1. Scheduling Chapter 19

2. Learning Objectives
Know what a Manufacturing Execution System production activity control is.
Understand typical priority scheduling rules and the impact they have on scheduling performance measures.
Recognize a simple job allocation procedure.
Explain the issues considered in employee scheduling.

3. Manufacturing Execution Systems
Manufacturing execution system (MES): an information system that schedules, dispatches, tracks, monitors, and controls production
Real-time linkage to:
MRP
Product and process planning
Systems that extend beyond the factory
Service execution system (SES): an information system that links schedules, dispatches, tracks, monitors, and controls the customer’s encounters with the service organization
LO 1

4. Work Center
A work center is an area in a business in which productive resources are organized and work is completed
Can be a single machine, a group of machines, or an area where a particular type of work is done 3

5. Loading
Infinite loading: work is assigned to a work center based on what is needed
No consideration to capacity
Finite loading: schedules each resource using the setup and run time required for each order
Determines exactly what will be done by each resource at every moment during the day
LO 1

6. Scheduling
Forward scheduling: the system takes an order and schedules each operation that must be completed forward in time
Can tell the earliest date an order can be completed
Backward scheduling: starts with due date and schedules the required operations in reverse sequence
Can tell when an order must be started in order to be done by a specific date
LO 2

7. Typical Scheduling and Control Functions
Allocating orders, equipment, and personnel
Determining the sequence of order performance
Initiating performance of the scheduled work
Shop-floor control
LO 2 5

8. Work-Center Scheduling Objectives
Meet due dates
Minimize lead time
Minimize setup time or cost
Minimize work-in-process inventory
Maximize machine utilization 6

9. Job Sequencing
Sequencing: the process of determining the job order on machines or work centers
Also known as priority sequencing
Priority rules: the rules used in obtaining a job sequence
Can be simple or complex
Can use one or more pieces of information
Common rules shown on next slide
LO 2

10. Priority Rules for Job Sequencing
1. First-come, first-served (FCFS) 2. Shortest operating time (SOT) 3. Earliest due date first (DDate) 4. Slack time remaining (STR) first 7

11. Priority Rules for Job Sequencing (Continued)
5. Critical ratio (CR) 8

12. Example of Job Sequencing: First-Come First-Served
Suppose you have the four jobs to the right arrive for processing on one machine
What is the FCFS schedule?
Do all the jobs get done on time?
Answer: FCFS Schedule
No, Jobs B, C, and D are going to be late 10

13. Example of Job Sequencing: Shortest Operating Time
Suppose you have the four jobs to the right arrive for processing on one machine
What is the SOT schedule?
Do all the jobs get done on time?
Answer: Shortest Operating Time Schedule
No, Jobs A and B are going to be late 11

14. Example of Job Sequencing: Earliest Due Date First
Suppose you have the four jobs to the right arrive for processing on one machine
What is the earliest due date first schedule?
Do all the jobs get done on time?
Answer: Earliest Due Date First
No, Jobs C and B are going to be late 13

15. Example of Job Sequencing: Critical Ratio Method
Suppose you have the four jobs to the right arrive for processing on one machine
What is the CR schedule?
Do all the jobs get done on time?
In order to do this schedule the CR’s have be calculated for each job. If we let today be Day 1 and allow a total of 15 days to do the work. The resulting CR’s and order schedule are:
CR(A)=(5-4)/15=0.06 (Do this job last)
CR(B)=(10-7)/15=0.20 (Do this job first, tied with C and D)
CR(C)=(6-3)/15=0.20 (Do this job first, tied with B and D)
CR(D)=(4-1)/15=0.20 (Do this job first, tied with B and C)
No, but since there is a three-way tie, only the first job or two will be on time 13

16. Scheduling n Jobs on Two Machines
Two or more jobs must be processed on two machines in a common sequence
Wish to minimize the flow time from the beginning of the first job to the finish of the last job
Use Johnson’s rule
LO 2

17. Steps to Johnson’s Rule
List the operation time for each job
Select the shortest operation time
If the shortest time is on the first machine, do first
If the shortest time is on the second machine, do the job last
For ties, do first
Repeat 2-3 for each remaining job
LO 2

18. Example of Job Sequencing: Johnson’s Rule
Suppose you have the following five jobs with time requirements in two stages of production. What is the job sequence using Johnson’s Rule?
Time in Hours
Jobs Stage 1 Stage 2 A B C D 13

19. Scheduling a Set Number of Jobs on the Same Number of Machines
Some work centers have enough machines to start all the jobs
Here the issue is the particular assignment of individual jobs to individual machines
Assignment method: a special case of the transportation method of linear programming
There are n things to be distributed to n destinations
Each thing assigned to one and only one destination
Only one criterion can be used
LO 2

20. Example : Assignment Method
Assignment Matrix Showing Machine Processing Costs for Each Job
LO 2

21. Example Step 1: Row Reduction
LO 2

22. Example Step 2: Column Reduction
LO 2

23. Example Step 3: Apply Line Test
LO 2

24. Example Step 4: Additional Reduction
LO 2

25. Example Optimal Solution
LO 2

26. Example Optimal Assignment and Their Costs
Job I to Machine E $3
Job II to Machine B 4
Job III to Machine C 2
Job IV to Machine D 5
Job V to Machine A 3
Total Cost
$17
LO 2

27. Personnel Scheduling in Services
Scheduling consecutive days off
Scheduling daily work times
Scheduling hourly work times
LO 4 21

28. Any Questions?
Scheduling