Understanding Kanban Size Calculation

You use the DFM Calculate Kanban Sizes program (RF31K22) to calculate the kanban size for replenishable, single card, and dual card kanbans. You select the process map and component items for which kanban sizes are to be calculated.

For each replenishable component selected, the system explodes through the pull chain and calculates the kanban size for each supply point. Non-cell supply points use this equation:

K_size = ∑(D_c) × R × (1 + SS ÷ 100) / H_R × P

If the supply point is defined as a machine cell, the system uses this equation to calculate the minimum production quantity to recover internal setup for independent machine cells:

K_cell = SU / TAKT - RT

If the supply point is defined as a machine cell, the system uses this equation to calculate the minimum production quantity to recover internal setup for dependent machine cells:

K_cell = ∑(SU + RT) / TAKT - RT_p

The replenishment interval of the machine cell to produce K_cell units is calculated, R_cell = [∑RT × (K_cell − 1)] + ∑(SU + RT + MV) for independent machine cells and R_cell = [RT_p × (K_cell − 1)] + ∑(SU + RT + MV) for dependent machine cells.

The minimum kanban quantity at the RIP is calculated using this equation:

K_RIP = ∑(D_c) x R_cell x (1 + SS ÷ 100) / H_R x P

The system determines whether the kanban has to be defined as a single or dual card kanban. Single card kanbans pull material to the line from POUR areas or to the RIP inventory area from general stores or directly from vendors. The POUR is replenished directly from the machine cell.

Dual card kanbans pull material from machine work centers where substantial set up times drive the requirement to produce components in batches. Dual card kanbans are setup as type 6 and are supported only for internal machine cells. Transactions resulting from checkout and check-in of kanban master records do not occur until the correct number of dual card kanbans have been processed. For example, the first of a 1 of 3 dual card kanban is checked out. The status is updated to wait-checkout. The second of a 1 of 3 dual card kanban is checked out. The status is updated to wait-checkout. The third of a 1 of 3 dual card kanban is checked out. All three kanbans are now updated to a checked-out status.

If K_RIP ≥ K_cell then a single kanban card can be used and if K_RIP < K_cell then a dual card kanban must be used.

The calculated kanban size is compared to the current size of the kanban in the DFM Kanban Master. Any net change in size is calculated and recommendations on changes to the kanban size are made. Kanban sizes and recommendations are written to the FF31K25 table. You use the Kanban Sizing Approval Application (PF31K27) to accept or reject the system recommendations.

If the recommendation is accepted, the total number of cards is calculated using: Number of produce cards = K_cell/K_Line, each of size K_cell and Number of move cards = K_RIP/K_Line, each of size K_RIP where K_Line is the minimum single card kanban quantity on the line:

K_Line = ∑(D_c) x R x (1 + SS ÷ 100) / H_R x P

Note: The system will round up the final kanban size number.

Nonreplenishable kanbans compensate for spikes in demand or support production of products that are not commonly manufactured. They are essentially single-use kanbans. If the component demand is marked nonreplenishable, then the system does not calculate a kanban size.

Nonreplenishable kanbans are not exported to base manufacturing. MRP is used to plan and schedule end items on a nonreplenishable kanban. Nonreplenishable kanbans use existing ad hoc kanban functionality.

This table provides parameter definitions:

Parameter	Definition
D_c	Demand at capacity.
H_R	Available hours for replenishment.
K_Cell	Minimum produce quantity to recover internal setup.
K_Line	Minimum point of usage kanban quantity.
K_RIP	Minimum point of resupply kanban quantity.
K_size	Kanban size.
MV	Move time for an independent cell.
P	Package size.
Q	Quantity consumed per unit.
Q_Order	Sales order quantity for the nonreplenishable parent item.
Q_BOM	Quantity of the component required per parent item.
R	Minimum replenishment time.
RT	Effective run time per unit.
RT_p	Effective pacing run time in a cell. This is the longest run time of all operations in a cell.
SS	Safety stock percent.
SU	Internal machine or cell setup time.
TAKT	Machine or cell TAKT time.