Når man taler om Kanban, er der faktisk tre definitioner. Dette skaber forvirring, da de tre betydninger ofte ombyttes eller misforstås fuldstændigt.

Kanban – a japanese noun

Firstly, there is the word Kanban. This is a Japanese word (a noun) which loosely translates to “signal card” or “signpost”.  Essentially the word is used to describe a physical sign which conveys some information. The word has been around in the Japanese lexicon for a long time, well before Toyota started adopting it to describe the just-in-time pull systems they developed as part of their manufacturing process. This leads to the second definition…

Kanban, hvilket betyder et Kanban-system

Kanban Systems blev først udviklet af Taiichi Ohno, en industriingeniør hos Toyota, helt tilbage i 1950'erne. Efter en rejse til USA blev han inspireret af, hvordan supermarkeder kunne bestille lige nok lager til at genopbygge de varer, som kunderne havde købt, og derved holde et overudbud af lager på et minimum.  

In the 1950s, Toyota competed with large U.S. companies Ford and General Motors. These well-established and wealthy organisations could afford to have an oversupply of stock in storage. However, Toyota could not!  They needed to find a way to maintain a steady flow of stock which arrives just at the time when it is needed, thereby reducing the need for expensive unused stock sitting in warehouses. 

Dette blev opnået ved at have et fysisk kort placeret i en kasse med dele. Efterhånden som delene er forbrugt, og æsken bliver tæt på tom, sendes kortet "opstrøms" til leverandøren. På kortet står en ordre på endnu en kasse med dele. Denne kasse bliver så leveret, lige som den gamle kasse bliver tom, og fylder derfor æsken med dele "just-in-time".

På japansk er et fysisk kort, der formidler nogle oplysninger, naturligvis kendt som en Kanban, og derfor blev Kanban Systems født. Men der er mere i det end det.  

As the card travels “upstream” in the manufacturing process, it is actually a “pull” signal indicating that the downstream part of the system is now ready for more items. So in a Kanban System, the upstream pull signal is the Kanban – it is NOT the item flowing downstream!!

Derfor er et Kanban System et system, hvor Kanbans (træksignaler) er i omløb. Og det sker, at Kanban-systemer bruges oftere, end vi måske tror.

One of the great benefits of a Kanban System is it protects the entity that issues the Pull signal from overburden. Imagine our manufacturing process again and its box of parts. Just imagine that instead of one box arriving, twenty arrive instead.  The station consuming the parts would be “overburdened” with excessive boxes of parts. This may not be a big deal in this example, but there are other situations where the overburden is a problem.

The Palace Gardens in Tokyo is such an example. It is a walled ornamental garden which is popular with visitors.  However, in springtime, the cherry blossom attracts more visitors than the garden can accommodate.  If all these visitors were allowed into the garden, it would cause excessive damage and not be a pleasant experience. To prevent the garden (the system) from too many visitors (overburden), a simple system is in place.  As visitors arrive, they take a card from a stack of cards located at the entrance gate. The number of cards available corresponds to the number of visitors the garden can comfortably accommodate. Once all the cards have been taken, no more visitors can enter the garden until an exciting visitor relinquishes a card.

Therefore we have a Kanban System in place.  The system being protected from overburden is the garden. The cards are Kanbans because they are a Pull signal indicating the garden can take more people.

Kanban-metoden

Finally, the 3rd definition of Kanban is The Kanban Method – the “agile” method used to manage knowledge work. It is the method that is compared to Scrum and often (and incorrectly) seen as an alternative!

Kanban-metoden bruger visuelle modeller, ofte afbildet som tavler (men ikke altid), til at visualisere det nuværende arbejdssystem. Og fordi kort bruges til at skildre de arbejdsgenstande, der flyder fra venstre mod højre (eller nedstrøms), er det forbundet, at kortene er Kanbans. De er ikke!!!

Det er en populær misforståelse, at Kanban (dvs. Kanban-metoden) placerer sedler på en væg og placerer dem i kolonner som To Doing, Doing og Done. Hej presto, en Kanban bestyrelse. Men der er mere i det end det.

Kanban-metoden var inspireret af Kanban Systems (systemer, hvor opstrøms træksignaler forekommer), som det ses hos Toyota og Palace Gardens. Som forklaret ovenfor beskytter disse upstream Pull-signaler systemet (teamet, organisationen osv.) mod overbelastning.

In order for The Kanban Method to have a Kanban System in place, there need to be upstream Pull signals in circulation.  This can only be achieved by limiting the number of Kanbans in circulation.

It is best described by the picture below.  As a Item 2 is pulled from Phase C to Done, it leaves behind a vacant position, a hole in the board, that can be filled by Item 5 flowing from the earlier Phase B. That, in turn, leaves another vacant position in Phase A which can be filled by Item 11 being pulled into the system from the Ideas column.

This vacant position which moves upstream, is actually the Kanban. It is an upstream Pull signal indicating the current phase can take (or Pull) a new item.  And these upstream Pull signals can only be achieved if the system has a limited amount of vacant slots. In this example a total of 8 items can only be on this system at any one time. In Kanban System, we call these limits, WIP limits.

So here is where the confusion lies. The Kanban Method uses Kanban Systems to manage knowledge work which protect the system from overburden.  There are many reasons why protecting the system from overburden is a good idea, but more on that another time.

Så i det væsentlige er der tre definitioner, når der refereres til Kanban. Det japanske ord (substantiv) betyder et signalkort. Kanban Systems, hvor Kanbans (opstrøms Pull-signaler er i omløb), og endelig Kanban-metoden. Ledelsesmetoden til styring af viden arbejde ved at bruge Kanban Systems til blandt andet at beskytte mod overbelastning.