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Unformatted text preview: as possible. 3. Remove the job from the list. 4. Repeat steps 2 3 until all slots in matrix are 5illed & all jobs are sequenced. 4QA3 F12 A. Gandomi 30 Job Process 1 Process 2 A
B
C
D
E 5
1
9
3
10 2
6
7
8
4 Pr 1 B D
0 1 Pr 2
● 1 C
15 C E A A
23 D
7 D E
13 B
0 B C
4 28 E
22 23 30 A
27 28 30 Johnson’s rule guarantees that the above schedule gives the best value (30) of makespan. 4QA3 F12 A. Gandomi 31 ●
● ● ● An extension of Johnson’s rule minimizes makespan in some three machine Rlow shops. First, recall that in a three machine Rlow shop, every job is processed Rirst on Machine 1, then on Machine 2 and then on Machine 3. The three machine problem can be reduced to a two machine problem if either one of the following condition is satisRied: min Ai ≥ max Bi or min Ci ≥ max Bi If that is the case, then the problem is reduced to a two machine problem: De5ine Ai’=Ai+Bi, Bi’=Bi+Ci Enter
Exit
M2
M3
M1
B
C
A 4QA3 F12 A. Gandomi 32 ●
●
● The problem of balancing an assembly line is characterized by a set of n distinct tasks that must be completed on each item. The time required to complete task i is a known constant, ti. The goal is to organize tasks into groups, with each group of tasks being performed at a single workstation. 4QA3 F12 A. Gandomi 33 ● ●
● Throughput time: The overall time it takes to complete an individual product from start to Rinish is called the throughput time. Cycle time: The interval between two successive products produced at a workstation is called the cycle time. The actual cycle time is the maximum workload assigned to a workstation. n ● = Let T ∑t i. For a cycle time of C, the minimum number of i=1
workstations possible is !T C # , where the brackets indicate " / $
that the value of T/C is to be rounded to the next integer. 4QA3 F12 A. Gandomi 34 ● ●
● One of the scheduling goals is the efRicient utilization of resources. An uneven distribution of workloads causes idle time in some workstations and results in an inefRicient utilization of resources. The objective of line balancing is to assign tasks to stations to minimize the cycle time, C. The general problem is difRicult to solve optimally, but effective heuristics are available(e.g., Ranked Position Weight) . 4QA3 F12 A. Gandomi 35 1. Calculate positional weights for each...
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This document was uploaded on 04/01/2014.
 Spring '14

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