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/SAPAPO/REM_PLAN_WAVE - Scheduling Algorithm - Wave Algorithm

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Functionality

The function module describes a planning algorithm that is particularly suited to production planning in a repetitive manufacturing environment. Its input parameters are an excerpt from the output parameters of the function module /SAPAPO/COLLECT_DATA_REM_HEUR. The module makes a scheduling proposal and a planning strategy. This can then be processed using function module
/SAPAPO/CREATE_SCHED_REM_HEUR in order to schedule as required in the liveCache.

The function module simultaneously schedules several products that are produced on the same resources (lines). The requirements from the individual products in the planning period form the basis for planning. The system first makes a net calculation for these requirements and then a lot-size calculation.

The prerequisites for using the module effectively are:

,,- that exactly one operation is relevant for planning

,,- that the products are on a low-level code, which means they cannot have any dependent requirements.

,,- that a PPM has been created per product for each production version. This means that a PPM must be created for each resource on which a product can be produced.

,,- that the planning period cannot begin until one day after the current date.

The following are not taken into consideration:

,,- Sequence-dependent setup

,,- Characteristics

,,- The exact start and end times of fixed activities

,,- The valid time period of production versions

Planning takes place as follows:

,,1) Net calculation for individual products

,,2) Lot-size calculation for individual products

,,3) Generation of a scheduling proposal for the products on the resources (lines).

PP/DS standard modules are used for net and lot-size calculations. The settings in the product master (such as the rounding value) are considered for the lot-size calculation.

The calculated lots form the basis for generating the scheduling proposal.

The scheduling proposal is generated using a special algorithm, which has three basic stages:

a) Backward scheduling starting from the end of the planning period (finite)

b) Forward planning starting from the beginning of the planning period (finite)

c) Scheduling orders for which, after completing steps a) and b), there is no free capacity within the planning period (infinite).

a) Backwards planning

Starting at the end of the planning period, planning is carried out period per period. Planning periods can be days, weeks or months. First of all, the system determines the lots which were calculated in 2) and whose requirements date is within the corresponding period. These lots are scheduled in three steps:

i.) Dispatching the lots on the preferred resource of the product

ii.) If there is no more capacity on the preferred resource, the system distributes remaining lots on alternative resources.

iii.) If there is no more capacity on the alternative resource either, the system moves remaining lots to the previous period. The lots with the earliest requirement date are moved first.

b) Forward planning

The system only carries out forward planning if finite planning of all lots was not possible in step a). In step b), the system tries to schedule all lots which have not yet been scheduled.

Starting at the beginning of the planning period, forward planning is carried out period per period. Planning periods can be days, weeks or months. First of all, the system determines the lots which were calculated in step a) and whose requirement date is within the corresponding period. The lots are scheduled in three steps:

i.) Dispatching the lots on the preferred resource of the product

ii.) If there is no more capacity on the preferred resource, the system distributes remaining lots on alternative resources.

iii.) If there is no more capacity on the alternative resource either, the system moves remaining lots to the following period. The lots with the latest requirement date are moved first.

c) Infinite planning

Infinite planning is used for lots which the system could not schedule in step a) or b) because there was not enough capacity within the planning period. These lots are planned infinitely in step c). They can be scheduled either at the beginning or the end of the planning period, depending on the overload profile which you selected in the heuristic settings.

Example

Notes

Further information

Parameters

ET_IO_REC_UNFIRMED
ET_SCHED_AONEW
EV_ERROR
IS_HEUR_SETTINGS
IT_ACT_SHIFT
IT_IO_REC_FIRMED
IT_IO_REC_UNFIRMED
IT_IO_RQMT
IT_LINES
IT_LOAD_FIRMED
IT_LOAD_UNFIRMED
IT_PERES_S
IT_PERES_W
IT_PRODLI
IT_PRODUCTS
IV_END_TIME
IV_START_TIME

Exceptions

Function Group

APO/SAPLPT_HEUR_REM

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