# What is Quality?

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Quality at Source Manufacturing Systems Analysis Professor: Nour El Kadri e-mail: nelkadri @ site.uottawa.ca. What is Quality?. Quality : The ability of a product or service to consistently meet or exceed customer expectations. - PowerPoint PPT PresentationTRANSCRIPT

Quality at Source

Manufacturing Systems Analysis

Professor: Nour El Kadrie-mail: nelkadri@ site.uottawa.ca

What is Quality?Quality: The ability of a product or service to consistently meet or exceed customer expectations.Not something tacked on, but an integral part of the product/service.Comes from the fundamental process, not from material or from inspection

What does a customer perceive as qualityPerformanceAestheticsFeaturesConformanceReliabilityDurabilityPerceived quality (eg: reputation)Serviceability

ExpectationsCustomers perceptions and expectations shift and evolve:With product life cycle:Features & functionality are critical in a leading-edge hi-tech productReliability, durability, serviceability are critical in a mature productWith an evolving industry, market or technology (cf: Quality & the Ford Model T)

Why is Quality Important?

Quality is:A critical basis of competition (ie: A critical differentiator)Critical to SC effectiveness (Partners demand objective evidence of quality measures, programs)A measure of efficiency & cost saving (Quality does not cost anything)NB: Quality as one key identifier of a High-Performance company

Cost of QualityPrevention Costs: All training, planning, customer assessment, process control, and quality improvement costs required to prevent defects from occurringAppraisal Costs: Costs of activities designed to ensure quality or uncover defectsFailure Costs: Costs incurred by defective parts/products or faulty services.Internal Failure Costs: Costs incurred to fix problems that are detected before the product/service is delivered to the customer.External Failure Costs: Costs incurred to fix problems that are detected after the product/service is delivered to the customer.

- Consequences of Poor QualityLiabilityLoss of productivityLoss of business:Dissatisfied customers will switchYou usually wont know why (
The Evolution of Quality ManagementCraft production: Strict craftsman concern for qualityIndustrial revolution: Specialization, division of labour. Little control of or identification with overall product quality

SPC (Statistical Process Control)

Quality Control ChartsDefinitionsVariablesMeasurements on a continuous scale, such as length or weightAttributesInteger counts of quality characteristics, such as # of good or badDefectA single non-conforming quality characteristic, such as a blemishDefectiveA physical unit that contains one or more defects

Types of Control Charts

Data monitored Chart name Sample size

Mean, range of sample variables MR-CHART 2 to 5 unitsIndividual variables I-CHART 1 unit% of defective units in a sample P-CHART at least 100 unitsNumber of defects per unit C/U-CHART 1 or more units

Control Factorsn A A2 D3 D4 d2 d32 2.121 1.880 0 3.267 1.128 0.8533 1.732 1.023 0 2.574 1.693 0.8884 1.500 0.729 0 2.282 2.059 0.8805 1.342 0.577 0 2.114 2.316 0.864

Control factors are used to convert the mean of sample ranges ( R ) to:(1) standard deviation estimates for individual observations, and(2) standard error estimates for means and ranges of samples

For example, an estimate of the population standard deviation of individual observations (x) is:x = R / d2

Control Factors (cont.)Note that control factors depend on the sample size n.

Relationships amongst control factors:A2 = 3 / (d2 x n1/2)D4 = 1 + 3 x d3/d2D3 = 1 3 x d3/d2, unless the result is negative, then D3 = 0

A = 3 / n1/2D2 = d2 + 3d3D1 = d2 3d3, unless the result is negative, then D1 = 0

Mean-Range control chartMR-CHART1. Compute the mean of sample means ( X ).

2. Compute the mean of sample ranges ( R ).

3. Set 3-std.-dev. control limits for the sample means:UCL = X + A2RLCL = X A2R

4. Set 3-std.-dev. control limits for the sample ranges:UCL = D4RLCL = D3R

Control chart for percentage defective in a sample P-CHART1. Compute the mean percentage defective ( P ) for all samples:P = Total nbr. of units defective / Total nbr. of units sampled

2. Compute an individual standard error (SP ) for each sample:SP = [( P (1-P ))/n]1/2

Note: n is the sample size, not the total units sampled.If n is constant, each sample has the same standard error.

