may be established to ensure a given level of process capability before shipping product to
customers. In that event, it is wise to establish guidelines for assessing the values for Severity,
Occurrence, and Detection to make the RPN as objective as possible.
Summary
The failure mode and effects analysis model can help teams decrease project scope and
complexity by focusing in on the primary failure modes of a process. Creating an FMEA is best
done by coordinating a cross-functional team and using objective and subjective knowledge to
identify accurate properties about the identified failure modes.
