Process orders are always scheduled at order creation. As prerequisite, master recipes with operations and resources must be maintained.
Scheduling of Planned and Process Orders
In the context of production planning, the following scheduling methods are available:
- Determination of basic dates
- Lead time scheduling
The determination of basic dates is only available for planned orders. Alternatively, you can use lead time scheduling. For process orders, only lead time scheduling is available.
When using the determination of basic dates, the system calculates the start and end day of the order based on data maintained in the material master (in-house production time). However, no phase times are calculated.
When using lead time scheduling, the system calculates exact start/end dates and times (including seconds) on order level based on phase duration data maintained in the master recipe. Furthermore, the system also creates capacity requirements on phase level which you can use for capacity planning. Since lead time scheduling is based on the master recipe (which contains exact information about phase duration), this approach leads to reliable planning data.
Note
From a business perspective, also using lead time scheduling for planned orders results in more reliable planning data. Furthermore, due to the fact that, when converting a planned order into a production order, the lead time scheduling is executed anyway, SAP recommends to also use lead time scheduling for planned orders to prevent the calculated dates changing significantly when converting the planned order into a production order.
Scheduling Time Elements of a Process Order
Depending on your business requirements, you can schedule orders either forwards or backwards in time: In forward scheduling, a process order is scheduled forwards in time starting from the basic start date (for example, manually entered or copied from the planned order); in backward scheduling, a process order is scheduled backwards in time starting from the basic finish date (for example, manually entered or copied from the planned order).
The above graphic shows all the possible elements contributing to the total lead time of a process order: The total lead time of a production order lies between the basic start date (BS) and the basic finish date (BF). The float before production lies between the basic start date (BS) and the scheduled start date of the first operation (SS), and the float after production lies between the scheduled finish date of the last operation (SF) and the basic finish date (BF). By specifying sufficient buffer times, you obtain better production stability as you can react to any unforeseen events that may occur in the production process. However, if your buffer times are too high, your production resource utilization might decrease. If necessary, for example in case of delays of other orders or a machine breakdown, the buffer times can be automatically reduced by the system.
The duration of an operation is defined by the duration of the individual phases. Each phase is scheduled using the scheduling formula stored in the resource data and the default values of phases in the master recipe. When a phase network is scheduled, the phase relationships are taken into account and the phase dates are carried over to the operation. The start time of the first phase plus the finish time of the last phase is the start and finish of the operation. In contrast to production routings, no inter-operation times can be maintained in the master recipe.
If a process order is being used to perform production for a sales order, then further time elements of the sales order will be taken into account to determine the final date of the process order.
Calculation of Phase Duration
As discussed in the previous section, the system schedules each phase of the order (provided that the respective control key of a phase is set up accordingly). However, we have not discussed yet how the system calculates the duration of each phase. As shown in the figure, the durations of phases are calculated based on formulas which are assigned in the resource.
Let us consider the following example: For phase 12, a processing time of 60 minutes is required based on a phase quantity of 1000 L. This information is maintained as standard value and base quantity in the phase. These values are used together with the resource formula and the phase quantity to calculate the phase duration. In our example, the formula is defined as follows:
The phase duration scales linearly with the phase quantity.
In our example, we produce 10000 L paint (phase quantity). Using the formula and the standard value, we obtain the following duration:
Phase duration: 10 hours (10000 L x 60 min / 1000 L)
When using, for example, forward scheduling, the system adds this duration to the specified phase start time (PhS) to calculate the phase end date (PhF).
Note
In addition to phase durations, the system also calculates capacity requirements for each phase (provided that the respective control key is set up accordingly). The calculation of capacity requirements follows a similar approach as the calculation of duration.