Introduction:
Sequencing model is another part of operation research which is not include in linear programming, used to minimise the production time and maximise the profit.
Sequencing model:
a) In sequencing model, the order or sequence in which the jobs are to be processed through machines so as to minimize the total processing time.
b) The total effectiveness, which may be the time or cost that is to be minimized is the function of the order of sequence. Such type of problem is known as SEQUENCING PROBLEM.
Assumptions:
a) Principal assumptions made for convenience in solving the sequencing problems are as follows:
b) 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. That is whether job is done first on the machine, last on the machine, the time taken to process the job will not vary it remains constant.
c) The time taken by the job from one machine to other after processing on the previous machine is negligible. (Or we assume that the processing time given also includes the transfer time and setup time).
d) Each job once started on the machine, we should not stop the processing in the middle. It is to be processed completely before loading the next job.
e) The job starts on the machine as soon as the job and the machine both become idle (vacant). This is written as job is next to the machine and the machine is next to the job. (This is exactly the meaning of transfer time is negligible).
f) 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).
g) The cost of keeping the semi-finished job in inventory when next machine on which the job is to be processed is busy is assumed to be same for all jobs or it is assumed that it is too small and is negligible. That is in process inventory cost is negligible.
h) 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.
i) There is only one machine of each type.
Applicability
a) The sequencing problem is very much common in Job workshops and Batch production shops.
b) There will be number of jobs which are to be processed on a series of machine in a specified order depending on the physical changes required on the job.
c) when number of critical patients waiting for treatment in a clinic and in Xerox centers, where number of jobs is in queue, which are to be processed on the Xerox machines. Like this we may find number of situations in real world.
