1

Process Improvement & Quality Engineering

Sam Berkhauer 2005

Process Orientated Six Sigma &Failure Mode and Effect Analysis

Sam BerkhauerP345

bs12@gre.ac.uk01634 883473

Schedule

GB13/12/2005Revision Q&A11

GB06/12/2005Pre-control Charts and Introduction to Quality Control10

GB29/11/2005Quick Change Over9

SB22/11/2005Process Variability Reduction8

GB15/11/20055s7

GB08/11/20055s6

GB01/11/2005Time Building and Team Selection5

SB25/10/2005FMEA and Process Orientated Six Sigma4

SB18/10/2005Application of The Seven Wastes on a Production Line3

GB11/10/2005Case Examples2

GB04/10/2005Introduction to the course and background to OEE1

LecturerDateLecture

2

TEXT

The Six Sigma WayHow GE, Motorola and Other Top Companies

Are Honing Their PerformancePeter S. Pande, Robert P. Neuman

& Roland R. Cavanagh

McGraw-Hill 2000 ISBN0-07-135806-4

TEXT

Other Six Sigma books are available at

Maritime Greenwichwhich can be

transferred

Introduction into Six Sigma

l Six Sigma is a quality management program to achieve “Six Sigma” levels of quality. It was

pioneered at Motorola in the mid-1980s by Bob Galvin, who succeeded his father and Motorola

founder.

l However it can be applied wherever the control of variation is desired. In recent years it has begun to

branch out into the service industry

l In statistics, sigma refers to the standard deviation of a set of data; "six sigma", therefore, refers to six

standard deviations.

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Introduction into Six Sigma

l Mathematically, assuming that defects occur according to a standard normal distribution, when a

1.5 sigma shift is taken into account, this corresponds to 3.4 quality defects per million pieces

manufactured.

l Initially, many believed that such high process reliability was impossible, and three sigmas (67,000

defects per million opportunities, or DPMO) was considered acceptable. However, market leaders have measurably reached six sigmas in numerous

processes

Introduction into Six Sigma

l Six Sigma Process Improvement is fundamentallyabout improving existing processes but it can mean

different things to different people

l This is because it has moved from being a statistical term to the name for a whole improvement initiative

that encompasses;

Introduction into Six Sigma

Vision

Way of Life

Philosophy

Goal

Value

Method

Symbol

Measure

Toolbox

Benchmark

4

? Sigma2 Sigma 3 Sigma

34.13%13.59%

2.145%

95%

68%

99.73%0.135% 0.135%

Distributions can be linked to probability – making possible predictions of

outcome or evaluation of the odds of an occurrence

In a Normal distribution, the standard deviations

from the mean tells us the % of distribution data and

the probability of occurrence

The area under a curve = probability or chance of

being in that region

A Graphical Representation of Six Sigma

What is Six Sigma?

l Is 99% – On time delivery– Availability– Conformance to specification etc

Good Enough?

l How would you feel about?– Unsafe drinking water for almost 15 minutes each

day?– No electricity for almost 7 hours each month?– 20,000 lost articles of mail per hour?

What is Six Sigma?

l The main aspect of Six Sigma is the use of a basic methodology

l That introduces improvement and analysis tools

l As time progresses variations of the methodology are introduced

l Six Sigma is usually introduced through training schemes

l There are mainly two types– Greenbelt Training– Blackbelt Training

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The Absolutes of Six Sigma Improvementl SSPI is concerned with the improvement of

existing processes and products

l The infrastructure that supports the activity is crucial and comprises these four elements ;

– Process– People– Tools– Training

The Absolutes of Six Sigma Improvement

l People– SSPI projects are team based with teams

comprising of people from the project area on a part-time basis

– Teams consist of Black and Green belt qualified people

– Green Belts are staff members that have been trained in the SSPI processes and the tool set

The Absolutes of Six Sigma Improvement

l People– Black Belts are Green Belt qualified and have further

training in the use of statistical tools and mentoring skills, they lead Green Belts

– Many companies also employ Master Black Belts whom mentor Black and Green Belts, as well as provide specialist support

– And finally a Champion, these people sponsor SSPI projects and conduct the corresponding phase review

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The Absolutes of Six Sigma Improvement

l Tools– All that implement Six Sigma must be able to apply

all tools– A range that include

l Change Management Toolsl Data Management or Statistical Toolsl Process Improvement Toolsl Project Management Tools

Performance Goals – What you’d get ….

