Print-in-place: planetary gearbox, herringbone, 4 : 1 — dimension sheet
Source: Xem Studio, https://xemstudio.com/objects/print-in-place-planetary-gearbox/  (sheet CC BY 4.0; files Xem Studio Design License, https://xemstudio.com/license/)
Basis: Xem Studio design; involute gearing per ISO 53 (20° basic rack), double helical 30°, normal module 1.5; one designed running gap of 0.40 mm
Catalog version: 2026-10-20

Overall (mm): length 112.0, width 112.0, height 48.0
- 3D print in place — prints already assembled, moving, in one job. Drawn at true size with no printer tolerance added; the 0.40 mm running gaps are part of the design.
- Running gap 0.40 mm per side, 0.80 mm on diameter — part of the design, drawn as is. On the 45° faces the same 0.40 mm is measured square to the face (0.57 mm along the axis).
- Bed: sun, three planets, ring and carrier all stand on the bed: the gears on their bottom faces, the carrier on its three pins (each a 45° cone in a planet's counterbore). The carrier grows up from the pins as three 45° cones that merge into one three-lobed dome above the gears.
- Support while printing: herringbone flanks lean 28° (base helix) and the carrier's underside is all 45° cone, 0.40 mm clear of the planet tops and bores; the sun's knob flares out at 45° above the carrier. Nothing is flat over air.
- Captured: the herringbone (two opposed 30° helices) locks each planet axially between sun and ring; each planet's 45° counterbore holds the carrier's pin base below it; the carrier's cones close over the planets above. Nothing can come out.
- Freeing it: hold the ring and turn the sun knob slowly in both directions until it runs smoothly (a screwdriver fits the slot); the carrier follows at a quarter of the speed.
- Motion: continuous; ratio 4 : 1 (sun : carrier, ring fixed); planets spin 1× the sun-relative-to-carrier speed. Checked in the transverse section through a quarter turn of the sun: min gap 0.454 mm in the section (≥ 0.40 square to the flanks).
- Involute teeth: 20° normal pressure angle, addendum 1.0 m, dedendum 1.25 m (ring: tips at 0.88 m inside the pitch circle, the catalog ring's rule); every tooth thinned so the running gap is 0.40 mm square to the flanks at the exact centre distance.

key  value  what
gap_mm  0.4  running gap per side on every moving interface (radial, axial, under captured parts) — part of the design, not a tolerance
module_n_mm  1.5  normal module
helix_deg  30.0  herringbone (double helical), 20° normal pressure angle, ISO 53 basic rack
teeth_sun  18  
teeth_planet  18  three planets
teeth_ring  54  
face_w_mm  12.0  all gears
ratio  4 : 1  sun in, carrier out, ring fixed
center_distance_mm  31.18  sun to planet
flank_gap_mm  0.4  square to the tooth flanks: sun and planet teeth thinned 0.20 mm per flank (0.226 in the transverse section), ring spaces opened 0.238 (measured in the model: 0.401 sun–planet, 0.402 ring–planet)
pin_d_mm  11.0  carrier pins, 45° base cone Ø14 on the bed
bore_d_mm  11.8  planet bores, 45° counterbore below
ring_od_mm  112  4 × Ø4.5 on Ø105
height_mm  48.0  to the top of the sun knob
planet_axial_play_mm  0.86  herringbone end play (computed)
carrier_holes  3 × Ø3.4 on Ø40  output
sun_shaft_d_mm  7.6  runs in the carrier's Ø8.4 centre bore

Files elsewhere (not hosted by Xem Studio; license as stated by the publisher):
- Xem Studio: Print-in-place mechanism design (geometry computed in the generator) — web — Xem Studio design — https://xemstudio.com/

Free files (Xem Studio Design License, Xem Studio; STEP + STL, 7 parts): https://xemstudio.com/files/hardware/print-in-place-planetary-gearbox/index.json
API: https://xemstudio.com/api/geometry?object=print-in-place-planetary-gearbox