HDP30 v1.0 (RevB)

A 3D-printable 30:1 pancake harmonic drive for any NEMA 17 stepper with a 5 mm shaft. About $3.96 of hardware per unit.

⚠️ Not yet load-cell tested. There is no torque, efficiency or backlash figure for this revision, and the HD20's numbers do not carry over, because the tooth module dropped from 0.8 to 0.55. Testing is queued. If you measure one before we do, open an issue and we'll credit you.

What changed from the HD20

60-tooth flexspline against a 62-tooth circular spline at module 0.55, so the reduction goes 20:1 to 30:1 at roughly the same pitch diameter, in a thinner stack.

Six parts were re-cut for the new profile: the flexspline, both circular splines, the wave generator, the ball cage and the output preloader. The interface plate, base preloader and shear pins are unchanged, and so is every piece of hardware: same 11 balls, same 30×42×7 bearing, same 8 screws, same 12 inserts. HD20 leftovers cover this build.

Which download

File	What's in it
hdp30-v1.0-step.zip	The 9 STEP parts. Start here, slice these.
hdp30-v1.0-3mf.zip	Convenience mesh export for slicers that won't take STEP. Does not include the two shear pins, which are STEP-only.
hdp30-v1.0-dxf.zip	The four tooth profiles from the harmonic maker.
hdp30-v1.0-everything.zip	All of the above, plus the README, BOM and photos.

Printing

PLA throughout except the flexspline, which must be PETG. It flexes every revolution and PLA will crack. Supports on the output circular spline and the interface; everything else prints unsupported. Random seam position on all parts.

Full build notes, bill of materials and the parametric model: README · robrotics.web.app/actuators/hdp30

CC BY-SA 4.0. No warranty: printed parts fail.