Failure Mode and Effects Analysis(FMEA)



  1. Introduction

Failure Modes and Effects Analysis (FMEA) is a methodology for analyzing potential reliability problems early in the development cycle. By performing this analysis earlier in the design process, it is easier to take actions to overcome these issues, thereby enhancing reliability through design.


  • “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 of those failures


Failures are prioritized according to how serious their consequences are, how frequently they occur and how easily they can be detected. The purpose of the FMEA is to take actions to eliminate or reduce failures, starting with the highest-priority ones.


FMEA is used to identify potential failure modes, determine their effect on the operation of the product, and identify actions to mitigate the failures. FMEA can also capture historical design information for use in future product improvement.

It can be used to perform the crucial step of anticipating what might go wrong with a product. While anticipating every failure mode is not possible, the design team should formulate as extensive a list of potential failure modes as possible.

Besides, FMEA identifies actions which can eliminate or reduce the chances of potential failures from recurring, it also helps users to identify the key design or process characteristics that require special controls for manufacturing, and to highlight areas for improvement in characteristic control or performance


Later it’s used for control, before and during ongoing operation of the process.

Ideally, FMEA begins during the earliest conceptual stages of design and continues throughout the life of the product or service

FMEA determines the Risk Priority Number(RPN) by multiplication of three input factors, Severity, Occurrence, and Detection, as follows:


RPN = Severity * Detection * Occurrence

  • Severity(S) is an assessment of the effect of potential failure mode to the next component, subsystem, or customer
  • Occurrence(O) is defined as the likelihood that a specific cause/mechanism will occur
  • Detection(D) is an assessment of the ability of current design control to detect a potential cause/mechanism



  1. Types of FMEA’s

There are several types of FMEAs; some used more often than others. FMEAs should always be done whenever failures would mean potential harm or injury to the user of the end item being designed. Among the types of FMEA are:

  • System – focuses on global system functions
  • Design – focuses on components and subsystems
  • Process – focuses on manufacturing and assembly processes
  • Service – focuses on service functions
  • Software – focuses on software functions



  1. FMEA Usage

FMEA provides the engineer with a tool that can assist in providing reliable, safe, and customer pleasing products and processes. Since FMEA help the engineer identify potential product or process failures, they can use it to:

  • Develop product or process requirements that minimize the likelihood of those failures
  • Evaluate the requirements obtained from the customer or other participants in the design process to ensure that those requirements do not introduce potential failures
  • Identify design characteristics that contribute to failures and design them out of the system or at least minimize the resulting effects
  • Develop methods and procedures to develop and test the product/process to ensure that the failures have been successfully eliminated
  • Track and manage potential risks in the design. Tracking the risks contributes to the development of corporate memory and the success of future products as well
  • Ensure that any failures that could occur will not injure or seriously impact the customer of the product/process





4.1 Assemble a cross-functional team of people with diverse knowledge about the process, product or service and customer needs. Functions often included are: design, manufacturing, quality, testing, reliability, maintenance, purchasing (and suppliers), sales, marketing (and customers) and customer service

  • Identify the scope of the FMEA. Useflowcharts to identify the scope and to make sure every team member understands it in detail
  • Fill in the identifying information at the top of your FMEA form
  • Identify the functions of your scope

  • For each function, identify all the ways failure could happen. These are potential failure modes. If necessary, go back and rewrite the function with more detail to be sure the failure modes show a loss of that function

“A failure mode is defined as the manner in which a component, subsystem, system, process, etc. could potentially fail to meet the design intent. Failure modes can fall into one of five categories; total failure, partial failure, intermittent failure, over-function (more occurred than planned), and unintended-function. Note that a failure mode in one component can serve as the cause of a failure mode in another component”


  • For each failure mode, identify all the consequences on the system, related systems, process, related processes, product, service, customer or regulations. These are potential effects of failure. Ask, “What does the customer experience because of this failure? What happens when this failure occurs?”

