A kanban store is a store in which consumption triggers replenishment: every item sits in at least two bins with a fixed quantity, and as soon as a bin is empty, the bin or its card goes back to the source as the order. The principle comes from the Toyota Production System, where Taiichi Ohno developed it from 1947 onwards, modelled on the supermarket (Wikipedia, Kanban). The number of bins follows from daily consumption times replenishment lead time plus a safety allowance, divided by the bin quantity. Prof. Wolfgang Bode of Osnabrück University of Applied Sciences shows how strongly the lead time drives the result: cut it from 6 to 3 hours and stock and shelf space fall by around 50%. We also supply die-cut and slit insulation parts through a kanban store, as part of our custom products. This article explains the cycle, kanban types, bins and signals, works through the number of bins for an insulation part and shows when kanban is the wrong tool.
Kanban storage, consignment stock and reorder point answer different questions
Purchasing teams often use the three terms in one breath, yet each settles something else. Kanban decides when to replenish and how much. Consignment decides who owns the goods until they are withdrawn. That is why the two combine well: a consignment warehouse can be topped up through kanban bins.
| Concept | What it governs | Trigger | Ownership until withdrawal |
|---|---|---|---|
| Kanban store | Timing and quantity of replenishment | Empty bin or card, fixed quantity | Customer, from delivery |
| Consignment warehouse | Ownership and invoicing | Withdrawal is reported and invoiced | Supplier |
| Commission warehouse | Sale of someone else’s goods by a trader | Sale to a third party | Supplier |
| Reorder point method | Timing of the order | Book stock reaches the reorder level | Customer |
The reorder point is calculated almost like kanban: daily demand times procurement time plus minimum stock (Wikipedia, Meldebestand). The difference lies in the signal. The reorder point method relies on book stock in the ERP and only works if every withdrawal is booked. Bode describes the same risk with automatic call-offs via feedback points and bills of materials: the quantities calculated by IT drifted further and further from actual demand over time, until material ran short. In a kanban store the signal sits on the shelf, and an empty bin cannot be booked wrongly. How a trader sells someone else’s goods in his own name is covered in the article on the commission warehouse.
How the two-bin kanban cycle works
The basic form needs neither software nor a card. The bin itself is the signal.
- At the point of use, each item has two bins one behind the other, usually in a FIFO rack that is loaded from the back (bott, kanban white paper).
- Parts are taken only from the front bin. Once it is empty, the operator puts it at a fixed return point and the rear bin slides forward.
- The empty bin or its card is the order. It states material, quantity, supplier or storage location and the point of use (bott). The label used by Würth Industrie Service adds bin quantity, batch and the customer part number.
- The source refills the bin with exactly the agreed quantity, without asking, and brings it back. SAP calls the span from status EMPTY to FULL the replenishment lead time.
- The full bin goes behind the one in use. If the second bin runs out before the delivery arrives, the quantity was calculated too tight.
Toyota puts the aim on its corporate website like this: make only what is needed by the customer, when it is needed, and in the amount needed. The kanban rules follow from that. Nothing is made or moved without a signal, the source delivers only flawless parts, and the number of cards is kept as low as possible, because every card stands for tied-up material (Wikipedia, Kanban). A case report in the trade magazine Industrial Production shows what this looks like day to day: the distributor Otto Roth has been refilling a barcode-based two-bin system at the intralogistics company Viastore since 2011. The driver usually comes on Wednesdays and swaps full bins for empty ones; 300 components run on kanban, while Viastore orders another 200 manually. Even a kanban store that runs well rarely covers the whole range.
Four kanban types differ by where the signal goes
| Kanban type | Signal goes to | Triggers | Typical use |
|---|---|---|---|
| Production kanban | Upstream production step | Production of a fixed quantity | In-house production |
| Transport or withdrawal kanban | Store or supermarket | Move to the point of use | Line supply |
| Supplier kanban | External supplier | Delivery under a framework agreement | Bought-in parts, C-parts |
| Signal kanban | Process with set-up effort | A whole batch once a minimum number of bins is reached | Stamping, large series |
The classification follows the Lean Enterprise Institute and the MES vendor Symestic. For purchasing, the last two rows matter most. A supplier kanban needs a framework agreement and a supplier whose delivery performance and quality you can rely on (Forum Verlag, kanban glossary). The Lean Enterprise Institute names the signal kanban specifically for stamping presses with short cycle times and long changeovers. That is exactly where kanban supply of stamped insulation parts comes in.
Kanban bins and kanban racks: fixed places, fixed quantities
Kanban bins are almost always small load carriers with a fixed place and a fixed quantity. The choice of bin goes a long way towards deciding whether the loop holds up in daily use.
