Designing Gears for 3D Printing

An FDM printer's practical resolution — nozzle diameter, extrusion width, and any elephant's-foot or over-extrusion error at the first layers — sets a hard floor on how fine a tooth it can reproduce accurately. Below roughly module × 4 ≈ nozzle diameter, the involute flank starts losing definition: tip corners round off and the root fillet fills in slightly, both of which quietly reduce the effective addendum/dedendum from the nominal values shown on each gear's page.

Resin (SLA/DLP) printers don't have this constraint in the same way — their resolution is set by pixel size and cure behavior, typically well under 0.1 mm — so module 0.3 gears that are marginal on FDM print cleanly in resin.

Orientation

Print with the gear's flat face down and the tooth axis vertical (exactly the orientation every STL download on this site is modeled in) so layer lines run parallel to the tooth's load-bearing flank rather than across it. Printing a gear "standing up" on its rim instead puts layer adhesion directly in the path of the meshing force, which is a common cause of teeth shearing off under load.

Fit and backlash

FDM parts typically print 0.1–0.3 mm oversize on external dimensions depending on the printer and settings; for a meshing gear pair this usually means adding a bit more backlash than the catalog default, or measuring a test print's actual pitch diameter against the parameter table on its gear page and compensating in the generator if you're designing a custom pair.

Bore fit

Printed holes usually come out slightly undersized (round holes print slightly polygonal/tight) — if a gear needs a press or slip fit onto a shaft or bearing, print a test bore or add 0.1–0.2 mm to the nominal diameter. See 3D Printable Gears for a shorter practical checklist, or Gear Materials for filament trade-offs.