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Glossary · Processes

3D printing

FDM

The most common type of 3D printing at home: a plastic strand is melted and applied layer by layer to form an object, similar to a hot glue gun.

Explained in more detail

Fused Deposition Modeling, also called FFF (Fused Filament Fabrication). A thermoplastic filament is heated above its melting temperature in the hotend and pushed out through a nozzle. The tracks are laid down layer by layer. The resolution in height is set by the layer height (typically 0.1 to 0.3 mm), in the plane mainly by the nozzle diameter. Pros: inexpensive machines and materials, a very wide choice of materials. Cons: visible layer lines and direction-dependent strength, because adhesion between layers is weaker than the material itself.

Where does the term come from?

FDM stands for Fused Deposition Modeling, roughly "modelling by depositing molten material". Scott Crump developed the process in the late 1980s, and his company Stratasys had the name protected as a trademark. For this reason the RepRap community introduced the free term FFF (Fused Filament Fabrication).

In practice

  • Strength depends on orientation: place parts on the bed so that the main load acts along the layers, not across them.
  • Overhangs up to about 45 degrees usually work without supports, and shallower overhangs need support structures.
  • For parts that are plugged into one another, allow 0.2 to 0.3 mm of clearance per side, and more for moving parts.
  • The first layer often decides the whole print: if it adheres cleanly and evenly, the rest usually goes well too.
  • The slicer shows you in advance how long a print takes; depending on size it is minutes to many hours.

Not to be confused

FDM and FFF are the same process with two names. Do not confuse them with resin printing (SLA, MSLA), where liquid resin is cured with light.

Frequently asked questions

What is the difference between FDM and FFF?

Technically none. FDM is Stratasys' original, trademarked name, and FFF is the free term from the RepRap community. Both describe printing with melted filament.

Is FDM printing suitable for beginners?

Yes, most home printers work with FDM. Devices and filament are cheap, and current printers largely calibrate themselves. For very fine figures with a smooth surface, resin printing is better suited.