AES explores robot vs. gantry for large-format additive manufacturing

The existing machines are all large-scale gantry-style 3D printers, machines with build areas on the order of 12 × 6 feet. The company was founded on the promise of large-format AM for tooling, and it continues to fill its capacity and backlog for these machines making composites layup and process tooling, forming and assembly tools, and even tooling for precast concrete, as well as large 3D printed production parts. Now, a robot for 3D printing provides more of the same kind of capacity — but also capacity that is in many ways different.

CEAD (Delft, Netherlands and Detroit, Mich., U.S.) provided the robotic AM system to AES as part of a partnership in which the company will serve as CEAD’s North American demo site. The AES team adopted software from Adaxis for robotic AM to realize the system’s potential for multiplanar 3D printing. During a recent visit to see the company’s new capability in action (see video below), I learned from AES co-founder Austin Schmidt what the team is coming to understand about the differences between large-format gantry AM and large-format AM on a robot.

Schmidt says one advantage for the robot was apparent from the start, even before it began running.

“Installation is way different,” he notes. “The robot is much easier to install and start using.”

Installation of a large-format gantry-style AM machine of the size AES employs (large enough for people to enter) is a matter of a few weeks. Depending on the size and sophistication of the machine, Schmidt says, installation takes 4-8 weeks for a team of three people. (Even longer if the floor needs to be dug to accommodate Z travel.) He says AES has come upon used gantry machines at attractive pricing that it had to decline because of the cost of relocation and installation. By contrast, installing the robot AM system took a team of three people only 3 days.

This advantage has implications beyond just the initial install. “The robot is much more mobile as a production resource,” Schmidt says. It can be more easily relocated to a different part of AES’ facility if capacity or workflow demands require it. A facility more reliant on robots over enclosed machines for large-format AM is more adaptable for reorganization over time.

By contrast, build speed is the gantry machine’s clear advantage. The rigidity of the machine structure allows for the mass of a more powerful extruder. Meanwhile, “The robot is limited to the weight that can hang on the end of its arm,” Schmidt says. AES is accustomed to 3D printing at rates exceeding 100 pounds per hour on its gantry machines, including in high-temperature materials such as carbon fiber-reinforced Ultem. The robot is too new for the team to know as well what deposition rates it can routinely expect, but it will be some fraction of this. (Schmidt notes a qualification: AES is using CEAD’s smallest robot model. Faster deposition would come with a larger and more powerful robot system.)

Meanwhile, build volume is the difference between the two platforms that could go either way. With a gantry machine, the build envelope is a box: easy to see and understand. With a robot, the build volume is — not that. The robot can pivot all the way around its own hub, and like a human arm, its lateral reach gets shorter as it reaches up higher. The result: “The build volume is essentially a doughnut,” Schmidt says. Imagining whether a given part will fit within this volume, or how to fit it within the volume, “can be challenging to wrap your head around.”

The Adaxis 3D printing software is valuable for determining how to design or position a part so it can be produced within the robot’s working envelope.

But more, this software unlocks what Schmidt expects to be the most transformative possibility of the robot system: multiplanar 3D printing.

Robot 3D printing at varying angles

“Multiplanar” refers to how, with the robot’s freedom to pivot the extruder, 3D printing does not have to be limited to parallel planes. Programming in Adaxis makes use of this freedom, providing for deposition paths that compress the material’s layer height in one region and extend it in another to allow for layers that change angle from one layer to the next. (The video below discusses this.) This multiplanar printing, which would be impractical at best on a gantry-style machine, allows for printing forms and features that would be impossible with a gantry moving in just XYZ.

“We can do things in one pass on the robot that would require multiple builds on the gantry,” Schmidt says. More significantly, “There are a lot of parts we used to no-bid because we could not make them on a three-axis machine.” By 3D printing in varying orientations throughout the build, the robot provides ways to generate shapes that would otherwise present unsupported overhangs if made on an XYZ gantry machine.

With this in mind, AES added more than just the robot and the software. To develop expertise in robot AM and to lean into the kind of geometric freedom the robot brings, AES also hired a new employee: Nick Luther will both run and master the CEAD system. AES is lean enough that new capacity calls for new staff. But in the case of this capacity in particular, Schmidt says the company also recognized the need for a mindset change. Luther is new enough that “he does not have our gantry-based methods ingrained.”