Chapter 10: Short-term Scheduling

Question 1

What is scheduling

Answer 1

Scheduling determines ‘when’ (the timing) and ‘how much’ (the quantity) of equipment, facilities, and human activities required.

Scheduling can be seen as the final step in the whole transformation process of turning raw materials into final products and services

Question 2

What is a constraint

Answer 2

It is a limitation that impedes the alternatives available to an organization

Question 3

Explain short-term scheduling

Answer 3

It is the process of allocating and managing resources on a daily or weekly basis to meet production requirements

Question 4

What are the benefits of short-term scheduling (pg 259)

Answer 4

• increases productivity
• improves customer service
• reduces costs
• enhances agility
• improves employee satisfaction
• optimizes equipment utilization

Question 5

What are the four main scheduling criterias (pg 262)

Answer 5

1. The time to complete a job should be minimized
2. Utilization of all resources should be maximized
3. Inventory of work in progress should be minimized
4. The time that customers have to wait should be minimized

Question 6

_____ system scheduling usually applies to a job shop type of operation

Answer 6

Low volume

Question 7

What is loading

Answer 7

Loading is assigning particular jobs to particular machines and workers. When loading takes place the jobs are assigned to the correct work centres

Question 8

What is a gantt chart

Answer 8

they are charts used to give a visual perspective of what can be expected and I used widely in loading and scheduling situations

Question 9

What is a load chart

Answer 9

Shows idle times and loading times for a list of work centers

Question 10

What’s the difference between finite loading and infinite loading

Answer 10

when finite loading is undertaken, the actual capacities available at each work center and the actual time taken for each job will be taken into account, with infinite loading jobs are loaded onto a work center without considering the available capacity

Question 11

_____ is also known as priority rules

Answer 11

dispatching rules

Question 12

What are the priority rules used for scheduling (pg 268)

Answer 12

• first in first out (FIFO): jobs or customers are assigned to machines or servers in the sequence in which they arrive at the work center, machine or serving point
• shortest processing time (SPT): jobs that take the shortest time to complete a scheduled first at a particular machine or work center
• earliest due date (EDD): involves selecting the task with the closest deadline from all available tasks as a priority, this disregards other factors like tus urgency or estimated completion time
• critical ratio (CR): jobs with the smallest ratio of time between the processing time and the due date a processed first
• slack per operation (S/O): the average select time available on each job is determined
• rush: the jobs of important customers are done first

Question 13

Priority rules are divided into _____

Answer 13

Local or global rules

Question 14

Explain local rules

Answer 14

Rules that take into account circumstances only for local conditions in a work center or at a particular machine (e.g. FIFO, SPT and EDD)

Question 15

Explain global rules

Answer 15

Rules that take into account circumstances at multiple work centers or machines (e.g, CR, S/O and rush)

Question 16

Explain vertical loading

Answer 16

Jobs are loaded onto a work center job by job

Question 17

Explain horizontal loading

Answer 17

The job with the highest priority is loaded first, thereafter the job with the second highest priority is loaded, this carries on until the job with the lowest priority is loaded last

Question 18

Explain horizontal loading

Answer 18

The job with the highest priority is loaded first, thereafter the job with the second highest priority is loaded, this carries on until the job with the lowest priority is loaded last

Question 19

What is sequencing

Answer 19

Sequencing determines the specific machines or work centers to be used. It determines the order in which machines will be used

Question 20

Differentiate between forward scheduling and back scheduling

Answer 20

Forward scheduling moves forward from a certain point in time, the usual departure point is the date of receipt of the order. Backward scheduling is done from the due date backwards

Question 21

Which performance measures are the most frequently used

Answer 21

• job flow time: this is the length of time that a job spends at a work center or machine. the processing time is included, as well as waiting time, transportation time and so forth
• job lateness: this is the length of the time the due date is exceeded, it is the difference between the due date and the delivery date
• make span: this is the time required to complete a group of jobs
• the average number of jobs: all the jobs that are in a work center or at a machine at any given time are seen as a work in progress and classified as such