Dandori

Changeover. In Japanese, it’s Dantorikae 【段取り替え】 or Dandori 【段取り】 for short. This word has always puzzled me — not because it’s hard to say, but because of what it actually means.

Most people involved in manufacturing know the word as a technical term: the process of switching a machine or production line from one product to another. However, the word itself has a much richer history, one that dates back to classical Japanese theater, Kabuki. Once you understand its origin, you start to see changeover — and preparation in general — in a new light.

Let’s begin with the word itself. The second part, “Torikae,” means to exchange or to swap. That part makes perfect sense in a manufacturing context. You’re swapping out dies, tools, fixtures, and settings. So far, so good.

But the first part of the word — “Dan” — is where it gets interesting. Dan does not mean a die, as many people in manufacturing assume. It means a step. A stage. A level.

Originally meaning a step or stage, the word evolved to mean a section within a story. In Kabuki—the intricate, centuries-old Japanese theatrical art form—each part of the story is called a Dan. A traditional Kabuki performance typically has five sections, five Dans, each representing a separate chapter of the drama. The flow of the story's plot and structure is called Dandori.

This means Dandori involves performance training. No one will go on stage without knowing their roles and moves. Everyone is fully aware of the story and what they need to do. They will spend hours preparing for the show.

That is Dandori.

Originating from Kabuki theater, Dandori entered the construction industry, and it is here that the philosophy truly takes shape. Japanese construction workers developed a guiding principle that has since spread well beyond building sites:

Dandori 80%, Work 20%.

At first glance, that ratio might seem extreme. Spending 80% of your effort on preparation and only 20% on the actual work? But the more you think about it, the more it makes sense. When preparation is thorough, the work itself becomes ‘beautiful’ — it flows smoothly. Problems are anticipated before they happen. Materials are exactly where they need to be. People understand their roles. Decisions are already made.

When preparation is missing, the opposite happens. The work turns into a constant cycle of improvising and firefighting. Time is wasted searching for tools, waiting for instructions, or fixing mistakes that could have been prevented. The 80% saved on planning is spent twice during execution.

The success or failure of any complex task mainly depends on how well the Dandori is prepared. It's not about how hard people work during the task, but about how effectively the stage was set beforehand.

Even before Shigeo Shingo formalized the SMED (Single-Minute Exchange of Die) methodology in the 1950s and 60s, the concept of Dandori was already deeply rooted in Japanese work culture. Long before stopwatches appeared on factory floors and changeover times were measured in seconds, people would say of a skilled worker that they had good Dandori — meaning they were exceptionally organized, well-prepared, and capable of creating the conditions for smooth, efficient work.

This is worth highlighting. The cultural respect for preparation and planning in Japan didn’t start with manufacturing. It goes back centuries, rooted in the discipline needed to stage a Kabuki performance. SMED didn’t invent the concept — it provided a scientific framework for it.

So what does it really mean to be good at Dandori? It goes far beyond tidying up a workstation or having the right tools nearby. Being skilled at Dandori involves working on two separate but connected levels: planning and preparation.

On the planning side, Dandori involves having a clear, well-thought-out approach to completing work efficiently. This isn’t vague intention — it’s a solid plan that specifies who does what, in what order, and by when. It considers dependencies: what needs to happen before something else can start. It outlines roles and responsibilities so no one is left waiting for directions. Importantly, it also includes a clear understanding of how time will be used — not just how long tasks will take, but when they will happen and in what sequence. Additionally, this includes training. What will the performance be without training?

On the preparation side, Dandori involves the physical work of getting ready before the main event starts. This is what Shingo later calls “external” setup — the tasks you can complete while a machine is still running, before the actual changeover begins. Gathering tools, pre-staging materials, confirming settings, and briefing the team are all done in advance so that when the changeover time arrives, everything runs smoothly.

The best analogy isn’t a factory at all — it’s a surgeon preparing for surgery or a chef doing mise en place before service starts. The actual performance is only as good as the preparation that came before it.

This is the deeper lesson hidden within a single Japanese word. Changeover isn’t just a technical issue to be optimized. It’s a discipline of preparation—a practice of setting the stage, act by act, so that the work can unfold smoothly.

Next time you walk a changeover on your shop floor, ask yourself: Do we have good Dandori? Is there a plan? Are roles clear? Is time tracked? Is the physical preparation complete before the clock starts?

If the answer is yes, you’re not just making a quick switch. You’re honoring a tradition that goes back to the origins of Kabuki. Prepare thoroughly, and let the show begin!