1. Scheduling

2. Learning Objectives
Explain what scheduling involves and the importance of good scheduling.
Discuss scheduling needs in high-volume and intermediate-volume systems.
Discuss scheduling needs in job shops. Use and interpret Gantt charts, and use the assignment method for loading.
Discuss and give examples of commonly used priority rules.
Describe some of the unique problems encountered in service systems, and describe some of the approaches used for scheduling service systems.

3. Last stage of planning before production occurs
Scheduling
Specifies when labor, equipment, facilities are needed to produce a product or provide a service
Last stage of planning before production occurs

4. Batch Production Process Industry Mass Production Project
Scheduled Operations
Process Industry
Linear programming
EOQ with non-instantaneous replenishment
Mass Production
Assembly line balancing
Project
Project -scheduling techniques (PERT, CPM)
Batch Production
Aggregate planning
Master scheduling
Material requirements planning (MRP)
Capacity requirements planning (CRP)

5. Objectives in Scheduling
Meet customer due dates
Minimize job lateness
Minimize response time
Minimize completion time
Minimize time in the system
Minimize overtime
Maximize machine or labor utilization
Minimize idle time
Minimize work-in-process inventory
There is no single scheduling rule that optimizes all of these performance criteria. We consider the trade-offs.

6. Scheduling Low-Volume Systems
Loading - assignment of jobs to process centers
Sequencing - determining the order in which jobs will be processed
Job-shop scheduling
Scheduling for low-volume systems with many variations in requirements

7. Assignment of jobs to process centers
Loading
Assignment of jobs to process centers
Perform work with most efficient resources
Use assignment method of linear programming to determine allocation

8. Loading
Infinite loading – jobs are assigned to work centers without regard for the capacity of the work center.
Finite loading – jobs are assigned to work centers taking into account the work center capacity and job processing times
Vertical loading / Horizontal loading
Forward scheduling – scheduling ahead from some point in time.
Backward scheduling – scheduling by working backwards in time from the due date(s).
Schedule chart – a form of Gantt chart that shows the orders or jobs in progress and whether they are on schedule.

9. Sequencing
Sequencing: Determine the order in which jobs at a work center will be processed.
Workstation: An area where one person works, usually with special equipment, on a specialized job.
Priority rules: Simple heuristics used to select the order in which jobs will be processed.
Job time: Time needed for setup and processing of a job.

10. If no order specified use first-come first-served (FCFS)
Priority Rules
FCFS - first come, first served
SPT - shortest processing time
EDD - earliest due date
CR - critical ratio
S/O - slack per operation
Rush - emergency
If no order specified use first-come first-served (FCFS)

11. Performance Measures of Priorities
Meeting due dates of customers or downstream operations.
Minimizing the flow time (the time a job spends in the process).
Minimizing work-in-process inventory.
Minimizing idle time of machines or workers. 9

12. Assumptions of Priority Rules
The setup of jobs is known
Setup time is independent pf processing sequence
Setup time is deterministic
There will be no interruptions in processing such as:
Machine breakdowns
Accidents
Worker illness

13. Two Work Center Sequencing
Johnson’s Rule: technique for minimizing completion time for a group of jobs to be processed on two machines or at two work centers.
Minimizes total idle time
Several conditions must be satisfied

14. Johnson’s Rule Conditions
Job time must be known and constant
Job times must be independent of sequence
Jobs must follow same two-step sequence
Job priorities cannot be used
All units must be completed at the first work center before moving to second

15. Johnson’s Rule Optimum Sequence
List the jobs and their times at each work center
Select the job with the shortest time
Eliminate the job from further consideration
Repeat steps 2 and 3 until all jobs have been scheduled

16. Sequencing Jobs Through Two Serial Process
Johnson’s Rule
List time required to process each job at each machine. Set up a one-dimensional matrix to represent desired sequence with # of slots equal to # of jobs.
Select smallest processing time at either machine. If that time is on machine 1, put the job as near to beginning of sequence as possible.
If smallest time occurs on machine 2, put the job as near to the end of the sequence as possible.
Remove job from list.
Repeat steps 2-4 until all slots in matrix are filled and all jobs are sequenced.

17. Work package Gantt Chart Input/Output Control
Monitoring
Work package
Shop paperwork that travels with a job
Gantt Chart
Shows both planned and completed activities against a time scale
Input/Output Control
Monitors the input and output from each work center

18. Scheduling Difficulties
Variability in
Setup times
Processing times
Interruptions
Changes in the set of jobs
No method for identifying optimal schedule
Scheduling is not an exact science
Ongoing task for a manager

19. Minimizing Scheduling Difficulties
Set realistic due dates
Focus on bottleneck operations
Consider lot splitting of large jobs

20. Scheduling Services Considerations
Scheduling services different from manufacturing
Inability to store or inventory services
Random nature of customer requests for service
Point of customer contact
Back-office operations
Front-office operations

21. Controls customer arrivals for service Reservation systems
Scheduling Services
Appointment systems
Controls customer arrivals for service
Reservation systems
Estimates demand for service
Scheduling the workforce
Manages capacity for service
Scheduling multiple resources
Coordinates use of more than one resource

22. The goal is to maximize the revenue generated by the fixed capacity
Yield Management
Yield Management – the application of pricing strategies to allocate capacity among various categories of demand.
The goal is to maximize the revenue generated by the fixed capacity
Fixed capacity
Hotel, motel rooms
Airline seats
Unsold rooms or seats cannot be carried over

23. Hospitals, police/fire departments, restaurants, supermarkets
Cyclical Scheduling
Hospitals, police/fire departments, restaurants, supermarkets
Rotating schedules
Set a scheduling horizon
Identify the work pattern
Develop a basic employee schedule
Assign employees to the schedule

24. Labor is very flexible resource
Employee Scheduling
Because:
Labor is very flexible resource
Scheduling workforce is complicated, repetitive task
Heuristics are commonly used
There is a lot if industry specific software available.

25. Service Operation Problems
Cannot store or inventory services
Customer service requests are random
Scheduling service involves
Customers
Workforce
Equipment