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?
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→
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)→
In my last post, I started to show the main reasons why EPEI leveling with a fixed repeating schedule so often fails (for details on EPEI leveling, see Theory of Every Part Every Interval (EPEI) Leveling). This post continues with more reasons and also gives some advice on how to reduce the damage or even increase its chances of success. It also has a suggestion for a test to determine if your system is ready for leveling.
Again, there seems to be a lean religion that claims that putting up a leveling box will lead to salvation. Well, Lean is not a religion or magic. Lean is hard work, and you actually need to understand what you are doing. Just copying something without understanding is a good way to fail, especially with leveling.Continue reading The Folly of EPEI Leveling in Practice – Part 2→
In my last post I presented the EPEI leveling pattern (also known as EPEC, EPEx, Heijunka, fixed repeating pattern, or simply leveling). While in theory this approach looks pretty solid, in my experience it rarely works in practice. In fact, most of these types of leveling that I have seen were complete rubbish. They were a dog-and-pony-show to please management at the expense of performance and shop floor efficiency.
Furthermore, lean manufacturing seems often to be confused with a religion. People believe that if you put up a leveling box your manufacturing system will have salvation. Well, Lean is not a religion. Lean is hard work, and you actually need to understand what you are doing. Just copying something without understanding is a good way to fail, especially with leveling.Continue reading The Folly of EPEI Leveling in Practice – Part 1→
Probably among the most popular leveling approaches is Every Part Every Interval (EPEI). Often, this is the method people mean when they talk about leveling (also known as heijunka[平準化]).
The theory about this type of leveling is not very difficult. Unfortunately, hard facts of reality often nullify any possible advantage of this type of leveling. In fact, most of these types of leveling that I have seen were complete rubbish. They were a dog-and-pony-show to please management at the expense of performance and shop floor efficiency. In this post I will explain to you how it is supposed to work in theory. In the next post I will explain why it rarely works in practice . Continue reading Theory of Every Part Every Interval (EPEI) Leveling & Heijunka→