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Unread 30-06-2004, 12:59
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Re: Gears in Inventor

Quote:
Originally Posted by sanddrag
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.
There is a model of an involute spur gear on cbliss.com:
http://www.cbliss.com/inventor/Parts...olute 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.
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Unread 30-06-2004, 20:03
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Re: Gears in Inventor

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.

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Unread 30-06-2004, 20:12
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Re: Gears in Inventor

Quote:
Originally Posted by Cory
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
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Unread 30-06-2004, 20:28
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Re: Gears in Inventor

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."
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Unread 01-07-2004, 11:48
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Re: Gears in Inventor

Quote:
Originally Posted by Clark Gilbert
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

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.
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Unread 01-07-2004, 23:32
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mech-q

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.
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