Operations Scheduling MBA 8452 Systems and Operations Management Operations Scheduling

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

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

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

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

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

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)

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

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?

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

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

Job Sequencing on One Machine Example--STR Rule Average lateness = 7.67 days Mean flow time = 22.33 days

Job Sequencing on One Machine Example--DDate Rule Average lateness = 5.17 days Mean flow time = 19.17 days

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

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

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

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

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

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

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

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