Microsoft Word - midterm_Fall_07_solution

Microsoft Word - midterm_Fall_07_solution - SECTION: 8 am...

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SECTION: 8 am 10 am PRINT NAME :_ SOLUTION (Circle One) MARSHALL SCHOOL OF BUSINESS UNIVERSITY OF SOUTHERN CALIFORNIA BUAD 311T: Operations Management For Accounting Majors Professor Ashok Srinivasan MIDTERM EXAM Fall 2007 QUESTION POINTS 1 ________ out of 25 2 ________ out of 10 3 ________ out of 20 4 ________ out of 15 5 ________ out of 20 6 ________ out of 10 TOTAL ________ out of 100 This exam consists of 6 questions on 12 pages including this cover sheet. The time limit on this exam is 1 hour 50 minutes. Answers should be concise and be confined to the space provided below the question. If calculations are involved, please make sure that your final answer is clearly visible.
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2 1) At Xootr Scooters (25 points) Xootr Scooters assembly process is a simple line flow with three workstations: deck assembly, wheel assembly, and packaging. Two types of scooters are made in this line, the Xootr-Ultra and the high-end Xootr-Street. The Xootr-Street has ultra-glide poly-urethane wheels. The market demand for Xootr-Ultra is the same as the market demand for Xootr-Street. The processing requirements are as follows: Deck Assembly: processing time is 1 minute per unit for both types of scooters. Wheel Assembly: processing time is 0.5 minute per unit for both types of scooters. Currently the production batch size at the wheel assembly is 100 units for each type of scooters. The assembly tools need to be changed before each batch. This set-up time is 20 minutes for Xootr-Ultra and 30 minutes for Xootr-Street. Packaging: processing time is 0.5 minute per unit for both types. Scooters are transferred between stations in individual units. The plant operates 24 hours a day, 7 days a week. a) (9 points) Suppose the firm just manufactures one type of scooter--the Xootr-Street. What is the production capacity of each step in isolation from other stations? Deck Assembly CT=1 min/unit Deck Assembly Processing rate = 1 / (1 min/unit) =1 unit/min = 60 units/hr Deck assembly capacity 60 scooters/hr Wheel Assembly CT for Xootr-Street= 0.5 min + (30 mins of setup time)/100 units per batch=0.8 min/unit Wheel Assembly Rate for Xootr-Street= (1/0.8)*60=75 units/hr Deck Assembly Wheel Assembly Packaging
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3 Alternatively, 100 Streets are produced in 30 +0.5*100=80 minutes ! Rate= (0/80)*60=75 units/hr Wheel assembly capacity 75 scooters/hr Packaging CT= 0.5 min/unit Packaging rate = 1 / (0.5 min/unit) =2 unit/min = 120 units/hr Packaging capacity 120 scooters/hr b) (5 points) Suppose the firm manufactures both types of scooters. The product mix is 1:1, that is, they assemble one batch of Xootr-Ultra’s followed by one batch of Xootr-Street’s. What is the production capacity of the Wheel Assembly step? Cycle Approach: Batch of Ultra: 20 min set-up + 50 minutes processing (100*0.5) = 70 minutes. Batch of Street: 30 min set-up + 50 minutes processing (100*0.5) = 80 minutes. Length of cycle = 70 + 80 = 150 minutes Number of units=100 Ultra + 100 Street = 200 units Processing rate = units/cycle length = 200 units/150 min * 60 min/hr = 80 units/hr Alternately, Average CT approach: CT for Ultra= 0.5 min + (20 mins of setup time)/100 units per batch=0.7 min/unit Rate= (1/0.7)*60=85.7 units/hr CT for Street= 0.5 min + (30 mins of setup time)/100 units per batch=0.8 min/unit
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Microsoft Word - midterm_Fall_07_solution - SECTION: 8 am...

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