Gear Designer

brett_sutton

I've created a simple gear designer using onshape variables.

To generate a gear copy the gear parts studio into your own document using the onshape 'Paste Tab' feature.

Change the few variables and you will have a gear to your requirements.

Note: the model is defined in ISO millimeters.

The following variables can be modified:
Teeth - the number of teeth on the gear
OD - The outside diameter of the gear including the teeth
SD - The diameter of the whole for the shaft
GearDepth - Controls how thick the body of the gear will be. Default is 1mm

The gear is also filleted but I regard the filleting as experimental. Currently the fillet is set to 0.25 of the Gear Depth. Let me know how that works for you.
To change the fillet modify the variable TeethFillet

You may also want to play with the Pressure Angle (PA) (advanced use only)
Read this wikipedia article before you make any changes to the PA.

https://en.wikipedia.org/wiki/Pressure_angle

You can find the gear designer here:

https://cad.onshape.com/documents/b768ab9bbb5c47e881285b7e/w/abab17d3a48c4dc989fd19d6

I'm looking for collaborators to create a series of parts studios for different gear types.

The idea is that a user can simply copy the required part studio into your own document tweak a few variables and generate a gear of the required type.

I've have no experience in generating gears but if others can contribute I'm happy to manage the document.

Brett

viru

@brett_sutton , Very nice information. Thanks!

mechanical_cad

Veeery nice @brett_sutton  I will definitely try it and use it!

bryan_lagrange

Nice work. Would love to have you on the motorcycle public project. Maybe you can do some gearing for it.

bradley_smith

Thanks for posting!  I finally realized how to do variables now.  Here is my workspace for a spur gear design if anyone is interested.
https://cad.onshape.com/documents/a6b98357d6b34ffdae14eca3/w/106813dd8c094f0abf06a8b3/e/2df13d8e5e67471b90c4e5c9

batista_hardy

Nice share. Cylindrical gears, live exhibits will include high speed hobbing, power skiving, grinding and optimum processing of large gears both on dedicated gear machines and five axis machining centers.  There will also be a series of inspection and measurement technologies for all types of gears and sizes including single flank roll testing, analytical gear inspection and surface roughness measurement.

brett_sutton

I don't understand what you are saying here?

john_wolter

Nice job, @brett_sutton! Gear purists will want an involute profile for the gear teeth, so I decided to try to create one.  It's at https://cad.onshape.com/documents/cea3d55a37034144a48c7924/w/8e2c2f54e7d7471b835b5c46/e/f52db21ecfd847c19fa5c4b6

jakeramsley

john_wolter said:

Nice job, @brett_sutton! Gear purists will want an involute profile for the gear teeth, so I decided to try to create one.  It's at https://cad.onshape.com/documents/cea3d55a37034144a48c7924/w/8e2c2f54e7d7471b835b5c46/e/f52db21ecfd847c19fa5c4b6

Why not fit a spline to those points rather than a bunch of lines?  Slightly better approximation, no?

edit:
Here's me modifying your solution to be used with splines.
https://cad.onshape.com/documents/c9a5ab9cc17f4a71b44f9828/w/fe9439076f8347d981a9c624/e/f8117c468d9249649a3ec575

john_wolter

jakeramsley said:

Why not fit a spline to those points rather than a bunch of lines?  Slightly better approximation, no?

Being pretty new to Onshape, I hadn't figured out how to get around the inability for the circular pattern tool in sketch to duplicate splines.  Thanks for showing the way!

PeteYodis

I am following along on this one.  It has my attention because of my past experiences and being involved in gear design and manufacture.  We did all shaper cutting - no hobbing.  Neat discussion.

True involute curves are pretty tricky things (the actions of involutes on involutes in gearboxes of varying materials is even more fun!).  Splines can come pretty close to approximating them, but sometimes not enough to satisfy some of the hardcore purists.  It's a matter of intent and what you are looking to get out of it. I'd be curious to hear more about peoples thoughts on this one.

PeteYodis

Sorry...this one is just translated, but it's close to the manufactured geometry.

https://cad.onshape.com/documents/d7179ec729b44594af76f7d1/w/b60cfba928314dd5a1fb4415/e/5998a3ab47d4420d85a0cfe5

dennis_20

@PeteYodis If the points are calculated accurately and if there are a good number of them and if they extend at least two points beyond the tooth boundaries then a normal spline is fine (so long as there are no deviation controls on the spline).  In SolidWorks I used a spreadsheet (Design Table) to calculate 19 points for the smooth spline.  I trusted this over the involute curve function that SWX has, partly because I don't like how it stays blue when it should be fully constrained.  The results were excellent for the metal prototyping I had done with the files.  Also, the spreadsheet allowed me to use this as a generic file and I only had to change DP, N, PA and a few other factors to easily make another gear.

A lot of times gear teeth are like screw threads - you don't need accurate geometry, just the accurate information for them to be manufactured.  However, with more and more items going to 3D printers the simplified geometry that has been used is no longer adequate so we need the accurate 3D geometry.  If Onshape were to develop an involute function for this purpose I'd suggest they do a better job than SWX did.  I'd also like to see a good set of generic parametric gear files be made by Onshape and made public.  Spur and helical in pinion, ring, and rack forms would be a good start.  They should be available in inch and metric versions.  Bevel, spiral bevel, worm, etc. should follow.

By the way, congrats on your position with Onshape!

