Construction Robots in Japan: Why Rivals Stopped Competing

Chapter 04

The Rebar Robot

Start with the work, not the machine

Reinforced concrete is steel in a grid, and at every intersection of that grid somebody ties the two bars together with wire.

Here is what that means over a shift, in the words of the national robot award that this chapter is about: a person ties 6,000 to 8,000 intersections in an eight-hour day, and the work is done bent over, for long periods. (Robot Award, checked October 3, 2026)

Sit with that number before we get to any technology. Six thousand, at the low end. One twist of wire every few seconds, all day, at the waist.

If you were choosing one task on a construction site to hand to a machine on humane grounds alone, it would be hard to find a better candidate.

What the machine is

Tomorobo, a rebar-tying robot, went on sale in January 2020. It is made by Ken Robotech, a company in Kagawa — not Tokyo — founded in 2013 and renamed to its present name in 2019. (Ken Robotech, checked October 3, 2026)

The award describes it as a ***collaborative* robot — one that does the work “in place of a person” while working alongside them — and notes that you automate the tying by simply setting a commercially available power tool into it**. It moves along the bars by itself and ties as it goes. (Robot Award, checked October 3, 2026)

No special tool. The one the steel fixer already owns.

The number that makes this interesting

In eight hours of operation, Tomorobo ties about 11,000 intersections. Against a person’s 6,000 to 8,000, that is about 1.3 times the output. (Robot Award, checked October 3, 2026)

One point three.

I want to dwell on that, because it is the least impressive number in this article and the most honest one. A machine that replaced a crew would be a headline. This one does slightly more than a person does, and it won a national award anyway.

What’s being bought here isn’t speed. It’s the eight hours of somebody’s back.

And the award’s own assessment agrees — it praises the robot for a simple mechanism, light weight and low cost, for being “very easy for the user,” and for reducing physical burden while addressing the labour shortage. Not for sophistication. For being light, cheap, and usable by the person already doing the job.

A company with an odd mission statement

Ken Robotech states its mission as creating “the world’s most human-friendly construction site.” (Ken Robotech, checked October 3, 2026)

That is a strange thing for a robotics company to say, and I think it explains the 1.3. If your goal were productivity, you would build something that removes people. If your goal is a site that is kinder to work on, you build something that crouches so a person doesn’t have to.

And it left

In February 2023, Ken Robotech set up its first overseas base: a subsidiary in Singapore. (Ken Robotech, checked October 3, 2026)

Then in September 2024, Tomorobo won the Minister of Land, Infrastructure, Transport and Tourism Award at the 11th Robot Award, a programme co-hosted by several Japanese ministries.

Notice the direction of travel, and notice the destination. Chapter 1 said Japan was not the leader in construction robotics, and that remains true. But a small company from a rural prefecture, building a deliberately cheap machine for one unpleasant task, has taken it to a country with some of the most aggressive construction-productivity policy anywhere.

That’s not the story I expected to find when I started this article. It’s better than the one I expected.

Chapter 05

Why Japan Is Pushing This Hard

The pressure is demographic, not commercial

I’ve referred to the labour shortage several times. Here is the version with a government target attached, because that’s what turns a worry into budgets.

Japan’s Ministry of Land, Infrastructure, Transport and Tourism runs a programme called i-Construction 2.0, accelerated from April 2024. Its stated goal is to reduce the people needed on construction sites by at least 30% by fiscal 2040 — that is, to raise productivity by 1.5 times — through automation in three areas: construction work itself, data linkage, and construction management. (Ministry of Land, Infrastructure, Transport and Tourism, checked October 3, 2026)

Read the target carefully, because the wording matters. It is not “build more.” It is build the same with thirty percent fewer people. The productivity figure is derived from the headcount figure, not the other way round.

That is a policy written by people who have looked at who will be available to work in 2040 and done the arithmetic.

What that changes about the robots

It explains the shape of everything in this article.

