Effective Ways to Determine Prospective Process and Assembly Problems

Process Failure Mode and Effects Analysis (FMEA) is a practice normally used to assess manufacturing and assembly processes at the system, subsystem or component levels. It is widely used in the automotive industry as well as other industries that focus to a great extent on making products, particularly when human safety is involved. This kind of FMEA focuses on likely failure modes within the process that are generated by manufacturing or assembly process deficiencies. Particular attention is given to any process step that may result in a safety risk for either the device operator working in the manufacturing or assembly of a product or the end-user of the item.

SAE J1739 provides rules on how to perform a process FMEA. It offers assessment criteria regularly used in the automotive industry for rating the severity (S) of failure effects, along with the likelihood of occurrence (O) plus the effectiveness of process controls to prevent or detect (D) the cause or failure mode before the failure reaches the customer. The Risk Priority Number (RPN) is often a measure helpful to assess risk and help determine critical failure modes. It is calculated by multiplying the Severity, Occurrence, and Detection values, RPN = S x O x D. Though it is true that larger RPN values normally indicate more critical failure modes, this is simply not always the case. In spite of the RPN value, always pay particular attention to any failure mode who has an effect resulting in a severity of 9 or 10.

A simple process FMEA example within SAE J1739 investigates each step involved in the process of applying wax to the inside of a car door. Each process step is looked at and rated in accordance with the risk that it poses. With this example, the 3rd step demands an operator to employ a spray wand to manually apply the wax. From the evaluation, this step is presumed to be the biggest risk area, since if it is not done right, then there could possibly be too light or too heavy a layer of wax put on the inside of the car door. This high-risk step would be the focus of our process FMEA analysis. The FMEA team would take a look at ways that this process step could be improved.

Beyond just the automotive industry, process FMEA is now more commonly utilized in the medical and health care industry, and it's now being used in numerous service industries. Typically here, the aim is to determine and prioritize processes which might be high risk and then conduct a process FMEA on them. For each process the group would identify probable failure modes where the failure modes would signify various ways that a process or sub-process step could fail to deliver the anticipated result.

In medical care, this may be an analysis of the process steps in place to assure patient safety. For instance, maybe the assessment team would consider the process involved prior to a surgical procedure, or some of the process steps linked to post operation recovery procedures to determine if improvements could be made.

After failure modes have been identified for the high-risk processes, then this team would identify possible effects for each failure mode. For the most critical effects a detailed analysis would be performed to discover the root cause, after which suggestions would be made to redesign the process either to get rid of the failure mode or reduce the risk, if it did indeed occur.

This information is intended to merely expose you to the concept of process FMEA. For detailed process FMEA examples as well as a more in-depth discussion on this topic, please make use of some of the resources on our website.

Rich Herman has been involved in reliability engineering for over 25 years and much of that time has been used working with FMEA. To learn more about process FMEA visit his website: FMEA and FMECA Templates