Chapter 6: Managing Quality

ÖZGE ÇELİK8th April 2011

Learning Objectives

• Explain quality robust products and Taguchi concepts

• Use the seven tools of TQM 1. Check Sheets 2. Scatter Diagrams 3. Cause-and-Effect Diagrams 4. Pareto Charts 5. Flowcharts 6. Histograms 7. Statistical Process Control Charts

Taguchi Concepts

• Engineering and experimental design methods to improve product and process design- Identify key component and process variables

affecting product variation

• Taguchi Concepts- Quality robustness- Quality loss function- Target-oriented quality

Quality Robustness

• Ability to produce products uniformly in adverse manufacturing and environmental conditions- Remove the effects of adverse conditions

- Small variations in materials and process do not destroy product quality

Quality Loss Function

• Shows that costs increase as the product moves away from what the customer wants

• Costs include customer dissatisfaction, warranty

and service, internal scrap and repair, and costs to society

• Traditional conformance specifications are too simplistic

Target-Target-

oriented oriented

qualityquality

Unacceptable

Poor

GoodBest

Fair

Quality Loss FunctionHigh lossHigh loss

Loss (to Loss (to producing producing organization, organization, customer, customer, and society)and society)

Low lossLow loss

FrequencyFrequency

LowerLower TargetTarget UpperUpper

SpecificationSpecification

Target-oriented quality Target-oriented quality yields more product in yields more product in the “best” categorythe “best” category

Target-oriented quality Target-oriented quality brings product toward brings product toward the target valuethe target value

Conformance-oriented Conformance-oriented quality keeps products quality keeps products within 3 standard within 3 standard deviationsdeviations

L = DL = D22CCwherewhere

L =L = loss to loss to societysocietyD =D = distance from distance from target valuetarget valueC =C = cost of cost of deviationdeviation

Tools of TQM

1. Tools for Generating Ideas• Check sheets• Scatter diagrams• Cause-and-effect diagrams

2. Tools to Organize the Data• Pareto charts• Flowcharts

3. Tools for Identifying Problems• Histogram• Statistical process control chart

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Hour

Defect 1 2 3 4 5 6 7 8

A

B

C

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Seven Tools of TQM

1. Check Sheet: An organized method of recording data

Seven Tools of TQM

2. Scatter Diagram: A graph of the value of one variable vs. another variable

AbsenteeismAbsenteeism

Pro

du

cti

vit

yP

rod

uc

tiv

ity

Seven Tools of TQM

3. Cause-and-Effect Diagram: A tool that identifies process elements (causes) that might effect an outcome

CauseCause

MaterialsMaterials MethodsMethods

ManpowerManpower MachineryMachinery

EffectEffect

Cause-and-Effect Diagrams

MaterialMaterial(ball)(ball)

MethodMethod(shooting process)(shooting process)

MachineMachine(hoop &(hoop &

backboard)backboard)

ManpowerManpower(shooter)(shooter)

Missed Missed free-throwsfree-throws

Rim alignmentRim alignment

Rim sizeRim size

Backboard Backboard stabilitystability

Rim heightRim height

Follow-throughFollow-through

Hand positionHand position

Aiming pointAiming point

Bend kneesBend knees

BalanceBalance

Size of ballSize of ball

LopsidednessLopsidedness

Grain/Feel Grain/Feel (grip)(grip)

Air pressureAir pressure

TrainingTraining

ConditioningConditioning MotivationMotivation

ConcentrationConcentration

ConsistencyConsistency

Seven Tools of TQM

4. Pareto Chart: A graph to identify and plot problems or defects in descending order of frequency

Fre

qu

en

cyF

req

ue

ncy

Pe

rce

nt

Pe

rce

nt

AA BB CC DD EE

Pareto Charts

Number of Number of occurrencesoccurrences

Room svcRoom svc Check-inCheck-in Pool hoursPool hours MinibarMinibar Misc.Misc.72%72% 16%16% 5%5% 4%4% 3%3%

