What are 7 steps in latest FMEA

AIAG+VDA
FMEA is joint publication. This is rewritten with some changed in key area. A
new method, supplemental FMEA for monitoring and system response (MSR) has been
added.

It provide a
means for the analysis of diagnostic detection & fault mitigation during a
customer operation for the purpose of maintaining a safe state or state of
regular compliance.

This is 5^th
edition which surpasses 4^th edition of previous FMEA.

In
manufacturing industries only technical risk come in scope of FMEA. It is team
oriented, analytical method to examine failure modes, failure effects &
failure causes.  We documented the
preventive & detection action also we recommend the action to reduce risk.

FMEA implementation should be fully planned to be fully effective.  FMEA method is integrated element of product
development & process development. It support to made control plan for
product.

What is FMEA
methodology?

FMEA process
is carried out in 7 step. These 7 steps are covered in 3 categories (System
Analysis-Step-1,2 & 3, Failure analysis and mitigation-Step 4,5 & 6,
Risk Commination-Step7)

PFMEA-Step-1 (Planning
and Preparation)

Purpose: –
To describe what product/processes are to be included or excluded for review in
PFMEA project.

Objective:-

1. Project
   identification,
2. project
   plan (In-tent, timing, team, task, tool, )
3. Analysis
   Boundaries (What to included/excluded)
4. Identification
   of baseline with lesson learned
5. Basis
   for structure analysis

For PFMEA we
follow 5T method to prepared pfmea project plan. Below table is
header, which to be filled while making PFMEA for each operation.

PFMEA-Step-2 (Structure Analysis)

Purpose: – To identify & breakdown the manufacturing
system into process item, process steps and process work element.

Objective: – To structure tree of process / process flow
diagram

A PFMEA is intended to represent the process flow as it
physically exists when “walking the process”.

Process item of
PFMEA is highest level of the structure tree/Process flow diagram.

Process step is
manufacturing operation or station. [It is focus
element here]

Process work element
is the lowest level of the process or structure tree. Each work element
is the main category of potential causes that could impact the process step.

PFMEA Step-3 (Functional Analysis)

Purpose: – To ensure that the intended functions/requirement
of product/process are appropriately allocated.

Objective: – To visualization of product or process
function. Make Function tree according to process flow diagram.

It becomes base for failure analysis. Function basically describe
what the process item, process step is intended to do. The description of
function need to be clear. It is always written in present tense.

Function of process
are basically product or process requirement/ Characteristics. Product Requirements
could be related to interface to design,

Function of process item: It begins at high level
descriptions. It can take into function such as internal function, external
functions or end user function. (Here we explain main function of process item- Example – Assemble components)

Negative
of “function of process item” will be failure effects.

Function of process step: – It describe the resulting product
features produced at the station. (Example –Pressing sintered bearing in
housing) [It is Focus element]

Negative
of “function of process step” will be failure modes.

Function of process work element describe the contribution of process step to
create the product features. (Example- Getting sintered bearing from chute
manually, press force required to press sintered bearing into housing.)

Negative
of “function of process work element” will be failure causes.

For understanding Function tree, think “what does it (Process) do? In chronically- Process work element – Process
step – Process item.  Also answer
from “How does it (Process) do? In order- Process item- process step-
Process work element.

 

PFMEA Step-4 (Failure Analysis)

Purpose: – To identify failure cause, failure mode &
failure effect in process.

Objective: – Identify process failure by using fish diagram
(4m) and establishment of failure chain. Here failure chain is FE (Failure
effect) – FM (Failure mode) – FC (Failure cause). Here Failure
mode is focus element (Key element).

Answer of the question “What
happened” from failure mode will give you Failure effect. Answer of the
question “Why happened” will give you failure
cause. So you have to focus more on failure mode.

Failure Effect: – Are related to function of process item.
These are described in term of what the customer might notice or experience.

Effect to be describe in three categories- 1. Internal
failure effect, 2. Shift to plant effect, 3. End User effect.

Failure Mode: – It is manner in which the process could
cause the product not to deliver or provide intended function. Failure mode can
be made through a review of past things gone wrong, reject or scrap reports,
and group brainstorming.

