Failure Modes Effect Analysis | FMEA

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

The FMEA Form
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

FMEA Inputs and Outputs
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.

Risk Priority Number (RPN)
Risk Priority Number (RPN)

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.