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Gear Designer
brett_sutton
Member Posts: 42 ✭✭✭
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
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
6
Comments
Twitter: @BryanLAGdesign
https://cad.onshape.com/documents/a6b98357d6b34ffdae14eca3/w/106813dd8c094f0abf06a8b3/e/2df13d8e5e67471b90c4e5c9
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
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.
https://cad.onshape.com/documents/d7179ec729b44594af76f7d1/w/b60cfba928314dd5a1fb4415/e/5998a3ab47d4420d85a0cfe5
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!
Thanks, by the way!
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).
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.
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
Can you post a link to the document you are making? Lots of people will be happy to help you debug
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
So yes use the spur gear script.
Bests,
Jani
cool, thanks!
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!
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.
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.