1.8 Seconds of dead air

1.68 Hours of dead air

< 2 Crashes4,100 Crashes

With Six Sigmawith 99%With Six Sigmawith 99%

For every week of TV broadcasting (per channel):

Out of every 500,000 computer restarts:

0.018 Months would not balance

60 Months would not balance

1 Mis-delivery3,000 Mis-deliveries

With Six Sigmawith 99%With Six Sigmawith 99%

For 500 years of month-end closings:

For every 300,000 letters delivered:

The Absolutes of Six Sigma Improvement

l Central to the operation of SSPI are two processes

l These are;– Improvement

Project Process

– Project ManagementProcess

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7

Simplified Six Sigma Conversion Table

63.4100.00%532099.98%46,21099.4%366,80093.9%2308,00069.2%1690,00030.9%

Your Sigma is….Your DPMO is …..If your Yield is….

Six Sigma Road Map

l Where would you start to implement Six Sigma?l How would you ensure the business environment is

suitable?

1. Establishing Management Commitment

2. Information Gathering

3. Training

4. Developing Monitoring

Systems

5. Process Processes to be

Improved are Chosen

6. Conducting Six Sigma Projects

Step 1:In order for Six Sigma to be successful, top level management and everyone below them must fundamentally believe in the strength of it.

Managers need to support all individuals and teams involved in improving the quality of the product or service or process.

Six Sigma Road Map

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Step 2:In this step information gathering through intensive communication with customers, suppliers, and employees takes place.

Information about the conditions of the processes, products and services that can be improved, are found and analyzed

Six Sigma Road Map

Step 3:Training this is the most important step and the organizations should strive to have all of its employees trained on Six Sigma on various levels.

An organization should have a mix of Black Belts and Green Belts for effectively implementing a Six Sigma project.

Black Belts are the all day problem solvers who also operate as team leaders in Six Sigma projects. Green Belts are the team members in Six Sigma projects.

Six Sigma Road Map

Step 4:In this step we develop a monitoring system that can be both internal and external. Internal like the amount of wastages and external like the customer satisfaction.

Six Sigma Road Map

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Step 5:In this step the business processes that are to be improved are chosen the problems that were identified are removed and valueless activities and sub processes are terminated.

Here the Six Sigma project is at a critical stage. Before improvements it is necessary that a plan is made and the changes are communicated throughout the organization.

Documentation of the improvements is very necessary so that these improvements can be replicated everywhere in the organization.

Six Sigma Road Map

Step 6:In this step the Six Sigma project is at its mature stage and the changes and improvements are made and analyzed by simulations and statistical methods and if any discrepancies are found then again the cycle is repeated

This approach relies heavily on advanced statistical methods that

complement and reduce the process and product variations.

Six Sigma Road Map

Once the initial stages have been completed, the actual Six Sigma

Methodologies can be implemented

Six Sigma Methodology

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A basic methodology to improve existing processes and is used as the road

map

The DMAIC Process

Tools are introduced

through each stage of the

methodology

Definel Purpose:To get the team established

with an agreed, clear opportunity and effective sponsorship

l Summary of Define Outcomes: The Project Champion, Project Charter, The Project Plan

l Milestone Questions: – Has the right team been set up?– Are they working well together?– Do they have a clear understanding of the

project?– Is it still beneficial to proceed?

Define - ToolsCUSTOMER

FOCUS ANALYSIS

CHAMPION SELECTION

PROJECT PLAN

QUAD OF AIMS

CRITICAL SUCCESS FACTORS

PROJECT GENERAL TOOL

BUSINESS IMPACT

ANALYSIS

TEAM SELECTION

BASELINING

COMMUNICATIONS PLAN

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Measurel Purpose:To involve users of the

process and gather data on current performance

l Summary of Define Outcomes: The Needs & Vision, The Stakeholder List, Baseline Process Capability, Collected Data

l Milestone Questions:– Understanding what is required?– Is everyone involved?– Has all the right data been collected?– Is it still beneficial to proceed?

