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Contents
Concept of scheduling
Objectives of scheduling
Issues and types of scheduling
© Kamal Subedi, 2016
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What is scheduling?
Scheduling can be defined as “prescribing of when
and where each operation necessary to manufacture
the products is to be performed.
It is also defined as “ establishing of time at which to
begin and complete each event or operation
comprising a procedure”.
The principle aim of the scheduling is to plan the
sequence of work so that the production can be
systematically arranged toward the end of completion
of all products by due date.
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How the function of scheduling differs?
Process Industries
Mass Production
Projects
Batch or Job shop Production
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Objectives of Scheduling
Meet due date
Minimize WIP inventory;
Minimize the average flow time through the systems
Provide for high machine/worker (time) utilization
(minimization of ideal time);
Reduce set up cost
Minimize production and worker costs
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Scheduling issues
Scheduling deals with the timing of operations.
Hospital Operating room use
Patient admissions
Nursing, security, maintenance staffs
Out patient treatments
College Classrooms and audiovisual equipment's
Students and instructor schedule
Graduate and under graduate students
Manufacture Production of goods
Purchase of goods
Workers
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Scheduling issues
Restaurant
Chef waiters, bartenders
Delivery of fresh food
Opening of dining areas
Air lines
Maintenance of aircraft
Departure timetables
flight crews, catering, gate, and ticketing personnel
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Forward Scheduling
With forward scheduling, processing starts
immediately when a job is received, regardless of its
due date.
Forward scheduling is commonly is used in job shops
where customers place their orders on “ needed as
soon as possible basis”.
Each job activity is scheduled for completion as soon
as possible, which allows you to determine the job’s
earliest possible completion date.
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The job is due at the end of week 10, but it can be finished as early as the
end of week 7. With forward scheduling, it is not unusual for jobs to be
finished before their due date. The disadvantage to finishing a job early is
that it causes an inventory buildup if items are not delivered before the
due date.
Contd..
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Backward Scheduling
With backward scheduling, you begin schedulingthe job’s last activity so that the job is finished righton the due date.
It is often used in assembly type industries andcommit in advance to specific delivery dates.
It is the process of assigning the start and finishingtime to the waiting jobs to be done when it is due, butdone before.
To do this, you start with the due date and workbackward, calculating when to start the last activity,when to start the next-to-last activity, and so forth.
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Contd..
Figure below gives an example of backward scheduling. Backward scheduling shows you how
late the job can be started and still be finished on time. When you are using backward
scheduling and forward scheduling together, a difference between the start time of the first
activity indicates slack in the schedule. Slack means that you can start a job immediately but
you do not have to do so. You can start it any time up to the start time in your backward
schedule and still meet the due date.
© Kamal Subedi, 2016
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