FMEA stands for Failure Mode and Effects Analysis and is a risk management tool for identifying potential failures. FMEA assesses the severity of the failure risk and how to diminish it. Overall, it includes identifying all possible risks in all parts of the product development process, such as design, assembly, and manufacturing. A well-performed FMEA can be time-consuming and expensive, but it is a vitally important component of proper risk management. There are several subtypes of FMEAs, depending on the product or process. This article focuses on the design FMEA subtype and how it applies to product development.
What is a DFMEA?
The D in DFMEA stands for design. It is a way to find possible risks arising from the product, either when creating a new product design or changing an existing one. With this process, you can identify risks earlier rather than later. Early identification not only saves time and money but also avoids high rates of injury and device failure. During the DFMEA you will identify possible failures arising from the product design, such as material properties, product geometry, tolerances, and system interfaces. There are four general areas of analysis to identify failures.
- Failure Mode: how the failure could occur
- Failure Cause: what caused the design to fail
- Failure Effect: the consequences of the failure
- The Severity of Failure: how severe the effect is and who or what it will impact
Why is DFMEA Necessary?
A quality manufactured product starts at the beginning. Early risk management is not only good manufacturing practice but is ethical. If you fail to perform a proper DFMEA, you risk producing a product that could seriously injure or kill someone.
Additionally, early investment in a DFMEA can save the manufacturer money. Manufacturing a new product is expensive but having to redesign an entire product because you did not identify a risk that caused a product failure is even more costly. Tooling changes, additional testing, recalls, and lawsuits are all expensive consequences of poorly thought designs.
Not only will the DFMEA save money and time, but it could make you money. Customer satisfaction increases when a product works well because customers are less frustrated and less likely to seek out your competition. Customers will continue to buy from you if they know they are getting a quality product.
If your product is a medical device, the FDA requires proof that you have identified the potential risks to the patient and user when using your device. They require written documentation of this process and that you have made modifications to the device to mitigate/minimize these risks as much as possible. While the FDA does not specifically call out using a design FMEA, it is an effective tool for risk management and is generally accepted. An alternative would be using the international standard ISO 14971. The difference is that DFMEA assumes the failure directly causes harm, while ISO 14971 focuses on hazards and hazardous situations and identifies the probability that those situations cause harm.
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How Do You Conduct a DFMEA?
1. Assemble your team
Before conducting the DFMEA you will need to assemble a multidisciplinary team. The team usually includes product design engineers, quality engineers, testing engineers, and production teams. Every production process or system should have a representative on the team who can identify potential failures. To adequately spot potential risks, the people involved should know about the current design and user requirements.
2. Conduct a design review
Once you assemble your team, begin by reviewing the design. During the design review, the team should identify the main components and determine their functions and interfaces.
3. Brainstorm potential failures
Next, brainstorm all possible failures that can result from using your device. The team should include any potential failure regardless of how minor. The type of failure generally falls into one of these categories:
- Full: failure that causes the entire device to fail
- Partial: failure that causes a part of the device to fail. The device may still work, but not to its full capacity
- Intermittent: irregular or unpredictable device failures
- Degraded: failure because of component wear and tear
- Unintentional: failure due to effects from outside forces such as an act of God or user error
4. List potential failure effects
For each failure identified in the previous step, the team documents the potential impact it would have. In a DFMEA these impacts are called effects. Effects can happen to the customer, the device, production, or the operator. Remember that each failure may have more than one effect. For example, a power surge could cause the device to fail or start a fire. Each effect identified should be listed separately.
5. Assign severity, occurrence, and detection rating
Every effect listed in the previous steps needs a severity, occurrence, and detection ranking. Each ranking is based on a relative scale from one to ten, and you will need to know the potential cause to determine each rank.
The severity rating depends on how severe the effect would be if a failure were to happen. Severity rankings are based on a scale from one to ten, with ten being the most severe. In our power surge example above, a fire would be a very severe effect, while product failure would rank lower. It is important to note that you need to know the device’s function to assign a severity rating. If the product is a Class III medical device keeping the patient alive, a device failure would be as severe as a fire.
Occurrence ranking is how often you expect failure to occur. Ranking the occurrence at a ten means that the failure is likely to happen constantly, whereas a one means it is not very frequent.
Detection ranking scores the failure on the probability the failure can be detected before the customer finds it. Failures having a high detection probability are ranked as one, while ten means that it is unequivocally uncertain. With harder-to-detect failures, it is best practice to have prevention controls rather than develop detection tools.
6. Calculate the RPN
RPN stands for Risk Priority Number and gives the relative risk ranking where the higher the number, the higher the risk potential. In a DFMEA each failure and effect identified previously has a risk priority number. To calculate this number, multiply severity by occurrence by detection. The RPN guides the development team on where to prioritize risk mitigation efforts. The higher the RPN, the higher the priority.
7. Determine if the risk is acceptable
In some cases, the RPN may be an acceptable risk, and no action is necessary. The definition of acceptable risk is subjective and varies by organization, industry, and by type of product. The acceptable risk for a cordless drill is different than for a ventilator or for a bassinet. Each organization should have a standard for determining what RPN value counts as acceptable.
8. Create an action plan
When the RPN falls outside acceptable limits, an action plan is required. The goal is to bring the RPN as low as possible or within acceptable limits. The team suggests actions that affect the severity, occurrence, and detection ranking. These actions could be design changes, additional testing, or product warning labels. For each action plan, you should assign a responsible party and a target completion date for implementation. This keeps your team accountable and product development moving forward.
9. Implement the plan
The final step is putting your plan to work. The team should work on fixing the highest RPN first and move down the line. Once you have implemented your RPN reduction plan, recalculate the RPN. The RPN should be within acceptable levels or as low as possible. If it is not, you will need to repeat the process.
As proven above, DFMEAs, when done thoroughly and correctly, can help eliminate risk and improve quality across multiple channels. If you are unsure how to perform a DFMEA on your product or would like some expert advice while navigating the regulatory process, contact us and we would be happy to help.
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