- Common choices are open-fronted storage bins, Euro boxes and other standard small load carriers (bott). Würth offers its kanban bin in four sizes to the VDA standard.
- Bin size follows the part and the quantity. Standard sizes are interchangeable and use rack, shelf and trolley space the same way (bott).
- The kanban rack is loaded from the back and picked from the front, with a separate level for empties. REYHER’s mobile rack offers 42 bin positions on eight levels and carries up to 1,000 kg.
- The point of use needs room for at least two containers of every part (Wikipedia, Kanban).
Card, barcode, RFID or scale: which signal pays off when
| Signal | Trigger | Effort | Suits |
|---|---|---|---|
| Empty bin | Bin at the return point | No IT | C-parts at the workstation |
| Kanban card | Card in the collection box | No IT, up to about 500 items | Getting started, internal loops |
| Barcode | Scan with scanner or app, order in the ERP | Scanners, labels | Mid-sized ranges, supplier kanban |
| RFID | Reader detects the tag on the empty bin | Tag €0.20 to €1.00, reader €500 to €3,000 | Large ranges with high frequency |
| Shelf scale | Sensor reports stock continuously | €50 to €200 per compartment | Bulk parts, consumables |
The cost figures come from the Industrie Fachwissen guide (January 2026). The laundry technology maker Kannegiesser shows how large a kanban loop can get: around 7,500 kanban bins and more than 2,800 items across seven sites, run partly through RFID kanban (Würth Industrie Service, press release 2026). A variant is the three-bin system, with one bin at the line, one in the factory store and one at the supplier (Wikipedia, Kanban).
Our advice is to start with the empty bin or a card. According to Symestic, physical cards only reach their limits at about 20 parallel loops. Below that, electronics add little, because they only speed up the report. Bode shows that a sensor cuts the time until demand is reported from a few hours to a few seconds, while picking and transport take as long as before. A bin quantity calculated wrongly stays wrong with RFID.
Calculating the number of kanbans: formula and worked example
Fabrico, Symestic, Tacto and the Infor LN documentation write the formula four different ways, but they all mean the same thing:
Number of kanbans = daily consumption × replenishment lead time in days × (1 + safety allowance) ÷ quantity per bin, rounded up to whole bins.
Wikipedia adds the lot size to the numerator, meaning the quantity from which the source produces again. It belongs in the calculation whenever the supplier only sets up from a minimum quantity. Average stock is estimated as half the number of bins times the bin quantity (Wikipedia, Kanban). For an insulation part the calculation looks like this: a motor maker builds 150 stators a day, each stator has 24 slots and needs 24 slot liner covers. The figures are an example; the method works for any series part.
| Parameter | Case A: made to order | Case B: called off from a supplier buffer |
|---|---|---|
| Daily consumption | 3,600 pieces | 3,600 pieces |
| Replenishment lead time | 10 working days | 3 working days (assumption) |
| Safety allowance | 20% | 20% |
| Quantity per bin | 2,500 pieces | 2,500 pieces |
| Calculation | 3,600 × 10 × 1.2 ÷ 2,500 = 17.3 | 3,600 × 3 × 1.2 ÷ 2,500 = 5.2 |
| Bins in the loop | 18 | 6 |
| Average stock | around 22,500 pieces | around 7,500 pieces |
Case A assumes ten working days, which is our upper limit of two weeks’ delivery time when the material is in stock. Case B assumes an agreed buffer at the supplier, so only call-off, picking and transport count. The same part then needs a third of the bins and a third of the stock. The lever is the lead time; the bin quantity comes second. Fabrico shows the same effect: halve the time from two hours to one and the requirement drops from 10 cards to 5.
The table works with many small bins. In a pure two-bin system, a single bin has to cover the lead time plus allowance on its own, which is how Industrie Fachwissen calculates it. In case A, each of the two bins would then have to hold 43,200 slot liner covers, 86,400 parts in the loop instead of 45,000. The two-bin principle is ideal for screws at an assembly station; for a series part at 3,600 pieces a day we plan with more, smaller bins.
On the safety allowance the sources disagree. bott generally uses about 10% in a two-bin system and lowers the buffer as the loop matures. Industrie Fachwissen and Fabrico work with 20%, Cleverence with 30%, and Symestic with a factor of 1.1 to 1.5. We recommend deriving the allowance from the measured spread of the lead time. Clock the real time from returning the empty bin to delivery of the full one. It often differs markedly from the planned time (bott), and anyone who estimates instead of measuring ends up with too high an allowance and too much stock (Symestic).
