Lean ManufacturingMaintenance management

Failure Mode Effect Analysis (FMEA)

The Failure Mode and Effect Analysis, also known as FMEA, was born in the US, at the end of the 40’s. This methodology was developed by NASA, with the final porpoise of knowing the real failures of the equipment and how reliable they are.


What is the FMEA?

Failure Mode Effect Analysis is a procedure that allows us to identify any sort of flaw on products, processes and systems; as well as evaluate and classify their defects, causes and identification elements, so we can prevent errors and have a documented prevention registry.

Why having a documented prevention registry?

A potential advantage of FMEA is that, this tool is a dynamic document, on which you can collect and classify a lot of information about products, processes and systems in general. Information is another capital of the Organizations.


FMEA: Types

You can apply this procedure to:

  • Products: Applying FMEA to a product works as a predictive tool to detect possible design flaws, raising probabilities of anticipating to the effects that a user can have, of the manufacture process can have.
  • Processes: Applying FMEA to processes works as a predictive tool to detect possible flaws in the manufacturing process, raising probabilities of anticipating to the effects that a user may have, or in further stages of the same process.
  • Systems: Applying FMEA to systems works as a predictive tool to detect possible flaws on software design, raising probabilities of anticipating to the effects that they may have on their operation.
  • Others: FMEA can be applied to any kind of process on which your goal is to prevent flaws trough analysis of their effects, and documenting their causes.

Potential Advantages of FMEA:

This analysis procedure has a series of advantages, for example:

  • This analysis procedure has a series of advantages, for example:
  • Identifying the possible flaws in a product, process or system.
  • Knowing the end of the product, process or system.
  • Identifying the effects that each possible flaw can produce.
  • Evaluating the criticality level of the effects.
  • Identifying the possible causes of the flaws.
  • Establish the reliability levels for failure detection.
  • Evaluate trough specific indicators the relation between: importance, currency and detectability.
  • Documenting the plans of action to minimize risk.
  • Identifying improvement opportunities.
  • Generate a “Know-How”
  • To considerate FMEA information as a capacitation resource of the processes.

When you must implement FMEA?

Is a procedure that enriches Organizations, so considering the implementation does not require specific conditions. Nevertheless, FMEA can become an essential support tool, for example:

  • New product/services design.
  • Processes design.
  • Preventive maintenance programs.
  • Stages of documentation of products and processes.
  • Stages of collection of information as a capacitation resource.
  • Customer demand.

FMEA is by far the methodology propose as prevention mechanism on the implementation of Lean Manufacturing. This is activated by means of the indicators when it is required to prevent the generation of problems.

FMEA (1)


Procedure to get FMEA done in a process – FMEAP

To develop FMEA, on first place you must first collect information; in this case the process must have enough documentation about all its composing elements. FMEA is a systematic procedure which steps are the following:

  • 1. Make a map of the process (Graphic representation of operations)
  • 2. Get a work team together (Kaizen Team), document the process, document the product, etc.
  • 3. To determine the critical steps of the process.
  • 4. To determine the potential flaws of each step of the process, their effects, and evaluate their severity level.
  • 5. Indicate the causes of each flaw, and evaluate their term.
  • 6. Indicate the controls (detention measures) that the Organization has to detect flaws and how the organization assess them.
  • 7. Quantify the risk for each flaw and take decisions accordingly.
  • 8. Execute preventive, corrective and improvement actions.

 

Make a map of the process

This step is aimed to graphicly represent the steps of each process. For this, we can use a block diagram, a flowchart, or a synoptic course of the process.

FMEA (2)

Get a work team together

Is always recommended to form a work team following the Kaizen projects structure. This teams are characterized for having a chief who has knowledge in FMEA, this person is in charge has to develop the methodology; is also require to have 3 or 4 people more, with skills and knowledge in the product and the process, so a this’ll be a multi-disciplinary team. Kaizen is crucial in the inclusion of the team, in regard to the process’ operators.

The Chief is in charge of:

  • Direct the methodology.
  • Coordinate meetings.
  • Get the work a has easier has possible.
  • Document advances.
  • Document results.

Other team members are in charge of contribute their knowledge and skills about the product and process, accordingly to the requirements that the Chief stablish.

As far as the team in formed, you must start the documentation process of the project FMEA, for this reason the document must have the following:

  • The serial number of the manufactured part in the process.
  • Part description.
  • Organization and area.
  • The name of the process.
  • Relation between the process’ analysis and the responsible of it.

