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.
Kanban
Kanban Card Design
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.
Supermarket vs. FiFo – What Requires Less Inventory?
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?
Theory and Practice of Supermarkets – Part 2
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!
Theory and Practice of Supermarkets – Part 1
Kanban, FiFo lanes, and supermarkets are the backbone of many pull system. Some people even define lean production through its use of kanban and supermarkets. Yet why are supermarkets so useful? First we will look at what exactly makes an inventory into an supermarket. My next post will then give tips and hints on the practical use of supermarkets on the shop floor.
Why Pull Is So Great!
One of the most significant insights of the Toyota Production System is its concept of pull production. While often misunderstood, the essence of pull production is a clearly defined limit on the work in progress. Push or pull actually has nothing to do with the direction of the information or material flow. But why does this limit on work in progress make so much difference? Why do pull systems vastly outperform push production systems?
The (True) Difference Between Push and Pull
One of the key differences in lean production is to use pull production rather than push production. While pretty much everyone knows (at least in theory) how to implement it using kanban, the underlying fundamental differences are a bit more fuzzy. But what exactly is the difference between push and pull? Also, what makes pull systems so superior to push systems?
It turns out that most definitions are going in the wrong direction. Even the names “push” and “pull” are actually not well suited to describe the concept. Neither are common illustrations, including the one here in the upper left.
Benefits and Flaws of CONWIP in Comparison to Kanban
In my last posts I discussed the basics of CONWIP systems (Constant Work In Progress) and answered some frequently asked questions Part 1 and Part 2 on CONWIP. Overall, CONWIP is a pretty cool alternative to kanban, also establishing a pull system. It has some very valuable advantages, but it also comes with some disadvantages. In this final post of my series on CONWIP, I will shed light on some of these advantages and disadvantages, especially in comparison with kanban, but also with drum-buffer-rope.