Chapter 01 Quality Control

8/9/2019 Chapter 01 Quality Control

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Chapter 1

Fundamentals of QualityGitlow, Oppenheim, Oppenheim and Levine


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Chapter 1Fundamentals of Quality

Learning ObjectivesUnderstand the definition of a processUnderstand variation and its causes in a processSpecial causes of variation

Common causes of variationUnderstand the two definitions of qualityGoal post viewContinuous improvement view

Understand the quality environment


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Chapter 1Fundamentals of Quality

Learning ObjectivesUnderstand the three types of qualityQuality of design or redesignQuality of conformanceQuality of performance

Understand the relationship between Quality and CostFeatures and priceUniformity and dependability

Understand the relationship between Quality and ProductivityUnderstand the benefits of improving quality

Know how to apply take-away knowledge


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Process Basics

Definition of a processA process is a collection of interacting components

that transform inputs into outputs toward a commonaim called a mission statement.

Manpower

Equipment

Materials/Goods

Methods

Environment

Inputs

Transformation ofinputs, value (time,place, form) is addedor created

Process

ManpowerEquipment

Materials/Goods

Methods

Environment

Outputs


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Definition of a process

It is managements job to optimize the entireprocess toward its aim.

This may require the sub-optimization of selectedcomponents of the process.


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Definition of a ProcessProcesses exist in all facets of organizations and

our understanding of them is crucialAdministrationSales and serviceHuman resources

MaintenanceCommunicationProduction

Relationships between people are processesAll processes can be studied, documented, defined,

improved, and innovated


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Definition of a processAn organization is a multiplicity of micro sub-

processes, all synergistically building to the macro

process of that firm.

All processes have customers and suppliers; thesecustomers and suppliers can be internal or externalto the organization.


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Variation in a Process

The outputs from all processes and theircomponent parts vary over time.

Time

Num

ber

of

Accidents

Actual Values(Variation amongactual values)

Ideal Value = 0

Variation between Ideal and Actual Values


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Variation in a processSpecial causes of variation are due to events

external to the usual functioning of a system.Examples could include (if they are not part of the system):New raw materialsA drunk employeeA new operator


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Variation in a processCommon causes of variation are due to the

process itself.Process capability is determined by inherent

common causes of variation.

Examples of common causes of variation include:Hiring, training and supervisory practicesLightingStress

Management stylePolicies and proceduresDesign of products or services


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Variation in a processEmployees cannot control a common cause of

variation and should not be held accountable for, orpenalized for, its outcomes.

Managers must realize that unless a change is

made in the process (which only they can make) theprocesss capability will remain the same.


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Process Basics

Workshop:The Drunk Employee


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More About the Feedback LoopA feedback loop relates information about outputs

from any stage or stages back to another stage orstages so that an analysis of the process can bemade.

Input Process Output

Feedback Loop


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More About the Feedback Loop

There are three feedback loop situations

no feedback loopspecial cause only feedback loopspecial and common cause feedback loop


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DEFINITION OF QUALITY

Goal Post View

Continuous Improvement View


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Goal post view

Conformance to valid customer requirements, thatis, as long as an output fell within acceptable limits,called specification limits, around a desired value,called the nominal value (denoted by m), or

target value, it was deemed conforming, good, oracceptable.


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Definition of Quality

No

Good,

Loss

No

Good,

Loss

Loss

Good,

No Loss

LSL USLNominal

QualityCharacteristic

m


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Goal post view (example)The desired diameter of stainless steel ball

bearings is 25 mm (the nominal value).A tolerance of 5 mm above or below 25 mm is

acceptable to purchasers.Thus, if a ball bearing diameter measures between

20 mm and 30 mm (inclusive), it is deemedconforming to specifications.If a ball bearing diameter measures less than 20

mm or more than 30 mm, it is deemed notconforming to specifications, and is scrapped at a

cost of $1.00 per ball bearing.


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Continuous Improvement ViewQuality is a predictable degree of uniformity and

dependability, at low cost and suited to the market.Losses begin to accrue as soon as a qualitycharacteristic of a product or service deviates fromthe nominal value.As with the goal post view of quality, once the

specification limits are reached the loss suddenlybecomes positive and constant, regardless of thedeviation from the nominal value beyond thespecification limits.


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Continuous improvement viewL(y) = k(y-m)2 = loss of deviating (y-m) units from

the nominal value of my= the value of the quality characteristic for a

particular item of product or servicem = the nominal value for the quality characteristic

k = a constant, A/d2

A = the loss (cost) of exceeding specification limits(e.g., the cost to scrap a unit of output)d = the allowable tolerance from m that is used to

determine specification limits.