FMEA (3)

 

To determine the critical steps of the process

In this stage you must make an initial analysis to identify the potential flaws that are affecting critically the process; this flaws are: health risks, to customers and employees; quality risks, and finally the availability of the raw materials; on this way you can identify the critical steps of the process. Is worth mentioning that this stage must develop with the constant company of process’ specialist.

In this example, we have selected as critical steps the cutting and sewing. Bear in mind that this process is aimed to stablish the analysis priorities, nevertheless, the remaining steps of the process must be documented just as the other.

 

To determine the potential flaws of each step of the process, their effects, and evaluate their severity level

For each of the steps of the process you must identify potential flaws. In the first place you must check the historic information and register the flaws that have happened before; in second place, you must identify with the assessment of the specialist, all the flaws that may occur on each step of the process. This identification must be done critically and analytically.

Then you must list all the related effects with the identified flaws.

¿What is a flaw mode?

Is the way a product or process may affect the compliance with the specifications, affecting the customer, employee or the next process.

There are multiple flaws, and this are represented in design analysis and in process analysis, for example:

  • Design Flaws: Broken, fractured.
  • Process flaws: Loose, wrong.

¿What is an effect?

An effect can be considered as the impact on the customer or the next process, when the flaw mode in materialized.

For example:

Potential Flaw FMEA

Once all the flaws and effects are listed, you can qualify the severity of the potential effects. You can use the following scale as guide:

Scoring FMEA

Is necessary to consider that in the case that a flaw as effects (customer7process) with different scorings, you must assign the higher value of severity of effects.

Severity FMEA

Indicate the causes of each flaw and evaluate their Frequency

In this stage you must relate the associated causes to each identified flaw on the last stage. Further, you must evaluate their Frequency.

To evaluate the Frequency of a FMEA oriented to a process, is recommended to use some criteria, whether based on a flaw probability, or possible indexes of flaws based in how many per piece, or in the index of the real Cpk capacity. You can use the following scale as guide:

Scoring Criteria FMEA

For example:

Frequency FMEA

 

Indicate the controls (detention measures) that the Organization has to detect flaws and how the Organization assess them

In this stage you must describe the type of control that you have to detect each flaw. Further, you must evaluate, in a scale from 1 to 10, la capacity of detection of itself; the higher it is the possibility to detect each flaw, the lower the scoring is. You can use the next scale as guide:

Scoring Inspection FMEA

For example:

Detection FMEA

 

Quantify the risk for each flaw and take decisions accordingly

The number of risk priority, also known as RPN (Risk priority number), is the product of the multiplication between the severity, the Frequency and the detectability. RPN, is a number between 1 and 1000, which tells us the priority that each flaw has, so it can be eliminated from the process/product.

When it is superior of 100 is a clear indication that prevention actions must be implemented, so the flaw’s happening Frequency, priority. Nevertheless, the goal is to deal with all the flaws; many experts agree that a RPN superior to 30 requires a focused display in the treatment of the flaw’s mode.

For example:

RPN FMEA

 

Execute preventive, corrective and improvement actions

Once you have stablished the priority of the flaw’s modes, you proceed to execute preventive, corrective or improvement actions. In this stage you have relevant information related with the process, the flaws and the detection controls. Then, FMEA team must stablish:

  • Recommended actions by flaw.
  • To assign responsible by action, related with the execution date.
  • Stablish a revision date.
  • Record the actions executed up to the revision date.
  • Calculate the RPN again.

Por ejemplo:

In this case have been suggested corrective actions, oriented to the flaws and their causes. Nevertheless, corrective, preventive and improvement actions can also be implemented. Focused in flaws, just as in causes and detection controls.

Once you have done the revision on the stablish date, to know the impact of the taken decisions you have to calculate again RPN.

For example:

RPN New FMEA


As previously said, FMEA constitutes a dynamic document, admits multiple revisions, observations and scorings according with the evolution of the process’. Likewise, is a priceless source of information related to equipment, that can be used for the prevention, correction and improvement display; also for personnel capacitation about equipment and process.

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Bryan Salazar López

By profession, Industrial Engineer, Master (c) in Logistics, specialized in productivity, with interest and experience in modeling processes under sustainability indicators. Founder of Ingenieriaindustrialonline.com, site where research contributions, articles and references are collected.

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