Constraints for Optimization
Use
During optimization, the system considers the various constraints in the schedule. A distinction should be made here between hard constraints, which the system must adhere to, and soft constraints, which the system tries to adhere to, but which it violates if necessary in order to find a solution that complies with the hard constraints.
The working time for a resource is, for example, a hard constraint: Therefore, during optimization the system is only allowed to schedule activities in working times. Requirements dates/times from sales orders are soft constraints. Therefore, the system is also allowed to schedule receipts after the requirements date/time. These delays can, however, be minimized during optimization.
Features
The constraints related to various scheduling objects are listed in the following tables.
Optimization
does not consider the scheduling parameters in the resources and the
detailed scheduling
strategies.
Resources
Scheduling Data |
Constraint |
Description |
Working and non-working times |
Hard |
The system can only schedule activities in working times during optimization. |
Hard |
|
|
Capacity |
Hard (default) Soft |
By default, the system schedules finitely during optimization. However, you can also specify that resources should be scheduled finitely in accordance with the entries in the master data, or as of a specific finiteness level. In the optimization profile, for multiresources, you can specify a capacity on a period basis that is different from the one specified in the master data. During optimization, the system loads the multiresource up to the value of the capacity defined in the optimization profile. You can, for example, define reduced capacities, thus reserving capacity in the optimized schedule for last-minute special orders. If you have specified in the optimization profile that optimization should schedule infinitely, optimization does not take the capacity into consideration. |
Orders
Scheduling Data |
Constraint |
Description |
Validity of the source of supply |
Hard (default) Soft |
In the optimization profile, you can define if the start or finish of the validity period are hard or soft constraints. You can choose between the following: · Consider the start and finish as hard constraints ·
Consider the start
as a hard constraint and the finish as a soft constraint · Do not consider the validity period |
Scheduling Data |
Constraint |
Description |
From a receipt element to a fixed requirement element (for example, a sales order) |
Soft |
The fixed requirements element defines a requirements date/time. Receipt dates/times are allowed to be later. The delays can be minimized during optimization. You cannot make any settings for this constraint. |
Soft |
The system retains the assignment of the receipt element to the requirement element, in other words, it takes into account the fixed pegging relationship and also tries to maintain the dates/times. However, it is not always possible to maintain the dates/times. |
Time Relationship Between Activities
Scheduling Data |
Constraint |
Description |
|
Between two non-fixed activities |
|
Hard |
The system is not allowed to violate the relationship; that is, the interval must not be smaller than the minimum interval, and the maximum interval must not be exceeded. |
Between a fixed and a non-fixed activity |
The relationship defines an earliest start or finish date/time for the non-fixed activity. |
Hard |
A relationship between a fixed and a non-fixed activity defines an earliest start or finish date/time or a latest start or finish date/time for the non-fixed activity. The latest start or finish dates/times are soft constraints for the optimization. You cannot make any settings for this constraint. The non-fixed activity may, therefore, be scheduled late. However, optimizing the delay costs can minimize delays. |
The relationship defines a latest start or finish date/time for the non-fixed activity. |
Soft
|
||
Other Manufacturing Levels
Scheduling Data |
Constraint |
Description |
Take into account orders from upstream or downstream manufacturing levels |
Hard (if defined as such in the optimization profile) |
In the optimization profile, on the Order Processing tab page, you can define whether the system must take into account time relationships or pegging relationships to orders from upstream manufacturing levels that do not lie within the optimization range. This also applies to orders from downstream manufacturing levels. |
You can define in the optimization profile if the system should take into account time relationships or pegging relationships to upstream orders that are not in the optimization problem.