Failure Modes Effect Analysis | FMEA

FMEA is a structured approach to:

• Identifying the ways in which a product or process can fail
• Estimating risk associated with specific causes
• Prioritizing the actions that should be taken to reduce risk
• Evaluating design validation plan (design FMEA) or current control plan (process FMEA)

Points to be covered

• To understand the use of Failure Modes Effect Analysis (FMEA)
• To learn the steps to developing FMEAs
• To summarize the different types of FMEAs
• To learn how to link the FMEA to other Process tools

Benefits of FMEA

• Allows us to identify areas of our process that most impact our customers
• Helps us identify how our process is most likely to fail
• Points to process failures that are most difficult to detect

Application Examples of FMEA

• Manufacturing: A manager is responsible for moving a manufacturing operation to a new facility. He/she wants to be sure the move goes as smoothly as possible and that there are no surprises.
• Design: A design engineer wants to think of all the possible ways a product being designed could fail so that robustness can be built into the product.
• Software: A software engineer wants to think of possible problems a software product could fail when scaled up to large databases. This is a core issue for the Internet.

What Is A Failure Mode?

• A Failure Mode is:
  The way in which the component, sub assembly, product, input, or process could fail to perform its intended function
  • Failure modes may be the result of upstream operations or may cause downstream operations to fail
• Things that could go wrong

Why FMEA ?

• Methodology that facilitates process improvement
• Identifies and eliminates concerns early in the development of a process or design
• Improve internal and external customer satisfaction
• Focuses on prevention
• FMEA may be a customer requirement (likely contractual)
• FMEA may be required by an applicable Quality Management System Standard (possibly ISO)

When to Conduct an FMEA ?

• Early in the process improvement investigation
• When new systems, products, and processes are being designed
• When existing designs or processes are being changed
• When carry-over designs are used in new applications
• After system, product, or process functions are defined, but before specific hardware is selected or released to manufacturing

History of FMEA

• First used in the 1960’s in the Aerospace industry during the Apollo missions
• In 1974, the Navy developed MIL-STD-1629 regarding the use of FMEA
• In the late 1970’s, the automotive industry was driven by liability costs to use FMEA
• Later, the automotive industry saw the advantages of using this tool to reduce risks related to poor quality

The FMEA Form

Types of FMEAs

• Design
  Analyzes product design before release to production, with a focus on product function
  Analyzes systems and subsystems in early concept and design stages
• Process
  Used to analyze manufacturing and assembly processes after they are implemented

FMEA: A Team Tool

• A team approach is necessary.
• Team should be led by the Process Owner who is the responsible manufacturing engineer or technical person, or other similar individual familiar with FMEA.
• The following should be considered for team members:
  – Design Engineers – Operators
  – Process Engineers – Reliability
  – Materials Suppliers – Suppliers
  – Customers

FMEA Procedure

• For each process input (start with high value inputs), determine the ways in which the input can go wrong (failure mode)
• For each failure mode, determine effects
  • Select a severity level for each effect
• Identify potential causes of each failure mode
  • Select an occurrence level for each cause
• List current controls for each cause
  • Select a detection level for each cause
  • Calculate the Risk Priority Number (RPN)
• Develop recommended actions, assign responsible persons, and take actions
  • Give priority to high RPNs
  • MUST look at severities rated a 10
• Assign the predicted severity, occurrence, and detection levels and compare RPNs

FMEA Inputs and Outputs

 

Severity, Occurrence, and Detection

• Severity
  • Importance of the effect on customer requirements
• Occurrence
  • Frequency with which a given cause occurs and
    creates failure modes (obtain from past data if possible)
• Detection
  • The ability of the current control scheme to detect
    (then prevent) a given cause (may be difficult to estimate early in process operations).

Rating Scales

• There are a wide variety of scoring “anchors”, both quantitative or qualitative
• Two types of scales are 1-5 or 1-10
• The 1-5 scale makes it easier for the teams to decide on scores
• The 1-10 scale may allow for better precision in estimates and a wide variation in scores (most common)

• Severity
  • 1 = Not Severe, 10 = Very Severe
• Occurrence
  • 1 = Not Likely, 10 = Very Likely
• Detection
  • 1 = Easy to Detect, 10 = Not easy to Detect

Risk Priority Number (RPN)

RPN is the product of the severity, occurrence, and detection scores.

Summary

An FMEA:

• Identifies the ways in which a product or process can fail
  • Estimates the risk associated with specific causes
  • Prioritizes the actions that should be taken to reduce risk
• FMEA is a team tool
• There are two different types of FMEAs:
  • Design
  • Process
• Inputs to the FMEA include several other Process tools such as C&E Matrix and Process Map.