Return of the FMEA

Last week I wrote about how to carry out a Failure Mode and Effects Analysis (FMEA) before you build a product. The idea is to look ahead to find all the risks you can foresee, and then prevent or mitigate them.

The method is straightforward, which means it can be applied in different contexts as needed. Some organizations, when they get large enough, find it useful to split the FMEA into two parts: 

1. a Design FMEA (DFMEA) to look specifically at the product design;
2. and a Process FMEA (PFMEA) to look at the manufacturing processes that will be needed in order to build the product once it is designed.

So to take last week's example of my friend's suitcase with the flimsy handle, a DFMEA would have evaluated whether the right plastic had been chosen for the job and whether the two little screws were enough to anchor it. But a PFMEA would have asked how the handle with its screws was actually going to be attached to the rest of the suitcase? Will those screws be tightened by hand, or by a machine? What torque will screw them in without either stripping the threads or ripping the fabric? Would it be easier and more reliable to replace the screws with brads, or would that fail more often? And so on.

In other words, in addition to the risks we discussed last week—that a product might fail in use or that someone might get hurt—the PFMEA team must also watch for risks that the manufacturing process might break down and create a bunch of unusable scrap. The kinds of operations where this last risk is a big worry are precisely those which manufacture on such a large scale that they regularly separate DFMEAs from PFMEAs in order to keep both of them a manageable size. 

But once you've gone through all this work, found all your relevant risks and prevented the ones that matter, once you are finally into production, then at last you are done. Right?

It depends.

Specifically, it depends on your overall risk profile. Because as soon as you go into production and start selling your product, the first thing you discover is that you didn't foresee everything after all. As one fellow commented on one of my posts in LinkedIn several months ago, "Things will fail in new and exciting ways that were never even thought of during FMEA." And he is absolutely right.

Partly this is because of the sheer cussedness of things, that even when you do the very best you know how to do, there's often some issue you never even thought to explore.

Another factor is that your customers may well prove creative in finding new use cases that you never dreamed of. This special talent was once summarized in the remark that "It is impossible to design anything that is foolproof because fools are so ingenious." 

What now?

One way or another, once your product is out in the market you will start getting information about how it is performing. Read the customer complaints as they come in. Ask your Service or Repair departments what kinds of issues they are seeing. All of this is raw data that helps you learn more about your product.

What do you do with this data? Well, in principle you should feed it back into the FMEA cycle. Pull the FMEA records off the shelf and revisit them. Is the actual performance that you see in the field consistent with what you expected? Or are there discrepancies? 

• Maybe the data tells you that you estimated some of your values wrong when calculating RPN for all the risks you identified. In that case plug in the new numbers, and see what that does to your overall calculations.
• It's also possible that you discover a risk you never considered before. In that case add it, and use the real-life data from the field to work out reasonable RPN values.
• When you are done with this part, then treat this review just like any other FMEA. Check whether you have any risks higher than your threshold value. (You could also use the data from the field to help you decide if your threshold is really in the right place.) If yes, plan an improvement of the product to address those risks; if no, then things are good. But even so, you should keep watching.   

Wow, this sounds like a lot of work. Do we really have to revisit every single FMEA on a regular basis? And how often is a "regular basis" anyway? Do we have to do this annually? Monthly? Weekly? Where will we find the time?

A fair question. Notice that I said "in principle." It really does depend on your overall risk profile. If you are making products that have a high risk of hurting people—medical devices, airplanes, space craft—then yes, you need to take this process very seriously. I can't tell you exactly how often to revisit your FMEAs, but you absolutely should keep abreast of all the news from the field and respond accordingly.

But if the risks inherent in your products are a lot milder, then your risk-mitigation activities can be less intensive as well. As with all aspects of your Quality system, your level of effort should be proportional to the scale of your operations and your risks. Of course at some level you always want to know what's going on with your products, so you can improve them and keep your customers happy. But you also have to keep it pragmatic.