PeteYodis

A lot of times gear teeth are like screw threads - you don't need accurate geometry, just the accurate information for them to be manufactured.  However, with more and more items going to 3D printers the simplified geometry that has been used is no longer adequate so we need the accurate 3D geometry.  

@dennis_20 You said it better than me. Depends on your intent. Here is some back discussion... https://forum.solidworks.com/thread/14104

 Thanks, by the way!

brett_sutton

OK, so that started a discussion.

I'm actually a complete novice with CAD and particularly gears and so wanted to create a resource for myself and others.

After posting the original designer I found a number of problems with the designer (including a ugly limitation with  onshape variables - which I believe is about to be fixed).

I also intended using this forum to document the designer but alas it appears that you can't actually update a post after its being commented on.

In short I'm completely re-doing the designer and looking for the best place to document it. At this point thingiverse is a likely candidate. Its just a shame that onshape doesn't provide a better way to document designs in the same way thingiverse does. I know onshapes core message is CAD but think what it would be like if CAD designers had ready to hand libraries, contributed by the community in the thousands. Onshape would become the go-to CAD system not just because it was the best CAD system but also because it had the biggest library of components that were well documented.

But I digress.  Once I've re done the design and got some documentation up I will have a more detailed look at some of the above posts and talk to some of you about including designer features that produce a more accurate model and for a greater range of gear types.  And yes my intention is for designer should be suitable for use with 3D printer (this is what I'm using it for).

PeteYodis

@brett_sutton Thanks for your work in this.  The better you can make it, the more the community can benefit.  This discussion is good.  Let's keep it going!

You could always place a tab in the document to document your document   The first tab in the document shows first to the user, so it might be a good place for your help or documentation.

bradley_smith

@jakeramsley 
I used the spline tool after I used constraints on line geometry to create the points for the involute curve.  I had to break it into two sketches: the first sketch had the line geometry and dimensions, the second sketch created the spline curve.  I tried doing all this in one sketch but the drawing would have issues regenerating the sketches.  
https://cad.onshape.com/documents/a6b98357d6b34ffdae14eca3/w/106813dd8c094f0abf06a8b3/e/2df13d8e5e67471b90c4e5c9

brian_carroll

Hey everyone, im pretty new to Onshape  but ive already learned a TON. I am using this gear designer but Im unable to change the number or teeth? I can change the variable but the number of teeth on the gear never change although the OD does. i keep ending up with strange looking 20 teeth gears. does anyone know what i am doing wrong?

Jake_Rosenfeld

Brian,

Can you post a link to the document you are making?  Lots of people will be happy to help you debug

angus_mclean

Same Problem. https://cad.onshape.com/documents/58e3da1063d6ac0f6a34537d/w/e0f8ea72555bf25f60da242d/e/59ba47a344c09a098174039a

Jake_Rosenfeld

@angus_mclean @brian_carroll The sketch in that Part Studio is not fully constrained and inherently unstable.  I would suggest using the "Spur Gear" custom feature instead:

https://cad.onshape.com/documents/5742c8cde4b06c68b362d748/v/c65839fc6078faeb4d2aece1/e/5e653835ca09dd3451bd9e3b

In case you have never used a custom feature, here is a page highlighting lots of Onshape highlighted custom features.  Scroll down to the "Start using Custom Features" video to learn how to use them:

https://www.onshape.com/featurescript

brett_sutton

I created this document just before feature script came out and then abandoned it as featire script is the right way of doing this.
So yes use the spur gear script.

janos_horvath

Very nice, thank you! I copied it. I found out that somehow when I change the parameters, the model collapses. So I made the circular pattern as a separate feature. This way it works nicely! Thanks again!

Bests,
Jani 

NeilCooke

@janos_horvath I believe the correct solution is to use the custom spur gear feature here https://www.onshape.com/featurescript 

janos_horvath

NeilCooke said:

@janos_horvath I believe the correct solution is to use the custom spur gear feature here https://www.onshape.com/featurescript 

Hi Neil,

cool, thanks!

garaza_odmatjaza

Hi!

I'm really glad I found the gear designer. Thanks! But I confronted a problem. As seen from the picture I need to twist the teeth of the gear. Unfortunately I have no idea how to do that. I tried Transform tool, but without any satisfactory results. Any hint or help will be much appriciated! Cheers!

Jake_Rosenfeld

@garaza_odmatjaza

How about this?
https://cad.onshape.com/documents/867823ae9e51850ebfc68070/w/f38fee0f073fe0c9375c6144/e/58de92769f6dbd77f08d3dbc

I created a gear with the custom feature, then put 1/64th of a helix on the center bore.  I then swept the face of the gear over the helix to create a gear with a twist. Finally, I deleted the original gear.

After all of this you could design that "+" shaped axis and use an extrude remove to cut it from the gear.

garaza_odmatjaza

Amazing, I'll try this. Thanks!

burt_harris891

Nice try.   My first experiment was to increase the number of teeth slightly.   Unfortunately that left a gap in the teeth.

It has been my observation that sketches alone have serious limitations when it comes to parameterized designs, but that this can usually be overcome using a combination of several sketches and feature repetition at a higher level than the sketch.   So for example, you might make a hub and tooth sketches, extrude them as separate parts (don't combine them yet.)   Then use a parameter-driven duplication of the tooth part, and finally use a boolean union operation.