SKEDSOFT

Introduction:

Sequencing model is the another part of operation research which is not include in linear programming, used to minimise the production time and maximise the profit.

Solution for sequencing problem:  N’ Jobs and Two Machines:

(a)    If the problem given has two machines and two or three jobs, then it can be solved by using the Gantt chart.

(b)   But if the numbers of jobs are more, then this method becomes less practical.

(c)    Gantt chart consists of X -axis on which the time is noted and Y-axis on which jobs or machines are shown.

(d)   For each machine a horizontal bar is drawn. On these bars the processing of jobs in given sequence is marked

Example 1. There are two jobs job 1 and job 2. They are to be processed on two machines, machine A and Machine B in the order AB. Job 1 takes 2 hours on machine A and 3 hours on machine B. Job 2 takes 3 hours on machine A and 4 hours on machine B. Find the optimal sequence which minimizes the total elapsed time by using Gantt chart.

Solution:

Total elapsed time for sequence 1,2 i.e. first job 1 is processed on machine A and then on second machine and so on.

Procedure: Draw X - axis and Y- axis, represent the time on X - axis and two machines by two bars on Yaxis.

Mark the times on the bars to show processing of each job on that machine.

Sequence 1,2 Total = elapsed time = 9 Hrs. (optimal sequence)

Both the sequences shows the elapsed time = 9 hours.

The drawback of this method is for all the sequences, we have to write the Gantt chart and find the total elapsed times and then identify the optimal solution.