As Japan’s aging population and shrinking construction workforce put growing pressure on the industry, Shimizu Corporation is turning to a new kind of 3D printing. The company has developed a spray-based system designed to fabricate large, curved, and reinforced concrete components. Unlike extrusion-based printers, it sprays a special concrete mixture from a robotic nozzle instead of laying down stacked layers. This allows the robot to build shapes that would be difficult or impossible to achieve with conventional concrete printing.
This approach allows concrete to be deposited from multiple angles and around steel reinforcement cages. That is a major shift for structural construction, especially in seismic regions where reinforced concrete is essential. Most existing concrete printers struggle when rebars are present. Spray-based printing removes that constraint and makes true structural 3D printing possible.
How Simulation Improves Spray-Based Printing
Spraying concrete is powerful but unpredictable. Material can rebound, drip, or spread depending on nozzle distance, angle, and how fast it sets. To control this, Shimizu partnered with Carnegie Mellon University’s Computational Engineering and Robotics Lab to develop a material spray simulator.
The software models how the concrete will travel through the air and form on the surface. Engineers can test toolpaths, spray angles, and speeds before printing begins. This makes it possible to choose the most accurate and efficient strategy in advance, reducing defects and wasted material. It also helps ensure the printed geometry matches the original digital design.
A Robot Built for Large, Reinforced Structures
The printing system combines a seven-axis robotic arm with a two-axis gantry, giving it nine degrees of freedom. It operates inside a build volume six meters deep, four meters wide, and three meters high. The nozzle can spray in multiple directions, even inside dense steel reinforcement cages.
In a recent demonstration, the robot produced a twisted concrete wall standing 2.5 meters tall, with both the top and bottom sections extending outward. The entire structure was printed in just four hours, showing the system’s ability to handle complex geometry at architectural scale, including overhanging and curved forms.
For Shimizu, this technology is not about novelty. With Japan’s construction workforce shrinking, automation is becoming essential. Spray-based 3D printing offers a way to reduce manual labor while expanding what architects and engineers can build with reinforced concrete.
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*All Photo Credits: Shimizu