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 Heuristics for Multi-Resource Planning (Primary Resource)

Purpose

You use the heuristic multi-resource planning (primary resource) (/SAPAPO/REM_HEUR_WAVE), if you produce several products in repetitive manufacturing from the same resources (lines) and prefer one specific resource because of costs, or other reasons.

In the settings for the heuristic you can determine the criteria the system should use to determine the preferred resource. The criteria can be either the priority of the mode(when using the PPM ) or the rate(when using iPPE).

Prerequisites

See Planning Heuristics in Repetitive Manufacturing (REM Heuristics) .

Process Flow

When using this heuristic, the system first of all tries to load the preferred resource and then the alternative resources to full capacity. Because of the wavelike calculation, the planning algorithm of this heuristic is also known as a wave algorithm .

The planning takes place in three steps:

  1. Finite backward scheduling , starting from the end of the planning period ( backward wave ).

    The lots with requirements dates in the last period are initially dispatched to the preferred resource of the corresponding product. If the preferred resource is fully loaded, remaining lots are divided across alternative resources. If, in the last period, the alternative resources are also fully loaded, surplus lots are put at the resources of the previous period.In this way the lots with the earliest requirements dates are moved first.

  2. Finite forward scheduling starting from the beginning of the planning period ( forward wave ).

    This step applies to lots that the system could not schedule finitely in the first step. The process is the same as in step 1: the lots whose requirements dates are in the first period, are dispatched to the preferred resource of the corresponding product. If the preferred resource is fully loaded, remaining lots are divided across alternative resources. If, in the first period, the alternative resources are also fully loaded, surplus lots are put at the resources of the following period.In this way the lots with the latest requirements dates are moved first. There are two options for moving lots, depending on your settings. The system either looks for the next gap, or it moves surplus lots to the next period.

  3. Finite or infinite scheduling of the remaining lots

    The step concerns lots that the system could not schedule finitely even in the second step. That is, there is no available capacity for them in the planning period. Depending on the settings, these lots can be scheduled finitely or infinitely at the end of the planning period, scheduled infinitely at the beginning of the planning period, or not scheduled at all.

    There are two alert situations:

    • Finite scheduling at the end of the planning period can result in delays.

    • Infinite scheduling at the end or at the beginning of the planning period results in capacity overload, sometimes with delays.

    • If scheduling does not take place at all, this can result in a shortage, sometimes with delays.