During optimization, the DS Optimizer considers the various constraints in the schedule. A distinction can be made between hard constraints, which the optimizer must adhere to. And soft constraints, which the optimizer tries to adhere to, but which it violates if necessary 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 optimizer is only allowed to schedule activities in working times. Requirements dates/times from sales orders are soft constraints. Therefore, the optimizer is also allowed to schedule receipts after the requirements date/time. These delays can, however, be minimized during optimization.
The constraints that the DS Optimizer can consider can be grouped by the scheduling objects that they relate to:
Resources
- Working and non working times
Working and non working times are a hard constraint. The optimizer can only schedule activities in working time during optimization.
- Rate of utilization
The rate of utilization is a hard constraint. The optimizer cannot change (increase or decrease) the rate of utilization of a resource.
- Capacity
By default the capacity is a hard constraint during optimization. The optimizer 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 multi resources, you can specify a capacity on a period basis that is different from the one specified in the master data. During optimization, the optimizer loads the multi resource 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 can schedule infinitely, optimization does not take the capacity into consideration.
- Setup times
Static setup times as well as dynamic setup times defined in a setup matrix are a hard constraint. The optimizer can minimize the duration of dynamic setup times by scheduling in a good sequence.
- Resource networks
Resource networks are considered as hard constraints. If defined, the optimizer must adhere to the allowed links that are defined in the resource network.
Orders
- Validity of the source of supply
The validity of the source of supply can be a hard or a soft constraint. 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.
- Do not consider the validity period.
- Consider the start as a hard constraint and the finish as a soft constraint. If the validity period is exceeded, optimization evaluates this as a delay in the objective function.
- Breakable activities
If activities are defined as non breakable, this is considered as a hard constraint for optimization. It means that an activity cannot be interrupted by a break.
Pegging Relationships
- From a receipt element to a fixed requirement element (for example, a sales order)
The pegging relationship between a receipt element to a fixed requirement element (for example, a sales order) is considered a soft constraint. 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.
- From a fixed receipt element (for example, a purchase order) to a requirement element
The pegging relationship between a fixed receipt element (for example, a purchase order) to a requirement element is considered a hard constraint. The fixed receipt element defines an earliest start date/time. The requirement element must be scheduled later. The resulting delays can be minimized during optimization.
- Dynamic pegging relationship
Dynamic pegging relationship are soft constraints. The system retains the assignment of the receipt element to the requirement element, in other words, it considers the fixed pegging relationship and also tries to maintain the dates/times. However, it is not always possible to maintain the dates/times.
- Fixed pegging relationship
Fixed pegging relationship are soft constraints. The system retains the assignment of the receipt element to the requirement element, in other words, it considers the fixed pegging relationship and also tries to maintain the dates/times. However, it is not always possible to maintain the dates/times.
Time Relationships Between Activities
- Between two non fixed activities
The time relationship between two non fixed activities is a hard constraint. The optimizer 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.
The time relationship between a fixed and a non fixed activity, for which the relationship defines an earliest start or finish date/time for the non fixed activity is a hard constraint. 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.
- Between a fixed and a non fixed activity - The relationship defines a latest start or finish date/time for the non fixed activity.
The time relationship between a fixed and a non fixed activity, for which the relationship defines a latest start or finish date/time for the non fixed activity is a hard constraint. 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.
Other Manufacturing Levels
Consider orders from upstream or downstream manufacturing levels.
In the optimization profile, you can define whether the system must consider time relationships or pegging relationships to orders from upstream manufacturing levels that do not lie within the optimization range. Likewise, you can define the same for downstream manufacturing levels.