The Quality Blog

I am in Japan this week training and mentoring in APQP and FMEA. Once here and working with my customer teams, I noticed how difficult it might be to understand the FMEA linkage.

Much has been said about the linkage between Design FMEA and Process FMEA. My thoughts on this are to be as prescriptive as possible. I am very much a supporter of the idea that there is an intermediate step between the two documents. That intermediate step is a Characteristic Matrix. The Characteristics Matrix is actually part of the QFD process, where the House of Quality converts Voice of the Customer to requirements definitions. Second phase has the requirements being translated to specifications at the platform, system or component level. This output enters the Design FMEA as the function with measures. Causes of failure once converted to dimension or feature is transferred over to the PFMEA, but confusion exists at this stage. Process people often state that they cannot do a Process FMEA without the Design FMEA. This is principally correct and wrong simultaneously. The outputs of the Design FMEA is what we need, and there are many parts where no outputs will be necessary. More on this point on a further blog entry. The Characteristics Matrix provides a clear way to transfer the Design FMEA outputs to the Process FMEA. The linkage exists in three areas:

• Characteristic
• Effect of Failure (on the customer)
• Severity assigned to the Design Failure Mode and Cause Mechanism.

These three items drive an additional Process FMEA effort for the process steps that affect theses characteristics. The Process FMEA does not have any choice on Severity for the characteristic as it is dictated by the Design FMEA. This assures that the Process is analyzed on its’ impact on that characteristic. For more on this idea stay tuned. Please comment if you want to continue this discussion.

I can think of no better technique than FMEA to get engineers together and “hash out” the possible failures of a design or process. The word HASH is appropriate because of all the ingredients necessary to get it to taste good. Many FMEA’s are not developed with enough ingredients to assure that the true issues come out.

All engineers believe they have done a great job, this is not what the FMEA is about. The FMEA is about where and when unknowns can affect performance. The testing and verification of the design or validation of the process should be a confirmation of the FMEA outputs. When risk is uncovered, the actions that come from the FMEA should affect both the design of the product and/or process but also the testing for verification and validation. Too many times we hear “we will test for that” But what if it fails? Will there be enough time to redesign and reconfirm the design? These issues should be discussed during the FMEA process.