FMEA Analysis | Detailed Guide
FMEA Analysis
Failure Mode and Effects Analysis (FMEA) is a structured
approach to discover potential failures that may exist within the design of a
product or process. Failure Mode are the ways in which a process may fail.
Effects are ways that these failures can result in waste, defects or harmful
consequences for the customer. Failure Mode and Effects Analysis (FMEA) is
designed to identify, prioritize, and limit these Failure Mode.
FMEA is not a good engineering option. Rather, it enhances
good engineering by applying the knowledge and experience of a cross functional
team (CFT) to assess the design progress of a product or process by assessing
the risk of failure.
A design initiated by the US Army, Failure Mode and Impact
Analysis (FMEA) in the 1940s, is a step-by-step approach to identifying all
possible failures in a manufacturing or assembly process, or a product or
service. It is a common process analysis tool
"Failure Mode" means the modes or modes in
which something may fail. Failures are any errors or defects, particularly ones
that affect the customer, and may be probable or real.
"Effect Analysis" refers to studying the
consequences of those failures.
Types of FMEA
- Design FMEA (DFMEA)
- Process FMEA
- Design FMEA
Design FMEA (DFMEA) explores the possibility of product
malfunctions, short product lives and safety and regulatory concerns:
- Physical Features
- Geometry
- Tolerances
- Interfaces with other components and / or systems
Engineering noise: environment, user profile, degradation, system interaction
Process FMEA
Process FMEA (PFMEA) refers to failure that affects
product quality, process reliability, customer dissatisfaction, and impacts
arising from safety or environmental hazards:
- Human factor
- Methods while processing
- Material Used
- Machines Used
- Measurement system influences acceptance
- Environmental factors on process performance
Why Perform Failure Mode and Effects Analysis (FMEA Analysis)
Historically, the sooner a failure is discovered, the less
it will cost. If delays in product development or launch are detected, the
effect is exponentially more devastating.
- Multiple options to reduce risk
- High ability to validate and validate changes
- Collaboration between product and process design
- Better Design for Manufacturing and Assembly (DFM / A)
- Low cost solutions
- Heritage, tribal knowledge and standard work usage
Ultimately, this methodology is effective in identifying the
process and fixing it quickly, so that you can avoid the bad consequences of
poor performance.
When to Perform Failure Mode and Effects Analysis (FMEA
analysis)
It sometimes happens that it makes sense to perform a failure
mode and impact analysis in following cases:
- When you are Launching a new product, process or service
- When you plan to do an existing process differently
- When you have the goal of improving quality for a specific process
- When you need to understand and correct the failures of a process
In addition, it is advisable to perform FMEA sometime
during the lifetime of a procedure. Quality and reliability must be
continuously investigated and improved for optimal results.
How to Perform Failure Mode and Effects Analysis (FMEA)
The FMEA is performed in seven stages, with important
activities in each phase. Stages been set different levels to ensure that only
appropriate team members are required to be present for each stage. The FMEA
approach used by Quality-One has been developed to avoid specific pitfalls that
make analysis slow and ineffective. Quality — A three-path model allows for
prioritization of activity and efficient use of team time.
There are seven stages for the development of FMEA:
- FMEA Pre-Work and Assemble the FMEA Team
- Path 1 Development (Requirements through Severity Ranking)
- Path 2 Development (Potential Causes and Prevention Controls through Occurrence Ranking)
- Path 3 Development (Testing and Detection Controls through Detection Ranking)
- Action Priority & Assignment
- Actions Taken / Design Review
- Re-ranking RPN & Closure
FMEA Pre-Work and Assemble the FMEA Team
Pre-work involves the collection and creation of key
documents. FMEA works smoothly through the stages of development when an
investigation into past failures and initial documents is made from its
inception. Initial documents may include:
·
Failure Mode Avoidance (FMA) Past Failure
·
Eight Discipline of Problem Solving (8D)
- · Boundary / block diagram (for DFMEA)
- · Parameter diagram (for DFMEA)
- · Process flow diagram (for PFMEA)
- · Attributes Matrix (for PFMEA)
- · Requirements to be included
- · Design and / or process assumptions
- · Initial Bill of Materials / Components
- · Known causes from surrogate products
- · Probable cause from interface
- · Possible reasons for design options
- · Possible causes from noise and atmosphere
- · Family or Baseline FMEA (Historical FMEA)
Previous testing and control methods used on similar
products
Path 1 Development (Requirements through Severity Ranking)
Path 1 includes the function, failure mode, failure effects,
and severity ranking. Pre-work documents help in this task by taking previously
captured information to populate the first few columns of the FMEA (based on
the selected worksheet).
The Work List must be written in a Work List-based context.
Each function must have an associated measurable value. Tasks may include:
- · Specifications of a design
- · Government manual
- · Program specific requirements
- · Product characteristics to be analysed
- · Desired process output
- · Complete job failure
- · Partial / degraded function failure
- · Intermittent failure
- · At work failure
- · Unexpected function failure
Effects are the consequences of failure, where each
individual effect is given a severity ranking. Actions are considered at this stage
if the severity is 9 or 10 then
Recommended actions that can be considered affect the design
of the product or process at high severity rankings (safety and regulatory) of failure
modes.
Path 2 Development - (Prevention Control through Potential Causes and Prevention Rankings)
The reasons are chosen from design / process input or
previous failures and, when applied to a specific failure mode, are placed in
the Cause column. Completed columns in path 2 are:
·
Possible causes / mechanism of failure
·
Current prevention controls (ie standard work,
previously successful design, etc.)
·
Ranking for each reason
·
Classification of special features when prompted
Path 3 Development (Testing and Detection Controls through Detection Ranking)
Path 3 development includes the inclusion of detection
control that verifies whether the design meets the requirements (for design
FMEA) or cause and / or failure modes that, if unspecified, can reach the
customer (for process FMEA ).
·
The columns completed in Path 3 are: Detection
Control and Detection Ranking
·
Actions are prescribed to improve control if
they are insufficient for the risks set out in Paths 1 and 2. Recommended
actions should address weaknesses in the test and / or control strategy.
·
Review and update of Design Verification Plan
and Report (DVP & R) or Control Plans are also possible outcomes of Path 3.
Action Priority & Assignment
Acts previously set out in Path 1, 2 or 3
are assigned a Risk Priority Number (RPN) for action follow-up.
The RPN is calculated by multiplying the
severity, occurrence, and probe rankings for each possible failure / effect,
cause and control combination. Actions should not be determined based on the
RPN threshold value. This is usually done and is a practice that leads to poor
team behavior. Completed columns are:
- · Review recommended actions and assign RPNs for additional follow-up
- · Assign action to appropriate personnel
- · Assign action on due dates
Actions Taken / Design Review)
The FMEA action is terminated when counter measures have
been taken and are successful in reducing the risk. The purpose of an FMEA is
to discover and mitigate risk. The risks that FMEA does not pose are considered
weak and non-value-added. The team effort did not improve and hence the
analysis was result in wasted time.
Re-Ranking RPN and Closure
After successful confirmation of risk mitigation actions,
the core team or team leader will re-rank the appropriate ranking value
(severity, occurrence, or detection). The new ranking will be multiplied to
obtain a new RPN. The original RPN is compared to the modified RPN and the
relative improvement of the design or process has been confirmed. Columns
completed in step 7:
- Re-ranked Severity
- Re-ranked Occurrence
- Re-ranked Detection
- Re-ranked RPN
- Generate new Actions, repeating Step 5, until risk has been mitigated
- Comparison of initial RPN and revised RPN