Magnetic filament does not turn a 3D printed part into a magnet. That is the single biggest misunderstanding buyers bring to this material, and it causes more disappointment than any real flaw in the filament itself. What gets sold as magnetic filament is, in almost every case, standard PLA loaded with real iron powder, which makes the printed part ferromagnetic: a magnet grabs onto it and holds on with real force, the same way it grabs an ordinary steel nail. The nail is not a magnet either. This guide covers what the material actually is, the real numbers behind Proto-pasta’s Magnetic Iron PLA data sheet, what it is genuinely good for, and where it falls short. For background on how it compares to plain PLA and other filament families, see the filament types overview.
What magnetic filament actually is
Proto-pasta’s Magnetic Iron PLA is the product most people mean when they say magnetic filament, and it defines the category. According to Proto-pasta’s own technical data sheet, it is a compound of standard PLA (NatureWorks 4043D, the same base resin behind Proto-pasta’s Conductive PLA) loaded with real iron powder at roughly 45 percent by weight. There is no rare earth magnet material in it and no small magnet hidden inside the print, just iron mixed into the plastic before extrusion and locked into the matrix once a part is printed.
Proto-pasta also sells a more concentrated High Density Iron HTPLA, built on a high temperature PLA base with 60 percent iron instead of 45. It delivers roughly twice the magnetic pull and, once heat treated, three times the temperature resistance of the original, though at a higher price with an extra processing step. Most buyers are better served by the standard 45 percent formula this guide focuses on.
Real numbers from the data sheet
Proto-pasta’s technical data sheet for Magnetic Iron PLA lists:
- Density: approximately 1.85 g/cc, about 1.5 times the density of standard PLA (roughly 1.24 g/cc)
- Iron content: approximately 45 percent by weight, maximum particle size 250 microns
- Induction at magnetic saturation: about 0.15 Tesla
- Relative permeability: between 5 and 8, independent of frequency up to 1 MHz
- Melt point onset: approximately 155°C
- Length per 500g spool: roughly 97 to 112 meters of 1.75mm filament, against 165 to 175 meters for standard PLA
Those magnetic figures are modest next to an actual magnet. A strong N52 neodymium magnet has a remanent flux density around 1.4 Tesla, nearly ten times the saturation point of Magnetic Iron PLA, which is why a printed part gets pulled toward a magnet with real force while remaining nowhere near a magnet itself.
The density is what catches people off guard first. A part that would weigh 30 grams in standard PLA comes out around 45 grams in Magnetic Iron PLA at the same infill, with a cold, dense feel closer to a die-cast part than plastic.
What it’s actually good for: sensors, props, and decorative metal
Proto-pasta’s own application list leans on look, feel, and magnetic attraction rather than function, matching what the material actually delivers. The projects that come up again and again:
- Decorative magnets and mounts. Fridge magnets, cabinet pulls, and small parts that cling to a magnetic strip or steel surface play to the material’s real strength.
- Cosplay and prop details. Rivets, buckles, trim, and emblems that need metal weight and a cast, matte finish print well in this filament without the cost of casting real metal.
- Sensor targets for reed switches and hall effect sensors. The material is ferromagnetic but not electrically conductive, unlike Proto-pasta’s own carbon-loaded conductive filament, so a printed target trips a sensor with no risk of shorting nearby circuitry.
- Educational demonstrations. A part printed half in Magnetic Iron PLA and half in standard PLA shows the difference between a ferromagnetic material and a true magnet hands-on.
- Faux cast metal and rusted finishes. Sculptures, emblems, and signage meant to look like aged iron can be finished with an actual rust patina instead of paint.
What it can’t do: permanent magnetism, strength, and staying rust-free
A print made from Magnetic Iron PLA will not pick up paperclips on its own. Repeatedly stroking a thin section across one pole of a strong magnet can induce a weak, temporary magnetization, since ferromagnetic materials retain some magnetization after exposure to a field, a property called hysteresis, but the effect fades quickly and does not survive being dropped or handled roughly. Real permanent magnetization needs an industrial magnetizing coil producing a field on the order of 2 Tesla, which would deform or melt a PLA print long before it finished.
Strength is the other place this material disappoints buyers expecting normal PLA performance. Proto-pasta’s own documentation and customer feedback describe it as more brittle than standard PLA and prone to snapping in long bowden tubes. The company says plainly that its metal-filled materials are for aesthetic purposes, with no claim to functional strength. If a design needs both a metallic look and real mechanical performance, print the structural body in nylon or standard PLA (see the PLA print settings guide for baseline numbers) and reserve Magnetic Iron PLA for the parts where the look and pull matter.
Rust is not automatic either. Proto-pasta markets the material as rustable through a specific process, a mix of hydrogen peroxide and white vinegar with salt added until saturated, applied to the surface and left to react. Left alone indoors, prints tend to hold their cast-metal finish for years without rusting on their own, but the iron sits at the surface of every layer, so long-term exposure to humidity, standing water, or outdoor weather is a real risk for anyone who wants to keep that fresh, unrusted look.
Print settings and nozzle wear
Magnetic Iron PLA prints close to standard PLA, with a few adjustments. Proto-pasta recommends a nozzle temperature between 185 and 215°C, hottest on the first layer for adhesion and cooler through the rest of the print to control stringing. No heated bed is strictly required, though Proto-pasta suggests keeping bed temperature between room temperature and 60°C, since going higher tends to worsen warping. First-layer speed should stay slow, around 10 to 20 mm/s, with the rest of the print running 20 to 80 mm/s.
Nozzle wear is real. The embedded iron powder is abrasive enough that Proto-pasta recommends 0.6mm or larger where possible, with 0.4mm acceptable and 0.25mm as a minimum for experienced users. A standard brass nozzle wears faster on this material than on plain PLA, and a wear-resistant or hardened nozzle stretches the replacement interval considerably, though Proto-pasta notes it is still easier on nozzles than steel-filled or carbon-fiber-filled filaments.
Two practical notes rarely make it onto a spec sheet. The filament is more brittle than plain PLA and snaps more easily in a long bowden tube than on a direct-drive setup. And skip the filament dryer: the metal holds heat longer than the surrounding plastic, and Proto-pasta warns that drying can anneal the material and make it more brittle, causing clogs rather than preventing them. Let spools acclimate at room temperature instead of trying to bake moisture out of them.
Practical project ideas
- A set of fridge magnets or cabinet pulls that grip a steel surface or magnetic strip without any embedded hardware
- Cosplay armor rivets, buckles, and trim pieces that need metal weight and a matte cast finish
- A reed switch or hall effect sensor target printed separately from any conductive parts in an enclosure
- A small rusted sign or sculpture finished with the hydrogen peroxide, vinegar, and salt patina method
- A side-by-side classroom demonstration piece that shows the difference between a magnet and a ferromagnetic material
Magnetic filament checklist
- Confirm the part only needs to attract a magnet, not generate its own field
- Use a 0.6mm or larger nozzle, or a wear-resistant nozzle, for longer service life
- Favor a direct-drive extruder where possible, since the filament is more brittle than standard PLA
- Set nozzle temperature between 185 and 215°C, hottest on the first layer for adhesion
- Skip the filament dryer and let spools acclimate at room temperature instead
- Do not rely on this material for load-bearing or functional parts
- Plan for real rust risk in humid or outdoor settings, or trigger it on purpose with peroxide, vinegar, and salt
- Pair the print with an actual magnet, ideally neodymium, rather than expecting the part to act as one