Measure - ToolsQRC ANALYSIS

GAUGE R&R

RESPONSIBILITY GRID

THREAT V OPPORTUNITY

ANALYSIS

COPIS ANALYSIS

CORRIDOR CONSERVATIONS

STAKEHOLDER IDENTIFICATION

PROCESS MAPPING

DATA COLLECTION PLAN

Analysel Purpose:To identify and quantify the

root causes of current performance

l Summary of Define Outcomes: The Data Displayed, The Process Analysed, The Vital Few Root Causes Selected

l Milestone Questions: – Have the causes been truly identified?– Are these causes verified and validated?– Have these causes been prioritised?– Has a process been analysed?– Is it still beneficial to proceed?

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Analyse - Tools

PARETO ANALYSIS

REGRESSION

VALUE ADDING ANALYSIS

MOMENT OF TRUTH ANALYSIS

FISHBONE ANALYSIS

Y2X ANALYSIS

HYPOTHESIS ANALYSIS

GRAPHING

Improvel Purpose:To identify and implement

performance improvements with support from process users

l Summary of Define Outcomes: The Cost Benefit Analysis, The Stakeholder Analysis, The Results from Pilots, The Implementation Plan.

l Milestone Questions: – Has a practical solution been developed

and adequately tested?– Has commitment been obtained from all

key stakeholders, so that the solution can be fully integrated?

– Is it still beneficial to proceed?

Improve - ToolsDESIGN OF

EXPERIMENTS

FORCE FIELD ANALYSIS

COST BENEFIT ANALYSIS

RISK ANALYSIS

CONTROL CHARTING

BRAINSTORMING

PROCESS DOCUMENTATION

MISTAKE PROOFING

RISK ANALYSIS

STAKEHOLDER ANALYSIS

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Controll Purpose:To achieve the predicted

benefits and sustain the performance improvements

l Summary of Define Outcomes: The Process back with the owners, Rewards and Measures analysed and modified

l Milestone Questions: – Has the process change been made and

is the process under control?– Has an analysis of the infrastructure been

completed to ensure that there is nothing that will undermine the change?

Control – Tools

CONTROL CHARTING

INFRASTRUCTURE

FORCE FIELD ANALYSIS

POST PROJECT REVIEW

MEASUREMENT PLAN

RAM ANALYSIS

SHARING KNOWLEDGE

ANALYSIS

R-DMAIC-V

l Recognize that current process need and can be improved (by team involved/owner).

l Definel Measurel Analyzel Improvel Controll Validate the improvements through continued

monitoring the process and the savings through at least additional 3 months

A variation of the DMAIC methodology

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A basic methodology of introducing new processes (also known as Design for Six Sigma).

DMADV

l Define the process and where it would fail to meet customer needs.

l Measure and determine if process meets customer needs.

l Analyze the options to meet customer needs. l Design in changes to the process to meet customers

needs. l Verify the changes have met customer needs.

The Best Methodology to Use

The DMADV methodology, instead of the DMAIC methodology, should be used when:

l A product or process is not in existence at your company and one needs to be

developed

l The existing product or process exists and has been optimized (using either DMAIC or

not) and still doesn't meet the level of customer specification or six sigma level

Example of a Small Manufacturing Company

A relative small electronic company engaged in designing and manufacturing UPS (Uninterruptible

Power Systems) and are in the infancy of implementing 6sigma and D.O.E (Design of Experiments). They are

looking for help on how to select 6sigma and DOE projects, for example in which area of the company can

we implement 6sigma and DOE.

The typical production process is;Design phase, production line (component pre-form,

component insertion, wave soldering, wiring, assemble EM to chassis, tests ...), warehouse management,

material flow, etc.

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Suggested Methodology to follow!

l Six Sigma projects can be applied in any functions of the organization where the customer (both internal and external) faces a problem.

l Convert these problem statements into your process characteristics and identify the root causes for the problems and attack them.

l For example:

Suggested Methodology to follow!

– Reduce time taken for designing a system– Reduce errors in Design– Reduce production time – Reduce testing time

l Start from the external customer and ask where you can improve or where they find problems with the company. Draw your process map from there.

l In your type of business which involves transactional activities there are lot of scopes for 6 sigma projects!