A failure effect is defined as the effect of a failure mode on the product/process function as perceived by the customer. They should be described in terms of what the customer might see or experience should the identified failure occur


  • Determine how serious each effect is. This is the severity rating, or S. Severity is usually rated on a scale from 1 to 10, where 1 is insignificant and 10 is catastrophic. If a failure mode has more than one effect, write on the FMEA table only the highest severity rating for that failure mode

  • For each failure mode, determine all the potential root causes. Use tools classified ascause analysis tool, as well as the best knowledge and experience of the team. List all possible causes for each failure mode on the FMEA form

A failure cause is defined as a design weakness that may result in a failure. The potential causes for each failure mode should be identified and documented. The causes should be listed in technical terms and not in terms of symptoms.


  • For each cause, determine the occurrence rating, or O. This rating estimates the probability of failure occurring for that reason during the lifetime of your scope. Occurrence is usually rated on a scale from 1 to 10, where 1 is extremely unlikely and 10 is inevitable. On the FMEA table, list the occurrence rating for each cause

  • For each cause, identify current process controls. These are tests, procedures or mechanisms that you now have in place to keep failures from reaching the customer. These controls might prevent the cause from happening, reduce the likelihood that it will happen or detect failure after the cause has already happened but before the customer is affected


  • For each control, determine the detection rating, or D. This rating estimates how well the controls can detect either the cause or its failure mode after they have happened but before the customer is affected

Detection is an assessment of the likelihood that the Current Controls (design and process) will detect the Cause of the Failure Mode or the Failure Mode itself, thus preventing it from reaching the Customer. Based on the Current Controls, consider the likelihood of Detection using standard tables for guidance


Detection is usually rated on a scale from 1 to 10, where 1 means the control is absolutely certain to detect the problem and 10 means the control is certain not to detect the problem (or no control exists). On the FMEA table, list the detection rating for each cause



  • Critical characteristics are measurements or indicators that reflect safety or compliance with government regulations and need special controls. If so, a column labeled “Classification” receives a Y or N to show whether special controls are needed. Usually, critical characteristics have a severity of 9 or 10 and occurrence and detection ratings above 3. This is Optional for most industries


  • Calculate the Risk Priority Number, or RPN (RPN = Severity * Detection * Rating). Also, calculate Criticality by multiplying severity by occurrence (S × O). These numbers provide guidance for ranking potential failures in the order they should be addressed The RPN is used to identify areas which require attention and prioritize them for additional quality planning or action



  • Identify recommended actions. These actions may be design or process changes to lower severity or occurrence. They may be additional controls to improve detection. Also, note who is responsible for the actions and target completion dates. These actions could include:
  • Area specific inspection
  • Testing or Quality Procedures
  • Selection of different components or materials
  • Limiting Environmental stresses or Operating Range
  • Providing monitoring mechanisms
  • Performing preventative maintenance
  • Inclusion of Back-up systems or redundancy


  • As actions are completed, note results and the date on the FMEA form. Also, note new S, O or D ratings and new RPNs



  1. FMEA Procedure: Flow Diagram



  1. When to use FMEA

6.1 When a process, product or service is being designed or redesigned, after quality function deployment

6.2 When an existing process, product or service is being applied in a new way

6.3 Before developing control plans for a new or modified process

6.4 When improvement goals are planned for an existing process, product or service

6.5 When analyzing failures of an existing process, product or service

6.6 Periodically throughout the life of the process, product or service



  1. Benefits of FMEA

FMEA is designed to assist the engineer improve the quality and reliability of design. Properly used the FMEA provides the engineer several benefits. Among others, these benefits include:

7.1 Improve product/process reliability and quality

7.2 Increase customer satisfaction

7.3 Early identification and elimination of potential product/process failure modes

7.4 Helps prioritize product/process deficiencies

7.5 Capture engineering/organization knowledge

7.6 Emphasizes problem prevention

7.7 Documents risk and actions taken to reduce risk

7.8 Provides focus for improved testing and development

7.9 Minimizes late changes in the design and its associated costs

7.10 Provides a catalyst for teamwork and idea exchange


  1. FMEA Example

FMEA for Constructive improvement of the Industrial Sewing Machine

The application of the FMEA for different elements and parts – which get defected frequently