One print, no glue: both flanges print in place, the top one on breakaway supports sized for a 0.4 mm nozzle, so each pulley comes off the bed finished.
GT-3M-20T+flange.stl — pulley 1, 20 teeth, without supportsGT-3M-30T-P2+flange.stl — pulley 2, 30 teeth, without supportsGT3M-20T-Assembly.stl — pulley 1 with both flanges and breakaway supports: print this oneGT3M-30T-Assembly.stl — pulley 2 with both flanges and breakaway supports: print this oneFree STLs are CC BY 4.0, printed size without print compensation. Open the design to change anything, tune the fit for your printer, or download STEP, DXF, SVG and the belt.
| Pulley 1 | Pulley 2 | |
|---|---|---|
| Pitch diameter | 19.10 mm | 28.65 mm |
| Outside diameter | 18.34 mm | 27.89 mm |
| Outside diameter, as built | 18.36 mm | 27.91 mm |
| Root diameter | 16.05 mm | 25.60 mm |
| Groove depth | 1.14 mm | 1.14 mm |
| Pitch line differential | 0.38 mm | 0.38 mm |
| Belt width | 10.00 mm | 10.00 mm |
| Face width (belt + clearance) | 11.30 mm | 11.30 mm |
| Minimum face width | 11.25 mm | 11.25 mm |
| Flange outside diameter | 24.36 mm | 33.91 mm |
| Flange past the OD | 3.00 mm | 3.00 mm |
| Minimum flange height | 1.70 mm | 1.70 mm |
| Belt | 86 teeth · 258.00 mm | |
| Centre distance | 91.38 mm | |
| Drive ratio | 20 : 30 · 1 : 1.5 | |
Read from the generator's Dimensions panel for this design, which opens with no warnings.
The 3D-printer classic done properly: a D-flat that keys onto the motor shaft, a set screw that bites into a captured nut instead of the plastic, and a 30-tooth partner held by two heat-set inserts.
Ready for an FRC robot: the bore fits REV ½" rounded hex shaft, with SH-50 retaining-ring grooves on both faces and a splined washer under each ring so nothing walks along the shaft.
Built like a machined part: ISO 773 keyways sized to 12 mm and 20 mm shafts, M5 set screws to lock them, and flanges drawn as bent metal plates instead of printed rims.
Big printed pulleys don't need to be solid: five and six spokes on a thin centre web cut plastic and print time, while the toothed rim stays full width for the belt.