4-19-07 management cycle time

4-19-07 management cycle time - Management of Manufacturing...

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Apr. 19, 2007 Leachman - Cycle Time 1 Management Management of Manufacturing Cycle Time of Manufacturing Cycle Time Prof. Rob Leachman Prof. Rob Leachman University of California University of California at Berkeley at Berkeley April 19, 2007 April 19, 2007
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Apr. 19, 2007 Leachman - Cycle Time 2 Agenda • Definitions of cycle time • Cycle time trends in the semiconductor industry • Economic importance of cycle time • General strategies and theory for cycle time reduction • Case-studies in cycle time reduction
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Apr. 19, 2007 Leachman - Cycle Time 3 Definitions of related terms Process flow – the series of manufacturing steps traversed by manufacturing lots of a particular product type or particular product family In semiconductor fabrication, typically, lots are started containing 25 wafers of a single product WIP (work-in-process) – the manufacturing lots in the factory not yet completed Moves – the number of wafers passed through one or more manufacturing steps within a short time horizon such as a production shift One move = one wafer completing one step
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Apr. 19, 2007 Leachman - Cycle Time 4 Definitions of Cycle Time Cycle time from customer point of view (“lead time”) is the time from order placed until order received = design, paperwork, data entry and communication time + manufacturing time (if any) + interplant shipment time (if any) + safety time (if any) + customer shipment time
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Apr. 19, 2007 Leachman - Cycle Time 5 Definitions of Cycle Time (cont.) Cycle time from manufacturing point of view (“cycle time”, “turn-around time” or “flow time”) Total manufacturing cycle time is the elapsed time from lot creation to lot completion – includes process time, transport time, queue time, hold time across all steps of the process flow Cycle time for a process step is the average time from track-out of previous step to track-out of this step
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Apr. 19, 2007 Leachman - Cycle Time 6 Definitions of Cycle Time (cont.) Standard cycle time is time to process one lot without interference (includes process time and move time but excludes queue time and hold time) – standard cycle time for each process step – standard cycle time for whole process flow • Standard cycle time remains fixed until the process spec, equipment, or lot size is changed. (It is also called theoretical cycle time .)
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Apr. 19, 2007 Leachman - Cycle Time 7 Measures of Cycle Time “Static cycle time” is calculated from the elapsed time for each lot. Usually, when one says “cycle time” one means “static cycle time”. “Dynamic cycle time” adds up the current average cycle time for each process step to estimate current cycle time from fab start to fab out. “Throughput time” (TPT) for a process step is calculated from the “WIP turns”. TPT for the factory is the sum of TPT’s for each process step: TPT = 0.5 (EOH + BOH) / Moves
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Apr. 19, 2007 Leachman - Cycle Time 8 Measures of Cycle Time (cont.) Throughput time (TPT) implicitly assumes all lots are interchangeable.
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This note was uploaded on 04/02/2008 for the course IEOR 130 taught by Professor Leachman during the Spring '07 term at University of California, Berkeley.

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4-19-07 management cycle time - Management of Manufacturing...

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