Can I 3D print timing belt pulleys?

Yes, for light-duty applications. Print in PETG or Nylon for durability. PLA works for prototyping but wears quickly. Use at least 4 perimeters and 50%+ infill for strength. The tooth profile may wear over time with heavy use.

What tooth count should I use?

Minimum 12 teeth for smooth belt engagement. 16-20 teeth is standard for 3D printers. Fewer teeth = smaller diameter but more belt bend stress. More teeth = larger diameter, smoother operation but takes more space.

Do I need flanges on printed pulleys?

Yes, flanges prevent the belt from walking off the pulley. Add 1-1.5mm flanges on both sides that extend 1mm above the tooth tips. Without flanges, the belt can gradually shift sideways and come off.

How accurate do the tooth profiles need to be?

GT2 teeth have a specific rounded profile for smooth engagement. FDM printing approximates this shape. For critical applications, orient the pulley so the teeth are in the XY plane. Resin printing gives more accurate tooth profiles.

3DPrintCalcs

Pulley Calculator — Timing Belt Pulley Design

Design timing belt pulleys with correct tooth profile and pitch diameter.

Belt TypeGT2 (2mm pitch) is standard on almost all 3D printers

Tooth Count

16-20T typical for printer axes; 12T minimum for clean belt engagement

Belt Width

6mm is standard on printers; 9mm and 10mm also common

Bore Diameter

Shaft hole diameter — 5mm for NEMA 17 stepper shafts

Flange Height

1-1.5mm; should extend ~1mm above the tooth tips to keep the belt on

How We Calculate This

Pulley Dimension Formulas

Pitch diameter = (Tooth count x Belt pitch) / Pi
Outside diameter = Pitch diameter - 2 x PLD (pitch line differential)
Pulley width = Belt width + Belt clearance (default 2mm, ~1mm per side)
Flange diameter = Pitch diameter + 2 x Flange height

The pitch diameter is where the belt centreline (its tensile cord) sits on the pulley, and it sets the effective drive ratio between two pulleys. The outside diameter is the tooth-TIP diameter, which is smaller than the pitch diameter by twice the PLD — the distance from the belt pitch line down to the tooth bottom. For GT2 that offset is 0.254mm per side, so a 20-tooth GT2 pulley has a pitch diameter of 12.73mm but an outside diameter of 12.22mm (the RepRap-documented value), not 11.2mm. Cutting the OD too small makes the teeth shallow and the belt skips.

Frequently Asked Questions

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Last updated: February 2026

All calculations are estimates. Always verify settings with test prints before committing to final prints.