Category Archives: Pull

Posts explaining how the pull system works and how to implement different pull systems.

The (True) Difference Between Push and Pull

Push Pull Illustration
Common, but misleading illustration of 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. Continue reading The (True) Difference Between Push and Pull

Benefits and Flaws of CONWIP in Comparison to Kanban

CONWIP go round with different parts like roller coaster seats with people
CONWIP-go-round with different parts – like roller coaster seats with people

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. Continue reading Benefits and Flaws of CONWIP in Comparison to Kanban

Frequently Asked Questions on CONWIP Systems – Part 2

Roller Coaster
CONWIP-go-round with different parts – like roller coaster seats with people

In the last two posts I described the basics of a CONWIP system and started with the frequently asked questions on CONWIP, where CONWIP stands for Constant Work In Progress. However, there are some more frequently asked questions that are also important for CONWIP. These I will explain here. The next and final post of this series will discuss the advantages and disadvantages of CONWIP. Continue reading Frequently Asked Questions on CONWIP Systems – Part 2

Frequently Asked Questions on CONWIP Systems – Part 1

CONWIP go round with different parts like roller coaster seats with people
CONWIP-go-round with different parts – like roller coaster seats with people

In the last post, I started with the basics of a CONWIP system, where CONWIP stands for Constant Work In Progress. However, there are some more frequently asked questions that are also important for CONWIP. These I will explain here.

Initially, I wanted to write one quick post explaining CONWIP. However, as it happens all too often, one post turns out to be not enough. It quickly expands into multiple posts of a series in order to give you a good, well-rounded overview of the topic. Hence, the frequently asked questions will be covered in two separate posts. After that, the fourth and truly final post of this series will discuss the advantages and disadvantages of CONWIP. Continue reading Frequently Asked Questions on CONWIP Systems – Part 1

Basics of CONWIP Systems (Constant Work in Progress)

Leviathan_Reactions
CONWIP -go-round with different parts – like roller coaster seats with people

There is broad agreement in industry that a pull system is in almost all cases better than a push system. The most famous way to establish a pull system is to use a kanban system. The idea of kanban is so much associated with pull production that the two terms are sometimes even used synonymously. However, there are other ways to implement pull. Another useful approach is CONWIP, standing for Constant Work In Progress and developed by Mark Spearman and Wallace Hopp in 1990.  In this small series of posts, I would like to go into the details of CONWIP and its similarities to and differences from kanban. This first post will explain the basics, the next two posts will go into more details by answering some frequently asked questions, and the fourth post will discuss advantages and disadvantages of CONWIP. Continue reading Basics of CONWIP Systems (Constant Work in Progress)

A Critical Look at Goldrath’s Drum-Buffer-Rope Method

Drum Buffer RopeEliyahu Goldratt developed different methods on how to manage production systems. These methods are nowadays known as the Theory of Constraints, or TOC for short. One key method described is called Drum-Buffer-Rope, or DBM for short. Similar to Kanban or CONWIP, it aims to constrain the work in progress (WIP) in the system. There is much discussion on which method is better than the other, although the result often depends heavily on with which method the respective author earns its living.  In this post I will present how Drum-Buffer-Rope works, and discuss its advantages and shortcomings. Continue reading A Critical Look at Goldrath’s Drum-Buffer-Rope Method

Theory and Practice on FiFo Lanes – How Does FiFo Work in Lean Manufacturing?

FiFo LaneFiFo lanes are an important part of any lean material flow. They are a very simple way to define both the material flow and the information flow. In this post I want to tell you why to use FiFo, how to use FiFo, and the advantages of FiFo, as well as show you a few examples of FiFo lanes. Continue reading Theory and Practice on FiFo Lanes – How Does FiFo Work in Lean Manufacturing?

How Many Kanbans? – Estimation Approach and Maintenance

Number of Kanban
How many Kanban?

In my previous two posts, I described how to calculate the number of kanbans (Post 1 and Post 2). However, this calculation is complex, and the result is nothing more than a very rough estimate. Hence my preferred method for determining the number of kanbans is, broadly speaking,  “just take enough, and then see if you can reduce them.” In this post, I would like to explain this approach and also discuss how and when to update the number of kanbans. Continue reading How Many Kanbans? – Estimation Approach and Maintenance