Average job flow time total flow timenumber of jobs

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Average Job Flow Time= (Total Flow-Time)/Number of Jobs Average Lateness= (Total Lateness)/ Number of Jobs = 447/8=56 < 82 = 192/8=24 < 50 G 3 3 9 C 7 10 17 E 9 1 9 28 B 14 33 33 H 21 54 44 A 27 81 32 F 27 108 52 D 31 139 40 -6 -7 -9 0 10 49 56 99
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Priority Sequencing Example Three orders are waiting at a drilling work center: orders A, B, and C Today’s date= shop date 150 Orders A B C Processing Time this Operation (HRS) 8 10 6 Order Due Date 155 160 162 Total Remaining Processing Time (Days) (including setup and run times only) 1 5 3 Lead Time Remaining (days) (including move, queue, setup, and run times) 4 10 16 Number of remaining operations 1 4 5 Time Available (days) 5 10 12 Critical Ratio 5/4= 1.25 10/10= 1 12/16= 0.75 Slack Time (Days) 1 0 (-4) Slack Time per Operation (Days)
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(Continued from previous slide) Prepare A dispatch list using the following rules: SPT EDD CR 1 st C A C 2 nd A B B 3rd B C A
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Using <POM-Windows> software to do Supplement Scheduling Problems.
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Multiple Machine Scheduling Computer simulation models are effective tools to determine which priority rules work best in a given situation Two-station flow shop: Johnson’s rule Step 1: Scan the process times at each workstation and find the shortest processing time among those not yet scheduled. Arbitrary break ties. Step 2: If the shortest process time is on workstation 1, schedule the corresponding job as early as possible. If the shortest process time is on workstation 2, schedule the corresponding job as late as possible. Step 3: Eliminate the last job scheduled from further consideration. Repeat steps 1 and 2. Linking manufacturing scheduling to the supply chain A: True integration requires the manipulation of large amounts of complex data in real time B: Advanced Planning and Scheduling (APS) systems seek to optimize resources across the supply chain and align daily operations with strategic goals. Typically, these systems have four major components: Demand planning Supply network planning Available-to-promise Manufacturing scheduling
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Sequencing Sequencing Johnson’s Rule Johnson’s Rule Time (hr) Time (hr) Motor Motor Workstation 1 Workstation 1 Workstation 2 Workstation 2 M1 M1 12 12 22 22 M2 M2 4 4 5 5 M3 M3 5 5 3 3 M4 M4 15 15 16 16 M5 M5 10 10 8 8 Example 17.5 Example 17.5
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Sequencing Sequencing Johnson’s Rule Johnson’s Rule Time (hr) Time (hr) Motor Motor Workstation 1 Workstation 1 Workstation 2 Workstation 2 M1 M1 12 12 22 22 M2 M2 4 4 5 5 M3 M3 5 5 3 3 M4 M4 15 15 16 16 M5 M5 10 10 8 8 Sequence = Sequence = M1 M1 M2 M2 M3 M3 M4 M4 M5 M5 - - - - - - - - Example 17.5 Example 17.5
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Sequencing Sequencing Johnson’s Rule Johnson’s Rule Time (hr) Time (hr) Motor Motor Workstation 1 Workstation 1 Workstation 2 Workstation 2 M1 M1 22 22 M2 M2 4 4 5 5 M3 M3 5 5 M4 M4 15 15 16 16 M5 M5 10 10 8 8 Sequence = Sequence = M1 M1 M2 M2 M3 M3 M4 M4 M5 M5 - - - - - - - - Workstation M2 (4) M1 (12) M4 (15) M5 (10) M3 (5) Idle—available for further work 0 5 10 15 20 25 30 Day 35 40 45 50 55 60 65 Idle 2 M2 (5) M1 (22) M4 (16) M5 (8) M3 (3) Idle 1 Example 17.5 Example 17.5
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Operations Scheduling Performance Measures Job flow time Make-span (total completion time) Past due Work-in-process inventory Total inventory Utilization Sequencing operations for one machine Single-dimension rules: EDD, FCFS, SPT
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  • Summer '18
  • Jonh
  • Management, SPT, average job flow, job flow time

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