Download - Shop Floor Planning
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PPCShop Floor Planning
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Job Shop Scheduling
Single processor scheduling. One product ata time from the machine / process
Flow shop scheduling. Job contains severaloperations that are to be performed in a specificorder. Operations are carried out in more thanone processor.
General shop scheduling
More than twomachines & two jobs. Flow of work can take anypattern.
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Case Scheduling Procedure
The adjacent tablegives details ofproduction time & duedates of 4 jobs.
Prepare scheduleby SPT & DD method.
Compare thetardiness obtainedfrom these methods.
Job Prod
Time
Due
Date
1 4 6
2 7 9
3 2 19
4 8 17
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Case Scheduling Procedure
(By - DD Method)Job
(a)
Due
Date
(b)
Processing
time
(c)
Completion
time
(d) = cum
of (c)
Tardiness
(d) = +ve
of (d) (b)
1 6 4 4 0
2 9 7 11 2
4 17 8 19 2
3 19 2 21 2
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Case Scheduling Procedure
(Single Machine) (By - SPT Method)Job
(a)
Processing
time
(b)
Due
Date
(c)
Completion
time
(d) = cum of
(b)
Tardiness
(d) = +ve
of (d)
(c)
3 2 19 2 0
1 4 6 6 0
2 7 9 13 4
4 8 17 21 4
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Johnsons Procedure
(Two Machines) Step 1: Determine the minimum processing time on either machine.
Step 2 A: If the minimum processing time occurs on machine 1,place the associated job in the first available position in thesequence.
Step 2 B: If the minimum processing time occurs on machine 2,place the associated job in the last available position in thesequence.
Step 3:
(a) The job sequenced by either step 2A or 2B is removedfrom consideration.
(b) Repeat the process starting from step 1, until all the jobsare sequenced.
(c) Ties can be broken arbitrarily.
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Case Flow Shop Scheduling
There are two machines& five jobs. All the jobsare first processed on
machine 1 & then onmachine 2. Theprocessing time of the
jobs on two machines isgiven in the table.
Design a schedulingprocess to minimize themake-span.
Jobs PT*
Mc-1
PT*
Mc-2
1 4 7
2 6 3
3 2 3
4 7 7
5 8 6
* PT- Processing Time. Mc- Machine
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2 6
1
3
2
1
2
7
M
1 J3 J1 J4 J5 J2
M
2 J3 J1 J4 J5 J2
5
1
3
2
0
2
7
3
0
Schedule Sequence using Johnsons Procedure
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Commonly Employed Rules for
General Job Shop Scheduling Earliest due date ( EDD). Priority is given
to the job with the earliest due date.
First in system first served (FISFS).Priority is given to the job that arrived first.
First come first served (FCFS). Priority
is given to the job that arrived at themachine first.
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Commonly Employed Rules for
General Job Shop Scheduling Least Slack First (LSF). Priority is given to the
processing of the job that has least slack. Slackis the difference between the due date & the
work remaining on the job. Shortest processing time (SPT). Priority is
given to the job with the shortest processing timeon the machine.
Least work remaining (LWR). Priority is givento the job with the least amount of processing tobe done.
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Case General Job Shop Scheduling
6 jobs are to beprocessed on threemachines (A,B,C) as perdetails given in the Table.For example, Job A willtake 3days on machine A,3days on B, & 2days onmachine C. Its due dateis 10 days.
Prepare schedules forgeneral job shop for therules discussed earlier.
Job Sequence &
Processing
Time
Due
Date
1 A(3),B(3),C(2) 10
2 A(5),C(2) 13
3 B(4),A(4),C(3) 124 B(3),C(5),A(2) 18
5 C(5),B(4) 14
6 C(2),A(5),B(5) 15
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Case General Job Shop Scheduling
EDD Sequencing
Job Sequence &
Processing
Time
Due
Date
1 A(3),B(3),C(2) 10
2 A(5),C(2) 13
3 B(4),A(4),C(3) 12
4 B(3),C(5),A(2) 18
5 C(5),B(4) 14
6 C(2),A(5),B(5) 15
Job EDD
Sequence
Due
Date
1 A(3),B(3),C(2) 10
3 B(4),A(4),C(3) 12
2 A(5),C(2) 13
5 C(5),B(4) 146 C(2),A(5),B(5) 15
4 B(3),C(5),A(2) 18
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Scheduling Rule : EDDTime 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22
Mach A
J-1 J-2 J-3 J-6 Idle J-4
Mach B
J-3 J-1 J-5 J-4 Idle J-6
Mach C
J-5 J-6 J-1 J-2 Idle J-3 J-4 Idle
Jobs
Finished 1
2
5 3
4
6
Case General Job Shop Scheduling
Gantt Chart
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Case General Job Shop Scheduling
EDD Sequencing - Tardiness
Job
Schedule
Process
Time &
Sequence
Processing
Time
Due
Date
Tardiness
1 A(3),B(3),C(2) 9 10 0
2 A(5),C(2) 15 13 2
3 B(4),A(4),C(3) 11 12 04 B(3),C(5),A(2) 11 18 0
5 C(5),B(4) 22 14 8
6 C(2),A(5),B(5) 22 15 7
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Case General Job Shop Scheduling
Gantt Chart
Scheduling Rule : FISFSTime 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22
Mach A
J-1 J-2 J-3 J-6 J-4 Idle
Mach B
J-3 J-1 J-4 J-5 Idle J-6
Mach C
J-5 J-6 J-1 J-2 J-4 J-3 Idle
Jobs
Finished 1 2 5
3
4 6
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Case General Job Shop Scheduling
FISFS Sequencing - Tardiness
Job
Schedule
Process
Time &
Sequence
Processing
Time
Due
Date
Tardiness
1 A(3),B(3),C(2) 9 10 0
2 A(5),C(2) 11 13 0
3 B(4),A(4),C(3) 19 12 74 B(3),C(5),A(2) 19 18 1
5 C(5),B(4) 14 14 0
6 C(2),A(5),B(5) 22 15 7
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Case General Job Shop Scheduling
Gantt Chart
Scheduling Rule : FCFSTime 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22
Mach A
J-1 J-2 J-3 J-6 J-4 Idle
Mach B
J-3 J-4 J-1 J-5 Idle J-6
Mach C
J-5 J-6 J-4 J-2 J-1 J-3 Idle
Jobs
Finished
2
5 1
3
4 6
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Case General Job Shop Scheduling
FCFS Sequencing - Tardiness
Job
Schedule
Process
Time &
Sequence
Processing
Time
Due
Date
Tardiness
1 A(3),B(3),C(2) 16 10 6
2 A(5),C(2) 14 13 1
3 B(4),A(4),C(3) 19 12 74 B(3),C(5),A(2) 19 18 1
5 C(5),B(4) 14 14 0
6 C(2),A(5),B(5) 22 15 7
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Summary of the Performance of
Scheduling Rules
Rule No of Tardy
Jobs
Ti
EDD 3 17FISFS 3 15
FCFS 5 22