Latest FMEA is ongoing 5th edition which has surpassed 4th edition of AIAG. Somewhere is called 1st edition as it is release jointly by AIAG+VDA.
By this post you will learn about 7- step steps of 5th edition of FMEA. You will learn about concept of PFMEA, basic requirements for preparing PFMEA, Linkage of 7 steps in FMEA. Will learn about severity, occurrence and detection rating, finally you will learn about changes in latest FMEA along with previous FMEA.
7 Steps approach 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 5th edition which surpasses 4th 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.
In which case FMEA is required?
In 3 cases we prepared FMEA.
Case-1:- New design, new process & new technology.
Case-2:- New Application of existing design & process.
Case-3:- Engineering change to existing design & process.
What are Types of FMEA?
- Design FMEA (DFMEA)
- Process FMEA (PFMEA)
- Supplemental FMEA (FMEA-MSR)
What collaboration should be between DFMEA & PFMEA?
Joint agreement should be done between the organization over effect & severity evaluation in supply chain starting with Tier-1, 2 & 3.
FMEA Should be carried out according to project plan. APQP is project timeline, we align FMEA as per APQP.
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,
PFMEA-Step-1 (Planning and Preparation)
Purpose: – To describe what product/processes are to be included or excluded for review in PFMEA project.
- Project identification,
- project plan (In-tent, timing, team, task, tool, )
- Analysis Boundaries (What to included/excluded)
- Identification of baseline with lesson learned
- 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
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.
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.