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Operations Scheduling

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Presentation on theme: "Operations Scheduling"— Presentation transcript:

1 Operations Scheduling
MBA 8452 Systems and Operations Management Operations Scheduling

2 Objectives Explain work center capacity
Describe infinite and finite loading, forward and backward scheduling Solve scheduling problems Explain scheduling in service operations

3 Scheduling Allocates resources over time (short-run) to accomplish specific tasks Examples Hospital: operating room, staff University: course, classroom, instructor Airline: flight departure, arrival, and crew Factory: product production, worker

4 Operations Scheduling
Work Center An area in a business in which productive resources are organized and work is completed Capacity and Scheduling Infinite loading Finite loading Forward scheduling Backward scheduling

5 Typical Scheduling and Control Functions
Allocating orders, equipment, and personnel to work centers Determining the sequence of job orders Initiating performance of the scheduled work Shop-floor control

6 Work-Center Scheduling Objectives
Meet due dates Minimize lead time Minimize setup time or cost Minimize work-in-process inventory

7 Some Priority Rules for Job Sequencing
First-come, first-served (FCFS) Shortest operating/processing time (SOT) Earliest due date (DDate) Least slack time remaining (STR) (due date - current date) - (remaining processing time) Smallest critical ratio (due date-current date)/(remaining processing time)

8 Job Sequencing Performance Measures
Average Lateness - meet due dates of customers or downstream operations Mean Flow Time - minimize the time a job spends in the process

9 Job Sequencing on One Machine Example
Six jobs are lined up for processing on one machine. Their processing times (in order of arrival) and due dates are listed below What is the sequencing schedule using FCFS, SOT, STR, or DDate rule?

10 Job Sequencing on One Machine Example--FCFS Rule
Average lateness = 9.3 days Mean flow time = 22.5 days

11 Job Sequencing on One Machine Example--SOT Rule
Average lateness = 5.67 days Mean flow time = 18 days

12 Job Sequencing on One Machine Example--STR Rule
Average lateness = 7.67 days Mean flow time = days

13 Job Sequencing on One Machine Example--DDate Rule
Average lateness = days Mean flow time = days

14 Job Sequencing on One Machine Example--Schedule Chart
Time (in days)

15 Job Sequencing on One Machine Some General Results
For job sequencing on one machine/work center, schedule completion time (makespan) is always the same regardless of the job order SOT minimizes average flow time and average waiting time Earliest DDate rule minimizes the worst (maximum) lateness

16 Job Sequencing on Two Machines Johnson’s Rule
Minimizes the time to complete all jobs in both work centers/machines (makespan) Procedure of Applying Johnson’s Rule List the operation times for all jobs Select the shortest operating time overall If the SOT is for the: 1st machine - schedule that job first 2nd machine - schedule that job last Repeat steps  and , until all jobs are scheduled

17 Job Sequencing on Two Machines Example--Johnson’s Rule
Five jobs need to be processed at two workstations with the following processing time requirement What is the best sequence of jobs that minimizes the flow time of all jobs? Answer: B-A-D-E-C

18 Job Sequencing on Two Machines Example--Schedule Chart
Makespan = 65 hours

19 Shop-Floor (Production Activity) Control Major Functions
1. Assign priority to each shop order 2. Maintain work-in-process quantity information 3. Convey shop-order status information 4. Provide actual output data for capacity control purposes 5. Provide quantity by location by shop order for WIP inventory and accounting purposes 6. Provide measurement of efficiency, utilization, and productivity of manpower and machines

20 Input/Output Control Work Center Input Output Planned input should never exceed planned output (in the long run) Focuses attention on bottleneck work centers

21 Personnel Scheduling in Services
Scheduling consecutive days off Scheduling daily work times Scheduling hourly work times

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