The Design Potential FMEA ensures that, potential failure modes and their associated causes or mechanism have been considered. This document includes a list of analysis of items that could go wrong based on experience and service history of similar components.
How to fill correctly an FMEA form?
The header of the FMEA form offers information about the name of the product being analyzed, information related to this particular document, as team members, dates, edition, etc.
The header of the Design FMEA form contains the following information:
1. FMEA Number: Enter the number of the Document;
2. Subsystem, Component: Enter the name of Subsystem and/or Component decided by the team;
3. Prepared by: Enter the name, tel. nr. Of the engineer responsible for preparing the FMEA;
4. Design Responsibility: Enter the department, supplier name, if applicable;
5. FMEA Date: Enter the date the original FMEA was compiled;
6. Model Year(s)/ Program(s): Enter the intended model year(s)/program(s) that will use and/ or be affected by the design being analyzed;
7. Key Date: Enter the initial FMEA due date, which should not exceed the scheduled production design;
8. Revision Date: Enter the latest revision date;
9. Core Team: List the names of responsible individuals;
10. Page: Enter number of pages include this document;
Then it comes the complex part related to the actual design, and different modes of failure of every function.
11. Item/ Function: Enter the name of the item being analyzed and/or the function of it.
12. Potential Failure Model(s): The component, Subsystem, System fail to meet or deliver the intended function. The potential failure mode may also be the cause of a potential failure mode in a higher-level system, or be the effect of one in a lower level component.
Typical failure modes:
- Inadequate Support
- Intermittent Signal
- Disengages too fast
- Does not transmit torque
- No Support
- Harsh Engagement
- Inadequate Signal
- No Signal
13. Potential Effect: Potential Effects of failure are defined as the effects perceived by the customer. Describe the effects of the failure in terms of what the customer might notice.
Remember that relationships exist between components, subsystems and systems level. The effect of a failure of a component can cause damage in the whole systems. For example, a part could fracture, which may cause the assembly to vibrate.
Typical failure effects could be:
- Erratic Operation
- Poor appearance
- Intermittent Operation
- Unpleasant Odor
- Operation Impaired
- Thermal Event
- Regulatory Non-Compliance
14. Severity: Is the rank associated with the most serious effect for a given failure mode. Reduction of this rank can be affected only through a design change. Severity should be estimated using the next Table as a guideline.
The evaluation criteria can be personalized by the team to meet their expectations.
Note: Failure modes with a rank of severity 1 should not be analyzed further. High severity rankings can be reduced by making design revisions.
15. Potential Cause of Failure: Potential cause of failure is defined as an indication of a design weakness, the consequences of which is the failure mode.
Typical failure causes:
- Incorrect material specified
- Inadequate Design Life Assumption
- Insufficient Lubrication Capability
- Inadequate Maintenance Instructions
- Incorrect Algorithm
- Excessive Heat
- Improper Tolerance Specified
- Improper Maintenance Instructions
- Improper Software Specification
- Improper Surface Finish Specification
- Inadequate Travel Specification
- Improper Friction Material Specified
Typical failure mechanism:
- Material instability
- Wear, Corrosion
- Chemical Oxidation
16. Occurrence (O): Is the likelihood that a specific cause/mechanism will occur during the design life. Preventing or controlling the causes of the failure through a design change is the only way to reduce this value.
Estimate the likelihood of occurrence of potential failure cause on a 1 to 10 scale. In determining this estimate, the following questions should be considered:
- What is the history, field experience with similar components or systems?
- Is the component similar to a previous level component or system?
- How significant are changes from a previous level component or system?
- Is the component different from a previous level component or is completely new?
- Has the component application changed?
- What are the environmental changes?
- Have preventive controls been put in place?
17. Current Design Control: List the design verification/ validation or other activities that have been completed, and that will assure the design adequacy.
It can be current controls that have been used with the similar or same design (design review, feasibility studies, prototype tests).
There are 2 types of design controls to consider:
- Prevention: Prevent the mechanism of failure or reduce the rate of occurrence
- Detection: Detect the cause/ mechanism of failure, before the item is released to production
Note! In some cases, is just detection, because the team has not identified any preventive controls. This could happen when the design is different from any old ones and doesn’t exists any prevention yet.
18. Detection (D): Is the rank associated with the best detection control listed in the design control. In order to achieve a lower ranking, generally the planned design control has to be improved.
19. Risk priority number (RPN): RPN = Severity (S) x Occurrence (O) x Detection (D)
20. Recommended Action: The intent of recommended action is to reduce rankings of S, O, D.
In general practice when S is 9 or 10 special attention must be given to ensure that the risk is addressed through existing design control or preventive/ corrective actions.
The following actions should be considered:
- Revised Design Geometry and Tolerances
- Revised Material Specification
- Design of Experiments
- Revised Test Plan
The following table indicates, besides Severity rank equal to 9 or 10, which ranking requires corrective action. Every organization determines a personalized ranking system, based on team analysis, experience, similar product service history.
The letters and numbers indicate:
N- NO corrective action needed
C- Corrective action needed
Orange Cells- Corrective action needed if the Detection rating is equal or higher than the given number
If Occurrence = 5 and Severity = 6 and Detection = 4 or higher, action is required.
The primary objective of recommended action is to reduce risk and increase customer satisfaction by improving the design.
Note: Only a design revision can bring about a reduction in the severity ranking.
21. Responsibility, for the Recommended Action: Enter the name of organization and individual responsible for each recommended action
22. Action Taken: After the action has been implemented, enter a short description of the action and effective date.
23. Action Result: After the preventive/ corrective actions has been identified estimate the result severity, occurrence, detection. Calculated record the resulting RPN. If no actions are taken, leave the columns blank.
Besides the theoretical explanation of the form we prepared an example, which you can find here: