Hitesh Products Ltd (HPL) produces an item, which requires shearing
operation first followed by punching operation. There are 5
different jobs to be processed, the processing times for which
are given below:
| Job |
1 |
2 |
3 |
4 |
5 |
| Shear time |
4 |
4 |
10 |
6 |
2 |
| Punch time |
5 |
1 |
4 |
10 |
3 |
|
Using Johnson's rule find the makespan of the
schedule.
Applying Johnson's rule to HPL, we find that the smallest processing
time occurs on job 2 on the punch. Since the minimum time is
on the second machine, job 2 is scheduled last.
Next, for the remaining jobs, we pick the second-smallest
processing time. This is 2 corresponding to job 5 on machine
1. Therefore job1 is scheduled first.
In the next step, we have a tie between Job 1on shear and job3
on punch. When ties occur, either job can be chosen. If we pick
job 1, then we have:
Continuing with this, the last two steps yield:
| Shear |
5 |
1 |
4 |
3 |
2 |
X |
| Punch |
X |
X |
5 |
X |
1 |
X |
4 |
3 |
2 |
|
X : machine is idle.
The makespan is 27 days.
|
