Johnson's Rules
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Johnson's Rules

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Johnson's Rule
1.   
What is Johnson's Rule         quespin.gif (22297 bytes)
2.    Objectives of Johnson's Rule
3.    Conditions for the Johnson's Rule
4.    Steps Involved In Johnson's Rule
5.    Example with Solution
6.    Simulation

    1.    What is Johnson's Rule
               
Johnson's Rule is a technique that can be used to minimise the completion time for                   a   group of jobs that are to be processed on two machines or at two successive work                   centres.
                                                                                                                                       
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    2.    Objectives of Johnson's Rule
            The Objectives of the Johnson's Rule are:

To minimise the processing time for sequencing a group of jobs through two work centres.
To minimise the total idle times on the machines.
To minimise the flow time from the beginning of the first job until the finish of the last job.
                                                                                                                             
   
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3.    Conditions for the Johnson's Rule
              In order for the technique to be used, several conditions must be satisfied:

Job time(including setup and processing) must be known and constant for each job at each work centre.
Job times must be independent of the job sequence.
All jobs must follow the same two-setup work sequence.
Job priorities cannot be used.
                                                                                                                            
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4.    Steps Involved In Johnson's Rule

       Johnson's Rule involves four steps:
        1.    All jobs are to be listed, and the processing time of each machine is to be listed.
        2.    Select the job with the shortest processing time.

                 paw_cy.gif (131 bytes)    If the shortest time lies on the first machine/work centre, the job is scheduled
                             first.
                 paw_cy.gif (131 bytes)    If the shortest time lies on the second machine/work centre, the job is scheduled
                          at the end.
                Ties in activity times can be broken arbitrarily.
        3.    Once the job is scheduled, go to step 4.
        4.    Repeat steps2 and step3 to the remaining jobs, working towards the centre of the
                sequence.

Example with solution by using Johnson's Rule    Example with Demo solution

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