Kupros Cu29 Filament Lets You 3D Print Copper Circuits on a Desktop FDM Printer

Copper 3D Printing Was Called Impossible. Kupros Disagrees.

When Ian Ramsdell started asking electronics specialists about 3D printing solid copper, he hit a wall. One expert told him flat out: copper cannot be 3D printed, and it never will be. What that expert did not know was that Ramsdell was already building on a confirmed laboratory experiment, one the US military had run and validated years earlier. That gap between impossible and already proven is the founding story of Kupros and its flagship product, Cu29.

Cu29 is a fully metallic, conductive filament engineered to print on standard fused deposition modeling machines. The filament extrudes alongside structural plastic in the same build, embedding conductive traces, signal routing, and antennas directly into a part as it prints. The pitch is straightforward: fewer wiring harnesses, fewer connectors, and structural-health sensing built into load-bearing components.

NASA, Northrop, and Boeing Pre-Ordered Before the Material Existed

Kupros accepted a prepaid order from NASA before Cu29 was finished. So did Northrop and Boeing. The orders came in at an Army xTech event in Tampa in 2022, after Ramsdell had licensed the underlying technology from a US Navy lab through a Department of Defense startup studio. KBR, the US Army DEVCOM, and several universities followed with their own pre-sales. Buyers put money down while the material science was still in development.

The Navy technology came from scientist Carson Holmes, whose 2017 proposal for a copper-based additive electronics process won the Office of Naval Research Design Innovation Award. The approach sat unused until Ramsdell licensed it in 2021. Rather than gamble on unproven science, he took on technology a national lab had already de-risked. A major electronics manufacturer had been trying to manufacture a similar material since the 1990s without success.

Why Copper Has Resisted 3D Printing for Decades

Copper is uniquely difficult. It is highly reflective, transfers heat efficiently, and oxidizes at the slightest temperature change. Those properties have frustrated copper printing across every process family. Kupros claims to have solved all three. In early high-voltage testing, the company pushed 12,500 volts through a Cu29 sample without failure. Ramsdell says they kept raising the current until the power supplies failed before they could reach destructive testing levels.

Against silver inkjet, the only comparable additive electronics material, Kupros claims Cu29 is 48,000 percent more conductive. Those figures are company-stated and await independent verification, but the positioning is clear. Cu29 is not meant to build bulk metal parts. The team has printed only five or six layer heights in the Z axis, mainly to test self-adhesion. The focus is on embedded electronics: a copper conductor laid into and onto polymer structures in a multi-material workflow.

Built for Hardware You Already Own

Additive electronics has historically required six- and seven-figure machines. Cu29 drops into the hardware already on the bench. Ramsdell has run it on sub-$300 desktop printers and on a Bambu Lab A1 Mini. The Prusa XL is in qualification as a recommended platform. It needs no printer modifications beyond a steel hotend, and Kupros claims the printed conductor is functional straight off the bed with no sintering, plating, curing, or chemical cleanup.

A space-grade variant called Cu29 Space is in development, targeting tin whiskering: a failure mode where tin conductors grow tiny metallic filaments that can bridge adjacent traces and short a circuit. That risk is especially acute in spacecraft, where a single short can end a mission and there is no opportunity for servicing. The Space variant is formulated to eliminate whiskering while printing traces from 0.2mm to 1.2mm on typical FDM hardware.

Cu29 won the TCT Materials Award at RAPID this year. For a sector still waiting on functional multi-material parts straight off the print bed, a conductive metal filament that runs on commodity hardware and has a space-grade line in the pipeline is a genuine step forward, provided the performance figures hold up under independent review.