Heuristics for Project Manufacturing and
Make-to-Order Manufacturing
Use
The process of project manufacturing and make-to-order manufacturing is supported by the heuristics described here.
Features
Heuristics for Project Manufacturing
Calculation of the Critical Path (SAP_PMAN_001)
With the heuristic SAP_PMAN_001, you identify operations without a float or with just a small float.
The heuristic determines all operations in a multi-level network of orders that have floats (that is, the interval between the latest and the earliest start date) that are equal to zero or that fall below a certain threshold value (defined by you). These operations are regarded as critical. These operations do not have to follow one another.
Partially confirmed operations are fixed and therefore, are taken into account during scheduling, but are not rescheduled. If you want the system to schedule these operations, you must interrupt these operations, in other words, you must remove the fixing of these operations.
The system calculates the critical path infinitely and in three steps:
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i. Backward scheduling
Starting from the end date of the network, the system carries out backward scheduling and determines the "latest start dates" of operations.
ii. Forward scheduling
The system then carries out forward scheduling (based on the latest start date from the backward scheduling run) and determines the 'earliest start dates' of operations.
The difference between the 'earliest' and the 'latest' position of the operation in the network is called the float. The float is a gross value that does not contain non-working times, for example.
iii. Critical path
The system calculates the critical path. If the float of an operation is smaller than the threshold value that you have defined in the heuristic, the operation belongs to the critical path.
Infinite Forward Scheduling (SAP_PMAN_002)
You use the heuristic SAP_PMAN_002 if the end date/time of the project or the sales order cannot be adhered to (for example, because the network of orders partly lies in the past and planning minimum intervals and planning offsets have been used, so that you must calculate a new end date/time.
The system calculates the new end date starting from either today's date, or from any date in the future. The heuristic reschedules the network and determines a new feasible situation.
You use this heuristic to carry out "compact" forward scheduling in two steps:
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i. Forward scheduling
The system carries out infinite forward scheduling, starting from today's date or the specified date, and determines the earliest date (the date nearest to today's date or to the specified scheduling date).
The result of this is a new project end date.
ii. Backward scheduling
The system carries out backward scheduling and determines the latest dates based on the new project end date/time.
The result of this is a compact network with relationships and pegging relationships that correspond to the minimum intervals.
Infinite Backward Scheduling (SAP_PMAN_003)
With the heuristic SAP_PMAN_003, you can backward schedule a network of orders starting from the end date/time.
You use this heuristic to achieve a compact network after having reduced planning or process-based minimum intervals or offsets along the critical path.
The heuristic adjusts the production plan to the new planning-related minimum intervals and planning-related offsets.
Planning with Project Manufacturing Heuristics
During planning with planning-related/process-related minimum intervals and offsets, the system behaves as follows:
· You can use the project manufacturing heuristics (SAP_PMAN_*) to carry out scheduling taking into account either the planning-related offsets/minimum intervals, or the process-related offsets/minimum intervals.
· If you use other heuristics, the system takes into account either the planning-related offset or the process-related offset, depending on which offset was most recently scheduled.
· If you select the indicator Use Planning-Related Minimum Intervals in the strategy profile, the system observes the planning-related minimum intervals during infinite and bucket-finite planning. Instead of using process-related minimum intervals, the system plans with the larger planning-related minimum intervals.
· If you use the project manufacturing heuristics (SAP_PMAN_*), you should select an order or operation at the highest MRP level, so that the system completely schedules the relevant network of orders.
· You should note that the project manufacturing heuristics (SAP_PMAN*) always schedule planned orders within the order validity, in other words, during scheduling no new source of supply is assigned, nor is a new explosion carried out.
Activities
You can find the heuristics in Customizing for Production Planning and Detailed Scheduling (PP/DS) under Maintain Heuristics.
See also:
Detailed Scheduling
Heuristics