Failure Modes and Effects Analysis
Risks to a product or a process can come from anything and anywhere. They are inherent in everything we do. In many cases, we can unknowingly design failure into your processes and products. But we can diagnose and prevent risks by using a tool called the Failure Modes and Effects Analysis, or FMEA.
FMEA is one of the most powerful tools in the Six Sigma / Lean Six Sigma / Operational Excellence toolbox. It is an extremely detailed, quantitative method of analyzing and documenting the failure modes of a process. It also a powerful means of facilitating consensus among your team’s subject matter experts. FMEA identify the key potential errors in a process, assign how severe the effects could be, look at how often they might happen, and identify how easy they are to detect. Through identification, issues can be prioritized, and those with the greatest impact can be remedied quickly. There are three vitally important benefits to constructing an FMEA. First, the document provides a thorough, quantitative assessment of all the defects and current controls for every process step. Second, it allows you to have an in-depth working knowledge of your process. Third, it allows a project team to track the actions, history, and improvements made to a process beyond the improvement project.
The role of the process FMEA is two-fold. You can either use it to look at a current process, or you can use it to assess the risk of a new solution. In the former, you look at what may go wrong with the current process so you can correct it before it happens. In this way, the FMEA is a proactive approach to risk assessment.
When examining new solutions, you use FMEA to prevent failures in the future after you’ve implemented the fixes. The FMEA should be dynamic, and entries should change as the process changes. It is not a one-time document but should be updated throughout the life of the product or process.
The key inputs for the FMEA are the inputs from the process maps and certain prioritized inputs from the Cause and Effect Matrix. The outputs are a set of corrective actions that will reduce the possibility of failure. You cannot perform an FMEA on your own. Regardless of how well you know the process, you will always miss something. The more people you include, the more successful the outcome of it will be.
There are two primary sections of the FMEA. The first section is called the initial assessment. This section is used to evaluate the initial conditions of a process. The second section documents the actions and history that you take from the initial assessment. After completing the initial assessment, the team then generates a list of actions to reduce the occurrence or increase the detection of some of the failure modes documented. The initial assessment is done as per the following steps:
- The first column of the process FMEA is called the “process step.” This comes directly from either your cause-and-effect matrix or your process map. You should use the highest process step available to construct your FMEA.
- The second column of the FMEA lists the potential failure modes. These are the ways that a process could fail to meet the process requirements or design intent.
- The third column of the FMEA includes the potential effects of these failure modes. Effects are the outputs that the immediate recipients of your products and services, otherwise known as your customers, care most about.
- The next column in the FMEA is the Severity column, in which you rank the severity of each failure effect. Some teams will choose to assess the Severity, Occurrence and Detection as they move through the FMEA.
- The next column of the FMEA is called “potential causes or mechanisms of failure.” These are the causes of each failure mode or failure effect. We want to describe these in terms of some input variable that can be corrected or controlled.
- The next column in the FMEA answers the question, “what are the existing controls and procedures that will either prevent the failure mode from occurring or detect it once it happens?
- Ranking severity number is an estimate of how severely the effect will impact the customer. You rank this on a scale of 1 to 10, with 10 being the most severe, and 1 being the least severe. Very high severity numbers are usually reserved for safety or liability issues. Low severity numbers are those that are unnoticeable or can be reworked locally and have no chance of escaping our area.
- Ranking occurrence number on a scale of 1 to 10. A ranking of 1 implies the failure cause is very unlikely to occur. In fact, you’ve almost never seen it happen. At the top end of the scale, with a ranking of 10, is a failure that is almost inevitable. It has happened in the past and will likely happen again.
- Ranking detection number on a scale of 1 to 10 to evaluate detection. According to the reference table, if your process automatically detects the failure and your controls will almost certainly detect the existence of a failure, you should rank the failure mode a 1.
- Calculating the Risk Priority Number Prioritization allows the team to focus on the “vital few” failure modes first. We prioritize the failure modes using the Risk Priority Number, or RPN. Mathematically, the RPN is the product of the values found in each row’s Severity, Occurrence, and Detection columns. The higher the number, the more severe the failure mode is, and the more attention it requires.
The second section of the FMEA allows teams to document the actions taken to avoid the risks identified in the first section and to record the history and results of these actions.
Please visit Failure Mode & Effects Analysis Training, Process Failure Mode & Effects Analysis (PFMEA) Training or Design Failure Mode & Effects Analysis (DFMEA) Training for your specific FMEA training needs.
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