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| The allocation of resources over time to accomplish specific tasks. |
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| A type of scheduling whereby customers are assigned to a definite time for order fulfillment. |
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| A type of scheduling that determines when employees work. |
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| A type of scheduling in which jobs are assigned to workstations or employees are assigned to jobs for specified time periods. |
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| The amount of time a job spends in the service or manufacturing system. Also referred to as throughput time or time spent in the system, including service. |
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| The total amount of time required to complete a group of jobs. |
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| The amount of time by which a job missed its due date or the percentage of total jobs processed over some period of time that missed their due dates. |
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| Work-in-process (WIP) inventory |
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| Any job that is waiting in line, moving from one operation to the next, being delayed, being processed, or residing in a semi-finished state. |
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| The sum of scheduled receipts and on-hand inventories. |
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| The sum of scheduled receipts and on-hand inventories. |
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| The percentage of work time that is productively spent by an employee or machine. |
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Used as a tool to monitor the progress of work and to view the load on workstations.
The chart takes two basic forms: (1) the job or activity progress chart, and (2) the workstation chart.
The Gantt progress chart graphically displays the current status of each job or activity relative to its scheduled completion date.
The Gantt workstation chart shows the load on the workstations and the nonproductive time. |
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| Scheduling Customer Demand |
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Definition
Three methods are commonly used to schedule customer demand:
Appointments assign specific times for service to customers.
Reservations are used when the customer actually occupies or uses facilities associated with the service.
Backlogs:
The customer is given a due date for the fulfillment a product order, or
Allow a backlog to develop as customers arrive at the system. Customers may never know exactly when their orders will be fulfilled |
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| A schedule that rotates employees through a series of workdays or hours. |
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| A schedule that calls for each employee to work the same days and hours each week. |
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The technical constraints imposed on the workforce schedule are the resources provided by the staffing plan and the requirements placed on the operating system.
Other constraints, including legal and behavioral considerations, also can be imposed. |
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are short-term plans designed to implement the master production schedule.
Operations scheduling focuses on how best to use existing capacity.
Often, several jobs must be processed at one or more workstations. Typically, a variety of tasks can be performed at each workstation. |
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| A firm that specializes in low- to medium-volume production and utilizes job or batch processes. |
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| A firm that specializes in medium- to high-volume production and utilizes line or continuous processes. |
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| A method of generating schedules in job shops whereby the decision about which job to process next is made using simple priority rules whenever the workstation becomes available for further processing. |
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| Priority sequencing rules |
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Definition
| The rules that specify the job processing sequence when several jobs are waiting in line at a workstation. |
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| A ratio that is calculated by dividing the time remaining until a job’s due date by the total shop time remaining for the job. CR = (Due date – Today’s date)/Total shop time remaining |
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| Setup, processing, move, and expected waiting times of all remaining operations, including the operation being scheduled. |
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| A priority sequencing rule that specifies that the job with the earliest due date is the next job to be processed. |
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| First-come, first-served (FCFS): |
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Definition
| A priority sequencing rule that specifies that the job arriving at the workstation first has the highest priority. |
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| Shortest processing time (SPT) |
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| A priority sequencing rule that specifies that the job requiring the shortest processing time is the next job to be processed. |
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| Slack per remaining operations (S/RO): |
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| A priority sequencing rule that determines priority by dividing the slack by the number of operations that remain, including the one being scheduled. |
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Definition
| A set of rules such as FCFS, EDD, and SPT, that bases the priority of a job on a single aspect of the job, such as arrival time at the workstation, the due date, or the processing time. |
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| Priority rules, such as CR and S/RO, incorporate information about the remaining workstations at which the job must be processed |
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| A set of rules that apply to more than one aspect of a job. |
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| Scheduling Jobs for Multiple Workstations |
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Definition
Priority sequencing rules can be used to schedule more than one operation. Each operation is treated independently.
Identifying the best priority rule to use at a particular operation in a process is a complex problem because the output from one process becomes the input for another.
Computer simulation models are effective tools to determine which priority rules work best in a given situation.
When a workstation becomes idle, the priority rule is applied to the jobs waiting for that operation, and the job with the highest priority is selected.
When that operation is finished, the job is moved to the next operation in its routing, where it waits until it again has the highest priority. |
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Definition
A procedure that minimizes makespan when scheduling a group of jobs on two workstations.
Step 1. Find the shortest processing time among the jobs not yet scheduled. If two or more jobs are tied, choose one job arbitrarily.
Step 2. If the shortest processing time is on workstation 1, schedule the corresponding job as early as possible. If the shortest processing time is on workstation 2, schedule the corresponding job as late as possible.
Step 3. Eliminate the last job scheduled from further consideration. Repeat steps 1 and 2 until all jobs have been scheduled. |
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| Labor-limited environment |
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Definition
An environment in which the resource constraint is the amount of labor available, not the number of machines or workstations.
The limiting resource thus far has been the number of machines or workstations available. A more typical constraint is the amount of labor available.
Assign personnel to the workstation with the job that has been in the system longest.
Assign personnel to the workstation with the most jobs waiting for processing.
Assign personnel to the workstation with the largest standard work content.
Assign personnel to the workstation with the job that has the earliest due date. |
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Term
| Advanced planning and scheduling (APS) systems |
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Definition
Systems that seek to optimize resources across the supply chain and align daily operations with strategic goals. Four characteristics of these systems are:
Demand Planning. This capability enables companies in a supply chain to share demand forecasts.
Supply Network Planning. Optimization models based on linear programming can be used to make long-term decisions.
Available-to-Promise. Firms can use this capability to promise delivery to customers by checking the availability of components and materials at its suppliers.
Manufacturing Scheduling. This module attempts to determine an optimal grouping and sequencing of manufacturing orders based on detailed product attributes, production line capacities, and material flows. |
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