Controversies with Six Sigma

l Six Sigma is controversial with the statistics profession.

l Some teachers of statistics are critical of the standard of statistical teaching found in Six Sigma materials.

l Others object to the idea that a single universal standard can be appropriate across all domains of application.

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Controversies with Six Sigma

l They argue that quality standards should be set on a case-by-case basis using decision theory or cost benefits analysis.

l Others suggest that Six Sigma, rather than being a true methodology.

l It is more often implemented to start an unending cycle of improvement and use of better tools on the industry day to day practices rather than to use advanced statistical theories that cannot be daily applied.

Six Sigma Tools

As previously mentioned Six Sigma is a process orientated improvement tool and

involves the use of a number of toolsdepending on the process to be improved

One particular tool is

Failure Mode and Effect Analysis

Six Sigma & Failure Mode and Effect Analysisl The FMEA method has many applications in

a Six Sigma environment, in terms of looking for problems not only in work processes and improvements but also in;

l Data collection activitiesl Voice of the customer effortsl Procedures

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What is Failure Mode and Effect Analysisl FMEA is systemised technique which

identifies and ranks the potential modes of a design or manufacturing process in order to prioritise improvement actions.

l FMEA is a disciplined approach for identifying and classifying the type, severity and detects ability of all modes of failure of a product or process.

What is Failure Mode and Effect Analysisl Is a method originally developed for systems

engineering, that is used to examine potential failures in products or processes

l It’s used to evaluate the prioritises of risksand helps determine remedial actions to minimise the risk of failure

l It is used in many formal quality systemssuch as ISO 9000 or ISO/TS 16949

Failure Mode & Effect Analysis

l FMEA was a technique initially use in the aerospace industry to find problems with an aircraft before it left the ground!

l It is a concept that looks into the future and determines where potential failures might be located

l However this is too idealistic and so the history and past failures are analysed

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Why is FMEA required?

l NEEDReassurance that causes, effects, and risks of system failures have been reviewed systematically.

l PREMISEYou own/operate/require/design/or are responsible for equipment essential to a system/process/activity which may be small or large, simple or complex. It may be a future plan, or be presently in operation.

Definitions of FMEAl FAULT:

Inability to function in a desired manner, or operation in an undesired manner, regardless of cause.

l FAILURE:A fault owing to breakage, wear out, compromisedstructural integrity, etc. FMEA does not limit itself strictly to failures, but includes faults.

l FAILURE MODE:The manner in which a fault occurs, i.e., the way in which the element faults.

Definitions of FMEA

l FAILED/FAULTED SAFE:Proper function is compromised, but no further threat of harm exists e.g., a smoke detector alarms in the absence of smoke.

l FAILED/FAULTED DANGEROUS:Proper function is impaired or lost in a way which poses threat of harm e.g., a smoke detector does not alarm in the presence of smoke.

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Definitions of FMEAl FAILURE EFFECT:

The consequence(s) of a failure mode on an operation, function, status of a system / process / activity / environment.

The undesirable outcome of a fault of a system element in a particular mode.

The effect may range from relatively harmless impairment of performance to multiple fatalities, a major equipment loss, and environmental damage,

Definitions of FMEAl FAILURE EFFECT:

For example.– All failures are faults; not all faults are failures. Faults can

be caused by actions that are not strictly failures.

– A system that has been shut down by safety features responding properly has NOT faulted e.g., an over temperature cut off.)

– A protective device which functions as intended e.g., a blown fuse has NOT failed.

Classical FMEA Questions (for each system element):

1. How (in what ways) can this element fail (failure modes)?

2. What will happen to the system and its environment if this element does fail in each of the ways available to it (failure effects)?

3. Will a failure of the system result in intolerable/undesirable loss? If NO, document and end the analysis. If YES,

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– Divide the system into its subsystems*. Ask this questions for each subsystem: Will a failure of this subsystem result in intolerable/undesirable loss? If NO, document and end the analysis. If YES,

– Divide each subsystem into its assemblies. Ask this question foreach assembly: Will a failure of this assembly result in intolerable/undesirable loss? If NO, document and end the analysis. If YES, continues this questioning through the subassembly level, and onward – into the piece-part level if necessary.

