In the PP Optimizer Profile, you can select whether you want to use the Linear Optimization method or the Discrete Optimization method. Only, if you choose the discrete optimization method, you can maintain, which discrete constraints are to be considered by the optimizer in the Discrete Constraints tab. You have learned in previous lessons that this will significantly increase the runtime requirements due to the nature of the planning problem and the algorithm used to solve it.
On the Discrete Constraints tab, you can define discrete constraints relating to:
- Capacity Constraints
- Lot Sizes
- Fixed Consumption
- Extended Lot Size Planning
For each type of constraint, you can define the duration (starting from today's date) for which the constraint is to be considered discrete.
Discrete Production Capacity Increase is valid for all production resources for which a capacity increase has been defined in the master data. You must define the corresponding extended capacity utilization rate in the Extended Capacity (%) column which can be found under Change Work Center → Capacity → APO Resource → PPO Capacity Constraints. If you have chosen the discrete optimization method and activate this indicator, the algorithm increases the capacity either for the full or zero amount of the capacity increase as defined in the work center or resource master and the corresponding cost for increasing production capacity gets applied.
You can define the horizon for which you want this discrete constraint to be considered. You can define a specific horizon, for example, in days or weeks. The discretization horizon starts from today's date, even if the planning horizon starts in the future or the past.
Regarding lot sizes, you have four options to define discretization in the Discrete Constraints tab:
- Minimum Production Lot Size
- Integral Production Lots
- Minimum Transportation Lot Size
- Integral Transportation Lots
If you choose Minimum Production Lot Size, you specify that you want the PP Optimizer to consider the minimum production data structure (PDS) lot size. You can define the horizon for which you want this discrete constraint to be considered. The discretization horizon starts from today's date, and can be defined in, for example, days or weeks. As a prerequisite, you must have defined either the minimum lot size in the PDS, or if a larger minimum lot size has been defined in the material master, the optimizer considers the value from the material master.
The PP Optimizer proposes production quantities per bucket as integral multiples of PDS lot sizes, if you have selected Integral Production Lots. The basis for integral multiple is that if a rounding value has been defined in the material master, the optimizer considers this value. If not, the PP Optimizer uses the typical lot size. The typical lot size is based on the following logic:
- If a fixed lot size is maintained, the corresponding quantity is returned.
- If a minimum lot size is maintained either in the material master or in the source of supply, the maximum of both minimum lot sizes is returned.
- If none of the above is applicable, the typical lot size is considered as 1 (fallback).
If you choose Minimum Transportation Lot Size, you specify that you want the optimizer to consider the minimum lot size calculated from the transportation lane lot size profile and transportation lanes. How the minimum transportation lot size is calculated depends on the option that you have chosen for Optimizer Transport Lot Size on the General Constraints tab. There, you have two options:
- Transportation lane
The algorithm calculates the transportation lot size based on the rounding values defined in the lot size profile of the transportation lane.
The minimum lot size is calculated as the highest value between the two: Minimum Lot Size from the Transportation Lane Lot Size Profile and Minimum Lot Size from the Transportation Lane.
The maximum lot size is calculated as the least value between the two: Maximum Lot Size from the Transportation Lane Lot Size Profile and Maximum Lot Size from the Transportation Lane.
- Transportation lane/location product
The algorithm calculates the transportation lot size based on the rounding value defined in the lot size profile of the transportation lane. If this value is not defined or is maintained as zero, then transportation lot size is used from the material master where the first preference is given to Fixed Lot Size and the second preference to the Rounding Value.
The minimum lot size is calculated as the highest value of the three: Minimum Lot Size from the Transportation Lane Lot Size Profile, Minimum Lot Size from the Transportation Lane and Minimum Lot Size from Product Master.
The maximum lot size is calculated as the least value between the two: Maximum Lot Size from the Transportation Lane Lot Size Profile and Maximum Lot Size from the Transportation Lane.
You can define the horizon for which you want this discrete constraint to be considered. The discretization horizon starts from today's date, and can be defined in, for example, days or weeks.
Finally, if you have chosen Integral Transportation Lots, you want the optimizer to use integral (integer-based) transportation lots during optimization. Transportation lots are also calculated based on the Optimizer Transport Lot Size selection on the General Constraints tab. If you have selected 1 (Transportation Lane), then the transportation lot size is picked from the Rounding Value from the transportation lane lot size profile. If you have selected 2 (Transportation Lane/Location Product), then the transportation lot size is picked from the Rounding Value from the transportation lane lot size profile. If that is not maintained, the transportation lot size is picked from the material master, first priority given to the fixed lot size followed by the rounding value.
If you want to consider the fixed consumption of material and production resources that was defined in the production data structure (PDS), you choose Fixed Material and Resource Consumption. You must have defined the fixed material and resource consumption in the corresponding PDS master data as a prerequisite.
In some rare cases, it may be required to consider sequence-dependent lot sizes as a constraint in the PPO. For this purpose, you can define the setup costs and setup times in the setup matrix. The PP Optimizer then considers the data entered there and optimizes the setup costs. In the results log of the optimization, an order sequence number is displayed for the planned orders. A prerequisite for this option is that you have maintained the corresponding master data as follows: In the resource or work center master data, you must set the Period Lot Size indicator (which is in the PPO Capacity Constraints tab of the APO Resource) to Sequence-Dependent Lot Size Planning. Furthermore, the production data structure (PDS) must contain a setup group.
