Timing belt

A closed toothed belt, sized to the two pulleys it runs on.

A closed toothed belt, built as one watertight loop rather than a chain of parts, and sized so it actually meshes with the pulley generator at the same profile and tooth counts.

Pick the profile by name. Pitch alone does not identify a belt: GT2-3M and HTD-3M share a 3 mm pitch and are not interchangeable, because their teeth are different heights. The name selects the whole row — pitch, tooth height and belt thickness together.

Tooth count is the primary input, and that is deliberate. A belt is sold by its tooth count, and pitch length is simply teeth × pitch — so the loop closes exactly, every time, with no rounding and no seam where the pattern meets itself. The centre distance is derived from it: given the belt and the two pulleys, there is exactly one distance at which the belt is tight, and the read-out tells you what it is. If you need the pulleys further apart, ask for more teeth.

Different pulley sizes are handled properly — the straight runs tilt, the wraps become unequal, and the length relation accounts for both.

Widths. Each profile is sold in a few standard widths: GT2-2M in 3, 6 and 9 mm; GT2-3M and HTD-3M in 6, 9 and 15 mm; GT2-5M and HTD-5M in 9, 15 and 25 mm. Nothing stops you printing another width, but those are the ones a stock pulley is cut for.

Read the Belt back row before printing. It is the continuous section every tooth hangs off, and it is the thinnest thing in the part — on GT2-2M it is thinner than the tooth it carries. Whether that prints is a question about *your* printer, so the row compares it against the minimum wall set in the 3D Print panel: at a 0.2 mm nozzle a GT2-2M back is comfortable, at 0.8 mm it is not.

Print it in something flexible. A timing belt has to bend around the pulleys; in PLA it will crack on the first revolution. TPU is the usual answer.

The tooth is a square bump rather than the true curvilinear form, because that is the shape the pulley generator cuts — matching the pulley you can print beats matching a catalogue drawing it does not follow.

1. Open the Generate panel from the left sidebar and choose Timing belt (under Gears & drives).
2. The belt drops in as one closed loop. The parameters open in the Properties panel, where you set them.
3. Pick the belt profile by name — GT2-2M, GT2-3M, GT2-5M, HTD-3M or HTD-5M.
4. Set the belt tooth count and width, then the tooth counts of the two pulleys it wraps.
5. Read the Centre distance row — that is where the pulleys have to sit — and the Belt back row before you print.