4. For each analysed element, what are the Failure Modes?

5. For each failure mode, what are the Failure Effects?

These “filtering” questions shorten

the analysis

and conserve

man hours.

Classical FMEA Questions (for each system element):

Applicationsl FMEA is most commonly applied but not

limited to design and manufacturingprocesses

l Design Failure Modes & Effects Analysis (DFMEA) identifies potential failures of a design before they occur

l DFMEA then goes on to establish the potential effects of the failures, their cause, how often and when they might occur and their potential seriousness

Applicationsl Process Failure Modes & Effect Analysis

(PFMEA) is systemise group of activitiesintended to;1) Recognise and evaluate the potential failure of

a product/process and its effect2) Identify actions which could eliminate or reduce

the occurrence, or improve detectability3) Document the process, and4) Track changes to process-incorporated to avoid

potential failure

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The Basic Process

Is to take a description of the parts of a system, and list the consequences if each part

fails. In most formal systems, theconsequences are then evaluated by three

criteria and associated risk indices:

SEVERITY (S)

LIKELIHOOD OF OCCURRENCE (O)and (note: This is also often known as PROBABILITY (P)

INABILITY OF CONTROLS TO DETECT IT (D)

The Basic Process

Each Index ranges from 1 (lowest risk) to 10 (highest risk). The overall risk of each failure is called Risk

Priority Number (PRN) and the product Severity (S), Occurrence (O) and Detection (D) rankings:

RPN = S x O x D

The PRN (ranging from 1 to 1000) is used to prioritise all potential failures to decide upon actions leading to

reduce risk, usually by reducing likelihood of occurrence and improving controls for detecting the

failure

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1. Describe Product or Process

l Describe the product/process and its function.

l An understanding of the product or process under consideration is important to have clearly articulated.

l This understanding simplifies the process of analysis by helping the engineer identify those product/process uses that fall within the intended function and which ones fall outside.

l It is important to consider both intentional and unintentional uses since product failure often ends in litigation, which can be costly and time consuming

2. Define Functionsl Create a Block Diagram of the product or process. A

block diagram of the product/process should be developed.

l This diagram shows major components or process steps as blocks connected together by lines that indicate how the components or steps are related.

l The diagram shows the logical relationships of components and establishes a structure around which the FMEA can be developed.

l Establish a Coding System to identify system elements. The block diagram should always be included with the FMEA form.

3. Identify Potential Failure Modes

l Identify Failure Modes. A failure mode is defined as the manner in which a component, subsystem, system, process, etc. could potentially fail to meet the design intent.

l Examples of potential failure modes include: – Corrosion – Hydrogen embrittlement – Electrical Short or Open – Torque Fatigue – Deformation– Cracking

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4. Describe Effects of Failure

l Describe the effects of those failure modes.

l For each failure mode identified the engineer should determine what the ultimate effect will be.

l A failure effect is defined as the result of a failure mode on the function of the product/process as perceived by the customer.

l They should be described in terms of what the customer might see or experience should the identified failure mode occur.

4. Describe Effects of Failure

l Keep in mind the internal as well as the external customer.

l Examples of failure effects include:– Injury to the user – Inoperability of the product or process – Improper appearance of the product or process – Odours – Degraded performance – Noise

5. Determine Causes

l Identify the causes for each failure mode.

l A failure cause is defined as a design weakness that may result in a failure.

l The potential causes for each failure mode should be identified and documented.

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5. Determine Causes

l The causes should be listed in technical terms and not in terms of symptoms.

l Examples of potential causes include: – Improper torque applied – Improper operating conditions – Contamination – Erroneous algorithms – Improper alignment – Excessive loading – Excessive voltage

6. Detection Methods/Current Controlsl Identify Current Controls (design or process). Current

Controls (design or process) are the mechanisms that prevent the cause of the failure mode from occurring or which detect the failure before it reaches the Customer.

l The engineer should now identify testing, analysis, monitoring, and other techniques that can or have been used on the same or similar products/processes to detect failures.

l Each of these controls should be assessed to determine how well it is expected to identify or detect failure modes.

6. Detection Methods/Current Controlsl After a new product or process has been in use

previously undetected or unidentified failure modes may appear.

l The FMEA should then be updated and plans made to address those failures to eliminate them from the product/process.

l Determine the likelihood of Detection. Detection is an assessment of the likelihood that the Current Controls (design and process) will detect the Cause of the Failure Mode or the Failure Mode itself, thus preventing it from reaching the Customer.

