NEMA Motor Mount Generator

NEMA 8, 11, 14, 17, 23 and 34 stepper motors and the 28BYJ-48 geared stepper. The hole spacing, pilot boss and shaft sizes follow the standard NEMA dimensions (for example NEMA 17: 31 mm hole spacing, M3 screws, 22 mm pilot, 5 mm D-shaft). Motors vary a little between makers, so measure yours if a fit is critical.

The line under the settings lists them for the part you made. A NEMA 17 plate 5 mm thick needs four M3×6 socket-head screws into the motor (longer ones bottom out in its 4.5 mm threads); the counterbores sink the heads flush. NEMA 23 and 34 motors have plain holes in their flange instead, so their M5 screws go through with a nut behind the flange. Frame screws (M3, M4 or M5) go through the flange holes or base slots.

The motor screw holes and the centre opening are slots. Fix the plate to your frame, loosely screw the motor on, pull the motor along the slots until the belt is tight, then tighten the screws.

Yes, for standard 20 × 20 mm V-slot or T-slot profiles. The two holes sit on the extrusion’s centre line, 10 mm from the bracket’s front edge; use M5 × 10 screws with M5 T-nuts or drop-in nuts.

Raise the Fit setting by 0.1 mm and print again. The default 0.2 mm suits most printers; the coupler and knob use a little less on the shaft so they grip, and the set screw locks them on the D-flat.

An eccentric cam on the motor shaft wobbles a lobed disc around a ring of pins. Each motor turn moves the disc back by one lobe, so a 14-lobe disc gives 14:1. Pins on the disc drive the output flange through oversized holes, which turns the wobble back into smooth rotation. The output turns the opposite way to the motor. It is compact, has very little backlash, and prints in five parts without supports.

The line under the settings lists it all: two bearings (6802 by default), four motor screws (M3 into a NEMA 14 or 17; M5 with nuts through a NEMA 23’s flange), one M3 set screw for the cam, four M3×12 screws for the lid – and, if you pick steel ring pins, the screws or dowel pins themselves. Screw the housing onto the motor, push the cam onto the shaft and tighten the set screw on the flat, press a bearing into the disc and slide it over the cam, drop the output flange onto the disc pins, press the other bearing into the lid, then screw the lid on (steel pins go down through the lid into the housing). A little grease on the pins makes it smoother.

Printed pins need no hardware and are fine for light jobs like turntables and camera mounts. For anything that carries load, use M3 or M4 screws or steel dowel pins: they are held at both ends (housing and lid), stay round and do not wear. Tick the printed sleeves so the disc rolls on smooth sleeves instead of rubbing on screw threads. Screws with a plain (unthreaded) shank work best without sleeves.

It is a printed gearbox: great for turntables, pan/tilt rigs, small robot joints and slow positioning, with little backlash. For heavier loads print the disc and housing in PETG with 4–6 walls, use steel pins with sleeves and the 6802 bearings. If the disc rubs or the gearbox feels stiff, raise the disc clearance by 0.05 mm; if it rattles, lower it.

For 3D printers, plotters, camera sliders, robot arms and other light machines, yes – print in PETG or ASA with 4 walls and 40% infill, and keep the default 5 mm thickness. For heavy loads or hot motors use metal brackets; PLA softens above about 55 °C, and a hard-working stepper can get that hot.