FILE NAME: FLOWPAR2
FUNCTION: Scheduling 2 work stations in parallel
OVERVIEW: FLOWPAR2 schedules jobs on 2 work stations in parallel. Each work station is assumed to have exactly the same processing capability. Unlike the FLOW1 worksheet, there are no solutions for lateness or due-date performance measures for workstations in parallel. The usual objectives in parallel scheduling are simply to minimize makespan or average flow time.
Makespan, as we defined earlier, is the total time to complete all jobs. To minimize makespan, a rule-of-thumb (heuristic) is used: jobs are sorted in descending order of processing time (longest time first) to get rid of problem jobs as soon as possible. To minimize average flow time, there is an optimal solution: sort in ascending order of processing time (shortest time first) to get as many jobs out the door as soon as possible.
After each sort, station 1 assignments are made in column H and station 2 assignments in column K. The formulas in these columns always assign the first two jobs to stations 1 and 2 respectively. Thereafter, jobs are assigned to the next available work station in the sequence listed in column E.
Ignore jobs numbered zero in the processing sequence.
INPUT: List job numbers and times B16..D20, then copy B16..D20 to E16..F20. Note: Job numbers, not names, must be used with this worksheet. If you want to use names, enter in column B.
Hold down the <CNTL> key and press A, B, C, or D to compute a schedule.
OUTPUT: The A and B macros are arbitrary and serve as benchmarks. Beginning and ending hour numbers for each job are shown in I16..M20. Ignore the jobs numbered zero in this range. The Gantt chart at the bottom of the worksheet converts the hour numbers to times of day. You can delete the blank rows in the Gantt chart if you like. For each schedule, makespan and average flow time are reported in cells I5 and I7.
MODIFYING THE WORKSHEET:
To add jobs, insert new rows at the row for job 3 in each of three sections of the worksheet: around rows 18, 27, and 33. In each section, copy the row of formulas above the inserted rows through the last row in that section. For the first section, just copy the formulas under G..S. The other columns for job numbers and processing times need to be input, and copied over as explained above. You can extend the Gantt chart to show additional work days by copying range P25..P50 to the right. To modify the Gantt chart for different work schedules, edit row 25 to show a sequence of work hour numbers, interrupted by labels for lunch and other breaks, In row 26, enter a sequence of times corresponding to the work hour numbers and labels.
1. Get Started
2. Workstation Production Models
3. Scheduling 2 Workstation in Series
4. Scheduling 3 Workstation in Series
5. Scheduling 4 and more Workstation in Series
6. Scheduling 2 Workstation in Parallel
7. Project Management - Daily Schedule
10. Gantt Charting