How to Make CONWIP Loops

CONWIP-go-round with different jobs: like a roller coaster with different people

CONWIP (Constant Work in Progress) is an easy way to establish pull production for custom-made products. Traditionally there is only one large loop for the product. However, there may also be situations where it is sensible to split a longer CONWIP loop into smaller segments. Let’s have a look at the details.

Read more

Should You Use Physical or Digital Kanban Cards?

One Process Kanban LoopKanban 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.

Read more

Different Ways to Establish a Pull System – Part 2

This is the second post on different types of pull production. It features the less commonly known approaches of triangle kanban, drum-buffer-rope, reorder point (surprise, yes, it is a pull system),  reorder period (also a pull system), and FIFO lanes. In my previous post I showed you the kanban system and its variant, the two-bin system, as well as CONWIP and the kanban-CONWIP hybrid.

Read more

Different Ways to Establish a Pull System – Part 1

Rope pullingPull production is one of the most important aspects of lean production. Its key feature is to have an upper limit on inventory that is not to be exceeded. The most well-known way to implement a pull system is by using kanban cards. However, there are many others. In this short series of two posts, I want to give you an overview of the different ways to implement pull systems, and discuss the pros and cons of them.

Read more

How to Ramp Up a Kanban System – Part 2: The Switch

fotolia_on-air_trimmedIn 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.

Read more

How to Ramp Up a Kanban System – Part 1: Preparation

Simple Kanban LoopDesigning 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.

Read more

Supermarket vs. FiFo – What Requires Less Inventory?

Supermarket vs FIFOTo 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?

Read more

Theory and Practice of Supermarkets – Part 2

grocery store market supermarket retail shop
How to use supermarkets correctly …

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!

Read more