Kanban (and pull systems in general) are a beautiful way to manage production. While the number of kanban cards should be verified periodically, for certain situations, however, it may be sensible to have additional kanban prepared. These extra kanban are added to the system on short notice to alleviate symptoms of other problems. However, please do not see this as a new and cool additional feature to your kanban system. Instead, if you have to use extra kanban, then something is going wrong. Such extra kanban are only an emergency fix and do not solve the underlying problem. Still, in some cases you do need an emergency fix. Let me explain:
Kanban and similar pull systems like CONWIP or POLCA are basic parts of lean production. They limit the maximum number of parts by attaching a sort of token (i.e., the kanban card) to the part, and return to the beginning when the part leaves the system.
These kanban can be physical cards or digital representations. In this post I look into when you should use a physical kanban and when you should use a digital kanban.
While Toyota did not invent the pull system, they did invent kanban, the genius idea of using cards of paper (and later other forms of information) to create a pull system for mass-produced goods. I recently was able to take pictures of Toyota kanbans, and would like to show and explain them to you.
In my last post I described how to prepare for the implementation of a kanban system. This post goes into more detail on the actual change to the new kanban system. You surely know that every part should have a kanban. But what do you do if you have more kanban than parts? What do you do if you have more parts than kanbans? Find the answers below.
Designing a kanban system on paper is much easier than implementing it on the shop floor. In many of my previous posts I discussed the design of a kanban system in detail. In these two posts I will discuss the steps needed to actually put the system on the ground. This first post is the preparation, and my next post will be the actual switch to the new kanban system.
A kanban is, in its basics, information to reproduce or reorder parts. Hence, in its most basic form it has to say “make me this part” or “bring me this part.” While such very simple kanban systems are possible, usually it helps to include other information on the kanban card. In this post I want to talk about the design details of a kanban card, especially what kind of information we should include on the card. Please note that the items on the list below are suggestions. Which ones you actually include depend on the system you want to establish.
To create pull production between two processes, you can add either a FiFo lane or a supermarket. In one case you will have the FiFo as part of a bigger kanban or CONWIP loop, and in the other case you split the value stream into two different kanban or CONWIP loops.
Some questions that I have been pondering are: Which one has less inventory for the same delivery performance? Is it better to use a big loop or two smaller loops for the WIP and delivery performance trade off?
In my last post, I described how supermarkets work in theory. But while knowing the theory helps, actually creating a working supermarket is much more difficult. Are there situations where supermarkets are not so useful? (Hint: Yes!). And what is needed to have a working supermarket? Let’s find out!