MKCAD - Configurable Timing Pulleys

I created a configurable 3mm GT2 timing pulley for MKCAD that lets you choose the number of teeth, bore, width, and flanges. It was designed under the assumption that the pulleys would be 3D printed. It’s available in MKCAD - Pulleys in Onshape. Here are a few examples of what you can generate:

Generic .5" hex pulley

VEXpro spline pulley

Super tiny 12T pulley

Stupid Flanges


Is the ID precisely .5"? We’ve gotten in the habit of oversizing our ID by as much as .05" to make sure it fits. More than once we’ve shown up to competition with a mission-critical print only to find out it didn’t fit.

You can define the diameter of the circular and hex bores to be whatever you like.

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Oh I guess I can’t read. Thank you!!

Here’s an example of how it’s configured:

I found this great spreadsheet and it allowed me to update 3mm GT2 model to be more accurate, and to create a 5mm HTD model.

Both are updated in MKCAD - Pulleys


Looks awesome! Great work Ty!!

This actually looks so cool! No longer do I have to take the face of the Vex pulley and create the pulley!

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Awesome work!

Have you printed any examples in each of the profiles? From my own experience doing generated HTD 3mm pulleys, they required some adjustments to the profile to get exactly the right fit.

I think that’d vary based on which printer you print with, as well as its settings and probably even how it’s feeling that day. With our ultimakers at the 319 shop, we haven’t needed to adjust the profile when printing profiles downloaded from sdp-si (which these are based off of). We have needed to play with the exact sizing of the bores, however, which is why I made them completely configurable here.

It should be noted that I haven’t tried to print the vexpro spline, and it isn’t tested because the motors don’t exist yet. I’ll update the design if it needs changes after our testing.

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Nice work, one little tiny fix, the HTD selection still displays as GT2 likely will cause my students some confusion. Thanks!

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Nice! I had made one a few months ago, but for htd 5mm, as well as one for sprockets. They aren’t configurations right now (uses variables) : (, but I plan to make them configurations soon.

Edit: I changed it to use configurations, as well as a few other options, such as hex bore (1/2 and 3/8), round bore, hole pattern, lighten, flanges, tolerance, and custom (nothing but the pulley, and the option for flanges and a round bore)

.05? not .005?

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Depends printer to printer, some are very accurate and some hold no tolerance

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Good catch. I’ve fixed the part’s name.

I added a configuration variable called Fit Adjustment that can be set anywhere from -0.05" to 0.05" (-0.04" to 0.05" on the GT2 pulley) and is defaulted to 0.00". Adjusting this value will allow you to tweak the shape of the grooves to fit the belt. Negative values will make the grooves deeper (and the pulley a bit smaller). Positive values will make the grooves shallower (and the pulley a bit bigger).

Printed a GT2 pulley on our Ultimaker 2 without making any size adjustments and it looks like it fits just fine.

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2 or 3 mm pitch? That looks closer to 3, but scale is weird.

GT2 3mm