In my last post, I talked about the value of time in manufacturing, focusing on cyclic or repeatable times. However, the bigger problems are often non-cyclic or fluctuating times. The main difference is that non-cyclic work is a fluctuation, and it causes all kinds of other waste, from excess inventory to additional waiting times. On the other hand, depending on how often the fluctuation happens, there may not be so much benefit in reducing its duration. Read on…
Fluctuation
Fluctuations on Continuously Moving Assembly Lines 3—The Value of Team Leaders
In my last two posts I described the impact of fluctuations on the duration of the work on a continuously moving assembly line. One key tool for reducing fluctuations on Toyota assembly lines is the team leader, the frontline support for operators. Team leaders reduce fluctuations in general by taking over irregular tasks like delivering material, taking away trash, and explaining situations to a manager. They also reduce especially long fluctuations by supporting the operators in their own work if there are problems, thus reducing stops of the line. This post will look in more detail at the beneficial effects of team leaders on a moving assembly line.
Fluctuations on Continuously Moving Assembly Lines 2—Waiting Times
In my previous post I posed the problem of decoupling fluctuations on continuously moving assembly lines. You cannot decouple using inventory; you can decouple only long-term fluctuations using capacity, while all other fluctuations are decoupled using time. In my last post I introduced the topic and urged you not to have workers between different stations to handle fluctuations. In this post I will look in more detail at the waiting time of the workers due to fluctuations in the work duration for the stations.
Fluctuations on Continuously Moving Assembly Lines 1—Don’t Move the Workers Around!
A lot of industries use continuously moving assembly lines. This is common in automotive, but also in many others. The challenge is to manage the fluctuations. You cannot decouple using inventory; you can decouple only long-term fluctuations using capacity, while all other fluctuations are decoupled using time. This is the first blog post of a series digging deeper into how to handle or NOT handle fluctuations on continuously moving assembly lines. This first post looks at the effect when workers move among different stations.
The Benefit for Denso of Reducing Fluctuations
I have written a lot about leveling and the value of fluctuation in previous blog posts. In this post I will show quantitatively what the benefit of reduced fluctuations is for Denso, part of the Toyota group and a supplier to many other car makers too.
On Leveling and Fluctuations—How Does Toyota Do Leveling?
My last two posts in this three-post series on leveling talked about fluctuations and leveling in general, and the challenges and costs associated with leveling. In this last post I will go into greater detail on how Toyota does its leveling. Because Toyota does this actually quite well.
On Leveling and Fluctuations—The Downsides of Leveling
In my last post I gave you a brief introduction to fluctuations and leveling. And, I already hinted that there are two downsides to leveling: properly set up it handles only fluctuations coming from upstream, and—what is rarely talked about—there is an increase in inventory and/or waiting time to decouple the fluctuations in leveling. The second one especially is widely ignored or even vehemently denied in industry, but it is definitely there. Let me show you!
On Leveling and Fluctuations—Introduction
Leveling (or Japanese heijunka) is a common topic in lean manufacturing. Leveling combats one of the three evils in manufacturing: unevenness or fluctuations (in Japanese mura). While reducing fluctuations is an excellent goal, it is unfortunately not free, and there is significant effort not only for implementing and maintaining the leveling system, but also on the way the fluctuations are reduced. While everybody talks a lot about the benefits of leveling, very few talk about the cost. This may be one reason why so many leveling systems fail. Let me show you the hidden not-so-nice side of leveling.