Failure Cause:– 

It is indication of why a failure mode could
occur. The consciences of failure cause is failure mode. Why writing failure
cause-We may include classic Ishikawa’s 4M- Man, Machine/Equipment, Material
(Indirect), Environment.

While making PFMEA users should start with the failure mode
and then identify related failure effects using the information in the #1
Function of process item column.

Here we build failure chain by using information in
functional analysis. FE will be related to “higher level element” of functional
analysis. (Here in photo, function of process item was assembly of component-so
negative of this will be assembly not happened). Same FM is negative to
“function of process step” (Here process step was axial alignment with max gap
of 0.3 mm required for component assembly, so negative of process step is
–assembly not happened because axial position not reached). FC will be why not
reached- reason could be related to 4M Change (Machine stopped before reaching
to the position). 

PFMEA Step-5 (Risk Analysis)

Purpose: – Risk analysis purpose is to estimate risk by
evaluating severity, Occurrence & Detection in order to prioritize the need
for action.

Objective: – To assign prevention control for failure causes,
assign detection control to failure cause/modes. Assign rating of severity,
occurrence and detection control for each failure chain. Evaluation of Action
Priority (AP).

Prevention Control: – Process planning to
minimize the possibility of failure occurrence. These prevention control
eliminates the failure cause & reduce its rate of occurrence.  Examples of PC are: – Poka Yoke- Subsequent
part cannot be made, Equipment/Operator maintenance, Work Instructions, etc.

Detection Control: – Detection control detect
the existence of failure cause & failure mode, either by automatic or by
manual method, before the item leaves the process or reach to next
station.  Examples of Detection control:-
Visual Inspection, Optical inspection by camera/Limit Samples, Vernier caliper
inspection, random inspection, etc.

Risk evaluation: – Each failure mode, failure cause &
failure effect relationship is assessed for its independent risk. Evaluation is
done over three rating criteria.

 Severity (S): – Stand
for severity of failure effect

Occurrence (O): – Stand for occurrence for failure cause.

Detection (D):- Stand for detection for failure mode.

Evaluation number is given from 1 to 10. Where 10 is highest
risk contribution. Severity is rating number associated with most serious
effect for a given failure mode.

Here Note: – Evaluation of failure effect should be mutually agreed by the customer
& the organization.

Severity Rating Table:-

Occurrence Rating Criteria in PFMEA:-

Action Priority: – After identifying failure modes and their
effect also including the rating for severity, occurrence & detection. We
further have to decide if further effort need to reduce the risk.

In new PFMEA, RPN number has been replaced by AP (Action
Priority). RPN is not alone adequate method of determining the need for action,
since RPM give equal weight to S, O & D. Due to different combinations of
S, O & D there could be similar risk number, which confused over how to
prioritize.

Action Priority is in 3 categories: –

Priority High (H)
– Action is required to improve prevention & detection control.

Priority medium (M)
– Action is required to improve prevention & detection control.

Priority Low (L)
–Action may be required or not.

PFMEA-Step-6 (Optimization)

Purpose: – Purpose of process optimization is
to determine action to mitigate the risk & access the effectiveness of
those action. End result is process which minimize the risk of producing &
delivering product that do not meet the customer expectation.

 Objective: – Primary
objective of optimization is to develop action that reduce risk by improving
the process. Identification of the action necessary to reduce the risk also Implementation
and documentation of action taken. Checking effectiveness of action taken
before and after. Here action represent a commitment to take a specific,
measurable & achievable action.

In process optimization we do process modification to
eliminates failure effect, reduce occurrence of failure cause (FC) &
increase the detection ability for FC & FM.

PFMEA is for continuous improvement of process.

In status we have to write- Open, decision pending,
implementation pending, closed & not implemented.

PFMEA- Step-7 (Result
Documentation) 

Purpose: – To summarize & communicates the result of
failure mode & effect analysis activity.

Objective: – Communication of result & conclusion of
analysis, communication of action taken to reduce risk, record of risk analysis
& risk reduction up-to acceptable level.

This document result represent technical risk of failure as
a part of development plan & project milestone.

Here i have only explained about PFMEA, related article on DFMEA and FMEA-MSR will be posted later.