March 30, 2015

Operations Scheduling - Review Notes

Chapter Outline of

Richard B. Chase, F. Robert Jacobs, Nicholas J. Aquilano, Operations Management for Competitive Advantage, 10/e, McGraw-Hill Higher Education, 2004

Manufacturing Execution Systems
The Nature and Importance of Work Centers
Typical Scheduling and Control Functions
Objectives of Work-Center Scheduling
Job Sequencing
Priority Rules and Techniques
Scheduling n Jobs on One Machine
Comparison of Priority Rules
Scheduling n Jobs on Two Machines
Scheduling a Set Number of Jobs on the Same Number of Machines
Scheduling n Jobs on m Machines
Shop-Floor Control
Gantt Charts
Tools of Shop-Floor Control
Input/Output Control
Data Integrity
Principles of Work Center Scheduling
Personnel Scheduling in Services
Scheduling Consecutive Days Off
Scheduling Daily Work Times
Scheduling Hourly Work Times
Summary for Revision

Manufacturing execution systems do scheduling.

Work Center

Work centers are areas in a business in which productive resources are organized and work is completed. It may be a single machine, a group of machines, or an area where a particular type of work is done. The work centers can be organized in a variety of ways including by function in a job-shop configuration; or by product in a flow, assembly line, or group-technology-cell configuration.

Scheduling and controlling functions of an operation are critical. The functions must be performed beginning with allocating orders, equipment, and personnel to work centers or the specified locations for short-run capacity planning. Next is the determination of the sequence of order performance or establishing job priorities. Initiating the scheduled work or dispatching of orders is followed by shop-floor control.

Loading - Infinite loading or Finite loading

A characteristic that distinguishes one scheduling system from another is how capacity is considered in determining the schedule. The scheduling systems can use infinite loading or finite loading.

Infinite loading occurs when work is assigned to a work center simply based on what is needed over time.

Finite loading actually schedules in detail each resource using the setup and run time required for each order.

Another characteristic, that distinguishes scheduling systems, is whether the schedule is generated forward or backward in time.

Processes can be machine limited or labor limited. Determining the sequence of orders and establishing job priorities are critical as is dispatching orders.

Shop floor control

Shop floor control is necessary to review job status and expediting late and/or critical orders when necessary. The schedule must be revised as necessary to reflect changes in order status.

Various priority rules work to satisfy job arrival patterns, the number and variety of machines in the manufacturing facility, the ratio of workers to machines in the shop, the flow pattern of jobs through the shop, the priority rules for allocating jobs to machines, and schedule evaluation criteria. Priority rules for allocating jobs to machines can use a variety of methods.

The objectives of work-center scheduling are to meet customer due dates, minimize lead-time, minimize set-up time, minimize work in process inventory, and maximize machine or labor utilization.

Role of Simulation

In manufacturing job shops, scheduling relies heavily on simulation to estimate the flow of work through the system to determine bottlenecks and adjust job priorities. Software packages are available to do this. In services, the focus is typically on employee scheduling using mathematical tools that can be used to set work schedules in light of expected customer demand.


Originally posted at 2utb2lsm2k7a/ 436

Updated 30 March 2015, 9 Dec 2011

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