Scheduling and Sequencing by Johnson Rule

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SCHEDULING & SEQUENCING

BY JOHNSON’S RULE

GROUP MEMBERS

GROUP MEMBERS  Rajendra kumarRajendra kumar

 PratikPratik  PuneetPuneet  PintuPintu

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DEFINATION

 Establishing the timing of the use of Establishing the timing of the use of

equipment, facilities and human activities in an

organization

 Effective scheduling can produce:-Effective scheduling can

1) Cost savings1) Cost savings

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Scheduling Difficulties

 Variability inVariability in

 Setup timesSetup times

 Processing timesProcessing times  InterruptionsInterruptions

 Changes in the set of jobsChanges in the set of jobs

 No method for identifying optimal scheduleNo method for identifying optimal schedule  Scheduling is not an exact scienceScheduling is not an exact science

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Minimizing Scheduling Difficulties

 Set realistic due datesSet realistic due dates

 Focus on bottleneck operationsFocus on bottleneck operations

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SEQUENCING

JOHNSON’S

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SEQUENCING

 SequencingSequencing: : Determine the order in which jobs Determine the order in which jobs

at a work center will be processed.

 WorkstationWorkstation: : An area where one person works, An area where one person works,

usually with special equipment, on a

specialized job.

 Priority rulesPriority rules: : Simple hierarchy Simple hierarchy

used to select the order in

which jobs will be processed.

 Job timeJob time: : Time needed for Time needed for

setup and processing of a job.

Everything is #1 Priority

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Priority Rules

 FCFS - FCFS - first come, first servedfirst come, first served  LTR - LTR - Least time requiredLeast time required

 LAR/LOR – LAR/LOR – Least activity required/Fewest Least activity required/Fewest

operations required

 EDD - EDD - earliest due dateearliest due date

 CRS - CRS - critical ratio schedulingcritical ratio scheduling

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JOHNSON’S RULE

 Technique for minimizing completion time for Technique for minimizing completion time for

a group of jobs to be processed on two

machines or at two work centers.



Minimizes total idle time

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Johnson’s Rule Conditions

 Job time must be known and constantJob time must be known and constant  Job times must be independent of Job times must be independent of

sequence

 Jobs must follow same two-step sequenceJobs must follow same two-step sequence  Job priorities cannot be usedJob priorities cannot be used

 All units must be completed at the first All units must be completed at the first

work center before moving to second

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Example Of Johnson’s Rule (Two Machines)

F 137 150 119 132 13 13 J B 123 137 104 119 14 15 I A 108 123 91 104 15 13 H J 94 108 79 91 14 12 G I 84 94 67 79 10 12 F E 70 84 53 67 14 14 E H 55 70 41 53 15 12 D D 42 55 32 41 13 9 C G 32 42 15 32 10 17 B C 15 26 0 15 11 15 A

St. Time End Time St. Time End Time

Sequence MC2 MC1 Time on M2 Time on M1 Job No.

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120 130 103 120 B 107 118 88 103 A 94 107 75 88 J 80 94 60 75 I 66 80 46 60 E 51 66 33 46 H 36 51 21 33 D 22 36 9 21 G 9 22 0 9 C

(By Johnson's Rule)

MC2 MC1

Sequence

So we can say that by using Johnson’s rule of scheduling Time

saved in this case is :- 150 – 140 = 10

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Johnson’s Rule for Three Machines

 ConditionCondition:-:-Largest time on Largest time on M2M2 should be should be less less

than

than or or equalequal to smallest time on to smallest time on M1M1 or or M2M2 or or both

both..

 If condition satisfied then we calculate:-If condition satisfied then we calculate:- R1 = M1 + M2R1 = M1 + M2

 R2 = M2 + M3R2 = M2 + M3

 This whole can be understand by the help of This whole can be understand by the help of

following

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example:-110 122 98 110 17 12 12 H 98 107 85 98 14 9 13 G 85 95 70 85 16 10 15 F 70 81 56 70 17 11 14 E 56 65 43 56 15 9 13 D 43 53 31 43 13 10 12 C 31 42 16 31 12 11 15 B 16 28 0 16 11 12 16 A

MC2 MC1 Time on M3 Time on M2 Time on M1 Job No.

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129 146 115 129 99 115 82 99 67 82 54 67 42 54 28 39

St. Time End Time

MC3 B 29 24 A 23 22 E 26 25 F 28 25 H 24 22 D 23 22 G 23 26 C 23 28

(BY JOHNSON'S RULE)

M2+M3 M1+M2 SEQUENCE R2 R1 Idle time on Machine-2 is:-122 – 84 = 38 Idle time on machine-3 is:-146 – 115 = 31

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125 137 110 121 95 110 B 114 125 95 107 79 95 A 97 114 79 90 65 79 E 81 97 65 75 50 65 F 64 81 50 62 38 50 H 49 64 38 47 25 38 D 35 49 25 34 12 25 G 22 35 12 22 0 12 C

St. Time End Time (BY JOHNSON'S RULE)

MC3 MC2

MC1

SEQUENCE

Total time saved by Using Johnson’s rule

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CONCLUSION

 Thus we can say that by using Johnson’s rule Thus we can say that by using Johnson’s rule

we can do more better sequencing of machines

and can save the time of production.

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