1212

44 33 22

5454

– 100100– 9393– 8888

– 7272

70 70 –

60 60 –

50 50 –

40 40 –

30 30 –

20 20 –

10 10 –

0 0 –

Fre

qu

ency

(n

um

ber

)F

req

uen

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nu

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Causes and percent of the totalCauses and percent of the total

Cu

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erce

nt

Cu

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nt

Data for OctoberData for October

Seven Tools of TQM

5. Flowchart (Process Diagram): A chart that describes the steps in a process

Flow Charts

MRI Flowchart1. Physician schedules MRI2. Patient taken to MRI3. Patient signs in4. Patient is prepped5. Technician carries out MRI6. Technician inspects film

7. If unsatisfactory, repeat8. Patient taken back to room9. MRI read by radiologist10. MRI report transferred to

physician11. Patient and physician discuss

1111

1010

20%20%

99

8880%80%

11 22 33 44 55 66 77

Seven Tools of TQM

6. Histogram: A distribution showing the frequency of occurrences of a variable

DistributionDistribution

Repair time (minutes)Repair time (minutes)

Fre

qu

en

cyF

req

ue

ncy

Seven Tools of TQM

7. Statistical Process Control Chart: A chart with time on the horizontal axis to plot values of a statistic

Upper control limitUpper control limit

Target valueTarget value

Lower control limitLower control limit

TimeTime

Statistical Process Control (SPC)

• Uses statistics and control charts to tell when to take corrective action

• Drives process improvement

• Four key steps- Measure the process

- When a change is indicated, find the assignable cause

- Eliminate or incorporate the cause

- Restart the revised process

An SPC Chart

Upper control limitUpper control limit

Coach’s target valueCoach’s target value

Lower control limitLower control limit

Game numberGame number

| | | | | | | | |

11 22 33 44 55 66 77 88 99

20%20%

10%10%

0%0%

Plots the percent of free throws missedPlots the percent of free throws missed

Inspection

• Involves examining items to see if an item is good or defective

• Detect a defective product• Does not correct deficiencies in

process or product

• It is expensive

• Issues• When to inspect

• Where in process to inspect

When and Where to Inspect

1. At the supplier’s plant while the supplier is producing

2. At your facility upon receipt of goods from the supplier

3. Before costly or irreversible processes4. During the step-by-step production process5. When production or service is complete6. Before delivery to your customer7. At the point of customer contact

Inspection

• Many problems• Worker fatigue

• Measurement error

• Process variability

• Cannot inspect quality into a product

• Robust design, empowered employees, and sound processes are better solutions

Source Inspection

• Also known as source control

• The next step in the process is your customer

• Ensure perfect product to your customer

Poka-yoke is the concept of foolproof devices or techniques designed to pass only

acceptable product

Service Industry Inspection

OrganizationWhat is

InspectedStandard

Nordstrom Department Store

Display areas

Stockrooms

Salesclerks

Attractive, well-organized, stocked, good lighting

Rotation of goods, organized, clean

Neat, courteous, very knowledgeable

Attributes Versus Variables

• Attributes• Items are either good or bad, acceptable

or unacceptable• Does not address degree of failure

• Variables• Measures dimensions such as weight,

speed, height, or strength• Falls within an acceptable range

• Use different statistical techniques

TQM In Services

• Service quality is more difficult to measure than the quality of goods

• Service quality perceptions depend on • Intangible differences between products

• Intangible expectations customers have of those products

Service Quality

The operations manager must recognize:

1. The tangible component of services is important

2. The service process is important

3. The service is judged against the customer’s expectations

4. Exceptions will occur

Determinants of Service Quality

Reliability

Responsiveness

Competence

Access

Courtesy

Communication

Credibility

Security

Understanding/ knowing the customer

Tangibles

Service Recovery Strategy

• Managers should have a plan for when services fail

• Marriott’s LEARN routine• Listen• Empathize• Apologize• React• Notify

Managerial Implications

• We will have plan for when services fail.

• We will recognize that the service is judged against the customer’s expentations.