Default Calculation Methods

Production > Capacity Planning, APS > APS Calculation Types > Default Calculation Methods

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The calculation methods are user-definable in APS. The most important methods are pre-configured in Beas.

 

Backward simulation

Backward simulation determines the latest possible start date without considering time reservations and material availability. This start date is written in the production order. No times are reserved. Fixed operation specifications are not considered in backward scheduling. Work orders that are logged in (started) are not specified as fixed.

 

Dispatch backward

In this method, dispatching is performed to the latest possible date taking time reservations into account. The planning flag is removed. Fixed operation specifications are not considered in backward scheduling. Work orders that are logged in (started) are not specified as fixed.

This method is used if the material should be purchased as late as possible. This method therefore works in a material-optimized way. Conversely, forward scheduling works in a resource-optimized manner.

 

Dispatch forward

This method calculates on a resource-optimized basis. Time reservations are considered. The planning flag is removed. Fixed operation specifications are considered. Work orders that are logged in (started) are fixed.

This calculation method is the default method for rough and detailed planning. In the graphical view you should generally work with forward scheduling. Resource-oriented planning is only possible with this method.

 

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Example: Dispatching commences from today regardless of the delivery date.

If the delivery deadline is exceeded, the operations are highlighted with a question mark.

 

Re-allocate forward

The "Dispatch forward" method calculates from the start date on a resource-optimized basis. Time reservations are considered. The planning flag is removed. Fixed operation specifications are considered. Work orders that are logged in (started) are fixed.

Special feature:

If the delivery date cannot be met, the transit time is reduced gradually and the resources are overloaded. An attempt is made to dispatch the order using different calculation concepts, so that the delivery date can be met. Where necessary, the resources are overloaded or the transit times are severely reduced, but the delivery date cannot be guaranteed at all times.

 

The procedure:

Default forward scheduling with saved priority
Reduce transit times to 80% and schedule forward
Reduce transit times to 50% and schedule forward
Reduce transit times to 5%, resources are overloaded by up to 150%

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Example: Same situation as with dispatching forward. The transfer times are compressed, which reduces the throughput time.

 

Catch Up

If an order is scheduled but not processed, the time reservation is in the past the next day. In this case, the time reservations must be moved to the present. The "Clear backlogs" calculation function is available for this.

All time reservations are moved from the past to the future. However, the order is retained. Resource limits, idle time, transfer time, and fixed operation specifications are not considered, which compresses the work sequences extremely. This compression is only performed for the work sequences that must be moved because they were not processed.

 

Example: 2 work sequences are in the past.

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After clearing the backlog:

Transit and idle times are cut and the first work sequence is moved forward.

The work sequences from 22 are not moved.

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