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Inventory Items

The Items tab is where an Inventory node’s stock is defined. Each item is one part number, with an opening quantity, a home zone, and a replenishment policy that tops it up on its own. Add items one at a time, or use Import Items to bring in a list.

What an item holds

Section titled “What an item holds”
FieldWhat it sets
Name (SKU)The name logic refers to when it takes or stores this item
ZoneWhich zone’s access time applies to a withdrawal
QuantityOpening stock at the start of the run
CapacityThe most the item can hold. Blank for no limit
Unit CostCharged to the entity for each unit it takes
Unit TimeHandling time per unit, in minutes

Replenishment

Section titled “Replenishment”

Leave these blank and the item never reorders. Fill them in and the inventory keeps itself stocked.

FieldWhat it sets
Reorder LevelThe stock level that triggers an order
Reorder QtyHow much to order, or the level to order up to
Reorder PolicyFixed Qty orders the same amount every time. Order Up To orders however much is needed to reach the figure above
Max Outstanding OrdersHow many orders may be in flight at once
Lead Time and Lead Time UnitThe delay from placing an order to the stock arriving
Holding CostA carrying charge per unit per hour of stock held
Ordering CostA fixed charge each time an order is placed

The trigger compares stock on hand plus stock already on order against the reorder level, so a slow supplier does not cause the same order to be placed over and over while the first is still in transit.

Reorder Level and Reorder Qty accept an expression, and it is worked out once at the start of each replication. That makes a variable a good master knob: put v_ReorderPoint on every item and a scenario can move the whole store at once. Entity attributes are not allowed, because no entity is involved when a reorder fires. Lead Time is different: it is sampled fresh for every order, so a distribution there gives genuine supplier variability.

Infinite Supply

Section titled “Infinite Supply”

Tick Infinite Supply and the item never runs out. It is the right answer for something you do not want to model the supply of: packaging tape, fasteners, water.

Be aware that infinite supply silently switches off the whole replenishment block. Reorder level, reorder quantity, policy, outstanding orders, lead time, and ordering cost are all still editable and all have no effect, with no warning. If you want reorder behaviour, leave it unticked and give the item a real quantity.

Capacity

Section titled “Capacity”

An item’s effective ceiling is the lower of its own Capacity and the inventory’s total capacity. Asking to store more than that ceiling stops the run with a clear error rather than waiting forever, so a failed store shows up as a message rather than as a model that hangs.

Cost and time

Section titled “Cost and time”

Unit Cost is charged to the entity that takes the stock, added to its running total in no value classification (see Costs in a model). Holding Cost and Ordering Cost are reported against the inventory itself.

Unit Time is the handling time per unit, in minutes, and it must be a plain number. It is added to the zone’s access time to give the total time a withdrawal takes.

Section titled “Related”