Even so, the result is never more precise than about 30%. Christoph Roser (AllAboutLean) writes that equally well-founded assumptions shift the result by 30% or more, and advises erring towards more bins. bott describes the route Toyota itself took: start generously, remove bins step by step and watch for the first shortage. After that, the quantity needs regular review. Industrie Fachwissen recommends a check once a year, and Otto Roth and Viastore also agree the parts list and consumption annually. The warehouse software vendor Cleverence recalculates as soon as consumption deviates by more than 15%.
A kanban store works under five conditions
- Consumption is regular. According to Bode, classic kanban only works really well with regular material consumption; in an XYZ analysis these are the X items.
- The item is cheap to buy and expensive to order. C-parts are goods with a low purchase value that cause high procurement costs (Paralescu, TU Wien). Industrie Fachwissen puts the internal cost per order at €80 to €150, for items often worth less than €10.
- Bins, quantities and locations are fixed. Every item has its place, and at least two bins stand at the point of use.
- The supplier keeps to time and quality. A defective part in the bin stops the line just as an empty bin does.
- People stick to the rules. Kanban expert Thomas Klevers calls the card the nerve cell of the system: anyone who knows what a missing card sets off will not let it vanish into an overall pocket (CETPM, Yokoten 05/2012).
At the time, Klevers estimated that kanban was used in only about 30% of the cases where it could work. As examples of untapped potential he named C-parts management and consumables such as lubricating oil and welding wire.
When a kanban store is the wrong tool
A kanban store is a tool for recurring demand. In the following cases we advise against it or towards another method:
- One-off parts, special orders and project work without repetition (Wikipedia, Kanban).
- Parts with many variants and very uneven consumption. Symestic calls 500 active part numbers with three pieces of annual demand each the wrong system.
- Expensive A-parts that justify individual planning in the ERP (Industrie Fachwissen).
- Lead times of 6 to 12 weeks, because the loop would then have to hold huge quantities.
- Ageing materials with an expiry date, which are better managed batch by batch on a FIFO basis in the ERP (Industrie Fachwissen).
- Bulky parts delivered in truck or container loads (Wikipedia, Kanban).
The German Wikipedia names one more case that applies directly to insulation parts: plastic and stamped parts where machine set-up takes so long that they are produced to stock.
Kanban for insulation parts: split the loop at the supplier
For a maker of motors, transformers or appliances, insulation parts are typical kanban candidates. Slot insulation, slot liner covers, phase separators and spacers cost little per piece, yet go into every machine, and their consumption follows the output of the line. They are drawing parts. The tool and the material sit with the manufacturer, even where C-parts service providers such as Würth Industrie Service include stamped and drawing parts in their kanban supply.
The Wikipedia objection holds for a loop in which every card triggers a stamping order directly. The tool would then have to be set up again for every bin. The answer is a split loop:
- On your side, a two-bin or supplier kanban runs with a fixed quantity per bin. Every empty bin is a call-off.
- At the supplier, a buffer sized to your consumption is kept. Parts are stamped in lots large enough to justify the set-up.
- When the buffer reaches its minimum, it triggers the next lot, just like a signal kanban.
The lot-size stock leaves your shelf and sits with the supplier. Your formula only contains the short lead time from case B. Whether such a buffer pays off for your part and how large it needs to be is something we can agree with you on request. If you still want the stock on your premises and only pay on withdrawal, that is a question of ownership and belongs in a consignment warehouse. We stamp the parts ourselves, as described under stamping and forming, using steel rule dies for samples and medium series and solid steel dies for large series (details in the article on stamped parts).
The material also decides how long a bin may last. Nomex can be stored indefinitely at 20 °C and 50% relative humidity (Seipp), and polyester film absorbs no moisture and contains no plasticisers. Pressboard, on the other hand, is hygroscopic and only stays dimensionally stable when stored to standard. For pressboard parts we therefore recommend smaller bin quantities, closed bins and strict FIFO withdrawal, so that no bin stands open at the line for months. With Nomex and polyester film the coverage can be longer.
Flat insulation parts do not need a tote full of loose pieces. We stack and package stamped parts in special packaging, apply ID numbers on request and pick kit packs. If, for example, all insulation parts for one stator go into one kit, the kanban card counts stator sets instead of single parts. Rolls are slit onto the core your machine needs, either through our roll slitting or as a job in contract slitting. We work to ISO 9001, and batches stay traceable.
To design a kanban loop we need the following details:
- Drawing, material and thickness, from 7 µm to 3 mm depending on the material
- Daily consumption or annual quantity and the preferred quantity per bin
- For rolls: width, length, core diameter and core material
- The tolerances
- Bin type, delivery rhythm and measured lead time, if available
We produce from a single piece and deliver within two weeks at most when the material is in stock. Send the details to our technical consulting team, who will work out the number of bins, bin quantity and delivery rhythm with you. We reply within 24 hours, Monday to Friday.
