OPMG 3000

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MBA 8452 Systems and Operations Management
Operations Scheduling
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Objectives

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

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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

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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

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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

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Work-Center Scheduling Objectives

• Meet due dates
• Minimize lead time
• Minimize setup time or cost
• Minimize work-in-process inventory

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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)

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Job SequencingPerformance Measures

• Average Lateness - meet due dates of customers or
  downstream operations
• Mean Flow Time - minimize the time a job spends
  in the process

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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?
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Job Sequencing on One Machine Example--FCFS Rule
Average lateness 9.3 days Mean flow time
22.5 days
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Job Sequencing on One Machine Example--SOT Rule
Average lateness 5.67 days Mean flow time 18
days
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Job Sequencing on One Machine Example--STR Rule
Average lateness 7.67 days Mean flow time
22.33 days
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Job Sequencing on One Machine Example--DDate Rule
Average lateness 5.17 days Mean flow time
19.17 days
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Job Sequencing on One Machine Example--Schedule
Chart
Time (in days)
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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

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Job Sequencing on Two Machines Johnsons Rule

• Minimizes the time to complete all jobs in both
  work centers/machines (makespan)
• Procedure of Applying Johnsons 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

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Job Sequencing on Two Machines Example--Johnsons
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
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Job Sequencing on Two Machines Example--Schedule
Chart
Makespan 65 hours
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Shop-Floor (Production Activity) ControlMajor
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

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Input/Output Control
Work Center

• Planned input should never exceed planned output
  (in the long run)
• Focuses attention on bottleneck work centers

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Personnel Scheduling in Services

• Scheduling consecutive days off
• Scheduling daily work times
• Scheduling hourly work times