Operations Scheduling and Sequencing

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Operations Schedulingand Sequencing

• Chapter 14
• Operations Management Goods, Services, and
  Value Chains, by D. A. Collier and J. R. Evans

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• Jean Rowecamp, clinical coordinator of nursing
  services, was faced with a deluge of complaints
  by her nursing staff about their work schedules
  and complaints by floor supervisors about
  inadequate staffing.
• The nurses complained they were having too many
  shift changes each month. Supervisors said they
  had too many nurses during the days and not
  enough at night and on the weekends.
• It seems that nothing she did would satisfy
  everyone. She couldnt schedule them more than 7
  consecutive working days and required at least 16
  hours between shift changes.
• Nurses were constantly asking her for special
  requests for personal time off, despite the
  negotiated procedures for bidding for shifts and
  vacation times.
• Jean lamented that she became an administrator
  and longed for the days when she was just a
  simple caregiver.

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Definitions

• Scheduling refers to the assignment of start and
  completion times to particular jobs, people, or
  equipment.
• Sequencing refers to determining the order in
  which jobs or tasks are processed.

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Scheduling in MRP Systems
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Staff Scheduling

• Translate forecast into (quantity, work timing)
  needs
• Determine mix of full-time / part-time
• Manage capacity to maximize service while
  minimizing costs

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Appointment Systems

• Determine time interval (e.g., 1 hour, 15 min)
• Determine workday length, time off-duty
• Consider overbooking
• Determine customer appointment rules e.g.
• Business customers have priority over residential
• Residential customers asking for rescheduling get
  lowest priority
• New customer installations have highest priority,
  then repair jobs, then maintenance

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Sequencing Terminology

• Flow time is the amount of time a job spent in
  the shop or factory
• Makespan is the time needed to process a given
  set of jobs.
• Lateness is the difference between the completion
  time and the due date (either positive or
  negative).
• Tardiness is the amount of time by which the
  completion time exceeds the due date.

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Sequencing Rules

• Shortest Processing Time (SPT)
• Focus minimize work in process, manageability
• Earliest Due Date (EDD)
• Focus avoid upsetting customer
• First Come First Served (FCFS)
• Focus equity
• Critical Ratio CR TimeToDueDate /
  ProcessingTime
• Focus tradeoff SPT and EDD

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Sequencing Example