Ferro-Magnetic Iron PLA Composite Filament

Real iron in every strand. This is Proto-Pasta's iron-filled PLA composite — actual iron powder blended into PLA, so the printed part is genuinely ferromagnetic: a magnet pulls on it hard and it behaves much like solid iron, even though it isn't a magnet itself. Prints come out with a dense, matte, cast-metal look and can be rusted to a real patina when you want one.

It's the practical choice when a part only needs to respond to a magnet. Rather than forging, casting, or milling steel for a mild magnetic job, you print the exact shape you want and let a strong magnet do the holding — magnet-ready terrain floors, removable panels and hatches, fixtures, and display pieces that snap into place.

Specs

• Material: iron-filled PLA composite (real iron powder, ferromagnetic)
• Diameter: 1.75 mm
• Density: about 1.85 g/cc — roughly 1.5× standard PLA, so parts feel weighty
• Finish: matte cast-metal as printed; rustable for a true iron patina
• Sizes: 100 g coil, 500 g spool, 1 kg spool
• Made in the USA by Proto-Pasta

Printing notes

• Nozzle temperature: Proto-Pasta lists 185–215 °C. For solid, high-infill prints like terrain floors, run hotter — around 220–230 °C — for consistent flow, especially with a hardened steel nozzle. Keep the first layer hot for adhesion.
• Bed: room temperature up to 60 °C — hotter can worsen warp
• Nozzle: the iron is abrasive, so a hardened or wear-resistant nozzle is best for extended use; plan on replacing plain brass eventually
• Nozzle size: 0.6 mm or larger preferred; 0.4 mm works; smaller is expert-only and prone to clogging
• Layer height: 0.15–0.20 mm balances quality and reliability
• Prints on a standard PLA profile. In filament form it's a little more brittle than regular PLA, so handle the strand with care.

Rust & finishing

Left alone, prints keep a stable matte metal finish. To weather them, apply a rusting solution and build up the patina; once you like it, seal with a matte clear coat or fixative so the rust doesn't rub off. A sealer also helps keep parts from rusting on their own in humid storage.

Pair it with strong magnets

Because the print only responds to a magnet, the hold comes from the magnet you pair it with. We recommend high-strength N52 neodymium magnets for a firm, reliable grab. For parts whose job is to hold, print them solid (around 100% infill) and 2–3 mm thick where the magnet sits, so there's enough iron for it to grab. Seat the magnet in the mating part and let the iron-filled print be the surface it locks onto.