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The Kanban system it is one of the most effective Lean Manufacturing tools for reducing inventory and bringing material flow in production back under control. The article begins by comparing the Push logic (still widespread in many companies) and the Pull logic, in which the actual demand drives every material movement, not forecasts.
Kanban is the operational signal that makes this logic concrete: a physical or digital card associated with a standard container that, when emptied, automatically authorizes replenishment. Three main variants exist (standard, batch, and signal), each suited for different contexts based on consumption regularity and batch size.
A central passage is system sizing: the correct number of tags is calculated from average demand, lead time, and safety stock, with a numerical example showing how each process improvement translates directly into reduced inventory.
Not all materials are suitable for Kanban: it works best for components with stable and repeated consumption, while for expensive, variable, or unpredictable lead time items, other policies are preferable. The article concludes by framing Kanban within the broader Lean system (JIT, production supermarket, and Takt Time) and with an invitation to gain field experience through the Lean Advanced course at Lean Factory School®.
Inventories become a problem when they grow more than real demandtake up space, absorb capital, and hide Process inefficiencies. Kanban is precisely for this purpose, to bring the flow back under control and to restart materials only when it is truly necessary.
In many companies, production still operates with a logic PushWhen you plan in advance based on forecasts, produce in batches, and push materials to downstream departments—regardless of what is actually needed at that moment. The result is almost always the same: high inventory, out-of-control Work In Process (WIP), space taken up by waiting materials, and capital tied up that doesn't create value.
Logic Pull It works in reverse: no department produces or moves material until the downstream process explicitly requires it. It is actual demand, not forecasting, that drives the flow. Each station only works when it receives a request signal from the downstream station.
Kanban is the operational tool that makes this logic concrete. It is not a theory: it is a physical and visual system that governs the flow of materials and information throughout the entire production chain and, in more advanced cases, up to suppliers.
Kanban means visual signal. In practice, it's a simple and very effective method for restoring inventory and managing information flow using a Pull logic.
In practice, Kanban is a Badge — physical or digital — associated with a container holding a standard quantity of a particular component. When the container is emptied, the tag returns upstream as a replenishment order.
There are two fundamental types:
The tag is not a simple post-it note: it's the operational signal that replaces production, picking, and transfer orders.
A well-constructed Kanban card displays:
This visual clarity is the system's strength: anyone, at any time, can understand the status of the workflow without accessing management software. Control is immediate and decentralized.
There isn't just one Kanban. The right variation depends on the process, the type of material, and how consumption manifests.
For each component, a number of containers with a fixed quantity is defined. Each container is associated with a tag: when the container is empty, the tag serves as a replenishment order for the internal or external supplier. This is the most widespread and immediate form to implement.
It works like standard Kanban, with one difference: the internal or external supplier does not start production upon receiving a single card, but waits for a certain number of cards to accumulate before starting. It is used when the minimum production or purchase lot is significantly larger than the quantity in a single container. It requires special boards for managing waiting cards.
It visually and physically reproduces the logic of the reorder point. The tag is not associated with a single container; it is sent to the supplier only after a certain number of containers or pieces have been consumed. It is the most suitable solution when consumption is less regular or supply lots are larger.
Kanban system sizing is the most critical step. Too many cards mean excess inventory; too few mean the risk of stockouts. The number of Kanban cards This is obtained by dividing the total requirement to be covered, i.e., average demand multiplied by lead time plus safety stock, by the quantity contained in each container.
The Medium question It is calculated by cross-referencing historical consumption from the last 6-12 months with forecasts for an equivalent period. The Lead Time It is the production time for an internal Kanban, or the procurement time for a Kanban to suppliers. security escort it takes into account the variability of demand and the desired service level: the higher the service level, the higher the safety stock needed and the lower the risk of stockouts. The choice is always a trade-off between warehousing costs and the cost of potential stockouts.
Suppose we manage a fitting flange on Kanban that is used on 8 out of 10 finished products.
The system therefore provides for 8 containers of 25 pieces in circulation. The maximum theoretical supply is 200 pieces — exactly what is needed, no more and no less.
If the upstream process improves and the lead time is reduced from 3 to 2 days, the number of tags required will be 6. Two fewer cards mean 50 fewer pieces in stock, in a controlled and measurable way. Every process improvement directly translates into a reduction in the number of cards: this is how Kanban makes continuous improvement visible.
Not all components They manage well with Kanban. Its maximum effectiveness is expressed on materials with regular, predictable, and repeated consumption: those that leave the warehouse every day, in similar quantities, to end up on the same lines.
