Design Nomenclature / Physical Model Making
FDM
Also called FFF, fused deposition modeling, fused filament fabrication, filament printing
Extruding molten thermoplastic in stacked paths. Cheap, forgiving, dimensionally decent. But the part is a stack of welded beads: strong along the paths, roughly half as strong across them. Layer lines are visible, overhangs need support, and the first layer decides whether the print survives the night at all.
In practice
"FDM" is a Stratasys trademark. The open-source world says FFF for exactly that reason and means the identical machine.
Not to be confused with
- SLACuring liquid photopolymer layer by layer with light. Resolution is set by optics rather than a nozzle, so fine detail and smooth walls come easily. The trade is real: parts arrive wet with uncured resin, need washing and a post-cure to reach final properties, and stay brittle and UV-sensitive for life.
- SLSFusing nylon powder in a heated bed layer by layer, with the unfused powder supporting the part. No support structures at all, so geometry no other process can build comes out in one piece: living hinges, captive parts, deep undercuts. Surfaces are uniformly matte and slightly porous — they dye beautifully and paint badly.