Fused Deposition Modeling (FDM) is an additive manufacturing process that builds objects layer by layer by heating thermoplastic filament and extruding it through a moving nozzle onto a build platform.
FDM is the most widely used form of 📝3D Printing, valued for its low cost and accessibility. The technology was patented by mechanical engineer Scott Crump, co-founder of Stratasys, in 1989. Because Stratasys holds the FDM trademark, the same process is often called Fused Filament Fabrication (FFF).
An FDM printer feeds thermoplastic filament from a spool into a heated extruder, which melts the material and deposits it through a fine nozzle, typically 0.4 mm in diameter. The print head traces each cross-section onto the build plate before moving up to add the next layer, which fuses to the one below as it cools. These movements follow G-code instructions produced when slicer software divides a digital model into horizontal layers.
Common filament materials include PLA, ABS, PETG, and TPU. FDM contrasts with resin-based stereolithography and powder-based selective laser sintering, generally offering lower resolution and visible layer lines in exchange for cheaper machines and materials.