# Gear Design - Teeth Fit [closed]

I am working on designing a set of gears for 3D printing. I have not done any gear design before - how should I improve the design to prevent gear slipping?

• By "gear slippage" are you referring to excessive backlash or teeth slipping from one tooth to the next?? Sep 29 '17 at 19:47
• Primarily teeth slipping, though I would like to minimize backlash if possible. Sep 29 '17 at 20:06
• Your question is too broad, be more specific. Sep 30 '17 at 13:32

Teeth on gears generally will not slip if your pitch and tooth profiles match properly, since the teeth would have to break off to slip. Minimizing backlash can be done by tight tolerance control.

Looking at the images you have it appears as though you've designed the teeth more freeform and by eye, rather than calculating the profiles (I could be wrong though). If you're working through CAD to completely design the gears, you can write a macro that will generate profiles based on any tooth profile.

The general process for this is create your drive gear however you like. Then create an idler gear with no tooth profile at all overlapping the drive gear. Subtract the interferance between the two parts from the idler, then rotate each based on your prescribed gear ratio. (how much you rotate each will depend on how accurate you need you profile to be). Repeat until you've completed one full rotation of whichever gear you're trying to make. - basic youtube video of how it works here https://www.youtube.com/watch?v=9MycFQKnZkA

Or you can go the pure math method of designing the gear tooth profile completely through mathematics. Which is much more complicated.

Easier still, use off the shelf gears!

• It's very cool to see that someone has inserted a link from a channel that I've been tracking for a long time. Sep 30 '17 at 0:50
• Am i also right to comment that the teeth will slip if it has parabolic/curved profile? Is the contact between the gears significantly reduced due to its shape? Sep 30 '17 at 1:54
• @JemEripol I'm not totally sure what you mean by parabolic/curved profile. Depending on the size of the gear and pitch circle a true parabolic curve may or may not give you constant contact between teeth. But if the pitch circles between two mating gears intersect at the point of contact your gears won't slip unless you break a tooth off or the axis of the gears moves. Sep 30 '17 at 13:41
• I'm not sure if I answered your question or not. To be clear though, teeth on gears don't slip if the gears are made properly. That's one of the primary reasons to use them over a belt-pulley system. For teeth to slip the teeth would have to break off, be sized incorrectly to allow them to flex out of the way under loading (EXTREMELY mis sized gears) or, the two axes have enough play in them the the teeth no longer touch, or the tooth profiles don't mesh properly. All of those are easy to tell just by looking at the gears. Oct 1 '17 at 2:06

In gear design, the most used tooth profile is the involute profile. I am not sure what do you mean by avoiding slipping(Velocity of sliding) because for two gears to move, there will definitely be slip as they have to maintain the contact while they transmit motion(except at the pitch point).

Since you are using a 3D printer, please use the cycloidal profile as a tooth profile which rolls without slipping. The reason people don't use it is the difficulty in mass manufacturing.(Although they are used in clocks and watches)