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Continuous improvement viewUnder the Taguchi Loss Function the

continuous reduction of unit-to-unit variation

around the nominal value is the mosteconomical course of action, absent capitalinvestment


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Continuous improvement view (example)Returning to the production of stainless steel ball

bearings. Every millimeter higher or lower than 25mm causes a loss that can be expressed by thefollowing Taguchi loss function:

L(y) = k(y-m)2 = (A/d2)(y-m)2 = ($1.00/5mm2)(y-25mm)2= (.04)(y-25mm)2


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Diameter of Ball Bearing (y) Value of Taguchi LossFunction L(y)

18 1.00

19 1.00

20 1.00

21 0.64

22 0.36

23 0.16

24 0.04

25 0.00

26 0.16

27 0.36

28 0.6429 1.00

30 1.00

31 1.00

32 1.00


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The Quality EnvironmentThe pursuit of quality requires that organizations

globally optimize theirsystem of interdependentstakeholders.

This system includes employees, customers,

investors, suppliers and subcontractors,regulators, the environment, and the community.


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Employees are the most critical stakeholdersof an organization.

According to quality expert Kaoru Ishikawa:In management, the first concern of thecompany is the happiness of people who areconnected with it. If the people do not feel

happy and cannot be made happy, thatcompany does not deserve to exist. . . Thefirst order of business is to let the employeeshave adequate income. Their humanity must

be respected, and they must be given anopportunity to enjoy their work and lead ahappy life.


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Types of Quality

There are three types of quality:Quality of design / redesignQuality of conformanceQuality of performance

The above types of quality create the neverending spiral of continuous improvement ofproducts, services or processes


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Quality of design

Quality of design / redesign focuseson determining the qualitycharacteristics of products that aresuited to the needs and wants of amarket, at a given cost; that is, qualityof design develops products from a

customer orientation.


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Quality of design / redesignQuality of design studies begin with consumer

research, service call analysis, and sales callanalysis, and lead to the determination of a productconcept that meets the consumers needs andwants.Next, specifications are prepared for the product

concept.


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Quality of conformanceQuality of conformance is the extent to which a

firm and its suppliers can produce products with apredictable degree of uniformity and dependability,at a cost that is in keeping with the qualitycharacteristics determined in a quality-of-design

study.The ultimate goal of process improvement and

innovation efforts is to create products and serviceswhose quality is so high that consumers (bothexternal and internal) extol them.


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Quality-of-performance

Quality of performance studies focus on

determining how the quality characteristicsdetermined in quality-of-design studies, andimproved and innovated in quality-of-conformancestudies, are performing in the marketplace.

The major tools of quality-of-performance studiesare consumer research and sales/service callanalysis.These tools are used to study after-sales service,

maintenance, reliability, and logistical support, aswell as to determine why consumers do notpurchase the companys products.


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Relationship between

Quality and CostFeatures and PriceFeatures and price determine whether a consumer

will initially enter a market segment; hence featuresand price determine market size.Dependability and uniformity determine a products

success, and therefore its market share, within amarket segment.


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Generally, products or services with more featuresor fancier features have higher costs to themanufacturer and higher prices to the consumerthan products or services with fewer or simpler

features.


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Dependability and UniformityUniformity and dependability create an inverse

relationship between quality and cost. When thedegree of uniformity and dependability of a productis high, the quality of the product is high, and theoverall cost to both the manufacture and the

consumer is less.This relationship is explained by the Taguchi Loss

Function.

1 5 R l ti hi b t


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1.5 Relationship betweenQuality and Cost


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ConclusionManagers must balance the cost of having many

market segments with the benefits of highconsumer satisfaction caused by small deviationsbetween an individual consumers needs and theproduct characteristic package for his market

segment. Also, managers must continually strive toreduce variation in product characteristics for allmarket segments.


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Stressing productivity often has the oppositeeffect of what management desires

Managements ability to improve the processresults in a decrease in defectives, yielding anincrease in good units, quality, and productivity


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Benefits of Improving Quality

Several benefits result from improving a process:rework decreasesproductivity risesquality improvescost per good unit is decreasedprice can be cutworkers morale goes up because they are not seen as the

problem. This last aspect leads to further benefits: less employee absenteeism less burnout,more interest in the job increased motivation to improve work.

This is called the chain reaction of quality

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Chapter 01 Quality Control