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7. Calculate the Risk

l Review Risk Priority Numbers (RPN). The Risk Priority Number is a mathematical product of the numerical Severity, Probability, and Detection ratings:

RPN = (Severity) x (Probability) x (Detection)

l The RPN is used to prioritize items than require additional quality planning or action.

8. Take Action

l Determine Recommended Action(s) to address potential failures that have a high RPN.

l These actions could include – specific inspection, – testing or quality procedures; – selection of different components or materials; – de-rating; – limiting environmental stresses or operating range; – redesign of the item to avoid the failure mode; – monitoring mechanisms; – performing preventative maintenance;– inclusion of back-up systems or redundancy

9. Assess Results

l Assign Responsibility and a Target Completion Date for these actions. This makes responsibility clear-cut and facilitates tracking.

l Indicate Actions Taken. After these actions have been taken, re-assess the severity, probability and detection and review the revised RPN's. Are any further actions required?

l Update the FMEA as the design or process changes, the assessment changes or new information becomes known

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Typical Worksheet FMEA Information

1. General administrative/heading information2. Identification number (from System Breakdown)3. Item name4. Operational Phase(s)5. Failure mode6. Failure cause7. Failure effect8. Target(s)9. Risk assessment (Severity/Probability/Risk)10.Action required/remarks

Failure Modes & Effect Analysis

l?

Work Sheet ExamplesP= Probabilities

S = Severity of Failure to the Vehicle

D = Likelihood that the Defect will Reach the Customer

R = Risk Priority Measure

No. Part Name/Part No.

Function Failure Mode Mechanism(s) & Cause(s) of Failure

Effect(s) of Failure Current Control

Recommended Corrective Action(s)

Action(s) Taken

P S D R1 Position

ControllerReceive a

demand positionLoose cable connection

Wear & Tear Motor fails to move 2 4 1 8 Replace faulty wire

Incorrect demand signal

Operator Error Position Controller Breakdown in a long-run

4 4 3 48 Q.C. checked

Intensive training for operators

2 Drive Receive Speed Demand

Incorrect Speed Demand being

Received

Fault in Position Controller's Output

Extensive Damage to the Machine

2 4 4 32 Indicator and Audile Warning

Measures Actual Speed

Incorrect Speed Reading

Wear & Tear Extensive Damage 4 4 5 80 Voltmeter

Improve Check Procedures

3 Motor Provides Voltage signal

Signal Loss Faulty Leads Unstable Control 3 5 4 60 Durability Test on Leads

Endanger OperatorsSerious Damage

Produce Final Product

Defects in Products

Incorrect MotionCustomers Complain 4 5 5 100 QC CheckedFaulty products are

IdentifiedIncreased Staff in

InspectionSet Up Customer

Complain Department

P.R.N.

1= Very Low or None

2 = Low or Minor

3 = Moderate or Significant

4 = High

5 = Very High or Catastrophic

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Failure RateA failure rate is the average frequency with which something fails.

Failure rate, often denoted by the Greek letter (lambda), is important in the fields of reliability theory and product warranties.

The failure rate depends on the failure distribution, which describes the probability of failure prior to a specified time.

Another way of expressing failure rate is the mean time between failure (MTBF), which is the “average" time between failures.

Failure RateThe failure rate is not always constant, so the hazard function is used to describe the instantaneous failure rate at any point in time.

The bathtub curve, a particular form of the hazard function, is a typical representation of the failure rate of a system during its operating life

The Bath Tub Curve

l The bathtub curve describes a particular form of the hazard function that comprises three parts:

–The first part is a decreasing failure rate, known as early failures or infant mortality.

–The second part is a constant failure rate, known as random failures .

–The third part is an increasing failure rate, known as wear-out failures .

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The Bath Tub Curve

l The bathtub curve is often employed to represent the failure rate of a product during its lifecycle.

l The product experiences early "infant mortality" failures when first introduced, then exhibits random failures with constant failure rate during its "useful life", and finally experiences "wear out" failures as the product exceeds its design lifetime.

