DFMEA in 10 Steps: A Comprehensive Guide
The steps for DFMEA implementation depend on certain company protocols and could vary across different industries, such as aerospace, medical, and automotive. While the process seems intimidating at first, it actually makes sense as a structured and logical approach to analysis. Below is an example of how to perform DFMEA in 10 steps:
1. List all system functions and design requirements
Break the product design into systems and components and organize them in a tree. The visualizations aid in illustrating how the overall design, systems, and component functions are related. For example, a LED emergency lighting might comprise the power circuits (to supply voltage to different portion of the product), LED panels (to emit light at desired brightness and color), battery pack(to provide power during power outage), and control units (the processor to control output rate, charging of battery and switch between operation modes).
2. Identify the potential failure modes
A failure mode is a design fails to meet user product specifications and/or its intended functions, among other requirements. Since a function of the seat system is to support the user’s weight, then a failure mode—one way this system could fail—is that the seat might break.
3. Determine what are potential effects of each failure mode and assign severity rating
A failure effect directly results from a failure mode that happens. Potential effects of a seat that breaks include the exposure of sharp edges, the collapse of the chair, and the injury of users. Based on a set criteria, it should assign a severity rating to these failure effects. The severity rating of 1 signifies that the effect has minimal customer impact. Failure effects with severity rating of 10 mean that the design failure affects customer safety or regulatory compliance.
4. Analyze the root causes of each failure mode
After designating a severity rating for a failure effect, look into the root cause(s) of the failure mode. Sometimes, a design failure cause lies in component function failures such as thin seats, weak aprons, sheared corner blocks, and loose fasteners for the failure mode “seat breaks”.
5. Assign occurrence rating and specify preventive controls
DFMEA prevention controls are specific measures being done to prevent failure causes from existing. Keep in mind that these refer to current preventive, or preventative, activities. An occurrence rating should be assigned according to how likely a failure cause will remain even with preventive measures already in place. Occurrence ratings can also range from one to ten where 1 means very unlikely or nearly impossible for the cause to occur with ongoing prevention controls, while 10 means very likely or almost a certainty for the cause to still exist, leading to imminent failure.
6. Detection controls and detection rating
DFMEA detection controls are existing procedures implemented to improve the capability of recognizing failure causes before finalizing the design drawings and specifications. Current detection activities might involve visual inspections, durability tests, and customer reviews. Whatever the methods, a detection rating should be assigned based on how likely these measures will discover failure causes. Scoring a detective control with 1 means that it can most certainly detect a failure cause, while a detection rating of 10 means that a failure cause may stay undetected even with ongoing controls in place.
7. Risk Priority Number (RPN)
In DFMEA, a risk priority number is primarily used to help teams prioritize which design failure modes to address. Get the RPN by multiplying all the DFMEA ratings—severity, occurrence, and detection. It is essential to note that the DFMEA scoring works relative to the other numbers. Suppose 3 different failure modes have RPNs of 60, 120, and 30 respectively, then consider to prioritize dealing with the second failure mode with RPN 120. A pre-determined RPN threshold value (e.g. 100 and above) can streamline the decision-making process for which failure modes to take action as well.
8. Create priority recommendations
Assign recommended actions with target dates to responsible personnel when RPNs exceed limits. Corrective actions should be taken to eliminate the failure, decrease the severity of failure effects or reduce the occurrence and detection scores.
9. Document corrective actions taken
Design Failure Mode and Effects Analysis can’t guarantee success. Docuement all corrective actions taken with date. This provides traceability for the DFMEA process. DFMEA documents should also be updated accordingly to help teams follow through and monitor their progress better.
10. Re-analyze RPNs to decide the next steps
At last, re-assign the risk priority numbers of target failure modes because some actions have been implemented to improve the design. When the design changes made have addressed all the risks, then the design can move forward to the next product development stage.
Longmax implements DFMEA in New Product Development to identify the risks and take immediate actions prior to tooling and production. The process helps us and our customers to higher quality standard and improve product reliability. If you have a product to design, please follow the above steps or check with our experts .