Kanban

Kanban (Japanese for "visual card" or "signal") is a workflow management method that coordinates production and replenishment using visual signals: a card, a column or an empty container indicates when and how much needs to be made or restocked. Its core principle is to produce only what the next stage consumes, so inventory nobody asked for does not pile up.

Born in the Toyota Production System in the 1950s, Kanban is one of the pillars of Lean manufacturing and a concrete example of a pull system (triggered by demand), as opposed to pushing production against a forecast. In plants that digitize their operations, it is part of what brings order to Manufacturing, where the board stops being made of cardboard and starts syncing with the ERP and the shop floor.

Beyond the factory, the same concept became popular in software and services teams as a board of columns (to do, in progress, done) that limits simultaneous work. In both worlds the idea is the same: make the work visible, limit what is in progress and move each unit only when there is capacity to receive it.

How a Kanban system works

The classic mechanics of a production Kanban rely on cards that travel with the material. Each container of parts carries a withdrawal card (it authorizes moving material from one stage to the next) and a production card (it authorizes making the batch that replaces what was consumed). When a workstation empties a container, it sends the card back upstream: that return is the order to produce. Nothing gets made without a card authorizing it, so total inventory is capped by the number of cards in circulation.

Three rules keep the system from getting out of control:

• Limit work in progress (WIP): each column or stage accepts a maximum number of units in process. When it fills up, it stops "pulling" new work until capacity frees up.
• Pull, don't push: a stage only produces when the next one has consumed. Actual demand, not a forecast, triggers every movement.
• Make the flow visible: the board shows where work piles up. An overloaded column reveals the bottleneck without the need for a report.

Why it matters for an operation

The value of Kanban is that it turns an invisible problem (excess inventory, unbalanced stages, stuck orders) into something you can see at a glance. By limiting work in progress, it reduces the capital tied up in stock, shortens cycle times and forces you to solve bottlenecks instead of covering them up with more inventory. It is also the operational foundation of practices such as Lean manufacturing, and it pairs with inventory turnover as a health metric.

A concrete example in Argentina

An auto parts maker in Córdoba's industrial belt that supplies a vehicle assembly plant moved from producing against a forecast (and piling up weeks of parts that were never ordered) to a Kanban scheme with standardized containers. Every time the assembly plant's line consumes a container of metal brackets, a signal fires that authorizes making exactly that replenishment batch. The typical result is less idle stock in the warehouse and fewer last-minute emergencies, because the plant produces at the pace of real consumption and not at the pace of a spreadsheet. In practice, many small and midsize manufacturers start with physical boards and move to digital boards connected to their management system as they grow.

Common mistakes

• Too many cards or a WIP limit set too high: if the limit is loose, inventory swells and the method loses its reason to exist. WIP is deliberately tuned downward.
• Using Kanban with very erratic demand or extremely slow-moving products: it works best with relatively stable, repetitive consumption; for extreme peaks, it is better to combine it with safety stock.
• A nice board, ignored rules: having columns is not Kanban. Without respected WIP limits and without pull logic, it is just a decorated to-do list.

Kanban vs MRP

Kanban and MRP are often presented as rivals, but they solve different things and many plants combine them: MRP plans what and when at an aggregate level, while Kanban regulates fine-grained replenishment on the floor.

In short, Kanban is a simple tool with a demanding discipline: its power is not in the cards but in respecting the limits and letting actual demand, not urgency, set the pace of the operation.