3. SCHEDULING
Scheduling is one of the most important elements in
production planning.
Scheduling calls for through understanding of all aspects of
the production process and is an outcome of the integration
of the efforts of planners in the planning group and the
people in the shop-floor.
Scheduling integrates the people, machine, materials,
customer demands, and quality requirements in finalizing the
priorities. Scheduling makes it possible by determining
starting and completion data each of the operations.
4. EXAMPLES OF SCHEDULING
Timetabling Scheduling of the Computer :A number
of different courses (tasks) have to be given using the
PC room(resource)
Workforce scheduling : Assign shifts for nurses and
doctors in a Hospital
Sports Scheduling
Drug Scheduling
5.
6. CONT……….
Scheduling effects from 2 environmental factors that are
internal and external to the organization.
Internal environment
External environment
7. OBJECTIVES OF SCHEDULING
Maximize throughput
Be predictable:
Minimize overhead
Balance resource use
Achieve a balance between response and utilization
Avoid indefinite postponement
Enforce Priorities
Give preference to process holding
Degrade gracefully under heavy loads
9. PRIORITY PLANNING
Planning is the process by which the elements
required to perform a task are determined in advance
of the job start. The process is as follows :
Operations soft constraints
Management policy constraints
Engineering hard constraints
10.
11. MASTER PRODUCTION SCHEDULING
Master scheduling is a part of scheduling.
A Master Production Schedule is a Schedule of the
completions of the end items and these completions are
very much planned in nature.
A MPS is also in management language referred to as the
master of all the schedules as this schedule provides the
production, planning, purchasing & top management, the
most needed information required for planning and
control of the whole manufacturing process or the
operation.
12.
13. OBJECTIVES OF MASTER SCHEDULING
Keeping the inventories
Setting up the due dates for the availability of items
Maintaining the customer service
Setting proper schedules
14. FUNCTIONS OF MASTER
SCHEDULING
Specifies planning periods as daily, weekly, or monthly.
Group work order processing
Tracks accuracy of order forecasting as percentage.
Classifies supply into types such as materials, purchased,
flow, work order, and transfer.
Schedule can be edited, changed, or consolidated.
15. PROBLEMS OF SEQUENCING IN
SCHEDULING
SHORTEST PROCESSING TIME (SPT)
WEIGHTED SHORTEST PROCESSING TIME (WSPT)
16. EXAMPLE:-
The data about a set of single operation jobs that is to be processed in
a CNC lathe and the processing times of the jobs in the given set of jobs
are as given in table.
Find the optimal sequence which will minimize the mean flow time and
also obtain the corresponding minimum mean flow time.
Job, j Processing time, tj
1 7
2 18
3 6
4 8
5 12
17. SOLUTION:-
For the given problem, the number of jobs is equal to
5. The jobs are arranged as per the SPT ordering.
Job, j Processing time, tj
3 6
1 7
4 8
5 12
2 18
Therefore, the job sequence which will minimize the
mean flow time is 3-1-4-5-2.
18. CONT
The computation of flow time for the optimal sequence
(3-1-4-5-2).
COMPUTATION FLOW TIME
Job, j Processing time, tj Completion time, cj(fj)
3 6 6
1 7 13
4 8 21
5 12 33
2 18 51
19. CONT
Since the ready time rj is zero for all the values of j, the flow
time (fj) = cj for all j.
Therefore,
1/5 ∑ Fj = 1/5 (6+13+21+33+51)
= 1/5 (124)
= 24.8 hours
Therefore, the optimal mean flow time = 24.8 hours.
20. WSPT
Example
Job, j Processing time, tj Weight , wj
1 7 1
2 18 2
3 6 1
4 8 2
5 12 3
Determine the sequence which will minimize the
weighted flow time of this problem. Also find the
corresponding weighted mean flow time.
21. SOLUTION:-
The weighted processing times of various jobs are
summarized by using the formula tj/wj, j = 1,2,3,4, and 5
Job, j Processing time, Weight , wj Tj/wj
tj
1 7 1 7
2 18 2 9
3 6 1 6
4 8 2 4
5 12 3 4
