To date, improvements in 3d printing have mainly focused on increasing resolution, decreasing print time, and diversifying the types of materials that can be used. If you went to CES in 2015, you’d see printers that could print circuit boards, create molds, and even print foods. However, all of these systems were still limited by the build volume; the reach of the robotic arm used to distribute printer material or the size of the resin bath and build platform in the case of SLS.

We became curious about questioning the fundamental mechanics of 3d printing and the limitations of the print volume. What if you wanted to print outside of this print volume? Could you print larger structures? What would that allow you to do?


That’s when we started brainstorming different methods for printing without the limitations of a fixed platform. We first focused on the basic mechanics. This printing platform would have to be mobile. It would have to carry the material around as it distributed is. We explored using base with treads or wheels with a robotic arm that could distribute printing material. This architecture could be successful for smaller prints but it was really just an extruder head on wheels. It solved the X and Y navigation across a flat plane, but not the Z problem. It was still limited by it’s vertical reach.


Whenever we get stuck, usually nature has a better solution. We looked into how ants build their structures. Each ant will pick up material, walk on top of the structure and lay that material to build the next layer. This was also interesting because ants can coordinate with each other, a swarm of medium efficiency nodes create a much higher efficient system.

Perhaps some kind of robot that was capable of climbing on the layer it just created would be the answer? We would need a material that was super light-weight; that could expand and harden rapidly. The material choice is critical because it will determine how the robot navigates.


If the whole point of printing outside the print section was to be able to print larger structures then we would need a material that would be small enough to carry around but expand as we distributed it. Naturally, expanding foam came into mind. It seemed like a good solution but achieving a high enough resolution to be useful might be a challenge. We’d either need to do some finishing work on the surfaces after the foam was distributed, or we’d need to figure out how to distribute the foam in a way that we could guide its expansion. Guiding the foam seemed like a simpler option. After a quick trip to Home Depot to pick up some foam and a bit of cardboard we created a prototype. The objective of the prototype was to see if foam guides would be effective at forming the foam as it came out.

We were surprised at how well the cardboard was able to guide the sticky foam. We had thought we would need some kind of chemical to coat the guides to make sure it was smoothly distributed, but it seemed to be working reasonably well on its own.

3D_Robot_01_Small_TaggedOnce we were happy with the material direction, we started looking into the architecture of the robot. How would it distribute the foam? How would it climb on the next layer? How would it balance on a wall of uncured foam? What happens when it runs out of foam or reaches the top of a structure?

We started leaning towards a four wheeled robot that had wheels specially designed to grip on the sides of the foam. A simple platform would make it easier to find something close to prototype with. We found a open source robot that used Arduino went ahead and ordered it.


As a first objective we wanted something challenging but simple enough that we though it could be achieved in a couple weeks. A hollow column would require the bot to distribute foam in one continuous circular motion. We thought this might be the easiest because all you have to do is turn left and make sure you don’t fall off the wall. We’re currently building out the prototype to draw a straight line and we’ll keep you guys in the loop with our progress towards a fully working prototype!

Lance Cassidy

About Lance Cassidy

Founder of DXLab Design, a hardware incubator out of Raleigh, NC. My goal is to inspire creative confidence in the maker community and encourage ambitious entrepreneurs to utilize design thinking. I’m inspired by multi-talented people who seek to innovate at the intersection of disciplines.