It explains the 1.3. If the problem were margin, a 1.3× machine is unremarkable. If the problem is that the person doing that job will not exist in fifteen years, a machine that lets one person do the work of 1.3 and go home with a working back is directly on target.

It explains the consortium. Thirty percent is not a competitive advantage anybody wins alone. If every contractor needs it, and none of them can hire their way out, developing separately is just paying three times for the same answer.

And it explains the choice of tasks. The jobs being automated first — layout, rebar tying — are not the glamorous ones. They’re the ones that are repetitive, physically punishing, and hard to staff.

I’m not going to relitigate the rest here

The wider digital side of this — machine guidance, GNSS, the drawings behind it — I’ve already written about in ICT Construction in Japan and BIM and production design. If you want the fuller picture of where the 3D data comes from before a robot can use it, start there.

The honest caveat about targets

One thing I’d ask you to hold lightly.

A 2040 target is a long way out, and the gap between a ministry’s goal and what turns up on an actual site is usually wide. I’ve worked on plenty of projects where the newest thing present was the coffee machine.

What I’d take seriously is not the number. It’s that the number exists, that it’s framed around people rather than output, and that the companies responded by forming a consortium rather than a race. Those are signals about direction, and direction is the useful part. The pace will be whatever it turns out to be.

Chapter 06

What Construction Robots in Japan Mean on Site

Ask what the half-day is made of

Here’s the number that reframed this article for me, and it comes from my own experience rather than a press release.

Setting out takes about half a day for one operation.

Not because marking lines is slow. Because of everything around it: moving the measuring instrument, setting it up, establishing the reference, checking it. The actual drawing of lines is the short part at the end.

Now put that next to chapter 3. Kajima’s layout robot is driven by an auto-tracking total station — the same instrument, on the same control point, set up by the same person.

So the honest question to ask about any layout robot is not “is it faster?” It is: faster at which part?

I’m not calling the figure wrong

Kajima reports roughly double the productivity on layout work, and I have no basis to dispute it. They measured it; I didn’t.

What I’d say is that a doubling of the printing does not halve the half day, if most of the half day was never printing. A robot that draws perfect lines at high speed still waits while somebody levels an instrument and verifies a control point.

This is the gap between a technology and a working day, and it is where most optimistic estimates go to die. If you are ever asked to evaluate one of these machines, that’s the question I’d put first: what does it do about the setup?

The thing nobody writes about

Now the observation that surprised me most, and I’d rather lead with it than bury it.

Almost no craftspeople know these robots exist.

Unless you work for a specialist contractor in that particular line of work, you haven’t heard of them. Not “have opinions about them” — haven’t heard of them.

I want to be clear that this is my own experience of ordinary building sites, not a survey. But it has held across the sites I’ve been on, and it changes how you should read every article about construction robotics, including this one.

What that does to the “will robots take our jobs” question

In chapter 7 I’ll answer that question. Here is the context for the answer.

That anxiety, where it exists, is largely a conversation happening outside the site — in trade media, in company strategy documents, in articles like this one. On the slab, the reaction to a layout robot isn’t fear. It’s “what’s that?”

You can read that two ways and both are true.

Optimistically: there’s no resistance to overcome, because there’s nothing to resist yet. When a machine does show up, it arrives as a curiosity rather than a threat.

Less comfortably: the gap between the policy in chapter 5 and the floor you’re standing on is wider than the press releases suggest. A national target for 2040 and a crew who have never seen one of these machines are both true at the same time.

So what should you actually expect?

If you come to work in Japan in the next few years:

• You will do setting out with a sumitsubo and a total station, like everyone before you
• You will probably not meet a layout robot, and definitely not every day
• If one turns up, nobody around you will be an expert either
• And the person who understands what the machine is working from — the control point, the drawing, the datum — will be the most useful person in the room

That last one is not a prediction about robots. It’s been true since the eighth century, which is roughly when somebody first snapped an ink line onto a Japanese building and everyone else worked to it.