The Bath Tub Curve

This highlights all procedures, processes machinery, etc, are most useful when the failure rates are constant

An Example of FMEA

Managers & Engineers at e-commerce company Nitwit.com wanted to make sure nothing went wrong with its process for updating the on-line catalogue.

Here are two problems they identified and the analysis they did:

1. The wrong artwork is used with a new itemSeverity = 5

Occurrence = 5Detection = 3

RPN = 5x5x3 = 75

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An Example of FMEA

2. Buyers can’t place an order for an itemSeverity = 8

Occurrence = 5Detection = 6

RPN = 8x5x6 = 240

Based on this assessment, the focused on the concern about being able to place orders and

developed preventive measures to ensure that all new products are posted to the ordering system

Benefits of FMEA

l Discover potential single-point failures.

l Assesses risk (FMECA) for potential, single-element failures for each identified target, within each missionphase.

l Knowing these things helps to:– Optimise reliability, hence mission accomplishment.– Guide design evaluation and improvement.

– Guide design of system to “fail safe” or crash softly.– Guide design of system to operate satisfactorily using

equipment of “low” reliability.

Benefits of FMEA

l Guide component/manufacturer selection.

l High-risk hazards found can be analysed to the piece-part level using FMEA.

l Hazards caused by failures identified in the FMEA can be added, if they haven’t already been logged.

l FMEA complements Fault Tree Analysis and other techniques.

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Principal Limitations of FMEA

l Frequently, human errors and hostile environments are overlooked.

l Because the technique examines individual faults of system elements taken singly, the combined effects of coexisting failures are not considered.

l If the system is at all complex and if the analysis extends to the assembly level or lower, the process can be extraordinarily tedious and time consuming.

Principal Limitations of FMEA

l Failure probabilities can be hard to obtain; obtaining, interpreting, and applying those data to unique or high-stress systems introduces uncertainty which itself may be hard to evaluate.

l Sometimes FMEA is done only to satisfy the altruistic urge or need to “DO SAFETY.”

l Remember that the FMEA will find and summarise system vulnerability to Single Point Failures, and it will require lots of time, money, and effort.

Principal Limitations of FMEA

l How does the recipient intend to use the results? Why does he need the analysis?

l When a facility proprietor learns the facility has 100s of 1000s of problems, frequently he panics, and demands “Critical Items Lists” or “Total System Redundification.” This leads to loss of focus on other, possibly deadlier, system threats.

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Disadvantages

FMEA is useful mostly as a survey method to identify major failure modes in a system. It is not able to discover complex failure modes

involving multiple failures or subsystems, or to discover expected failure intervals of particular failure modes. For these, a different method called Fault Tree Analysis or Cause & Effect

Analysis or

Fishbone Diagrams

Fishbone Diagrams

What is it?A simple tool that can be used to structure and group

the causes that lead to an effect

Fishbone Diagrams

How is it applied?Each team member writes their ideas for potential X’s on

a post-it and these are put on a wall

The post-its are reviewed for common themes which are grouped together and given a “header”

It is seen as a creative thinking tool to generate, collect and group information

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Fishbone DiagramsPoints to remember!

l Take your time – this is important.

l What is the central theme?

l It might be one of the existing post-its.

l It might be the cluster has more than one central theme, in which case you should separate it into two

clusters.

l The description must be specific and consistent.

l The header must stand on its own.

ExampleHewlett-Packard is proud of its reputation for high quality

products and services.

Because of this it was especially concerned with the problems that it was having with its customers returning

defective toner cartridges.

About 2000 of these were being returned every month.

The team suspected that not all returns were actually the result of a faulty product, which is why the team decided

to investigated the problem.

The cause and effect diagram which they generated is shown

Example

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Example ResultsThree major problems were identified

1. Some users were not as familiar as they should have been with the correct method of loading the cartridge

into the printer or in being able to solve their own minor problems

2. Some of the dealers were also unaware how to solve the minor problems

3. There was clearly some abuse of the Hewlett-Packard’s ‘no-questions-asked’ returns policy

Example Results

The team went on to using problem solving methods and made suggestions, which tightened up their returns

policy as well as improving the way in which customers were instructed on how to use the

products.

The results were impressive.

Complaints in almost all areas shrank to a fraction of what they have been previously.

Questions

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