Shop Order Infinite Scheduling

Infinite scheduling is the process used to schedule shop orders for. For sites that use Advanced Planning Board (APB), infinite scheduling will be used when scheduling orders from shop orders and other places in the application, and the Constraint Based Scheduling (CBS)scheduler will be used when scheduling shop orders in APB.

If you choose forward scheduling, the system calculates the end date for the shop order based on the earliest start date that you specified. With backward scheduling, the system calculates the start date based on the specified need date. When the shop order is created and scheduled, it is also possible to set the shop order to use manual scheduling. When using manual scheduling, all operations are set to the manual scheduling schedule direction, and the user can manually set start and finish dates on the operation. When the shop order is set to manual scheduling, the infinite scheduler is no longer involved and it is up to the planner to handle the scheduling.

The infinite scheduler can handle multiple shop orders, but it always treats each shop order as if it is the only one in the system, with few constraints on resources and capacity. When selecting which resource on a work center should be used, the system selects the least loaded resource for the work center for the time span when the operation should be scheduled. It is also possible to manually decide which resource should be used, by updating the Preferred Resource field on the shop order operation. When the operation is started on a resource, the Preferred Resource field will also be updated with the resource that the operation was started on. If the shop order is rescheduled with infinite scheduler after that, it will use that resource, if available.

Shop order infinite scheduling considers the following constraints:

Maximum hours per operation
Forward or backward scheduling (manually scheduled orders and operations are not considered)
Parallel operations, i.e., operations can be performed independently of each other
Operation overlap, i.e., can the succeeding operation be started before the previous operation is finished or not.
One resource per work center per operation
Work center calendar
Queue time
Transport time
Include set up time in overlap, i.e., if the calculated overlap should start with set up, or if the set up can start already before the defined overlap
Work center calendar
Work center utilization
Operation efficiency
Work center resource efficiency
Preferred resource

Rescheduling of individual shop orders can be performed immediately, but in some cases shop order operation scheduling is done in the background. For example, when a calendar connected to a work center is regenerated and the scheduled start or scheduled finish date no longer exists as a work day in the generated calendar or when Reschedule Shop Orders by Site is executed.

When scheduling the following rules are used:

Work Center Utilization: The utilization is the percentage of effective work hours per day (out of the total work hours for the day in the work center calendar). The default value is 100. For example, if utilization is defined as 50 for a work center which uses an eight hour day calendar (8:00 A.M. to 4:00 P.M.), the effective work hours will be from 8:00 A.M. to 12:00 noon. The shop order scheduler will schedule a two hour operation from 8:00 A.M. to 10:00 A.M. if the scheduling direction is forward and from 10:00 A.M. to 12:00 noon if the scheduling direction is backward. The utilization percentage has no effect on scheduling if operations are scheduled by CBS or the Advanced Planning Board.
Operation Efficiency: The operation efficiency affects only the run time, not the setup time. When operation efficiency is set to less than 100% (default value) the remaining run time for machine and labor will be increased. This will result in an increased value for remaining manufacturing hours which could affect the scheduled start and/or stop date of the operation. When changing the operation efficiency, the change will also affect the standard cost of the operation. Changing the operation efficiency can be done on specific operations, if there is running-in periods for a while, which temporarily will affect the performance of the operation.
Work Center Resource Efficiency: The resource efficiency affects both run time and setup time. If the resource efficiency is less than 100% (default value), the operation will be scheduled during a longer time period, because the setup and run time will increase. Only scheduling is affected (start and finish date on the operation), not remaining manufacturing hours. Changing resource efficiency can be done if there are different machines (resources) operating in the same work center with different capabilities.

The time to schedule is the remaining manufacturing time, and how this is calculated is based on the Base Remaining Hour On work center parameter. The options are Remaining Quantity or Reported Time. If the work center has this parameter set to Reported Time, and 4 out of the planned 8 planned hours are reported, the remaining manufacturing time will be set to 4 and when the operation is rescheduled, 4 hours will be scheduled for this operation, even if no quantity is yet reported on the operation.

Infinite scheduler only considers remaining machine time when the operation is scheduled. If the operation is planned with only labor time, the operation will be scheduled with the same start and finish time. APB scheduling logic is far more powerful and considers many additional constraints, including constraints on labor resources, capacity, and tools.

Shop Order Infinite Scheduling

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