Gears in Inventor

I am getting myself acquainted with Inventor 7 so that I can work on the Inventor submission next year. One thing that I don’t know how to create are gears. I have seen that many times, cylinders are used in place of gears, but I have seen fully-modeled gears, and I would like to know how to create them on my own. Any help is appreciated.

I would say check out www.cbliss.com and www.firstcadlibrary.com and take a look at some of the gears in both of those sites. Take one and download it and then “reverse engineer” it in inventor. I think you will prob learn alot by doing that and also you might find a few personal tricks by Ed Sparks at the FIRST cad library or by the content found at cbliss.com

Good Luck and keep us updated if you find any short cuts on creating gears.

You can make one tooth profile and then revolve it around in the sketch. Real gears have an involute curve on the tooth, but you can approximate it with an average radius. However, your best bet is getting ones someone else made, even though they probably don’t have involute curves either. It’s hard to make a drawing good enough to cut gears from (because of the involute) but the constant radius should be just fine for an inventor model.

another way to do this that i have found that works is to make a cylinder the size of the gear then create a new sketch on the surface perpendicular to the gear surface. Draw 1 tooth and do a circular pattern to the radius of the cylinder then extrude that away. Poof you have a gear.

http://www.chiefdelphi.com/forums/showthread.php?t=27622
This may be useful (it’s about cutting gears, but the CAD principles are the same).

Thank you all for your help. I don’t actually plan on using it to make my own gears, but I’m just a nut when it comes to precision and accuracy in anything like this I create. Again, thanks for all your help and I’ll get back to you on how it worked out.

Here are some gears for the downloading.

http://www.cbliss.com/inventor/Parts/PowerTransmission/

Martin Spur Gears 169 sizes
14.5 and 20 degree Pressure angle
http://www.cbliss.com/inventor/Parts/PowerTransmission/Martin Spur Gears.zip

I have downloaded the gears from the link above and they seemed to work great for me. All the gears in our transmission are from Martin. But I found this link after I had already created gears. Phil Dolan from Autodesk told me about the link, I also noticed Dez mentioned it.

The best thing you can do is find a spec sheet on the gears you need to create!

There is a model of an involute spur gear on cbliss.com:
http://www.cbliss.com/inventor/Parts/PowerTransmission/Involute Gear.zip

The creation of the involute curve is done via an embedded Excel spreadsheet, which by itself is worth looking at to see how it works.

Be aware that this generates a pretty massive file, especially for large #'s of teeth. Cybersonics used this model for the basis of some gears we used in our machine last season, but created toothless “dummies” for general CAD modelling and substituted the involute ones only where appearance made it worth the overhead.

Why even waste your time drawing them?

Sure, it’s a good skill to have, but when I was working on models of gearboxes and such, the last thing I wanted to do was take hours to draw gears, when there were accurate enough readily available models for my purposes.

Cory

Just if there is a gear that I can’t find readily available, I’d like to be able to at least know how to model it myself. This is partially a “to see if I can do it” thing

Heck with drawing gears all together. I guess you could bother with it when working on models for animation in 3d Studio Max or something. One thing I picked up from reading countless CAD prints from Andy Baker was that his gears were always just cylinders. This keeps unnecessary lines off your CAD prints and makes orthographic views and section views more visually pleasing. If you are making a 3d model to show off it will also be easier on your computer since it wont have to process all the teeth and faces. Even when making individual prints of just the gear keep the teeth off and make a note saying something like “Altered purchased gear.”

This works for standard gears. But when you need say a 12 pitch 30 deg pressure angle 15 tooth gear, then you’re kind of out of luck. You really do need to model the gear, teeth and all. Especially of you’re using a rapid prototyping machine to make the real one :wink:

Fortunately this is pretty rare, but it does happen. One simplification I have used is to make a cylinder with diameter= Pitch Diameter-Dedendum and then make a trapezoid on the edge that has a height of addendum+dedendum and whose top is an arc covering the angle 360/(3*N). The bottom is twice that. This gives a pretty good looking gear without it getting huge in terms of file size. It also makes it easy to check and make sure you don’t have problems with center distances etc. Of course you don’t have to do the whole gear for that, just the section making contact.

i use mech-q plug-ins for AutoCad. they offer a free dowload that allows you to draw involute gears of any size, pitch, etc. you can then import the 2d drawing into inventor and do a simple extrusion. they also have plug-ins for sprockets. all-in-all it goes really quickly and you don’t need to know anything about autocad to use it effectively.