Workload control, planning algorithm

The workload-control planning method is basically a leveling algorithm that levels the production plans of several items simultaneously. If the production plan in a particular plan period creates an overload of the available production capacity, LN moves a part of the production plan to an earlier or later period. If the available materials are insufficient, LN also responds by moving part of the production plan.

This algorithm is applied to plan units for which the Master Planning Method field in the Plan Unit (cprpd6100m000) session is Workload Control.

The planning procedure is started by running a master-plan simulation in one of the following sessions:

The complete algorithm consists of three steps:

  1. Generate the non-constraint plan
  2. Backward planning
  3. Forward planning

You can skip the backward or the forward planning step by setting the Backward Planning and Forward Planning parameters in the Work Load Control Parameters (cpwlc2101m000) session. For details, see Workload control, backward and forward planning.

The effect of these planning steps is demonstrated graphically in the Workload control, a graphic example topic.

A description of the steps of the planning algorithm:

  1. Generate the non-constraint plan
    LN generates a production plan in which capacity and material constraints are ignored. In this plan each item is produced exactly when it is needed. This plan is generated in the same way as described for the infinite planning method. For details, see Infinite master planning. Note This step is skipped if the Starting Point WLC field in the Work Load Control Parameters (cpwlc2101m000) session has the Current Master Plan value.
  2. Backward planning
    Backward planning starts from the non-constraint production plan and replans this production plan by considering any material and capacity constraints. All plan periods are planned one by one, starting from the last period, and working backward up to the first plan period. If the production volume cannot be planned completely due to material or capacity constraints, part of it is moved to the preceding period.
  3. Relative priority of plan items

    The order in which the items are planned in each period has a great influence on the resulting plan. This order can be defined by specifying a priority rule in the planning parameters on the basis of factors such as:

    • Moved production volume
    • Material and production costs
    • Priority of the plan item
    For details, see Workload control, to compute planning priorities. If the algorithm arrives at the first plan period, and the production volume in that period exceeds the capacity or material constraints, the method fails to generate a feasible plan in which all desired delivery dates are met.
  4. Forward planning
    The forward planning always results in a feasible plan. However, it is possible that a production volume is delivered late. The forward planning step starts at the first period and plans the periods one by one. Production volumes that cannot be planned completely due to material or capacity constraints, are moved to the next period.
Capacity constraints

The capacity requirements of the plan items are recorded in the Bill of Critical Capacities (cprpd3130m000) session. Only the resources for which the Constraint check box in the Resources (cprpd2100m000) session is selected are considered a constraint in the planning. LN assumes an infinite capacity for the other resources.

The division of capacity requirements over the plan periods is determined by the value of the Capacity Consumption Based On field in the Work Load Control Parameters (cpwlc2101m000) session.

Capacity constraints are only considered in the planning if the Consider Capacity Contraints check box is selected during a master-plan simulation.

Material Constraints

The material requirements of the plan items are recorded in the Bill of Critical Materials (cprpd3120m000) session. Only the materials for which the Constraint check box in the Items - Planning (cprpd1100m000) session is selected are considered a constraint in the planning.

Material constraints are only considered if the Consider Material Constraints check box is selected during a master-plan simulation.

Note

If the Number of Iterations field in the Generate Master Planning (cprmp1202m000) session is greater than zero, LN always starts by creating a non-constraint plan. The material constraints can be considered during subsequent iterations.

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