Do you want to be proactive in recognising and evaluating potential product failure modes? Do you want to reduce or eliminate the probability of a failure or defect ever getting to your customer? If you’re answering yes to these questions, design failure mode and effects analysis (DFMEA) could be perfect for you. Let’s explore further.
Overview: What is DFMEA?
Design failure mode and effects analysis is typically described as a systematic group of activities fundamentally intended to:
- Recognise and evaluate potential failures of a product
- Assess the effect of the failure
- Document what actions can be taken to reduce or eliminate the failure occurring
We should evaluate the use of DFMEA whenever we have a product or service that’s being designed or redesigned or, for example, has a significant change of use.
Fundamental to developing a DFMEA is understanding and assigning Severity (S), Occurrence (O), and Detection (D) as well as the resultant Risk Priority Number (RPN = S*O*D). We will explain these terms in subsequent sections. (If you are keen to know more about FMEA in general and industry standards, look at SAE J1739.)
2 benefits and 1 drawback of DFMEA
Reducing or eliminating the probability of a failure ever reaching the customer is a fundamental element of a Six Sigma approach, so let’s explore some benefits and drawbacks of using DFMEA.
1. Reduce redesign timing and cost
We can achieve the greatest value by starting the DFMEA before a product failure mode has been incorporated into the product design.
2. Document risk reduction
Having a formal process and record of your risk and defect reduction actions is hugely helpful as you design and develop your product. It’s also great for sharing knowledge across teams and designing out failure.
3. It takes time and resource to successfully implement DFMEA
Development and delivery of a high-quality DFMEA takes time, resources, and commitment — all of which need to be recognised and accounted for in project and work task planning.
Why is DFMEA important to understand?
By using DFMEA, we have a logical and systematic group of activities that helps us design and deliver robust designs and products.
You can define all your potential failure modes and the effects of these failures
There can be many potential failure modes, and these should be described in physical or technical terms. The effects of a failure can be described as experienced by the downstream customer and a Severity (S) of the failure effect rated and assigned.
You can analyse all the potential causes for failure
There is likely to be more than one cause per failure mode — especially when considering operating conditions and customer usage. For all potential causes, an assessment of how often this cause of failure will happen is assigned, known as Occurrence (O).
You can assess your current failure management techniques and decide if further action is required
All the current controls in place to detect causes of failure modes are documented and assessed for their effectiveness, known as Detection (D). Calculation of a Risk Priority Number (RPN = S*O*D) can be used to agree recommended actions to further mitigate risk.
An industry example of DFMEA
High-performance internal combustion engines are complex machines with multiple potential failure modes and some catastrophic effects of failure. When developing an all-new internal combustion engine, the design team of a global car manufacturer embraced DFMEA early in the project.
Assembling a well-trained team of engineers and diligently working through the many failure modes, effects, and causes, they reviewed what preventive actions were possible and appropriate. Further, they agreed what special actions needed to be taken to reduce the risk of failure or defect ever getting to a customer.
The engine launched to a global market two years ago and has one of the best reliability records of any high-volume technology and performance engine to date, in many ways thanks to the correct and timely utilisation of DFMEA.
3 best practices when thinking about DFMEA
As with many process-driven activities, there are some fundamentals to get right and help us with delivery. Let’s explore three of these.
DFMEAs are a “before-the-event” action, not an “after-the-fact” exercise. Time spent properly completing a DFMEA at the beginning, when product changes can be most easily and inexpensively implemented, will minimise late-change crises.
Make sure the team is up to speed on how to conduct a DFMEA. Assembling the right cross-functional team with good knowledge and experience of conducting DFMEAs is key.
Keep with it, and make the DFMEA a living document. It’s a significant investment in time and resources to generate a DFMEA, so don’t lock it away in a file. Keep it active and visible throughout the product life cycle.
Frequently Asked Questions (FAQ) about DFMEA
1. What’s an acceptable RPN?
There is no simple answer — it will depend upon your products, processes, and quality history. Review those high Severity failures coupled with medium to high Occurrence, and design these failure modes out.
2. Can I use software to generate my DFMEA?
Yes, there are many software packages that help with the construction of the DFMEA and process steps, but there is no such thing as auto-generation.
3. Who should be involved in DFMEA?
Ideally, a cross-functional team that is likely to include design engineers, test and analysis engineers, manufacturing engineers, supplier and product quality engineers, plus service and logistics will take part in building the DFMEA.
A closing thought on DFMEA
If you want to minimise the risk of errors or defects ever reaching your customers, consider utilising DFMEA as it’s a proven qualitative and systematic approach that delivers results.