The PDCA (Plan-Do-Check-Act) is one of the best-known lean methods, and one of the key philosophies for continuous improvement. However, despite its apparent simplicity, there are many struggles involved with its proper use. It seems that especially the Act part is challenging. Hence, let me dig deeper into why and how to Act in the PDCA.
On Facts vs. Opinions
In lean, as well as in many other areas, facts hold much more value than opinions. But what are facts, and what are opinions? Unfortunately, this is not black and white, but a big gray area. This blog post is based on a question by a reader on my earlier post “Why It Is So Important for Managers to Listen!” Let’s dive deeper into how to distinguish facts from fiction, and how to get facts in the first place…
Never Skip a Step in a Chaku Chaku Line!
Chaku Chaku lines and many other manufacturing cells and manufacturing lines have one (or more) operators working on different processes throughout the cycle. However, with this multi-machine handling, a worker must not skip a process if there are technical problems. Doing so—even with the best intentions—will increase fluctuations and cause waste. Let’s have a look at an example of why skipping steps is not so good.
Continuous Improvement Loops in Aviation—Part 2

Commercial aviation is among the safest modes of transport. This is thanks to a continuing improvement process spanning decades (and still ongoing). In this series of posts I will look at how aviation safety improved, using the passenger safety instructions as an example. My first post showed you how it was before the FAA and how it is now. This post looks in particular how the passenger safety institutions (i.e., the cards and the briefings) improved since 1940 thanks to the FAA. Now, pay attention!
Pacing of Flow Lines 2 – Continuously Moving Line
In my last post I described the pacing of pulse and unstructured flow lines. Another common way to structure the pacing of flow lines is the continuously moving line. In this type of line, the parts are always moving, and the processes and workers move along with the part until the process is completed.
Continuous Improvement Loops in Aviation—Part 1

Commercial planes are one of the safest ways to get around. Accidents are rare, and your likelihood of dying in a plane is very small compared to all other modes of transportation. However, this was not always the case. Safety in modern aviation is the result of many improvement iterations. Let’s have a look at how aviation improved one of its aspects, namely the passengers’ knowledge of what to do in the case of an emergency.
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.