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Automotive Manufacturing Quality Control

Guide to Failure Mode and Effects Analysis (FMEA)

In a competitive market, identifying problems and defects early on is of significant importance. Customers place high expectations on manufacturers, and failure to deliver quality and reliability can prove very costly. Developed in 1950, FMEA (Failure Mode and Effects Analysis) is one of the most effective ways of reducing the risk of failure and maintaining higher quality throughout the manufacturing process. In this article, we’ll look at FMEA in more detail, covering the types that exists, how to perform FMEA, and when to take corrective action.

What is FMEA?

FMEA is a qualitative and systematic tool that helps manufacturers identify risks and predict failures with a product or process. In addition, FMEA can also be used to find potential causes for failures and the likelihood of a problem or defect occurring before it happens. It works by thoroughly analyzing designs and processes, providing a range of benefits for businesses, including the reduction of waste, improved customer satisfaction and higher profit margins.

DFMEA, PFMEA, and FMECA

To fully understand FMEA, it’s important to understand the different types that exist. There are three main categories for FMEA – FMEA, PFMEA, FMECA. We will cover each one in more detail in this section.

DFMEA – Design Failure Mode and Effects Analysis

Design FMEA looks deeper at the possibility of product-specific malfunctions, product lifespan and safety concerns regarding:

  • Material Properties
  • Geometry
  • Tolerances
  • Interfaces with other components and/or systems
  • Engineering Noise: environments, user profile, degradation, systems interactions

DFMEA helps engineers detect issues and defects in products early on so they can be addressed and corrected immediately. It is deployed across a range of industries including automotive, software, healthcare and more.

PFMEA – Process Failure Mode and Effects Analysis

Process FMEA focuses on identifying failures that impact product quality and reduce the reliability of certain processes. It can also identify failures that cause customer dissatisfaction, or lead to safety or environmental concerns regarding:

  • Human factors
  • Methods followed while processing
  • Materials used
  • Machines utilized
  • Measurement systems impact on acceptance
  • Environment Factors on process performance

PFMEA does this by conducting a detailed analysis of each step in the process and scoring it out of 10. They are scored on severity, occurrence, detection and risk priority number (RPN).

FMECA - Failure Mode, Effects & Criticality Analysis

This method involves quantitative failure analysis that creates a series of links between potential failures, the impact on the mission, and the cause of failure. It is different to FMEA but still falls under the same category. It builds upon the FMEA process by not only identifying potential failures but investigating and isolating these failures through a series of actions. The extra criticality analysis action taken by FMECA compares the probability of failure against the impact of the consequences, allowing manufacturers to focus on the most serious risks. FMEA is required for this criticality analysis to take place.

How is FMEA scored?

As previously mentioned, FMEA conducts a detailed analysis of products and processes and scores it out of 10 on severity, occurrence, detection and risk priority number (RPN). In this section, we will look at this scoring in more detail. FMEA is usually scored out of 10, but in some cases is scored out of 5; the higher the number, the higher the risk,

FMEA is scored on the following variables:

  • Severity: This is the impact of the failure. In most cases, severity exceeding a score of 8 will require a fault tree analysis. This estimates the probability of the failure by breaking it down into sub-elements.
  • Occurrence: This is the chance of a failure happening. A low score could represent a failure that happens every 10 years, while a high score could mean a failure that occurs as regularly as every hour.
  • Detection: This is the likelihood of the failure being detected. Low scores mean it has a high chance of being detected. A high score means it’s likely the issue won’t be identified.
  • Risk Priority Number (RPN): This is a calculation of all the above scores to give an overall score to a failure. Usually, a failure scoring over 80 RPN requires correction which ideally leads to a lower RPN number.

Why Perform FMEA?

FMEA is one of the most reliable methods used to detect failures earlier. Historically, detecting failures earlier means they’re easier to fix and cost less money. There are several benefits to deploying a FMEA system:

  • Captures the knowledge of a team
  • Improves the quality, reliability, and safety of processes
  • Logical, structured approach to identifying failures
  • Reduces process development time
  • Reduces cost
  • Documents and tracks risk reduction activities
  • Helps to identify critical-to-quality characteristics
  • Provides historical records
  • Increases customer satisfaction and safety

All the benefits of FMEA are realized because organizations can identify failures earlier and carry out corrective action based on the severity of the issue.

When to Perform FMEA

Now that you understand the value, it’s important to also know when it makes sense to perform Failure Mode and Effects Analysis (FMEA). You should consider performing FMEA when:

  • You are designing a new product, process, or service
  • You are planning on changing an existing process
  • You have a quality improvement goal for a process
  • You need to understand and take corrective action against a failure

Even when none of the above apply, it’s recommended to perform a FMEA occasionally throughout the lifetime of a process. The quality and efficiency of products and processes should be consistently examined to ensure optimal results and customer satisfaction.

The 7 Steps in FMEA

FMEA is separated into different activities and knowing each of the seven steps will help you successfully perform FMEA. This approach is designed to avoid typical pitfalls and ensure an effective analysis.

  • Step 1: Planning and Preparation

    FMEA needs to begin with purposeful and careful planning. The management team is responsible for setting the scope of the analysis.

  • Step 2: Structure Analysis

    This is used to identify and break down processes into sequential steps, interfaces, and logistical elements. The purpose of this is to facilitate a complete understanding of the process.

  • Step 3: Function Analysis

    The FMEA team should outline the primary function of a product or process and how this function is facilitated. Using the sequential steps identified in Step 2, each element can be analyzed separately in terms of both function and corresponding requirements.

  • Step 4: Failure Analysis

    This step is used to identify and visualize imperfections in products and processes. This is known as a “failure chain” and incorporates mode, effect and cause of failure.

    • Failure Mode: Represents any way in which a product or process could fail to meet its intended function.
    • Failure Effect: The consequences of a failure mode.
    • Failure Cause: Indicates why a failure mode could occur.

    Determining a potential cause of a failure mode, which leads to a failure effect and triggers a failure cause, is the primary focus of FMEA.

  • Step 5: Risk Assessment

    This is where FMEA is scored on severity, occurrence, and detection to give the failure a risk priority number (RPN). Each failure is then placed in an action priority level of “high, medium, or low” based on evaluations. This is to ensure failures that might pose the highest risk to production, quality and cost are addressed first.  

    • High Risk: Action to prevent and/or detect failure must be taken.
    • Medium Risk: Its recommended action is taken to prevent and/or detect failure.
    • Low Risk: Action to prevent and/or detect failure can be taken but is not required.

  • Step 7: Documentation

    The results and steps taken when FMEA is performed should all be documented. A FMEA study is not finished until this step is completed.

A Failure Mode and Effects Analysis (FMEA) is an analytical method of quality management. If you would like more information on FMEA and Quality Management Systems (QMS), Plex’s advanced smart manufacturing platform provides more detail.