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Operations Management and Strategic Management · Operations Planning

Production Scheduling, Sequencing and Control

Updated 10 October 2026 · Fact-checked

Scheduling fixes when each job starts and finishes on each machine. Sequencing decides the order of jobs at a work centre using rules like FCFS, SPT and EDD. Routing sets the path, loading assigns work, and Gantt charts track progress. To solve a problem, apply the rule, compute completion times, then flow time and lateness.

Understand Scheduling, Sequencing and Production Control

Production control makes sure the plan turns into output on time. It works through a chain of linked activities: routing, loading, scheduling, dispatching and follow-up. Each answers one question.

Routing decides the path and operations a job follows: which machines, in what order. Loading assigns jobs to work centres so that capacity is used without overload. Scheduling fixes the time: when each operation starts and ends. Dispatching releases the work orders, materials and tools to the shop floor. Follow-up (expediting) compares actual progress with the schedule and corrects delays.

Sequencing is the choice of order when several jobs wait at the same machine. Because you cannot do all jobs at once, the order changes how long jobs wait and how many are late. Common priority rules are:

  • FCFS (First Come First Served): serve in order of arrival. Simple and seen as fair.
  • SPT (Shortest Processing Time): do the shortest job first. It minimises average flow time and average number of jobs in the system on a single machine. Long jobs may wait a long time.
  • EDD (Earliest Due Date): do the job with the earliest due date first. It minimises the maximum lateness on a single machine.
  • LPT (Longest Processing Time): longest job first. Used when big jobs must be started early.

A Gantt chart is a bar chart with time on the horizontal axis and machines or jobs on the vertical axis. A load chart shows the work booked on each centre. A progress chart shows planned against actual. Gantt charts are easy to read, but they do not show dependencies between jobs well and are hard to update for large shops.

Scheduling can be forward (start from the release date and find the earliest finish) or backward (start from the due date and work back to the latest start).

Key rules to remember

Flow time of a job
Flow time = Completion time − Arrival (release) time
If all jobs are available at time 0, flow time equals completion time.
Average flow time
Σ Flow times ÷ Number of jobs
SPT gives the minimum on a single machine.
Lateness
Lateness = Completion time − Due date
Negative means early. Tardiness = maximum of (lateness, 0).
Average number of jobs in the system
Σ Flow times ÷ Total processing time (makespan)
Valid when all jobs are available at time 0 and there is no idle time, on one machine. Useful for comparing rules on one machine.
Completion time of a job
Completion time = Sum of processing times of all jobs up to and including it
Valid for one machine with no idle time.

How to solve Scheduling, Sequencing and Production Control questions

Use this method for any sequencing or scheduling question on one machine, and for descriptive questions on production control.

  1. 1Read which rule is asked: FCFS, SPT, EDD or LPT. Note the arrival order for FCFS.
  2. 2List each job with processing time and due date in a table.
  3. 3Arrange the jobs in the order the rule gives. For ties, keep arrival order unless told otherwise.
  4. 4Compute cumulative completion times down the new order.
  5. 5Calculate flow time and lateness for each job: lateness = completion − due date.
  6. 6Total the columns and find average flow time, number of late jobs and maximum lateness.
  7. 7Compare the rules and state which suits the objective, such as SPT for speed and EDD for due dates.
  8. 8For theory, answer in the order: routing, loading, scheduling, dispatching, follow-up, with one line each.

Quickest way: Table with running total

When to use it: For numerical sequencing questions with four to six jobs on one machine.

  1. Draw columns: Job, Time, Completion, Due, Lateness.
  2. Sort jobs by the rule first: smallest time for SPT, earliest due date for EDD.
  3. Fill the completion column by adding each time to the previous completion.
  4. Subtract due date from completion. Write 0 for tardiness if negative.
  5. Add completion times and divide by number of jobs for average flow time.
  6. Check that the last completion equals the sum of all processing times.

Common mistakes in Scheduling, Sequencing and Production Control

  • Computing completion time with the job's own time only, not cumulative time.

    Students forget that jobs wait for those before them on the same machine.

    Fix: Always add the processing time to the previous job's completion time.

  • Sorting by due date when SPT is asked, or the reverse.

    Rule names get mixed up under time pressure.

    Fix: Write the rule's sort key at the top: SPT = shortest time, EDD = earliest due date.

  • Treating negative lateness as a penalty when averaging tardiness.

    Lateness and tardiness are used as the same thing.

