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Wednesday, February 15, 2023

The Prevention Power of Failures Modes and Effects Analysis (FMEA)

Failure modes and effects analysis (FMEA) is a step-by-step approach for identifying all possible failures in a design, a manufacturing process or assembly process, or a final product or service. “Failure modes” means the ways, or modes, in which something might fail. Failures are any errors or defects, especially ones that affect the customer and can be potential or actual. “Effects analysis” refers to studying the consequences, or effects, of those failures.

What Is An FMEA?
  • A tool used to evaluate potential failure modes and their causes.
  • Prioritizes Potential Failures according to their Risk and drives actions to eliminate or reduce their likelihood of occurrence.
  • Provides a discipline/methodology for documenting this analysis for future use and continuous process improvement.
This analytical technique is used by manufacturing / engineering teams as a means to assure that, to the extent possible, potential failure modes and their associated causes or mechanisms have been considered and addressed. Due to its systematic approach it has a number of benefits for process and product development and improvement.

Why do FMEA? 
  • Identifies potential “manufacturing or assembly” process failure modes.
  • Identifies potential “product related” process failure modes.
  • Assesses the potential customer effects of the failures.
  • Identifies operator safety concerns.
  • Identifies process variables on which to focus controls for occurrence reduction / elimination or detection of the failure conditions.
  • Develops a ranked list of potential failure modes ranked according to their affect on the customer, (both external & internal), thus establishing a priority system for corrective actions.
  • Feeds information on design changes required and manufacturing feasibility back to the design community.
Ultimately, this methodology is effective at identifying and correcting process failures early on so that you can avoid the nasty consequences of poor performance.

When to Perform FMEA
There are several times at which it makes sense to perform a Failure Mode and Effects Analysis:
  • When you are designing a new product, process or service
  • When you are planning on performing an existing process in a different way
  • When you have a quality improvement goal for a specific process
  • When you need to understand and improve the failures of a process
In addition, it is advisable to perform an FMEA occasionally throughout the lifetime of a process. Quality and reliability must be consistently examined and improved for optimal results.  An FMEA also documents current knowledge and actions about the risks of failures, for use in continuous improvement.

How to Perform FMEA
Failure mode and effects analysis might be implemented differently, depending on the organization. As such, the number of steps involved may also differ by organization. As a general process, FMEA steps include the following: 
  1. Create a team of employees who have collective knowledge or experience with the system, design or process and customer needs. This includes employees with experience in customer service, design, maintenance, manufacturing, quality, reliability, testing and sales.
  2. Identify the scope of the system, design, process, product or service. Define the purpose of the system process, service and design.
  3. Break down a system, design or process into its different components.
  4. Go through system, design or process elements to determine each possible issue or single point of failure.
  5. Analyze the potential causes of those failures as well as the effects the failures would have.
  6. Rank each potential failure effect based on decided criteria such as severity, likelihood of occurrence and probability of being detected. Organizations can use a risk priority number to score a system, design or process for risk potential.
  7. Determine how to detect, minimize, mitigate and solve the most critical failures. This helps keep failure effect risks low by creating a list of potential failures and corrective actions to take.
  8. Revise risk levels as needed.
The purpose of the FMEA is to take actions to eliminate or reduce failures, starting with the highest-priority ones. The failures are prioritized according to how serious their consequences are, how frequently the occur, and how easily they can be detected. FMEA RPN is a numerical assessment of the risk priority level of a failure mode/failure cause in an FMEA analysis. is calculated by multiplying Severity (S), Occurrence (O) Or Probability (P), and Detection (D) indexes. Severity, Occurrence, and Detection indexes are derived from the failure mode and effects analysis:

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.

It is important to note that neither RPN nor criticality are foolproof methods for determining highest risk and priority for action. Severity, occurrence, and detection are not equally weighted: their scales are not linear; and the mathematics hides some surprises. Use RPN and criticality as guides, but also rely on your judgment.

An effective FMEA identifies corrective actions required to prevent failures from reaching the customer and to assure the highest possible yield, quality and reliability. Taking action transforms the FMEA from a paper chase into a valuable tool. By taking action in preventative means you are adding value to the customer which can be a competitive advantage.

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