lean (and friendly) fmea 17aug15 · than a tool to focus on preventing problems and reduce ......

Lean (and friendly…) FMEA

Amnon Ganot, CREGertron Ltd.

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2014 RAMS –Tutorial 4B – Ganot

Introduction Some industries such as automotive, defense, and semiconductor use specific standards for performing classical Failure Modes and Effects Analysis (FMEA)

Eventually, most often it becomes a form filling exercise to provide a deliverable document rather than a tool to focus on preventing problems and reduce risks

Many companies do not have the requirements neither the budget nor the time to conduct a classical FMEA

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Introduction (cont.) Today’s move to lean product development, reduced costs and shorter development time makes it even harder to use traditional FMEA approaches

After looking at some limitations of typical FMEA methods, this presentation offers an alternative way to achieve the core benefits of FMEA while reducing the negative perceptions of FMEA

The presented method also offers a more human‐friendly Significance Rank Index (SRI) replacing the synthetic RPN one

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Agenda Motivation FMEA Definition Risk Priority Number (RPN) Limitation to Using RPN FMEA – The "Lean" way Subject Matter Expert (SME) team based The “Lean” alternative to RPN Recommended Action Aggregation and Prioritization Summary

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Vocabulary Detection – a ranking considers the likelihood of detection of the failure mode

or mechanism. Failure Mode – the manner in which the item or operation potentially fails to

meet or deliver the intended function and associated requirements. Failure Mechanism – the specific reason for the failure mode. FMEA – Failure Mode & Effect Analysis Lean – Less waste Occurrence – a ranking number associated with the likelihood that the failure

mode and its associated cause will be present in the item being analyzed. RPN – Risk Priority Number Severity – a ranking number associated with the most serious effect for a given

failure mode. SME – Subject Matter Expert SPF – Single Point Failure SRI – Significance Rank Index

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How About not Doing an FMEA?

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Motivation

Reliability goals become more and more demanding… Development cycles become shorter… …AS a result, we have to implement more comprehensive & lean reliability methodologies….>

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FMEA Definition

An FMEA (Failure Mode and Effect Analysis) is a systematic method of identifying and preventingproduct and process problems before they occur

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FMEA Definition (cont.)

What it does Used to generate a list of potential failures, evaluate their

effects, and rank their severity Identifies ways to reduce or eliminate the chance for

failures

When to perform? During new product development Evaluate a design change on existing product New application of existing product

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FMEA Definition (cont.)

What it outputs List of potential failure modes Recommended actions dealing with high RPN items

Summarizes the list of actions in order to: Eliminate causes of product failure modes Reduce the rate of failure occurrence Improve product defect detection if process capability

cannot be improved

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Severity Rating

EffectSeverity of Effect on Product (Effect on Customer) Rank

Failure to Meet Safety and/or Regulatory Requirements

Potential failure mode effects safe vehicle operation without warning or involves noncompliance with government regulation.

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Potential failure mode effects safe vehicle operation with some warning or noncompliance with government regulation.

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Loss or Degradation of Primary Function

Loss of primary function (vehicle inoperable, but does not affect safe vehicle operation)

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Degradation of primary function (vehicle still operates, but at a reduced level of performance).

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Loss or Degradation of Secondary Function

Loss of secondary function (vehicle still operates, but comfort or convenience functions do not work).

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Degradation of secondary function (vehicle still operates, but comfort or convenience functions perform at reduced levels).

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Annoyance

Appearance item or audible noise, (vehicle still operable but not conform, annoys more than 75% of customers).

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Appearance item or audible noise, (vehicle still operates but not conform, annoys 50% of customers).

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Appearance item or audible noise, (vehicle still operable but not conform, annoys less than 25% of customers).

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No Effect No discernible effect 1

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Occurrence Rating

Likelihood of Failure Occurrence of Causes (Incidents per items or vehicle)

Occurrence Rank

Very High > 100 per 1000> 1 per 10

10

High

50 per 10001 in 20

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20 per 10001 in 50

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10 per 10001 in 100

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Moderate

2 per 10001 in 500

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0.5 per 10001 in 2,000

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0.1 per 10001 in 10,000

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Low

0.01 per 10001 in 100,000

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<0.001 per 10001 in 1,000,000

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Very Low Failure eliminated by preventive control 1

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Detection RatingDetection Opportunity Detection by Process Control Detection

RankDetection

LikelihoodNo Detection Capability No current process control; cannot detect; is not analyzed. 10 Near Impossible

Not Likely to Detect at any Stage Failure and errors (causes) are not easily to detect (e.g.: random process audits).

9 Very Remote

Problem Detection Post-Process Post-Process failure mode detection by operator using visual, tactile, or audible means.

8 Remote

Problem Detecting of Source In-station failure mode detection by operator using visual, tactile, or audible means, or by attribute gages.

7 Very Low

Problem Detection Post-Process Post-processing failure mode detection by operator via variable gages or in-station by operator using attribute gages.

