Bài giảng Operations Management - Chapter 10: Quality Control

Quality ControlMcGraw-Hill/Irwin Copyright © 2012 by The McGraw-Hill Companies, Inc. All rights reserved.You should be able to:List and briefly explain the elements in the control processExplain how control charts are used to monitor a process, and the concepts that underlie their useUse and interpret control chartsPerform run tests to check for nonrandomness in process outputAssess process capabilityStudent Slides10-*Quality ControlA process that evaluates output relative to a standard and takes corrective action when output doesn’t meet standardsIf results are acceptable no further action is requiredUnacceptable results call for correction actionStudent Slides10-*InspectionAn appraisal activity that compares goods or services to a standardInspection issues:How much to inspect and how oftenAt what points in the process to inspectWhether to inspect in a centralized or on-site locationWhether to inspect attributes or variablesStudent Slides10-*Quality control seeksQuality of ConformanceA product or service conforms to specificationsA tool used to help in this process:SPC Statistical evaluation of the output of a processHelps us to decide if a process is “in control” or if corrective action is neededStudent Slides10-*Control ChartA time ordered plot of representative sample statistics obtained from an ongoing process (e.g. sample means), used to distinguish between random and nonrandom variabilityControl limitsThe dividing lines between random and nonrandom deviations from the mean of the distributionUpper and lower control limits define the range of acceptable variation10-*Student SlidesVariables generate data that are measuredMean control chartsUsed to monitor the central tendency of a process.“x- bar” chartsRange control chartsUsed to monitor the process dispersionR charts10-*Student SlidesStudent Slides10-*Used to monitor the central tendency of a processStudent Slides10-*Used to monitor process dispersionStudent Slides10-*Student Slides10-*Attributes generate data that are counted.p-Chart Control chart used to monitor the proportion of defectives in a processc-Chart Control chart used to monitor the number of defects per unit10-*Student SlidesOnce a process has been determined to be stable, it is necessary to determine if the process is capable of producing output that is within an acceptable rangeTolerances or specificationsRange of acceptable values established by engineering design or customer requirementsProcess variabilityNatural or inherent variability in a processProcess capabilityThe inherent variability of process output (process width) relative to the variation allowed by the design specification (specification width)10-*Student SlidesStudent Slides10-*Quality is a primary consideration for nearly all customersAchieving and maintaining quality standards is of strategic importance to all business organizationsProduct and service designIncrease capability in order to move from extensive use of control charts and inspection to achieve desired quality outcomesStudent Slides10-*