Metal 3D Printing Filament: Two Materials Hiding Behind One Name

Two products, one misleading label

Walk into any filament shop and search 'metal.' You will get results that share a name but could not be more different. One is plastic with metal dust in it. The other is mostly metal and turns into a solid steel part after a trip through a furnace. The word 'filament' covers both, and that is a problem.

Here is the clean breakdown, based on a deep dive by 3DBite that finally separates the two.

Category one: metal composite filament

This is PLA or PETG with 40 to 60 percent metal powder mixed in by weight. The metal never leaves the plastic. What you print is a plastic part that is heavier, denser, and, after sanding, looks convincingly metallic.

Copper-fill and bronze-fill are the common ones. Iron-fill does something stranger: soak the finished print in salt water or vinegar and the surface iron rusts for real, which is exactly what prop makers want for weathered pieces. Stainless, brass, and silver fills exist too.

The catch is abrasion. Metal particles are harder than a brass nozzle, so a hardened steel nozzle is not optional here. Print it on brass and you will widen the bore until your extrusion goes sloppy. The upside is that any standard FDM printer handles it once you swap the nozzle. The result stays plastic, though. You cannot weld it or machine it like metal.

Category two: sinterable metal filament

This is the furnace route, and it is far more serious than the name implies. BASF's Ultrafuse line and The Virtual Foundry's Filamet line carry 80 to 90 percent metal by weight in a polymer binder. You print the part, burn out the binder, then sinter it at 1,000 to 1,400 degrees Celsius. What comes out is metal, not plastic dressed up as metal.

The shrinkage is the part beginners miss. As the binder leaves and the particles fuse, the part shrinks roughly 15 to 20 percent on every axis. A 100mm print comes out near 80 to 85mm. You compensate by scaling up the model first, then tap or drill the precision features after sintering. Manufacturers call it near-net-shape for that reason.

The metal range is genuinely wild: 316L and 17-4 PH stainless from BASF, and from The Virtual Foundry a list that runs through bronze, copper, aluminum, high-carbon steel, tungsten, Inconel 718, and titanium. A desktop printer laying down a filament that is 80 percent titanium, sent to a sintering service, can return a near-solid titanium part. That is not a gimmick.

How the two compare

Composite filament costs about 25 to 45 dollars a kilo and needs only a hardened nozzle. Sinterable filament costs far more per spool and the real expense is the furnace or the sintering service. BASF routes you to ELNIK for catalytic debinding and sintering; The Virtual Foundry's Filamet can be thermally debound in the sinter cycle itself, though you still need a real sintering furnace, not a kitchen oven.

The practical takeaway

If your goal is a metal-looking chess set or a weathered cosplay sword, buy composite and invest in a good hardened nozzle and some sandpaper. If you actually need a stainless bracket you can tap and bolt, save for sinterable filament and budget the sintering service, because the furnace alone will cost more than the printer.

The name tricks people into buying the wrong spool. Now you know which question to ask before you check out: do I want it to look like metal, or do I want it to be metal?