# How to sweep a profile along two rotation axes? (how to model globoid worm gear)

I'm new to blender and I'm looking for some help of modeling a globoid worm gear. Here's a website that explains what globoid worm gear is.

There's this video that demonstrates modeling a globoid worm gear, and it's method is calculating the parametric equation of each tooth profile and generates the worm directly. However, I find this "adding material" method against the natural sense of worm making process ("removing material"), and that' where my question came along.

What I wish to achieve is modeling the globoid worm by removing material of a hourglass-like cylinder object and here's by ideal steps

1. generate a hourglass shape
2. construct a tooth profile
3. rotate and sweep the tooth profile with respect to two axes and get the tooth body.
4. use boolean operation to remove the tooth body on cylinder to get the globoid worm.

Here's a simple sketch I draw that I hope to convey my idea precisely.

The part I'm struggling with is the 3. part because I cannot find the suitable function to sweep a profile along two rotating axes at the same time. As you can see in my sketch below, the first axis is around the center line of the hourglass and the second axis is around the gear.

THANKS!

That can be a "screw" and a "simple deform" modifiers:

Make a profile (bottom left below).

Set the external part into a vertex group.

Add a screw modifier (use 'calculate order' to set the orientation of the faces correctly).

Add a simple deform modifier. Stretch mode and centered on an empty placed at the center of the screw. Use Z axis to deform around it and the vertex group to be deformed (so only the external part).

Then tune the modifier factor (or scale the empty) so that it corresponds to the wanted circle.

• Thanks for the help. However, this is not the globoid worm I'm looking for because the tooth surface of the worm doesn't match with the gear Commented Dec 11, 2020 at 22:18

I'm no Blender wizard, yet, and I haven't found a native/vanilla tool to get your desired result, but I did see this addon pop-up a few days ago, which might do exactly what you want. Radial Array Tool Addon

Let's hope someone with a bit more experience in Blender shows up in the comments and shows us how to do it without 3rd party addons!

• Thanks for the suggestion! I'll check out this addon and see if it works Commented Dec 11, 2020 at 22:19