3D Printing the Strongest Link: Carbon‑Fiber Chain Tests for Industrial Loads

Writer’s note: No heavy machinery was harmed during this write‑up; the prototypes, however, were not so lucky.

Summer interns at Markforged routinely explore the limits of our advanced 3D‑printing technology. Last summer, two interns set a bold goal: create a single carbon‑fiber‑reinforced chain link capable of lifting a 10‑ton cement truck. They believed that a truly industrial‑grade printer should be able to support such a load.

Their first design was a conventional oval‑link chain, a geometry that is ubiquitous in commercial chains. The link was sized for tensile testing on an Instron 5582 Universal Testing Machine (UTM) at Olin College of Engineering, whose 100 kN capacity allowed us to evaluate prototypes up to the weight of a cement truck without risking heavy equipment.

For those curious about chain manufacturing, the process is a marvel of engineering; see this How It’s Made video for a fascinating behind‑the‑scenes look.

Initial prototypes revealed a key challenge: carbon fiber’s directional strength. The chain links were printed entirely from Concentric Fiber fill, which resists tensile forces along the fiber direction but offers limited lateral stiffness. When the link was pulled, the sides bowed inward, leading to premature failure—an issue rarely seen in steel links, which are more isotropic.

To counteract this, the interns added a central reinforcing member that prevented buckling of the sidewalls. The resulting design required a 72‑hour print using six spools of carbon fiber.

When the final link was tested on the Instron, it broke just 50 lb shy of the machine’s maximum capacity—nearly meeting the 10‑ton lift target. While the engineering factor of safety is lower than what a typical cement truck owner might expect, the result demonstrates the industrial‑grade strength achievable with Markforged’s high‑performance materials.

Want to try this yourself? Explore the Mark Two printer and download the STL files below.

STL File