Page 606 - Introduction to Business

580 PART 6 Managing Business Operations, Management Information Systems, and the Digital Enterprise

Control Decisions

LEARNING OBJECTIVE 8
Outline the control decisions about scheduling and quality.
Once the operations manager has designed the production system and its products
and has planned the production rate and the materials required along with their
supply sources, as well as the inventory levels, he or she still has to make two major
control decisions: scheduling and quality.

Scheduling

scheduling Allocating available Scheduling decisions allocate available production resources to tasks, jobs, orders,
production resources to tasks, jobs, activities, or customers in a given time period. The capacity design decision con-
orders, activities, or customers in a
given time period strains the production rate decision, which in turn restricts the scheduling deci-
sion. A production schedule indicates what is to be done, when, by whom, and with
what resources. Scheduling decisions vary with the type of process: project, job,
batch, line, and continuous. In this introductory treatment, we consider the sched-
uling decision only for job processes.
One of the most widely used scheduling tools is known as the Gantt chart, first
proposed by Henry Gantt in 1917. Exhibit 16.15 illustrates a scheduling decision for
a job process using a Gantt chart.
In this example, there are fours jobs A, B, C, and D that have to be scheduled in
three work centers I, II, and III. The route stipulates the sequence in which jobs
need to visit the work centers, as well as the machine hours required at each work
center. For instance, first job D needs to go to work center I and be processed for
three hours; next job D needs to go to work center III and be processed for two
hours; and finally job D needs to go to work center II and be processed for one hour.
The decision that the operations manager faces is how to schedule the jobs in the
work centers so that all jobs are finished as soon as possible. The Gantt chart for the
case where jobs are scheduled in the order A, B, C, D is
• Job A is scheduled at work center I for hours 1 and 2, then at work center II for
hours 3 to 5, and then at work center III for hours 6 to 9.
• Job B is scheduled at work center III for hours 1 and 2, then at work center II
for hours 6 and 7 (because hours 1 and 2 are not feasible, and hours 3 to 5 are
already assigned to job A), and then at work center I for hours 8 and 9.
• Job C is scheduled at work center II for hours 8 to 10 (because job C requires
three hours, hence hours 1 and 2 are not sufficient and hours 3 to 7 are already
assigned to jobs A and B), then at work center III for hour 11, and then at work
center I for hours 12 to 14.
• Job D is scheduled at work center I for hours 3 to 5 (because hours 1 to 2 are
already assigned to job A), then at work center III for hours 12 and 13 (because
hours 1 to 5 are not feasible, hours 6 to 9 are already assigned to job A, hour 10
is not sufficient, and hour 11 is already assigned to job C), and then at work
center II for hour 14.
According to this first schedule, all four jobs can be finished in 14 hours.
Now consider the second Gantt chart where jobs were scheduled in the order D,
C, B, A. This second schedule is superior because all jobs are finished in 13 hours.
The operations manager would keep trying different job schedules in order to find
the one schedule where all jobs are finished as soon as possible.
Variations of the Gantt chart can also be used for scheduling decisions in proj-
ect and batch processes.

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