Inventor 2021 Pulley Generator

I copied the MKCad 5mm HTD and 3mm GT2 pulley generators in Inventor 2021. The controls are all in one form, with options for the profile, tooth count, tooth width, flange, flange width/height, flange chamfer, bore style (circular, hex, none), and bore size.

Also included are belt generators for both 5mm HTD and 3mm GT2. The controls for these are also in a form, with options for both pulley sizes and belt width. It automatically calculates the exact center distance, and shows the teeth in mesh for each pulley.

Warnings for the belt generators:

  • The teeth in mesh function may not be 100% accurate, there’s probably off-by-one errors depending on what your configuration is.
  • If there are missing or extra teeth on the “corners,” just edit the values in the “Missing or Extra Teeth” form. I couldn’t figure out how to get rid of the miscounts in every case.
  • I don’t guarantee that the result will be accurate if you input an invalid configuration (200 tooth pulley with 100 tooth belt, etc)

Inventor 2021 Belt and Pulley Generators.zip (1.7 MB)

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Huh, neat!

It’s a nice file that shows how to parametrically create something that looks like a timing pulley. Unfortunately, the tooth shape is not correct.

By the tooth profile being “incorrect,” I’m going to assume that you mean the tooth profile is not an exact inverse of the official tooth profile given by belt manufacturers.

This is intentional.

When making a pulley, if you copy the tooth profile exactly, the teeth on the belt will have a hard(er) time slipping into and out of the grooves on the pulley.

This tooth profile, being the same one used by the MKCad generator, has been tested by many teams to be effective, especially when 3d printed.

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No. What I’m saying is the tooth profile is not the correct profile for a GT2-3mm pulley. It may work with the loose tolerances of a 3d printer, but it is not correct. The profile in your file has only one arc plus the fillets at the top of the teeth. The actual profile should have several different arcs. The depth of the valley is also over .1 mm too shallow.


The purple line is the profile from your file, the light blue profile was created in Gearotic. The Gearotic profile is correct, but is made up of many short line segments, so it can take a long time to mill.

p.s. This topic shows the correct design for GT2-3mm: Timing Pulley Design Tutorial

So it turns out that there actually was a bug in the GT2 generator where I used the pitch diameter of the pulley as the outer diameter, that’s been fixed in the file below. That addresses my generator being shorter than the official profile.

As to the other differences: those are intentional. They make it easier to get the belt into and out of the pulley when the pulley is printed, and it has been shown to work fine by every team that has used the MKCad generator.

Pulley Generator v1.2.ipt.zip (301.4 KB)

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I’ve never had a problem putting belts on or off pulleys printed from the Gearotic files. I think anyone using this generator should be aware of the incorrect tooth profile and make their own decision on whether or not to use it. I know what my decision is.

I mean, if nothing else, people could probably just modify it to produce “proper” geometry, though we’re going to be sticking with the MKCad / 3d print optimized pulleys