pic: Team 148 - 2011 - Raptor

[Tristan Lall]

Originally Posted by JVN

There are lots of ways to do this. Some of my favs:

1. Pull out your handy Machinist's Handbook and sketch the tooth profile by hand.

2. Buy one of those gear profile generation programs and get it to spit it out for you.

3. Download the gear from somewhere online. bostongear.com has all their gears available online.

For this year's robot we used option 3. I downloaded the gear I wanted from Boston gear, then traced over the tooth in Solidworks (eliminating splines with simple arcs, so it would import cleaner into our laser cutter's NC program). I grabbed this sketch, dropped it into a new sheetmetal part and away we went...

-John

A few more options:

1. It's surprisingly easy to generate a real involute using equations; this and this explain how to do it in Pro/E (but any CAD software ought to be able to do the same).
2. If you can make do with an approximation instead, either follow the second method in the link above, or get GearGen (I think it's shareware*) from here or here. (It's a DOS program, so the interface might be a little unfamiliar nowadays....) This makes a sort of segmented polyline when exporting, with arcs that (as near as I can determine) are approximate. But thanks to modern, fast computers, you can create an arbitrarily large gear and scale it down to whatever degree of precision you need—so this isn't a problem so long as your CAM software won't choke on the geometry. (Note that all of those facets will make 3-D CAD really slow to regenerate; use the equation in that case, or just approximate it for visual purposes.)

*Does anyone even use that term anymore?