Yuqian #6 - Production Planning 3

Question 1

After planning at each of our levels for material, staffing, etc comes sequencing. What is sequencing?

Answer 1

We prioritise jobs assigned to a resource using some sequencing technique, policy, and/or heuristic, usually to achieve an objective such as most efficient machine/staff utilisation

Question 2

Define the following terms related to sequencing: flowtime, makespan, tardiness, and critical ratio

Answer 2

Flowtime - time for job to flow through system

Makespan - time for group of jobs to be completed

Tardiness - difference between late jobs due date and its completion time

Critical ratio = (time remaining)/(work remaining) = 1 if job is on schedule, >1 if job is ahead of schedule, and <1 if job is behind schedule

Question 3

Johnson’s Rule is a technique that can be used to determine a sequence. What are the steps involved in this technique?

Answer 3

Question 4

Use Johnson’s Rule to to sequence the operations in the table below

Answer 4

Question 5

What are the five assumptions we make when using Johnson’s Rule?

Answer 5

1. Job time must be known and constant
2. Job times must be independent of sequence
3. Jobs must follow same two-step sequence
4. Job priorities cannot be used
5. All units must be completed at first work centre before moving to second

Question 6

Scheduling is the last stage of planning before production begins, and can yield cost savings and productivity increases if done correctly. What are two difficulties with scheduling?

Answer 6

1. Variability - setup times, processing times, interruptions, changess in set of jobs
2. Uncertainty - not an exact science, so no exact method for identifying optimal schedule

Question 7

Scheduling is the last stage in the planning process before production begins. What does it involve?

Answer 7

Establishes the timing of the use of equipment, facilities and human activities in an organisation

Question 8

What are the 9 objectives of scheduling?

Answer 8

Minimise: job lateness, response time, completion time, time in system, overtime, idle time, work-in-process inventory

Maximise: machine/labour utilisation, meeting of customer due dates

Question 9

What is the difference between an infinite and a finite scheduling system?

Answer 9

Infinite: Loads jobs without regard to capacity, then levels the load and sequences the jobs

Finite: Sequences jobs as part of loading decision. Resources are never loaded beyond capacity

Question 10

Refer to lecture notes about Hungerian method to make sure you understand it

Answer 10

MaNuFaCtUrInG