The Sofeast Group’s head of New Product Development, Andrew Amirnovin, explains what a dFMEA (Design Failure Mode and Effects Analysis) is, when it’s used and why, and the 8 secrets you need to bear in mind to successfully implement yours.
This is a tool we use for de-risking product designs at an early stage, reducing the chances of defective products being manufactured and making their way into the hands of consumers.
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What is a dFMEA and its purpose?
A dFMEA or ‘design failure mode and effects analysis’ is a risk analysis process that is done by your product engineering team during the earlier stages of the product design and development in order to find and fix possible flaws that could cause defects, failures, and reliability issues in your product once it has been mass produced. Its purpose is to act as a safety net, preventing the most serious issues from getting into a manufactured product.
Most dFMEAs will follow a template with several steps to logically follow in order to find as many failure modes as possible and group them into those which are more severe and more likely to impact your business and customers and those which are less (these failure modes are each assigned an RPN or risk priority number). Then you can decide how to fix them, concentrating on the most serious first, naturally. Then, perform the dFMEA again to assess whether the fixes put in place to the design have solved or at least greatly reduced the issues. by seeing if the RPN numbers are now much lower. If so, the dFMEA has been successful. (01:29)
How to implement your dFMEA?
As mentioned, you will fill out a template (usually in a spreadsheet) containing steps that will help you de-risk the product design.
(We recommend taking a look at how the template is structured in this resource about the FMEA from Sofeast.)
The template we use includes ten steps which are summarized below:
- Have a very thorough understanding of the product design and its systems, functions, and requirements – your engineering team needs to have an intimate knowledge of the product inside and out before they can start analyzing it and discovering potential failure modes.
- Brainstorm failure modes – your team needs to discuss the potential failure modes which are any ways that the product may not reach your or your customers’ standards or needs. They will vary per product and they should bear in mind that consumers sometimes do outlandish things with products, so they should take into account actions that might seem unlikely or silly. For example, what if a rocket for a space shuttle fails to ignite during launch?
- List the failure modes’ effects and assign severity ratings from 1-10 for each – each failure mode’s effect/s need to be listed and they can be given a severity rating out of ten. 1 or 2 may be a slight annoyance, whereas 9 or 10 could be a risk to life.
- Figure out the causes of each failure – the failure modes will be caused by something, but what? The engineers need to explore root causes which could be design, component, or function-related.
- Implement mistake-proofing and/or other preventive measures and assign occurrence ratings from 1-10 – when you know the causes, it’s time to consider how to stop them from occurring. Measures will be put in place to fix or stop them from occurring and then you should assign an occurrence rating on how likely the failure mode is to occur WITH the measures in place.
- Put in place detection activities and assign detection ratings from 1-10 – detection activities such as inspections and testing will be put in place so it’s possible to keep tabs on potential issues as we go through product development and manufacturing (for example, if the product inspector is aware of an issue and is especially looking out for it, it’s less likely to escape their attention) and you will assign another rating that indicates how likely it is that such a failure will be detected before the product leaves the factory.
- Calculate the RPN (Risk Priority Number) per failure – each failure mode needs an RPN number. This number represents the overall risk and it can be calculated with this calculation: Severity x Occurrence x Detection = RPN. It might be helpful to set a limit beyond which a failure mode must be fixed. This will also help you know if a fix has been effective later on, too.
- Recommend fixes – based on the RPN numbers, prioritize which failure modes to work on starting with the most severe. The engineers will focus on these, making recommendations for improvements to solve the issues.
- Carry out the fixes suggested by the engineers – carry out the improvements recommended by the engineers, while documenting them carefully in the template (this information can be used later on in subsequent production or by inspectors, etc). Perhaps you might alter the product design or use different materials or components. This will then be followed by product validation testing.
- Re-calculate the new RPN number following the improvements – once the failure modes have been fixed you can re-evaluate whether their RPN numbers have decreased by running another dFMEA. If the improvements have worked and the RPN numbers are lower, do you deem the risk of problems to be low enough to move on to the next NPI phase and start developing the product further and then, eventually, manufacturing it? (04:40)
The 8 secrets of dFMEA implementation that will set you up for success.
Many product engineers are familiar with the dFMEA, but sometimes they’re done and the improvements just aren’t obtained. This can be because mistakes are made during the implementation of the analysis. Based on our years of experience, here are 8 secrets that will help you implement the dFMEA successfully and get the results you need from it:
1. Create a dedicated team
To successfully implement your dFMEA you must create a team of experts drawn from your design, manufacturing, mechanical and electrical engineering, quality, reliability, and test engineering teams because all together they will know the product design well enough to agree on potential failure modes and their root causes. The key is to miss nothing!
2. Nominate an experienced ‘project manager’
Without a project manager, it’s easy to miss meetings or lose important information. Nominate one of the team, preferably someone from the quality or reliability departments who is familiar with de-risking designs and the dFMEA and has rich work experience, to be PM.
The PM will coordinate meetings, ask searching questions (more on this later), and document the failure modes and other info in the template.
3. Do a thorough risk analysis
It’s quite possible to miss one of the critical failure modes that could happen, leaving it undocumented and untracked. Meetings are mandatory and no corners can be cut. Time should be given to fully explore the failure modes and do thorough brainstorming.
4. Ask the right questions
The PM needs to be very experienced, otherwise, they may fail to ask ‘the right questions’ leading to critical failure modes being missed.
5. Ask the ‘5 whys’ to get to the root cause of failure modes
What are the right questions?…the PM needs to push the team to answer why each failure mode could occur. The 5 whys interrogative technique developed by Toyota is a helpful technique here. Given each reason, ask why again a further four times, each time constructing the question in relation to the next answer and finally getting to the root cause.
Here’s an example of when an engine doesn’t start:
- Why? – The battery is dead.
- Why? – The alternator is not functioning.
- Why? – The alternator belt has broken.
- Why? – The alternator belt was well beyond its useful service life and not replaced.
- Why? – The vehicle was not maintained according to the recommended service schedule (root cause).
6. Implement preventive actions
Your various engineers will suggest preventive actions to fix the failure modes. Now you need to implement them! If not, the failures will keep happening and this happens quite often. Once again, the PM should also be responsible for assigning individuals or teams the preventive actions and following up that they have done the work.
7. Test that the fixes are effective
Once preventive actions have been implemented, you must assess whether the potential failure modes discovered in the dFMEA are still failing in the product. To do so you will do tests, such as overloading the system, placing the product in a hot or cold environment, or pushing the product to its limits. If the failure doesn’t occur where it used to, then you can be satisfied that the fix has worked.
8. A more mature dFMEA
The last secret is to perform another dFMEA in order to calculate new RPN numbers for the failure modes. Are they lower? If so, the fixes put in place have been a success and you can keep on going through the NPI process towards manufacturing.
In order to keep track of the fixes and to assure that they aren’t reoccurring for some reason later on, a common approach is to perform ORT (ongoing reliability testing) where you periodically test the products (redoing the tests done in secret 7) to give yourself peace of mind that the preventive actions implemented after the dFMEA are still effective and working properly, even in subsequent batches of the product being made some time after the initial dFMEA was performed. (09:01)
The dFMEA is an important de-risking tool for products and should be implemented early on in the NPI process before EVT 1 or at EVT. It’s especially important to use it to analyze products that could cause safety issues for the customer should a failure occur, such as vehicles, electronics, medical devices, etc.
Do you have any questions about performing a dFMEA? Leave a comment, please, and contact me if you have any questions.