Bài giảng Operations Management - Supplement 7: Learning Curves

Learning CurvesMcGraw-Hill/Irwin Copyright © 2012 by The McGraw-Hill Companies, Inc. All rights reserved.You should be able to:Explain the concept of a learning curveMake time estimates based on learning curvesList and briefly describe some of the main applications of learning curvesOutline some of the cautions and criticisms of learning curvesEstimate learning rates from data on job times7S-*Student SlidesLearning curveThe time required to perform a task decreases with increasing repetitionsThe degree of improvement is a function of the task being doneShort, routine tasks will show modest improvement relatively quicklyLonger, more complex tasks will show improvement over a longer interval 7S-*Student SlidesThe learning effect is attributed to a variety of factors:Worker learningPreproduction factorsTooling and equipment selectionProduct designMethods analysisEffort expended prior to the start of workChanges made after production has begunChanges in work methodsChanges in tooling and equipmentManagerial factorsImprovements in planning, scheduling, motivation, and control7S-*Student SlidesThe learning effect is predictableThe learning percentage is constantEvery doubling of repetitions results in a constant percentage decrease in the time per repetitionTypical decreases range from 10 to 20 percent7S-*Student SlidesEach time cumulative output doubles, the time per unit for that amount should be approximately equal to the previous time multiplied by the learning percentage.If the first unit of a process took 100 hours and the learning rate is 90%:UnitUnit Time (hours)1= 1002.90(100)= 904.90(90)= 818.90(81)= 72.916.90(72.9)= 65.6132.90(65.61)= 59.0497S-*Student Slides7S-*Student SlidesIf the learning rate is 90, and the first unit took 100 hours to complete, how long would it take to complete the 25th unit?7S-*Student SlidesThe learning factor approach uses a table that shows two things for selected learning percentages:Unit value for the number of repetitions (unit number)Cumulative value, which enables us to compute the total time required to complete a given number of units.7S-*Student SlidesIf the learning rate is 90, and the first unit took 100 hours to complete, how long would it take to complete the 25th unit?How long would it take to complete the first 25 units?7S-*Student SlidesUseful application areas:Manpower planning and schedulingNegotiated purchasingPricing new productsBudgeting, purchasing, and inventory planningCapacity planning7S-*Student SlidesLearning rates may differ from organization to organization and by type of workBase learning rates on empirical studies rather than assumptions where possibleProjections based on learning curves should be regarded as approximations of actual timesBecause time estimates are based on the first unit, care should be taken to ensure that the time is validIt is possible that at some point the curve might level off or even tip upward7S-*Student SlidesSome of the improvements may be more apparent than real: improvements in times may be caused by increases in indirect labor costsIn mass production situations, learning curves may be of initial use in predicting how long it will take before the process stabilizesThe concept does not usually apply because improvement in time per unit is almost imperceptible7S-*Student SlidesUsers of learning curves fail to include carryover effects from previous experiencesShorter product life cycles, flexible manufacturing, and cross-functional workers can affect the ways in which learning curves may be applied7S-*Student SlidesLearning curves have strategic implications for:Market entry when trying to rapidly gain market shareAs volume increases, operations is able to move quickly down the learning curveReduced cost  improved competitive advantageUseful for capacity planningCan lead to more realistic time estimates, thus leading to more accurate capacity needs assessment7S-*Student Slides