    Fix: Lateness can be negative. Tardiness is zero for early jobs. Use the term the question uses.

  • Confusing scheduling with sequencing.

    Both deal with timing of jobs.

    Fix: Sequencing is the order of jobs at a centre. Scheduling gives the actual start and finish times for all operations.

  • Mixing up routing, loading and dispatching in theory answers.

    The terms sound alike and are learnt as a list.

    Fix: Remember: routing = path, loading = which centre, scheduling = when, dispatching = release orders, follow-up = check progress.

  • Claiming SPT always minimises lateness.

    Students overgeneralise SPT's benefits.

    Fix: SPT minimises average flow time. EDD minimises maximum lateness. Say which objective each serves.

Worked examples

Example 1

Four jobs arrive in the order A, B, C, D at one machine, all available at time 0. Processing times (days): A 6, B 2, C 8, D 4. Due dates (day): A 9, B 4, C 20, D 10. Find the sequence under FCFS and SPT, and compare average flow time and number of late jobs.

Show the solution
  1. FCFS order: A, B, C, D. Completion times: A = 6, B = 8, C = 16, D = 20.
  2. FCFS flow times total: 6 + 8 + 16 + 20 = 50. Average = 50 ÷ 4 = 12.5 days.
  3. FCFS lateness: A = 6 − 9 = −3, B = 8 − 4 = 4, C = 16 − 20 = −4, D = 20 − 10 = 10. Late jobs: B and D = 2.
  4. SPT order: B (2), D (4), A (6), C (8). Completion times: B = 2, D = 6, A = 12, C = 20.
  5. SPT flow times total: 2 + 6 + 12 + 20 = 40. Average = 40 ÷ 4 = 10 days.
  6. SPT lateness: B = 2 − 4 = −2, D = 6 − 10 = −4, A = 12 − 9 = 3, C = 20 − 20 = 0. Late jobs: A only = 1.
  7. Check: last completion is 20 = 6 + 2 + 8 + 4 in both cases.

Answer: FCFS: average flow time 12.5 days, 2 late jobs. SPT: sequence B-D-A-C, average flow time 10 days, 1 late job. SPT is better on both measures here.

Example 2

Using the data in the previous example, sequence the jobs by EDD and find the maximum lateness. State how the result compares with SPT.

Show the solution
  1. Order by due date: B (4), A (9), D (10), C (20).
  2. Completion times: B = 2, A = 2 + 6 = 8, D = 8 + 4 = 12, C = 12 + 8 = 20.
  3. Lateness: B = 2 − 4 = −2, A = 8 − 9 = −1, D = 12 − 10 = 2, C = 20 − 20 = 0.
  4. Maximum lateness = 2 days (job D). Late jobs = 1.
  5. Flow time total = 2 + 8 + 12 + 20 = 42. Average = 42 ÷ 4 = 10.5 days.
  6. SPT had maximum lateness of 3 days (job A) and average flow time of 10 days.

Answer: EDD sequence B-A-D-C gives maximum lateness of 2 days and average flow time of 10.5 days. EDD has lower maximum lateness than SPT (3 days), while SPT has the lower average flow time (10 days).

Exam tips

  • For MCQs, memorise the single objective of each rule: SPT for average flow time, EDD for maximum lateness, FCFS for fairness.
  • In written answers, define routing, loading, scheduling, dispatching and follow-up in one line each, then add a short example.
  • Always show the table with completion, due date and lateness. Step marks are given for each column.
  • When asked about Gantt charts, mention both uses (scheduling and progress control) and one limitation.
  • Check that the final completion time equals total processing time before you write the answer.

Practice questions from Operations Planning

Scheduling, Sequencing and Production Control: frequently asked questions

What is the difference between scheduling and sequencing?

Sequencing decides the order in which jobs are processed at a work centre. Scheduling goes further and fixes the start and finish time of each operation on each machine.

Which sequencing rule is best?

No rule wins on every measure. SPT gives the lowest average flow time on a single machine, and EDD gives the lowest maximum lateness. Choose the rule that matches the objective in the question.

What are the stages of production control?

Routing, loading, scheduling, dispatching and follow-up. Routing sets the path, loading assigns work to centres, scheduling sets times, dispatching releases orders, and follow-up checks progress.

What is a Gantt chart used for in production?

It shows jobs or machines against time as bars. You use it to plan schedules, see machine loading and compare planned with actual progress.