• Manufacturer: Proto-pasta
  • Color: Iron-filled Metal Composite
  • Printability: Easy, if you have a hardened nozzle
  • Enclosure: no


Proto-Pasta Iron-Filled Metal PLA is a Composite PLA filament with a high percentage of iron particles. There’s so much iron that the filament is easily attracted by magnets, as demonstrated in the above video. Models produced with this filament have a higher density than regular PLA model, which gives them a more weighty feel. According to the manufacturer, you can also “rust” the models to produce a rust-like appearance, though we did not try this ourselves.

This is an abrasive filament and will require a hardened nozzle. We use an E3D Nozzle-X on our Prusa I3 Mk3 and had no issues. The nozzle had a diameter of 0.4mm.

We printed three models: yet another filament sample keycard edition, Niffler by Alsamen, and a Sir Layersalot at 49% scale. Usually we print our SirLayseralots at 60% but this time we ran a little short on filament and had to downsize.

Print quality was great with some minor stringing, and a little bit of a rough bridge on the filament sample. It’s possible that some other tuning would have corrected these issues. We tested the magnetic properties of the prints and found that magnets readily snapped to the 3D printed model, and that prints could easily be held upside down, or even sideways, by the magnets. If you need to print something that attracts magnets, then this is a good filament to use.

The downside of this filament is cost. The cost per spool ($43 for a 500g spool) is already expensive, but consider that the density of the material means that it won’t go as far as typical PLA. The weight might be there, but the length is less. So you’re really paying up as much as four times as much as a spool of high-quality PLA. However, metal fills are unique filaments that yield unique results.


Proto-Pasta Iron-filled Metal PLA, Yet Another Filament Sample Keycard Edition
Yet Another Filament Sample Keycard Edition, Bottom
Proto-pasta Iron-filled Metal PLA, Niffler by Alsamen
Niffler, Side
Niffler, Front

As you can see we had a few issues with our camera — captured images that were a little bit darker than we would have preferred.

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