6 Low

Problem Detection at Source In-station failure mode or error (cause) detection by operator via variable gages or by automated in-station controls that notify the operator. Also gaging on set up; first piece inspection.

5 Moderate

Problem Detection Post-Process Post-processing failure mode detection by automated controls that detect nonconforming parts and prevent further processing

4 Moderately High

Problem Detection of Source In-Station failure mode detection by automated controls that detect nonconforming parts and prevent further processing on them

3 High

Error detection with Problem Prevention

In-station error (cause) detection by automated controls that detect an error and prevent bad parts from being made

2 Very High

Detection does not Apply; Error Prevention

Error (cause) prevention via fixture design, machine design, or part design. Bad parts cannot be made; product and process error-proofed.

1 Near Certain

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Risk Priority Number (RPN)

Risk Priority Number (RPN) is a numerical ranking of the risk of each potential failure mode/cause, made up of the arithmetic product of the three elements: severity of the effect, likelihood of occurrence of the cause, and likelihood of detection of the cause.

RPN = Severity (S) x Occurrence (O) x Detection (D) Numbers range from 1 to 1000

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Limitation to Using RPN Subjectivity of RPN

Since the components of RPN severity (S), occurrence (0), detection (D) are each subjective ratings, the RPN value is subjective in nature

It only has application in helping the FMEA team prioritize issues for corrective action within a given FMEA, and cannot be used to assess risk across different FMEAs

Limitations of Detection The detection scale is controversial for some companies and

practitioners, and as a result, some have chosen not to use detection ranking at all

A minority of companies and corresponding applications use the severity and occurrence scale (without detection) and then prioritize issues by the product of S x 0

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Limitation to Using RPN Holes in the Scale

Although the RPN is an integer scale, it is not continuous Many of the numbers in the range of 1 to 1000 cannot be formed from

the product of S, 0, and D This creates 'holes' in the scale These holes are the cause of the most serious problems in interpreting

the RPN

Duplicate RPN Numbers All possible products of S, 0, and D include many duplicate numbers It is difficult to accept that failures whose severities range from 1 (not

noticeable except by the most discerning customer) to 8 (inoperable with loss of primary function) can be evaluated as having the same importance

For example, a severity of 1, occurrence of 8, and detection of 8 has the same RPN value as a severity of 8, occurrence of 4, and detection of 2

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Limitation to Using RPN RPN Thresholds

It is tempting for management to use thresholds for RPN values and require defined action if the RPN value exceeds the given threshold

In most cases, this is a flawed approach, as it can easily become a numbers game

High Severity by Itself High severity is high risk, regardless of the RPN. Therefore, it

is always necessary to address high severity in addition to high RPN

Mathematical Manipulation As most RPN methods are based on ordinal scale by which

data can be sorted, but does not allow for relative degree of difference between them, any mathematical manipulation such as multiplications (SxOxD) are meaningless

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FMEA – The Lean Way

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Lean FMEA – in a nutshell

Functional FMEA – Top down Subject Matter Expert (SME) team based Significant Rank Index (SRI) Recommended Actions Aggregation & Prioritization

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Functional FMEA – Top down

In reliability engineering, two different analytic approaches, inductive and deductive methods are being used

The main characteristic of inductive methods is bottom‐up approach, i.e. they start with analysis of specific initiating events (e.g. component failures) and on that basis investigate the effect of that event at the system level and determine the possible faulty states of the system.

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Functional FMEA – Top down (cont.)

One of the biggest disadvantages of this method is the fact that it is not effective in investigation of possible event combinations which can also initiate system fault (e.g. complex redundancies, interfaces, etc.).

Therefore it cannot be used for the reliability quantification of the system in total

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The deductivemethod is predominantly used for reliability quantifications

The main characteristic of this method is top–down approach, i.e. it first postulate system fault or unwanted initiating event and then investigate which component dysfunctions (failures) or behaviors contribute to this event.

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Top‐Down vs Bottom‐Up

Bottom‐UpTop‐Down

Can investigate only single point failures (SPF)

Can investigate combination of failures (e.g., parallel units) as well as interfaces issues)

Investigating all possible hardware failures

Investigating only thosehardware failures that contributes to a high RPN (SRI) level

Can be conducted only after design completion

Can be conducted early from the concept stage

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Subject Matter Expert (SME) team based

The Classic Way Assembled from a cross‐functional team of people with

diverse knowledge about the process, product or service and customer needs. Functions often included are: design, manufacturing, quality, testing, reliability, maintenance, purchasing (and suppliers), sales, marketing (and customers) and customer service

The Lean Way First stage team is composed of the facilitator and a

Subject Matter Expert (e.g., Project manager, System Engineer)

Final stage team is as in the classic way24


Significant Rank Index (SRI)

The classic RPN has 1 to 1000 levels in a numeric format which make it difficult for human to remember and interpretas well as it consumes much time to set the right level (especially to come to a consensus within a large team)

The SRI is composed of a much less levels as well as it uses human symbols.

