ch 8 - FrankMatejcikSDSchoolofMines&Technology 1 TM 663...

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Frank  Matejcik  SD School of Mines & Technology 1
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Frank  Matejcik  SD School of Mines & Technology 2 TM 663 Operations Planning October 29, 2007 Dr. Frank J. Matejcik CM 319 Work: (605) 394-6066 Roughly 9-3 M-F Home: (605) 342-6871 Frank.Matejcik@.sdsmt.edu
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Frank  Matejcik  SD School of Mines & Technology 3 TM 663 Operations Planning Dr. Frank Joseph Matejcik South Dakota School of Mines and Technology Rapid City 6th Session: Chapter 8: Variability Basics Chapter 9: The Corrupting Influence of Variability
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Frank  Matejcik  SD School of Mines & Technology 4 Agenda Factory Physics Chapter 6: A Science of Manufacturing Chapter 7: Basic Factory Dynamics (New Assignment Chapter 8 Problems: 6, 8 Chapter 9 Problems: 1-4)
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Frank  Matejcik  SD School of Mines & Technology 5 Tentative Schedule Chapters Assigned 9/10/2007 0,1 ________ 9/17/2007 2 C2: 4,5,9,11,13 9/24/2007 2, 3 C3: 2,3,5,6,11 10/01/2007 4, 5 Study Q’s 10/08/2007 Holiday 10/15/2007 Exam 1 10/22/2007 6, 7 C6:1, C7:4,6 10/29/2007 8, 9 C8:6,8 C9: 1-4 11/05/2007 10 11/12/2007 Holiday 11/19/2007 Exam 2 Assigned 11/26/2007 13, 14 12/03/2007 15 12/10/2007 16, 17 12/17/2007 Final Note, Chapters 11 & 12 skipped this year
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Frank  Matejcik  SD School of Mines & Technology 6 Variability Basics God does not play dice with the universe. – Albert Einstein Stop telling God what to do. – Niels Bohr
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Frank  Matejcik  SD School of Mines & Technology 7 Variability Makes a Difference! Little’s Law: TH = WIP/CT, so same throughput can be obtained with large WIP, long CT or small WIP, short CT. The difference? Penny Fab One : achieves full TH (0.5 j/hr) at WIP=W 0 =4 jobs if it behaves like Best Case, but requires WIP=27 jobs to achieve 95% of capacity if it behaves like the Practical Worst Case. Why? Variability! Variability!
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Frank  Matejcik  SD School of Mines & Technology 8 Tortise and Hare Example Two machines: subject to same workload: 69 jobs/day (2.875 jobs/hr) subject to unpredictable outages (availability = 75%) Hare X19: long, but infrequent outages Tortoise 2000: short, but more frequent outages Performance: Hare X19 is substantially worse on all measures than Tortoise 2000. Why? Variability!
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Frank  Matejcik  SD School of Mines & Technology 9 Variability Views Variability: Any departure from uniformity Random versus controllable variation Randomness: Essential reality? Artifact of incomplete knowledge? Management implications: robustness is key
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Frank  Matejcik  SD School of Mines & Technology 10 Probabilistic Intuition Uses of Intuition: driving a car throwing a ball mastering the stock market First Moment Effects: Throughput increases with machine speed Throughput increases with availability Inventory increases with lot size Our intuition is good for first moments g
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Frank  Matejcik  SD School of Mines & Technology 11 Probabilistic Intuition (cont.) Second Moment Effects: Which is more variable – processing times of parts or batches?
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This note was uploaded on 04/25/2010 for the course IE 654 taught by Professor Smith during the Spring '10 term at 카이스트, 한국과학기술원.

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ch 8 - FrankMatejcikSDSchoolofMines&Technology 1 TM 663...

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