Quality Management
Quality ManagementSession 12Dimensions of Quality, Quality costDIMENSIONS OF QUALITYPerformanceReliabilityDurabilityServiceabilityAestheticsFeaturesPerceived QualityConformance to Standards
1. Performance2. ReliabilityRefers to the product performing its intended operation for a specified period of timeExpressed in probabilityWhat does a reliability of 0.9 mean?2. ReliabilityFailureA change from the operational to non-operational; statusThree types of failureEarly failureRandom failureWearout failure
2. ReliabilityOverall reliability is obtained by multiplying the probabilities of all the components that can cause failureRp = R1.R2.R3RnWhen a system has parallel redundancyRp = R1+ R1(1-R2)= 1-(1-R1)(1-R2)Reliability of n parallel components isR = 1-[(1-R1)(1-R2) (1-Rn)]
2. ReliabilityA flow control system consists of three components in series, with individual reliabilities 0.90, 0.95 and 0.85. A failure of the system costs $5,000.What is the reliability of the system?What is the long run expected cost of failure?What would be the reliability of a complete parallel backup system?What should be the maximum amount of funds that should be expended for a parallel system? Solution Rp = 0.90 *0.95 * 0.85 = 0.73Probability of failure is 0.27.Therefore expected cost is 0.27 * $5000 = 1350c) The redundant system also is expected to be reliable 73% of time. The reliability of the combined system will be the reliability of the primary system plus the 73% of the expected 27% failureRp = 0.73 +(0.27)(0.73) = 0.93
The long-run expected cost of failure is (0.07) ($5000) = 350The cost has been reduced from 1350 to 350.Hence the cost should be less than 1000Solution ReliabilityCan be expressed as a product failure rate, or mean time between failures(MTBF)Failure rate (FR) measures The number of failures during an operating period, orThe number of failures among the product testedFR = number of failure/operating time (number tested)MTBF = 1/FRReliabilityOne hundred artificial heart valves were tested for 20,000 hours at a lab research center and 6 valves failed during the test.a) what is the percentage of failures?b) what is the number of failures per unit yearc) how many failures can be expected per year for every 100 installationsd) what is the mean time between failures?SolutionA) FR = 6/100 = 6%B) Operating time = total time non-operating time= 100(20,000) 6(20,000)/2= 19,40,000 unit hoursFR = 6/19,40,000 = 0.000003 failures per unit-hour0.000003(24 hours)(365) = 0.026 failures per unit-yearC) (0.026 ) (100) = 2.6 failures per yearD) MTBF = 19,40,000/6 = 3,23,333.3 unit-hours per failureQuality control toolsCheck sheetFlow chartHistogramPareto chartRunchart Fishbone diagramControl chartCase: shortening telephone waiting timeA bank is employing a call answering service
The main goal in terms of quality is zero waiting time - customers get a bad impression - company vision to be friendly and easy access
The question is how to analyze the situation and improve quality14The current processCustomer BOperatorCustomer AReceivingPartyHow can we reduce waiting time?15Makes customer waitAbsent receiving party Working system of operators Customer OperatorFishbone diagram analysisAbsentOut of officeNot at deskLunchtimeToo many phone callsAbsentNot giving receiving partys coordinatesComplainingLeaving a messageLengthy talkDoes not know organization wellTakes too much time to explainDoes not understand customer16Daily averageTotal numberAOne operator (partner out of office)14.3172BReceiving party not present6.173CNo one present in the section receiving call5.161DSection and name of the party not given1.619EInquiry about branch office locations1.316FOther reasons0.81029.2351Reasons why customers have to wait(12-day analysis with check sheet)17Pareto Analysis: reasons why customers have to waitABCDEFFrequencyPercentage0%49%71.2%10020030087.1%15025018Ideas for improvementTaking lunches on three different shiftsAsk all employees to leave messages when leaving desksCompiling a directory where next to personnels name appears her/his title19Results of implementing the recommendations ABCDEFFrequencyPercentage100%0%49%71.2%10020030087.1%100%BCADEFFrequencyPercentage0%100200300BeforeAfterImprovement20CONTROL CHARTSIn general, how can we monitor quality?Assignable variation: we can assess the causeCommon variation: variation that may not be possible to correct (random variation, random noise)By observingvariation inoutput measures!2122
Source: http://msi6.com/MSI6/QualityZone/QzoneJuranTrilogy.aspx23Quality Costs
Four categories of cost of quality are:
Prevention costs are costs of all activities that are designed to prevent poor quality from arising in products or services. Appraisal costs are costs that occur because of the need to control products and services, to ensure a high quality level in all stages, conformance to quality standards and performance requirements. Internal failure costs are costs that are caused by products or services, not conforming to requirements or customer/user needs, and are found before delivery of products and services to external customers.External failure costs are costs that are caused by deficiencies found, after delivery of products and services to external customers, which lead to customer dissatisfaction.23Quality Costs
Cost of Poor Quality 25 .PPTExamples of Prevention ExpenseQuality PlanningTraining and EducationProcess DefinitionCustomer SurveysPreproduction ReviewsTechnical ManualsDetailed Product EngineeringEarly Approval of Product SpecificationsPurchase Cost TargetsProcess Capability StudiesPreventive Maintenance Supplier QualificationJob DescriptionsHousekeepingZero-Defect ProgramCost of Poor QualityCost of Poor Quality 26 .PPTSupplier CertificationEmployee SurveysSecurity ChecksSafety ChecksReviews:Operating ExpendituresProduct CostsFinancial ReportsCapital Expenditures
Examples of Appraisal ExpenseTestInspectionProcess ControlsTrain QA PersonnelProduct AuditsQuality Systems AuditsCustomer SatisfactionSurveys and AuditsPrototype InspectionAccumulating Cost DataCost of Poor QualityCost of Poor Quality 27 .PPTSupplier ProblemsScrap and reworkLate deliveriesExcess inventoryEquipment Downtime Accidents, InjuriesAbsenteeismUnused ReportsMissed Schedule CostLost Sales (any cause)
Examples of Internal Failure CostsSubstandard ProductScrap or ReworkRe-inspectionRedesign/Engineering ChangeProcess ModificationsPayroll ErrorsAll Expediting CostsOff-Spec/WaiverAbandoned ProgramsCost of Poor QualityExamples of External Failure CostsProduct RecallHandling ComplaintsCustomer ServiceCaused by ErrorsProducts ReturnedAnalysis of ReturnsEvaluation of Field StockLate Payments andBad Debts
LawsuitsReportsSales and serviceReturns and allowancesFailure
Lost Sales Because of Customer Dissatisfaction!Cost of Poor QualityThe ratio of the individual category costs to total costs varies widely. Many companies exhibit ratios which look like the following:Quality Cost CategoryPercent of TotalInternal Failure25 to 40External Failure25 to 40Appraisal10 to 50Prevention.05 to 5What Does Reality Look Like?Cost of Poor Quality
