Line-Side Stock and Container Sizing

Why it matters

Line-side stock is the quantity of material ready for production at the point of use. It is not the same as the total stock in the warehouse. Even if the material belongs to the right part, when it stays in a distant waiting area it may not meet the need of the point of use on time. Stock calculation is therefore not only a quantity calculation; it defines at which moment, in which container and at which place the quantity is usable. Consumption, container quantity and delivery interval are taken from the plan for every part. Instead of calculating a record whose source and point of use are unclear, the definition must first be completed. Distributing the same total arbitrarily to different addresses does not provide continuity at the point of use.

The basic need is the consumption during the time from one delivery until the next usable delivery moment. A protection with an explicit rationale is added to it. In the simple model in which deliveries are regular, consumption is taken as constant; if there is a high draw depending on the product sequence, checks are needed in shorter time windows. The protection quantity is not an unlimited addition that hides chronically insufficient replenishment. It must be known which delay or consumption change it will cover. After the container quantity is chosen, the required quantity is converted into full containers. Because of rounding up, the real stock target can be larger than the calculated lower bound. This difference is also kept visible in the layout and stock assessment; it does not vanish at the end of the calculation.

Container size is not just unit capacity. External dimensions, full mass, grip, protection of the part and empty container return are parts of the same design. A large container may require fewer changes; but it can force the worker to reach far or carry a heavy load. A small container makes access easier but can create more container changes and more frequent transport. Two containers holding the same number of parts do not have to use the same space. Internal volume affects the suitability for the material; external volume affects the layout load. One being sufficient does not prove the suitability of the other. Containers that have not been verified as stackable are not stacked on paper.

Stock, route and safe area are solved together. Lengthening the interval can reduce transport departures; but it enlarges the quantity at the point of use. Letting containers spill into the aisle is not a workable solution for this new quantity. Using a smaller container does not by itself reduce the space need of more containers either. The options are compared with the same demand, the same delivery condition and the same safe passage limit. The aim here is not to find the lowest-looking stock number but to build a supply arrangement that can be sustained without interrupting consumption and without creating a physical hazard. When the capacity and access result is written next to the calculated quantity, the decision can be reassessed by another person too. Keeping the stock target also depends on separating unsuitable parts from the usable quantity. Even if the physical count looks high, a quantity that has to be held apart for quality reasons gives no consumption assurance. This separation is kept in the same way in the calculation and at the point of use. The linked kanban calculator is for the whole replenishment loop and the circulating containers. If there is preparation and transport time after the signal, a line-side target sized only by the visit interval is not treated as equal to this loop; the full delay is calculated separately.

Formula