Imagine a company that assembles electric motors. Of the 300 items in the bill of materials, about 240 are standard components: screws, gaskets, connectors, bearings—items consumed daily with little variability. Kanban works perfectly for these: standard containers, cards, automatic replenishment. No planner needs to worry about them. The remaining 60 items are expensive components, specific to the model, or with long and unpredictable lead times: MRP, or a dedicated supply agreement is needed here.
The rule of thumb is simple: if a component is used in 80% of your finished product codes, with stable consumption and a reasonable lead time, Kanban is almost certainly the right solution. If, on the other hand, the component is expensive, bulky, variable, or critical, it’s worth considering other management strategies.
There is also an even simpler form of classic Kanban, suitable for small and very low-value components: the method “empty for full”. Two containers are used: when the first one is emptied, it is refilled using the second one as a buffer stock. In effect, it is a Kanban with two cards, where the reorder signal is the empty container itself.
Kanban is not an isolated tool: it is the operating mechanism that brings to life the Just in Time (JIT). In JIT, each department only begins its production activity if the downstream department has requested a specific item in defined quantities. The Kanban is precisely the signal that triggers this request, and the mechanism propagates backward along the entire chain, all the way to the suppliers.
Inside the system, the supermarket It is the controlled storage point where Kanban-managed materials are picked up by the downstream process and replenished by the upstream process. It is not a traditional warehouse: it is a precisely sized, visible, and self-managed buffer thanks to the tags.
The Takt Time — the pace at which the market absorbs products — is the reference that governs the entire system: it defines the speed at which the Kanban must turn and therefore the number of cards needed to maintain flow without accumulating unnecessary stock.
Those who introduced Kanban in production often recall a seemingly trivial detail: the first day when no one had to look for anything. No calls between departments to know if the material had arrived. No emergency meetings to manage a shortage. The bin was in its place, the card had been returned, the flow was running on its own. It's not magic: it's the result of a system designed to make the actual production status visible—and to make problems emerge before they become emergencies.
Understanding Kanban is relatively simple. The real difficulty lies in choosing the right materials, sizing the cards well, and making the system work stably over time. These are exactly the steps where DIY implementations get stuck.
For those who want to avoid the most common mistakes and start with a solid foundation, Lean Factory School® propose the course Lean AdvancedA day in the classroom with simulations on a real physical product, where the Kanban system is designed, calculated, and tested directly on the field, according to the school's motto: Learn by doing.
In Push logic, production is planned in advance based on forecasts: materials are pushed to downstream departments regardless of actual demand, often generating high inventory, out-of-control WIP, and tied-up capital. Pull logic works in the opposite way: no department produces or moves material until the downstream process explicitly requests it. The Kanban system is the operational tool that makes this Pull logic concrete, using physical or digital tags to trigger replenishment only when there is a real need.
There are three main variants of the Kanban system. The Kanban standard it is the most widespread: each container has an associated tag, and when it is emptied, the tag automatically becomes a restocking order. The Kanban batch size it works similarly, but the supplier waits for more cards to accumulate before starting production: this is indicated when the minimum production or purchase batch is larger than the quantity of a single container. Kanban signal, instead, it reintroduces the reorder point logic: the signal is sent only after a certain number of containers have been consumed, and it is suitable for less regular consumption or larger supply lots.
The number of labels is obtained by dividing the total requirement to be met (i.e., average demand multiplied by lead time, plus safety stock) by the standard quantity contained in each container. For example, with an average demand of 50 pieces/day, a lead time of 3 days, safety stock of 30 pieces, and containers of 25 pieces, the result is 8 labels. A fundamental aspect: if the lead time improves (e.g., drops from 3 to 2 days), the number of labels needed is reduced proportionally, making every process improvement visible and measurable.
Kanban works best for components with stable, predictable, and recurring consumption: screws, gaskets, connectors, bearings, and, in general, anything that is used frequently and in similar quantities. A good rule of thumb is that if a component is used in the 80% of finished product codes with a reasonable lead time, Kanban is almost certainly the right choice. For expensive, model-specific components with long or unpredictable lead times, however, other policies such as MRP or dedicated supply agreements are preferable. For small, very low-value materials, there is also the ’empty-for-full“ method, a simplified version using only two bins.
Kanban is not an isolated tool, but the operational mechanism that brings Just In Time (JIT) to life: each department starts production only when it receives a request signal from the downstream process, and this mechanism propagates backward along the entire chain to the suppliers. Within the system, the productive supermarket it is the controlled storage point where Kanban-managed materials are picked and replenished: it is not a traditional warehouse, but a precisely sized and self-managed buffer via tags. The Takt Time, or the pace at which the market absorbs products, defines the speed of the entire system and therefore the number of tags needed to maintain the flow without accumulating unnecessary inventory.
Copyright © 2026 Bonfiglioli Consulting. All rights reserved. P.I. 02646871208 Privacy Policy | Cookie Policy | Adjust Preferences