Sequencing Model Flashcards
It is the selection of an appropriate order in which a number of jobs (operations) can be assigned to a
finite number of service facilities (machines or equipments) so as to optimise the outputs in terms of time, cost or profit.
Sequencing
Assumptions
> The processing times Ai and Bi etc, are exactly known to us
and they are independent of order of processing the job on the
machine. (i.e.) the lime taken to process the job will not vary it
remains constant.
The given processing time includes the transfer time and
setup time.
Each job once started on the machine, the processing
shouldn’t stop in the middle. It is to be processed completely
before loading the next job.
The job starts on the machine as soon as the job and the
machine both become idle.
The cost of keeping the semi-finished job is assumed that it is
too small and is negligible (Zero inventory cost).
There is only one machine of each type.
While processing, no job is given priority (i.e. the order of
completion of jobs has no significance. The processing times
are independent of sequence of jobs).
No machine may process more than one job simultaneously
(This means to say that the job once started on a machine, it
should be done until completion of the processing on that
machine).
(4) Types of Sequencing Problem
- ‘n’ jobs are to be processed on two machines.
- ‘n’ jobs are to be processed on “m” machines in the given order.
- ‘n’ jobs are to be processed on three machine
- two jobs are to be processed on ‘m” machines in the given order
If the problem given has two machines and two or three jobs, then it can be solved by using the
Gantt Chart
> But if the numbers of jobs are more, then Gantt Chart becomes less practical.
Gantt chart consists of X-axis on which the time is noted and Y-axis on which jobs or machines are shown.
For each machine a horizontal bar is drawn. On these bars the processing of jobs in given sequence is marked.
Sequence problems can also be solved by
Johnson Bellman Rule
