Get Email UpdatesDefinition of Failure Mode and Effects Analysis
Failure Mode
The manner in which the product/part or service does not meet the customer’s expectations
Effects Analysis
A study of the effects of failure on the function or purpose of the product/part or service The customer could be external to the company, or internal (within the company). It is considered a reliability planning tool, but it has also become a method for prioritizing alternative actions (that do not deal with failure modes), e.g., in the Six Sigma process.
FMEA is a systematized group of activities intended to:
- Recognize and evaluate the potential failure modes and causes associated with the designing and manufacturing of a product
- Identify actions which could eliminate or reduce the chance of the potential failure occurring
- Document the above process.
It increases the likelihood that potential failures, and their effects and causes, will be considered prior to the final design and/or release to production. The key to the actions in this Reliability Analysis method is to plan preventive actions. A completed FMEA, which should be applied in an iterative process, contains a great deal of information about the product or process. It can be used as the starting point for later control plans, trouble-shooting guides, preventive maintenance plans, etc.
Key Things To Keep In Mind
“One of the most important factors for the successful implementation of an FMEA program is timeliness… Up front time spent properly completing an FMEA well, when product/process changes can be most easily and inexpensively implemented, will minimize late change crises.” AIAG FMEA Instruction Manual (3rd Edition)When going through the FMEA process, it is also important to remember to base your decisions on data, not on hunches! It should occur very early in the planning cycle. FMEA teams will find themselves spending more time than usual early on, which will lead to leveraged savings later on. The use of data to verify the relationships between root causes and effects, to establish accurate rating criteria, and to determine effective preventive actions is one of the critical-to-success factors in the FMEA process.
Costs vs. Benefits
Lots of Tedious Work → Increased success of implementation, & knowledge well captured by the cross-functional team.
Do not expect the up-front investigation and analysis to be quick or easy, but the extra initial work will typically provide an excellent payback.
Types Of FMEA: Design FMEA (DFMEA), Process FMEA (PFMEA)
At the DFMEA level, it is usually recommended to study each subsystem separately, and each component separately. Their inter-relations can be evaluated in the System FMEA.
The System FMEA examines system deficiencies caused by potential failure modes between the functions of the system. This includes the interactions between the systems and the elements of the systems.
The PFMEA is conducted on a process, whether it be in a manufacturing or a service environment. It is generally recommended to study each machine or sub-process separately. Their inter-relationships can also be studied in a System FMEA. Service FMEAs are usually not preceded by a DFMEA.
Design FMEA DFMEA – Objectives
- Maximize system quality and reliability
- Minimize design-based failure effects on the system
- Should also take into account DFM/A/(X) principles
Process FMEA PFMEA – Objectives
- Maximize system quality, reliability, & productivity
- Minimize production process – based failure effects on the system
- Minimize variation around the design specs due to the process
The key difference in the objectives between the two is the focus of the FMEA. When conducting a DFMEA, the team must remember to think in terms of the causes and effects of failure modes due to the design itself. The causes usually involve product design variables that can be specified by the design team.
Design for Manufacturability/Assembly All other (DFM/A/(X) considerations should be included in the DFMEA as well, e.g., tooling access, robustness to sources of process variation, ability of product to be produced at planned production rates, maintainability, etc. In a PFMEA, the team will be focused on those failure modes and causes that could result from the production or service process itself rather than from the design of the product.
Typical Team Structure:
Design Team:
- Responsible Design Engineer* – Leader
- Test Engineer/Technician
- Reliability/Quality Engineer
- Marketing/Product Manager
- Material Management/Purchasing
- Field Service Engineer/Technician Process
Typically,
the responsible designer will lead the DFMEA team. It is important to have cross-functional participation on the team, including at least some of the members from the after PFMEA team.
Process Team:
- Responsible Manufacturing/Process Engineer** – Leader
- Design Engineer*
- Quality/Reliability Engineer
- Tooling Engineer/Technician
- Material Management/Purchasing
- Responsible Operators
- Maintenance Technician
- Manufacturing/Process Engineer**
Usually, but not always, the leadership of the team changes to the responsible process engineer. This person ideally would have also been on the DFMEA team; and the DFMEA team leader would stay on as a member of the PFMEA team. Several other team members, but not all, could change to reflect a heavier emphasis on the process under study.
The FMEA Quality Lever – Where To Put The Effort
If you apply the energy sooner, or further away from the introduction of the product or service, you will get much more leverage for your effort. Waiting to make the improvements or fixes after production starts will require a lot more effort.
In the above diagram, the further upstream you make changes, the more impact you will make.
Where To Spend The Effort? — Total Time Spent
In the sequential approach to product development, more time is typically spent on debugging the product after it is released to the market. In the concurrent approach, more time is spent in the up-front planning. However, there will usually be much less time spent later on the post-production problem solving.
Spending more planning man hours up front does not mean that the product release time is pushed back. The cross-over point of these two overlaid graphs does not mean anything. Q Which approach has less area under the curve? Why? A The concurrent approach very often results in 20-40% fewer man hours of total development time, due to the effectiveness of the up-front planning.
The main purpose of FMEA: Besides making customers happier by minimizing potential failures, identifying necessary changes early, & prioritizing improvement efforts, FMEA also provides:
- A formal record of reliability and safety analysis ← The completed FMEA should become part of the design package.
- A starting point in the preparation of field service policies ← And for preparing trouble-shooting guides.
- A starting point for a preventive maintenance data base ← From the resulting prioritized preventive actions.
- An indicator for test point location and sequencing ← From the identified
causes, & also from the resulting prioritized preventive actions.
FMEA Quiz
- An FMEA is primarily considered a problem-solving tool.
Incorrect. FMEA is primarily a reliability planning tool which considers the effects and causes of potential failure modes on the function or purpose of the part or service. - A DFMEA evaluates the potential failure modes and causes associated with the manufacturing of a product
Answer: Incorrect. A DFMEA evaluates the potential failure modes and causes associated with the design of a product - The use of data to verify the relationships between root causes and effects is one of the critical-to-success factors in the FMEA process.
Answer: Correct - FMEA teams will find themselves spending more time than usual early on in the planning process, which will usually lead to delayed product introductions.
Answer: Incorrect. By spending the extra time on an FMEA early on in the planning process, there should be less time spent later debugging the product or service at its introduction to the market. - At the DFMEA level, it is usually recommended to study each subsystem separately, and each component separately.
Answer: Correct - The objectives of a PFMEA include minimizing production process – based failure effects on the system but usually not minimizing variation around the design specs due to the process. Answer: Incorrect. The objectives of a PFMEA usually include both.
- When doing both a DFMEA and a PFMEA, it is important to keep the same team members throughout both FMEA processes.
Answer: Incorrect. It is typical for some (but not all) of the team members, and maybe even the team leader, to change for the PFMEA to reflect the emphasis on the process, rather than the design, of the part or service. - Besides prioritizing improvement efforts, FMEA can also provide a formal record of reliability and safety analysis.
Answer: Correct
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