Failure mode and effect analysis (FMEA) was one
of the first systematic techniques for failure analysis.
It was developed by reliability engineers in the 1950s
to study problems that might arise from malfunctions
of military systems
Most COMMON Types of FMEA's
Design (Potential) Failure Modes and
• Focus is on potential design- related failures
and their causes.
Process (Potential) Failures Modes and
• Focuses is on potential process failures and
● Focus is on potential process –related
failures and their causes.
▪Main drive is to understand the process through the
identification of as many potential failures as possible.
o e.g. Incorrect material used
● PFMEA typically assumes that the design
● Development of Recommended Actions is
targeted at eliminating the Root Cause of
the potential failures.
•Identifies Process Functions
•Identifies potential failure
•Assesses effect of failure!
•Identifies causes of failures!
•Identifies process controls!
•Identifies confirmed Critical
•Provides an objective base for
PFMEA's - who
•A team effort - including!
•However it is a moving feast
● Process Flow Diagram (PFD)
● Process Failure Mode and Effects
● Process Control Plan (PCP)
Diagram, P- Diagram,
Plan & Report
Using a simple mechanical pencil -conduct a Process FMEA
PFD Feeds PFMEA
Identify the Function(s)
● Function is a description of what the
Process does to meet the requirements
➢Related to process specification and product
➢Comes from the PFD operation description column
● Functions can be described as:
➢Do this operation…
➢To this part or material…
➢With this tooling or equipment…
Effect of Failure
but not to the
Fails height check
causing rework(3) if
corrosion leading to
2 types of controls
Prevent the Cause/mechanism or failure mode/effect from
occurring or reduce their rate of occurrence
Detect the cause/mechanism and lead to corrective action
Re-rating RPN After Actions Have
▪ Severity typically stays the same.
▪ Occurrence is the primary item to reduce / focus on.
▪ Detection is reduced only as a last resort.
▪ Do not plan to REDUCE RPN with detection actions!!!
o 100% inspection is only 80% effective!
o Reducing RPN with detection does not eliminate failure mode,
or reduce probability of causes
o Detection of 10 is not bad if occurrence is 1