OM CH: 10 Flashcards
Two types of short-term scheduling
forward scheduling
backward scheduling
What does forward scheduling cause?
It can and probably will cause WIP. This is the case because a buffer is planned in.
Is backward scheduling leaner?
Yes.
Gantt charts
visual representation of tasks that need to be done at a certain time.
What is the goal of Input/output control?
The goal is to decrease WIP. Throughput time decreases.
What is Input/output control?
Alignment of input and output. So release a new task only when the previous task has been accomplished.
What is used to accomplish Input/output control
ConWIP cards. (Control WIP cards)
ConWIP cards are a schedule in which an employee can calculate the workload per time unit. He can decide to place an extra employee at t working station during rush hours.
Two methods in Scheduling
Priority rules
Critical ratio method
Priority rules
First come first served
Shortest Processing Time
Longest Processing Time
Earliest Due Date
When First come first served?
tasks that come in first, are finished first, fairest in eyes of customer
When Shortest Processing Time?
(often seen as best technique, because often shorter tasks have an earlier due date)
When Earliest Due Date?
When meeting a deadline is important.
What is flow time?
Sum of all finish times
Utilization in scheduling methods
Sum of all processing times / flow time
Average number of jobs in the system
flow time / Sum of all processing times
Critical ratio method
(Due date - todays date) / Processing time
for determining which task has the highest priority
- pretty intuitive formula
Theory of constraints
step-by-step guide companies can follow when dealing with constraints in production process.
The goal of theory of constraints
to create a more flexible production process and increase the throughput when necessary
Steps in the theory of constraints
- Identify constraints
- Plan to overcome constraints
- Focus resources on overcoming constraints.
- Decrease the effects of the constraints by offloading work or expanding capacity.
- Identify new constraints. Start from 1
Control principal in the theory of constraints
Has the drum, buffer, rope.
drum
bottleneck is the speed of the process
buffer
Introduce buffer so that the bottleneck works al the time
rope
align the pace of non-bottlenecks with that of the bottleneck