3. Set 3-std.-dev. control limits:UCL = P + 3SPLCL = P 3SP

Control chart for individual observations I-CHART1. Compute the mean observation value ( X )X = Sum of observation values / Nwhere N is the number of observations

2. Compute moving range absolute values, starting at obs. nbr. 2:Moving range for obs. 2 = obs. 2 obs. 1Moving range for obs. 3 = obs. 3 obs. 2Moving range for obs. N = obs. N obs. N 1

3. Compute the mean of the moving ranges ( R ):R = Sum of the moving ranges / N 1

Control chart for individual observations I-CHART (cont.)4. Estimate the population standard deviation (X):X = R / d2Note: Sample size is always 2, so d2 = 1.128.

5. Set 3-std.-dev. control limits:UCL = X + 3XLCL = X 3X

Control chart for number of defects per unit C/U-CHART1. Compute the mean nbr. of defects per unit ( C ) for all samples:C = Total nbr. of defects observed / Total nbr. of units sampled

2. Compute an individual standard error for each sample:SC = ( C / n)1/2

Note: n is the sample size, not the total units sampled.If n is constant, each sample has the same standard error.

3. Set 3-std.-dev. control limits:UCL = C + 3SCLCL = C 3SC

Notes: If the sample size is constant, the chart is a C-CHART. If the sample size varies, the chart is a U-CHART. Computations are the same in either case.

SPC & Cost of QualityDeming (Promoted SPC in Japan):The cause of poor quality is the system, not the employeeMgmt is responsible to correct poor qualityJuran (Cost of Quality: Emphasized need for accurate and complete identification of the costs of quality) :Quality means fitness for useQuality begins in knowing what customers want, planning processes which are capable of producing the required level of quality

From Quality to Quality AssuranceChanging emphasis from Quality to Quality Assurance(Prevent defects rather than finding them after they occur)New techniques for Quality Improvement (eg: TQM, Six Sigma):New quality programs (Provide objective measures of quality for use of customers, SC partners, etc.)Baldridge AwardISO 9000/14000 CertificationIndustry-specific programs (eg: TL9000(Telecom))

Energy needed to close doorDoor seal resistanceCheck force on level groundEnergy needed to open doorAcoustic trans., windowWater resistanceMaintain current levelReduce energy level to 7.5 ft/lbReduce force to 9 lb.Reduce energy to 7.5 ft/lbMaintain current levelMaintain current levelEngineering characteristicsCustomer requirementsImportance to customer54321Easy to closeStays open on a hillEasy to openDoesnt leak in rainNo road noiseImportance weighting7533210669

Source: Based on John R. Hauser and Don Clausing, The House of Quality, Harvard Business Review, May-June 1988.

23xxxxxx*Competitive evaluationxAB(5 is best)1 2 3 4 5= Us= Comp. A= Comp. BTarget valuesTechnical evaluation (5 is best)Correlation:Strong positivePositiveNegativeStrong negativexxxxxxxxxxxABABABBABAAAAAAABBBBBBRelationships:Strong = 9Medium = 3Small = 1

Taguchi analysisLoss functionL(x) = k(x-T)2wherex = any individual value of the quality characteristicT = target quality valuek = constant = L(x) / (x-T)2

Average or expected loss, variance knownE[L(x)] = k(2 + D2)where 2 = Variance of quality characteristic D2 = ( x T)2

Note: x is the mean quality characteristic. D2 is zero if the mean equals the target.

Taguchi analysis (cont.)Average or expected loss, variance unkownE[L(x)] = k[ ( x T)2 / n]

When smaller is better (e.g., percent of impurities)L(x) = kx2

When larger is better (e.g., product life)L(x) = k (1/x2)

TQM Total Quality Management: A philosophy that involves everyone in an organization in a continual effort to improve quality and achieve customer satisfaction.The TQM Approach:Find out what the customer wantsDesign a product or service that meets or exceeds customer wantsDesign processes that facilitates doing the job right the first timeKeep track of resultsExtend quality initiatives to include suppliers & distributors.

Elements of TQMContinual improvementCompetitive benchmarkingEmployee empowerment (eg: Quality circles, etc.)Team approachDecisions based on factsKnowledge of toolsSupplier qualityIdentify and use quality championDevelop quality at the sourceInclude suppliers

Criticism of TQMCriticisms of TQM include:Blind pursuit of TQM programsPrograms may not be linked to strategiesQuality-related decisions may not be tied to market performanceFailure to carefully plan the program

Obstacles to Implementing TQMPoor inter-organizational communicationView of quality as a quick fixEmphasis on short-term financial resultsInternal political and turf warsLack of: Company-wide definition of qualityStrategic plan for changeCustomer focusReal employee empowermentStrong motivationTime to devote to quality initiativesLeadership

Six SigmaSix Sigma (eg: Jack Welch @ GE):Statistically: Having no more than 3.4 defects per millionConceptually: A program designed to reduce defects

Six Sigma progra

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