hw9_Sp09 - IEOR 130 Methods of Manufacturing Improvement...

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1 IEOR 130 Methods of Manufacturing Improvement Spring, 2008, Prof. Leachman Homework assignment 9, due May 5, 2009. As discussed in class, one means of controlling the WIP level and the cycle time in a factory is by controlling the release of new work into the factory. The basic idea behind this approach is to regulate the workload in the factory to a constant level. There are different ways of measuring workload, as illustrated in the next several problems. 1. Perhaps the simplest means of regulating the workload is by fixing the total number of lots in the factory at any one time. This constant WIP ("CONWIP") policy is easy to understand and implement: Once the factory WIP has reached the target level, new lots are released only as old ones are finished and leave the factory. (a) Suppose the target WIP level is 200 lots. The average cycle time per lot from release to factory output is 50 days. On average, how many lots leave the factory each day, and how many new ones are released into the factory? (Hint: Apply Little's Law.) (b) Suppose the bottleneck work center is visited 5 times by each lot as it moves through the process flow. The processing time at each visit is 5 hours per lot. There are five identical machines in the bottleneck work center with 90% availability. What is the utilization of total time and the utilization of available time in the bottleneck work center? Assume the factory operates 24 hours per day, seven days per week. (c) Suppose the factory management wants to increase the production rate. To do this, what must happen to the target WIP level? (d) If management decreases the target WIP level by a certain amount, what will happen to the production rate?
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2 2. A more sophisticated approach for scheduling releases of new lots is to measure workload in terms of machine hours of work for the bottleneck. A target level is established for the total machine hours of bottleneck workload within the factory. The total workload from WIP for the bottleneck is computed and compared to the target level. New lot releases are made only as allowed by the difference between target and actual workload. This method is called "Workload Regulation." (a) Suppose the factory WIP level is 200 lots. Let us define "layer 1" as the set of operations from factory start up to and including the first visit to the bottleneck work center. Layer 2 includes all operations after the first visit up to and including the second visit, etc. Layer 6 is all operations after the fifth visit to the bottleneck to the end of the process flow. Suppose the WIP level is distributed as follows: Layer 1 - 21 lots Layer 2 - 34 lots Layer 3 - 39 lots Layer 4 - 45 lots Layer 5 - 41 lots Layer 6 - 20 lots What is the total workload for the bottleneck work center (expressed in machine hours)? (b) Suppose the target workload for the bottleneck work station is 2500 hours. According to the
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This note was uploaded on 03/16/2010 for the course ORMS 130 taught by Professor Leachman during the Spring '10 term at University of California, Berkeley.

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hw9_Sp09 - IEOR 130 Methods of Manufacturing Improvement...

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