Failure mode and effects analysis - an overview

1. FMEA
Failure Mode and
Effects Analysis
Andreea Precup

2. FMEA History
• First used in the 1960s in the US Aerospace
Industry by NASA in the Apollo program (“It is a
procedure for analysis of hardware items to determine those
items contrbuting the most to system unreliability and crew
safety problems.”)
• In the 1970s the Automotive Industry was driven
by liability costs to use FMEA
• Later, the Automotive Industry saw the
advantages of using this tool to reduce risks
related to poor quality

3. What is FMEA?
FMEA is an analytical methodology used to
ensure that potential problems have been
considered and addressed throughout the
product and process development process.
FMEA is a tool for risk management and
continual improvement. It is a key part of APQP.

4. Types of FMEA
• Product (Design) FMEA
• focuses on part function, on the design of the product
• does not rely on process controls to overcome
potential design weaknesses, but it does take the
technical and physical limits of the manufacturing
process into consideration
• Process FMEA
• focuses on the manufacturing steps of the product

5. Process FMEA

6. When to conduct a PFMEA?
• when new products/processes are being designed
• when existing designs or processes are being
changed
• when existing designs are used in new applications
• periodically throughout the product/process lifetime
• in case of field issues or production issues the
rankings should be revised

7. Identify the team
Define scope and criticality limits
Identify functions, requirements and specifications
Identify potential failure modes
Identify potential effects  assess the SEVERITY level
Identify potential causes  assess the OCCURENCE level
Identify current controls  assess the DETECTION level
Calculate the Risk Priority Number and assess according to criticality limits
Establish recommended actions where in order, assign provisional
ratings. After actions implementation, check efficiency and give final
ratings. If satisfactory, FMEA is completed, if not further actions are
needed.

8. PREPARATION

9. FMEA Team
• cross-functional
• team leader should be expert in FMEA process
• team members need to have deep knowledge of
the product and process to be analysed
• Quality Management representative will
represent the customer

10. SCOPE AND CRITICALITY LIMITS
• Scope: establishes the boundary of the analysis,
it defines what is included and excluded
• Criticality limits: at what level of risk actions to
decrease it are required

11. FUNCTIONS, REQUIREMENTS AND
SPECIFICATIONS
Identify and understand the functions,
requirements and specifications relevant to the
defined scope. The purpose is to clarify the item
design intent or process purpose.
Input data is gathered: e.g. product definition and
specifications, special characteristics, temporary
process definition, process flow chart.

12. ANALYSIS

13. Process FMEA considerations
• the product as designed will meet the design
intent
• the incoming parts/materials are correct
• failure modes can, but will not necessarily occur

14. POTENTIAL FAILURE MODE
The manner in which the process could potentially
fail to meet the requirements.
Needs to be described in technical terms.
Each function may have several failure modes:
- absence
- stop
- degraded
- intermittent
- unconvenient
- unplanned

15. POTENTIAL EFFECTS
The effects of a failure mode as perceived by the
customer.
Several effects may be identified for a failure mode, but for the
purpose of the analysis only the worst case should be considered.
SEVERITY
An assessment of the level of impact of a failure
on the customer

16. POTENTIAL CAUSES
An indication of how the failure mode could occur.
Only specific errors or malfunctions should be listed, no ambuguous
phrases should be used.
Several causes might be identified. Each should be treated on a
separate line.
OCCURENCE
Likelihood that the cause of a failure mode will
occur

17. CURRENT CONTROLS
Those activities that prevent or detect the cause of
the failure mode or the failure mode.
Can be focused on: - prevention (eliminate or reduce occurennce)
- detection (identify  associated CAs)
Controls focused on prevention will provide the greatest return.
DETECTION
An assessment of how well the current control
scheme can detect the cause of the failure mode

18. ASSESSMENT

19. Risk Priority Number (RPN)
RPN = S x O x D
RPN ranges from 1 to 1000.
RPN is used to prioritize concerns/actions. The
greater the value of the RPN, the greater the
concern.

20. RECOMMENDED ACTIONS
The intent of these actions is to reduce the overall
risk and the likelihood that the failure mode will
occur.
In general, preventive actions (reducing the
occurence) are preferable to detection actions.

21. • Reduce SEVERITY ranking: only a product design
revision can reduce the S ranking
• Reduce OCCURENCE ranking: by removing or
controlling one or more of the causes of the
failure mode through a process design revision
• Reduce DETECTION ranking: error proofing or a
redesign of the detection methodology.
Increasing the frequency of inspection is usually
not an effective measure and should only be
used as a temporary measure until permanent
preventive/corrective actions can be
implemented

22. MGIC ACTIONS PRIORITIZATION
1. S = 10  actions to reduce O and D to 1
2. S = 8 or 9  actions to reduce RPN to 50
3. Criticality above the one imposed by the
customer or the FMEA applicant  actions to
reduce criticality at or below requirement
4. Criticality evaluated by the FMEA team as too
important (based on knowledge and
experience)  actions to reduce criticality

23. LINKAGES
• FMEA is not a stand-alone document
• It is linked to
• the Product FMEA
• the Process Flow Chart
• the Control Plan

24. SUMMARY
An FMEA:
– Identifies the ways in which a product or
process can fail
– Estimates the risk associated with specific
causes
– Prioritizes the actions that should be taken to
reduce risk
– Is a living document