1. CHAPTER SEVENTEEN SCHEDULING Chapter 17 Scheduling

2. CHAPTER SEVENTEEN SCHEDULING MTSU Management 36217-2 Overview of Production Planning Hierarchy Capacity Planning 1. Facility size 2. Equipment procurement Aggregate Planning 1. Facility utilization 2. Personnel needs 3. Subcontracting Master Schedule 1. MRP 2. Disaggregation of master plan Long-term (Chapter 5) Intermediate-term (Chapter 12) Short-term (Chapter 17) Intermediate-term (Chapters 12 and 14) Short-term Scheduling 1. Work center loading 2. Job sequencing

3. CHAPTER SEVENTEEN SCHEDULING MTSU Management 36217-3 Have the correct amount of resources at the right time and in the right place Meet the job’s due date - customer service Utilization of the organization’s resources - productivity The Scheduling Problem

4. CHAPTER SEVENTEEN SCHEDULING MTSU Management 36217-4 Build A A Done Build B B Done Build C C Done Build D Ship JANFEBMARAPRMAYJUN On time! Scheduling Manufacturing Operations High-volume Intermediate- volume Low-volume Service operations

5. CHAPTER SEVENTEEN SCHEDULING MTSU Management 36217-5 Work Center #1Work Center #2 Output High-Volume Systems Flow system: High-volume system with standardized equipment and activities Flow-shop scheduling: Scheduling for high-volume flow system –line balancing (Chapter 6) –design of work systems (Chapter 7)

6. CHAPTER SEVENTEEN SCHEDULING MTSU Management 36217-6 High-Volume Success Factors Process and product design Preventive maintenance Rapid repair when breakdown occurs Optimal product mixes Minimization of quality problems Reliability and timing of supplies

7. CHAPTER SEVENTEEN SCHEDULING MTSU Management 36217-7 Outputs are between standardized high- volume systems and made-to-order job shops Three basic issues –run size of jobs –timing of jobs –sequence in which jobs should be processed Intermediate-Volume Systems (1 of 2)

8. CHAPTER SEVENTEEN SCHEDULING MTSU Management 36217-8 Intermediate-Volume Systems (2 of 2) Economic run size Base production on a master schedule developed from customer orders and forecasts of demand

9. CHAPTER SEVENTEEN SCHEDULING MTSU Management 36217-9 Low-Volume Systems A variety of unique (customized) jobs arrive at the shop Someone must analyze each job regarding its routing (which work centers it will be required to visit), and the required amount of resources needed at each work center Typically the customer is told when the job will be finished (due date) The jobs are moved through the required work centers as each becomes available according to a scheduling system

10. CHAPTER SEVENTEEN SCHEDULING MTSU Management 36217-10 Scheduling Low-Volume Systems Loading - assignment of jobs to process centers Sequencing - determining the order in which jobs will be processed

11. CHAPTER SEVENTEEN SCHEDULING MTSU Management 36217-11 Loading Approaches (1 of 2) Infinite loading –assumes capacity of a work center is infinite –priority sequencing rule then used –managers may need to respond to capacity overload conditions

12. CHAPTER SEVENTEEN SCHEDULING MTSU Management 36217-12 Loading Approaches (2 of 2) Finite loading –projects the starting and stopping times of each job at each work center –takes into account capacities of each work center and the processing times of jobs so that capacity is not exceeded In special cases, an algorithm such as the assignment method may be used

13. CHAPTER SEVENTEEN SCHEDULING MTSU Management 36217-13 Everything is #1 Priority Sequencing Determine the order in which jobs waiting at a work center will be processed One approach is to use priority rules (simple heuristics) to select the order in which jobs waiting in line will be processed

14. CHAPTER SEVENTEEN SCHEDULING MTSU Management 36217-14 Examples of Priority Rules FCFS - first come, first served SPT- shortest processing time DD- due date CR- critical ratio

15. CHAPTER SEVENTEEN SCHEDULING MTSU Management 36217-15 Examples of Performance Measures for a Job Shop Scheduling System (1 of 2) Job flow time – the length of time a job is in the shop at a particular workstation; includes processing time, wait time, transportation time Average job flow time – the sum of the flow time for each job in a group divided by the number of jobs Makespan – total time needed to complete a group of jobs; sum of processing times

16. CHAPTER SEVENTEEN SCHEDULING MTSU Management 36217-16 Examples of Performance Measures for a Job Shop Scheduling System (2 of 2) Job lateness – the length of time the job completion time is expected to exceed the time the job is due Average lateness – the sum of the lateness for each job in a group divided by the number of jobs Average number of jobs – average work- in-process for a group of jobs; total flow time/makespan

17. CHAPTER SEVENTEEN SCHEDULING MTSU Management 36217-17 Two Work Center Sequencing Johnson’s Rule –technique for minimizing completion time for a group of jobs to be processed on two processes or at two work centers. –minimizes total idle time of the two processes Several conditions must be satisfied

18. CHAPTER SEVENTEEN SCHEDULING MTSU Management 36217-18 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 (flow shop) Job priorities cannot be used All units must be completed at the first work center before moving to second

19. CHAPTER SEVENTEEN SCHEDULING MTSU Management 36217-19 Example Problem first last

20. CHAPTER SEVENTEEN SCHEDULING MTSU Management 36217-20 Used as a visual aid for loading and scheduling Purpose is to organize and clarify the actual or intended use of resources in a time framework Two most commonly used types –load chart –schedule chart Gantt Chart

21. CHAPTER SEVENTEEN SCHEDULING MTSU Management 36217-21 Figure 17-2 Gantt Load Chart

22. CHAPTER SEVENTEEN SCHEDULING MTSU Management 36217-22 Example Problem first last C A D B Data Entry Verify time

23. CHAPTER SEVENTEEN SCHEDULING MTSU Management 36217-23 Scheduling Approaches Forward scheduling –scheduling ahead, from some point in time Backward scheduling –scheduling by working backward from the job’s due date

24. CHAPTER SEVENTEEN SCHEDULING MTSU Management 36217-24 Input/Output Control Used to manage work flow so that queues and waiting times are kept under control Input to a work center is compared to the output of that work center for some time period An imbalance indicates management should investigate

25. CHAPTER SEVENTEEN SCHEDULING MTSU Management 36217-25 Service Operation Problems Cannot store or inventory services Customer service requests are random Scheduling service involves –Customers –Workforce –Equipment Duh! Where’s Dilbert?

26. CHAPTER SEVENTEEN SCHEDULING MTSU Management 36217-26 Scheduling Service Operations 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