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Significant Rank Index (SRI) ‐ example

Severity (Failure Category): S: Safety CA: Catastrophic CR: Critical MA: Major MI: Minor

Occurrence (Failure Probability) P: Probable R: Remote I: Improbable

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Severity (Failure Category): Safety A failure that may cause death to a person Catastrophic A failure that may cause sever injure or major

system damage Critical A failure that may cause minor injury or

inability to perform primary mission Major A failure that may cause degradation in

mission performance (parametric failure) Minor A failure that does not influence system

performance but may result in unscheduled maintenance (FRU consumption)

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Occurrence (Failure Probability): Probable Will occur several times in the life of an

item Remote Unlikely but possible to occur in the life

of an item Improbable So unlikely, it can be assumed

occurrence may not occur

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Recommended Actions Aggregation & Prioritization In the classic FMEA, for each analysis line there should be at

least one recommended action which might sum up to hundreds of them while some of them are repeated (e.g., PM, BIT, ALT etc.)

In the Lean FMEA we are aggregating and categorizing the recommended action in one table

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Recommended Actions Aggregation & Prioritization ‐ example

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Classical Vs Lean FMEA

Lean FMEAClassical FMEADeductive: Top DownInductive: Bottom UpTeam is comprises of Subject Matter Expert

Team is comprises of CrossFunctional Team

Significant Rank Index (SRI)Risk Priority Number (RPN)

Recommended ActionsAggregation & Prioritization

???

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Summary

Functional FMEA – Top down Subject Matter Expert (SME) team based Significant Rank Index (SRI) Recommended Actions Aggregation & Prioritization

The presented Lean‐MTBF method offers an alternative way to achieve the core benefits of FMEA while reducing it's negative perceptions.

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Where to Get More Information Carl S. Carlson, “Effective FMEAs: Achieving Safe, Reliable, and Economical Products and

Processes using Failure Mode and Effects Analysis”, Book, John Wiley & Sons Relationship of Functional Specifications to Design FMEAs in Mitigating Reliability Risk During

Project Development, G. Michael Smith, E‐Z‐GO, ARS 2005 Prerequisites for a Comprehensive and Successful FMEA, Amnon Ganot, Gertron Ltd., ARS

2013 The Basic of FMEA. Robin E. McDermott, Raymond J. Mikulak, Michael R. Beauegard Fundamentals of Failure Modes and Effects Analysis. John B. Bowles Standard for Performing a Failure Mode and Effects Analysis (FMEA) and Establishing a

Critical Items List (CIL) (DRAFT). Flight Assurance Procedure (FAP) – 322 – 209 A Modified FMEA Approach to Enhance Reliability of Lean Systems, Karthik Subburaman,

University of Tennessee Lessens Learned for Effective FMEAs, Carl S. Carlson, Reliasoft Corporation, RAMS 2012 Supe‐RPN – Optimal Prioritizing of Potential Failures Detected by FMEA, Alon Sneor, Nadav

Haas, Amnon Ganot, ARS 2010

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Amnon GanotAmnon Ganot is an independent consultant and instructor in the area of Design For Reliability (DFR), Design For Maintainability (DFM), FMEA, Life Data Analysis, System Reliability Modeling and Analysis, Accelerated Testing Techniques and System Engineering methodologies. He has more than 35 years of experience in System Engineering and Project Management in a variety of industries including Robotics, Medical, Telecommunications and Graphic Arts. Amnon is working part time with Orbotech Ltd. (Yavne, Israel) as Orbotech's Reliability Expert, responsible for writing and implementing reliability and maintainability methodologies, including integration in the PLM (Project Lifecycle Management). Amnon also serves as RAMS (Reliability, Availability, Maintainability and Safety) knowledge focal point for all of Orbotech's divisions and subsidiaries worldwide. Amnon also instructs and coaches Orbotech's and its subsidiaries’ employees worldwide in DFR and DFM. Prior to that, Amnon was the Director of RAMS and standard compliance at Orbotech. As an independent consultant, Amnon is Hewlett‐Packard's Reliability consultant in Israel. Amnon holds a B.Sc. in Electrical Engineering from the Technion – Israel Institute of Technology and a Masters in Business Administration (MBA) from Tel Aviv University (Israel). He is an ASQ Certified Reliability Engineer (CRE). Amnon is also a lecturer at the ARS (Applied Reliability Symposiums) in Europe and the USA as well as at the RAMS symposium and was leading the "Hardware System Reliability" working group activities under the sponsorship of the Office of the Israeli Chief Scientist.Contact Information:

Gertron Ltd.Tel: +972‐54‐4942373Fax: +972‐3‐941‐0685Mail: [email protected]: www.gertron.org

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Questions?

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lean (and friendly) fmea 17aug15 · than a tool to focus on preventing problems and reduce ......

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