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【正文】 Allowances 20 If the worker received a performance rating of on the Assemble Units activity and 400 units were assembled during the study, what is the labor standard for this operation? 38 Example: Work Sampling 1) Compute the average time per assemble: = Total Minutes of Assembly Work Number of Units Assembled = .8(480)/400 = .960 minutes per unit 2) Compute the normal time per unit: = (Average Time per Unit)(Performance Rating) = .960() = minutes per unit 39 3) Compute the labor standard: = Normal Time/(1 – Allowance Fraction) = (1 .20) = minutes per unit Example: Work Sampling 40 Predetermined Time Standards ? Commonly used for new operations or new products ? When labor standard must be determined in advance of performing an operation ? Utilize data that have been historically developed for basic body movements, elements of operations, and entire operations ? Many predetermined time standard systems are used: ? Work factor ? Methodstime measurement (MTM) ? Basic motion time (BMT) study ? … and others 41 Predetermined Time Standards Suitable Jobs ? Job performed by many workers over a pact area ? Tasks may involve little repetition, but if repetitious – the cycles are very long ? Workers must be observed by a single analyst ? A moderate degree of accuracy in the labor standard is desirable, but a time study is too costly ? Only large elements of work need to be observed ? Little detail is needed in setting the time standard 42 Subjective Methods Suitable Jobs Any job or group of jobs in which: ? Very accurate labor standards are not required, or ? The cost of time study, predetermined time standards, and work sampling is prohibitive 43 Learning Curves At the start of production runs: ? Workers are unfamiliar with their tasks ? Time it takes to produce the first few units is high As the workers learn their tasks: ? Their output per day increases up to a point ? Then their output levels off to a rather constant rate 44 Learning Curves ? Most aircraft manufacturing tasks experience an 80% learning rate ? Laborhours required to assemble an aircraft is reduced by a factor of as the production quantity doubles ? If first aircraft assembled requires 100 laborhours ? Second aircraft would require 80 laborhours ? Fourth aircraft would require 64 laborhours ? Eighth aircraft would require laborhours ? … and so on 45 Learning Curves 10 20 30 40 50 60 70 80 90 100 110 120 130 20 80 40 100 60 Unit Number (n) 120 LaborHours for nth Unit Aircraft Assembly 80% Learning Curve 46 Learning Curves By analyzing workers’ learning situations, we are able to estimate: ? The average number of laborhours required per unit for N units in a production run ? The total number of laborhours required to produce N units in a production run ? The exact number of laborhours required to produce the nth unit of a production run 47 Learning Curves Three approaches to learningcurve problems are: ? Arithmetic analysis ? Logarithmic analysis ? Learning curve tables 48 Learning Curves Arithmetic Analysis ? The simplest approach to learningcurve problems ? If we wish to find the laborhours required to produce n units, and n just happens to be a number that is one of the doubled values, then this approach works 49 Example: EZ Machine Shop (A) Learning Curve Arithmetic Analysis EZ Machine Shop has a contract to manufacture 100 turbines. The first 20 turbines have been pleted. The laborhours required for a portion of the pleted turbines are liste
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