Gears

Every place I've worked that actually manufactured their own gears, has had programs and/or internal CAD modules that helped in the geometrical construction of them. I see gears all the time that, once you get into the grit of the calculations, aren't geometrically correct, though they do look nice.

On a side note... I've worked in drivetrain at two companies now, one as a contractor, and almost all of that was done with simplified gear assemblies due to the system load.

As cmalco suggested, the method of making gears depends on the use.

If it is simply a gear which will be shown in a model, or rendering, they creating something that "looks right" and displays and loads fast should be the goal.

If the plan is to send the gear to a machine shop, or even a 3D printer, then more care needs to be taken.

I've used Camnetics a few times and am always impressed with the results: http://camnetics.com/

I've made a simple parametric spur gear, and even with the equations sometimes the geometry looks wrong.. It would be great to have something that is reliable and free !

I like to manually design gears and the method I use is to sketch a tooth-gap profile and then using a helix as a center curve you can cut out the gear teeth. It is not necessary to use an involute, it is much easier just to use a circle for the tooth flanks and play around with the sizes. You won't see a big difference! The same way I also designed bevel gears. In the next step I would like to try to design hypoid gears which is pretty challenging :)

Hi,

I would like to point to a model I posted back on December 5th, 2016:

Grabcad model

For modeling a TRUE Involute Helical Gear in Solidworks

So I think I have refined a model for an: “Involute Helical Gear Generator - xxxxxxxxxxx.SLDPRT” Or, as attached and have set Global Variables for: CW Rotation, 20 Teeth, 30 Deg Helix Angle, 20 Deg Pressure Angle “Involute Helical Gear Generator - CW 20T 30 Deg 20 PA.SLDPRT” "DiametralPitch"=.878...

This was my attempt to cerate an "Involute Helical Gear Generator" in Solidworks

I would appreciate any feed back from the "gear heads" out there if my approach is correct.

Thanks

The main 3D modelling software I use these days is Alibre Design, a low cost but very feature rich and easy to learn an use product. This software in some areas even out performs many of its much more expensive rivals. In the past, I generated gears using an old version of Solid Edge ( V12 ), as it had an excellent tool for this. I could export gear as a stp file or as my Alibre Design software can open Soild Edge files directly I could just open them. The only problem is they are just dumb solids. I joined Alibre Design forum, should have done this years ago, and discovered a free add on python scripting tool. This tool has built in functions for generating gear profiles, though I am uncertain of how close to a true involute tooth is produced. But as I am not using this to directly machine gears it does not matter. I have gears made by a specialist gear manufacturer with good gear making machines and skilled men operation them, i just supply a specification. Here is a link to Alibre Design Group on GrabCad https://grabcad.com/groups/alibre-design-users/discussions/useful-tricks-and-idears-to-get-the-most-out-of-our-software. I have a post on this forum as regards to generating gears with this tool. As i am new to this tool I have, at this stage, developed a script to generate plain spur gears from required module and number of teeth. I am also working on scripts to generate helical and bevel gears

There is an add-on program for solidworks and Inventor. Its called geartrax by camnetics link http://camnetics.com/

The GearTrax page says "very affordable" (which turns out to be USD 1295). I would love to use something like this, but it needs to be free of charge. My model is intended for the hobbyist and for 3D printing.

In addition, it seems to use a licensing dongle:

>The hasp (dongle) may be installed on any computer (it does not need to be a server) on the Network.

I work for a company that manufactures gears, we use specific software to generate the profiles and data sheets for manufacturing. This software allows me to export a DXF, which I can then use to create an accurate 3D representaion if required.

Hey guys,

here are some new generated gears for you! All drawn in Catia.

Grabcad model

Stepped Planet Assembly

A stepped planet gearbox is a special epicyclic gearbox which allows to achieve quite high ratios, to handle high speed input shaft rotation und has a high efficience though, as there are less tooth contacts than in two sequential planetary stages. The shown model has a total ratio of i_tot = 12,...

Hi,

long time no post in the group. In my spare time I tried some "manual" design of involute spur gears. Therefore all starts with the excel calculation of an involute which can be imported into the CAD system.

With the involute in the CAD you're now able to design different tooth flanks and define the tooth geometry.

First I generated a tooth gap (negartive tooth imprint) and made the circle pattern. Finally you can cut this geometry from the gear's basic body.

Since you have the involute it is possible to play around with profile shift, which just means to use different areas of the involute.

Here is a positive profile shift x=0,5:

Here is a negative profile shift x=-0,5:

And here the overview to show the differences:

Finally I tried to design some tooth flank crowning which is actually not that difficult. I hope it is visible in the pictures (look at the tooth tip). Tooth profile crowning is not that easy as it deviates from the calculated involute so you need a complete new calculation sheet.

I hope you liked it ;-)

I use "e-assistant", which has a series of CAD plugins - these generate an accurate 3d ISO/DIN profile in your CAD software, from whatever parameters you decide on. Eg you can change the tooth form, profile shift etc then it generates the gear from in 3d.

Licence is hourly so it's affordable for small start-ups :-)

https://www.eassistant.eu/en/cad-plugins.html

Now added the process of hobbing a helical gear, satisfying to see =)

Grabcad model

Gear Hobbing of Helical Gear

Continuing my manufacturing series here is the hobbing process to cut a helical gear. This process was ivented by Hermann Pfauter who is known to be one of the pioneers for gear manufacturing. For the design of the hobbing tool I want to thank https://grabcad.com/constantin.stancescu for his amaz...

I hope you like!

I have two parametric NX files that I use to generate gears. For spur gears I use NX11 Gear Template, it's pretty accurate. For bevel gears I use Parametric Bevel gear Set for NX. Not quite as accurate, more of a "reasonable facsimile" suitable for low speed, low precision gear sets.

Check my 3d samples of different gear here on grabcad. All the tooth surfaces are generated in Exel by VBA macros from spiralbevel.com

Excel make the tooth surface in iges. You import iges into your gear blank to cut teeth. Very accurate - specificly for CNC gear manufacturing