Simple 3D Gear design software recommendation

[Leadhead]

Could anyone recommend a "Simple 3D Gear design software" please. Would like to generate and machine a couple of bevel gears for 90deg transmission. Not for a strenuous operation, just a mechanical lifter. Looked at Gearotic but that is way over the top. Hopefully open source programme is available.
Any advise appreciated.

[m_c]

There's nothing simple about gear design, especially once you get more complicated than a basic spur gear.

Best option would be to find somebody with a copy of gearotic who's willing to produce the code you need, or just buy a couple ready made gears.

[Leadhead]

m-c - Not completely unfamiliar with relatively simple gear design. Just do not want to revise and re-teach myself at this time.
But would like to experiment with a couple of things. This would totally frustrate any third party!
The bevel gear add-in for F360 produces what I want but it is a trade off between graphic presentation and real gear form. But studying this to see if it will suffice in this instance. I need to cut with a vertical axis and radial toolpath, so will not be generically correct in any case. But I will will cut a pair and see. Maybe try printing the same in nylon on a metal core.

[komatias]

m-c - Not completely unfamiliar with relatively simple gear design. Just do not want to revise and re-teach myself at this time.
But would like to experiment with a couple of things. This would totally frustrate any third party!
The bevel gear add-in for F360 produces what I want but it is a trade off between graphic presentation and real gear form. But studying this to see if it will suffice in this instance. I need to cut with a vertical axis and radial toolpath, so will not be generically correct in any case. But I will will cut a pair and see. Maybe try printing the same in nylon on a metal core.

Could you not just buy the gears off the shelf? They are not that expensive from the likes of beltingonline?

[Leadhead]

George - That`s not the spirit of it?? - Jigsaw mentality - more fun to do it, than what you end up with.

[EddyCurrent]

Any decent CAD software has a polar array function, meaning you only need draw one tooth. also it should be possible to get a tooth cross section from somewhere (I haven't looked but feel confident)

[magicniner]

The bevel gear add-in for F360 produces what I want but it is a trade off between graphic presentation and real gear form.

That is stunningly poor!
I'm Shocked!

[MartinS]

The bevel gear add-in for F360 produces what I want but it is a trade off between graphic presentation and real gear form.

I also have often looked at the "pretty pictures" that these cad systems have produced and wondered just what the shape of the tooth is based on. Is it a true involute created from first principles, or is it part of an arc of a circle which just "looks right".

Also, I cannot figure out how you are going to machine a bevel gear with just three axes. (I will muse on it.........).

A previous post mentioned taking the cross section of a tooth and extending it forwards and back. Beware of this approach as the tooth surface shape changes along it's length.



At the small end of the gear the involute tooth surface is generated from a small base circle diameter, whilst at the large end a larger BCD is used. You can see from the pic above that from the root outwards, the radius of curvature of the tooth surface is constantly changing up to the tooth tip. But this point radius of curvature changes from small end to large end also.

With a spur gear the involute shape can be machined onto a cutter (e.g. disk milling cutter to end mill) and the gear form cut with indexing from tooth to tooth. This approach won't work with a bevel.


Thought!
How good is CAD and/or CAM at "topological milling"?

If the gear is mounted with the PCD on the XY plane so it can be indexed per tooth, can the tooth space be roughed out and then finished with a ball ended cutter? It could be somewhat rough if at all possible.


Another way is



Mount the gear as above but via a 4th axis on an inclined plane. Then the tooth can be generated with a straight sided cutter in successive passes whilst rotating the gear. The yellow in the pic is a rack relative to the two rotating gears. Therefore each tooth flank is conjugate to a straight sided cutter (e.g. 20 deg included angle end mill). Therefore this principal can be used to cut the tooth surface!

Hope this helps


PS

You are wanting to make a straight bevel not a spiral?

Martin

[m_c]

Martin, thanks for clarifying the BCD/scaling issue.

From what I gather, Leadhead is planning on machining the gear, by mounting the blank flat on the machine I.e. so the gear axis and spindle are in the same plane.

If you've not seen it before, you might want to have a play with Gearotic (www.gearotic.com). It's written by Art (the original man behind Mach), and allows you to design/simulate all sorts of weird mechanisms. It originally started as just a gear designer, but has grown. The only limitation without a license, is you can't export different file formats, but if you do license it, it can produce various 3D file formats, or even generate the required G-code using either 3 or 4 axis.