written 7.8 years ago by | modified 2.8 years ago by |
Mumbai University > Mechanical Engineering > Sem 7 > Production planning and control
Marks: 5M
Year: Dec 2015
written 7.8 years ago by | modified 2.8 years ago by |
Mumbai University > Mechanical Engineering > Sem 7 > Production planning and control
Marks: 5M
Year: Dec 2015
written 7.8 years ago by |
Sequencing is concerned with an appropriate selection of a sequence of jobs to be done on a finite number of service facilities (like machines) in some well-defined technological order so as to optimize some efficiency measure such as total elapsed time or overall cost, etc. for example, the well known sequencing problem is to determine the sequence in which two or more jobs should be processed on one or more machines in order to optimize some measure of effectiveness. A general sequencing problem may be expressed as follows:
Suppose there are n jobs (1,2,3,….,n) each of which has to be processed one at a time at each of m machines A,B,C…… the order of processing each job through the machines as well as the time required by the jobs on each of the machines is also given. The problem is to select from the (n!)m theoretically possible sequences (or combinations) that sequence (or order) for processing the jobs which optimizes (minimizes) the total elapsed time (i.e., the total time for the start of the first job upto the completion of the last job).
Remark. Theoretically, a solution by simple enumeration is always possible but in actual practice the computation of effectiveness for a given sequence can be quite complex, and the number of cases for enumeration makes this approach quite prohibitive even for moderate values of m and n.
GENERAL ASSUMPTIONS
The following assumptions are generally made in sequencing problems.
BASIC TERMINOLOGY