topic Re: Are the spur gears involute? in Fusion Design, Validate & Document Forum

Are the spur gears involute?

nmakaroglouU36GX — Mon, 02 Oct 2023 08:22:41 GMT

Hello to all, my question is how can I check if the spur gears that I can create are involute? I am using the GF spur gear generator add-in. Thank you for any answers.

Re: Are the spur gears involute?

TheCADWhisperer — Mon, 02 Oct 2023 11:52:57 GMT

@nmakaroglouU36GX

What are your gear specs?

Can you File>Export your *.f3d file to your local drive and then Attach it here to a Reply?

You could lay out the involute curve yourself to verify the geometry...

Re: Are the spur gears involute?

nmakaroglouU36GX — Mon, 02 Oct 2023 13:27:54 GMT

My gear specs are Module 5mm for both gears, 21 and 42 teeth, 50mm gear height and pressure angle of 20 degrees. I have attached the file. Sorry for my ignorance, but how can I lay the involute curve to verify the Geometry?

Re: Are the spur gears involute?

MRWakefield — Mon, 02 Oct 2023 15:51:46 GMT

According to the checks I've just performed on the 21 tooth gear in your example they look pretty good to me (I didn't check the larger gear as I'm assuming it would be a similar result). I exported the small gear's (pinion) Sketch1 and opened it in Draftsight and compared it to geometry produced by two of my own generators that I've written in the past. Here's the result of overlaying them all:

The blue is your profile, the yellow is from my involute curve generator and there's also some white geometry from another one of my generators which you can't see because it's hidden behind the other geometry. As you can see they match just about perfectly.

If you don't want or know how to create the geometry yourself you can use one of the many gear geometry generators online. Just we aware that such generators often produce an approximated curve as it's often not required to have an accurate involute curve. Real gears are usually made on very specialised machinery and often these generators are only used for production of a drawing or to create a representative model etc.

More info:

https://khkgears.net/new/gear_knowledge/gear_technical_reference/involute_gear_profile.html

Hope this helps.

Re: Are the spur gears involute?

nmakaroglouU36GX — Mon, 02 Oct 2023 16:39:03 GMT

Thank you very much for your detailed response! Yes the bigger one was created from the same add-in as the smaller one, so they are both involute spur gears, that's really good news! I have tried using the gear generators from different websites but as you said they aren't very detailed and/or problematic when trying to import the file to a software (e.g. Ansys which I am using for my thesis). I am trying to create the spur gears on Inventor but they aren't involute from the beginning, so the fact that Fusion 360 creates the gears I need without many extra steps is very much appreciated.

Re: Are the spur gears involute?

etfrench — Mon, 02 Oct 2023 17:23:07 GMT

That's curious. How do you know spur gears in Inventor are not involute?

Re: Are the spur gears involute?

nmakaroglouU36GX — Mon, 02 Oct 2023 17:37:36 GMT

Well, I firstly found this video: https://www.youtube.com/watch?v=wGGhyY9NIww

But then I wanted to double check so I created this same question but in the Inventor Forum: (https://forums.autodesk.com/t5/inventor-forum/are-the-spur-gears-involute/m-p/12279116/highlight/true#M910120)

That is why I believe they aren't involute, unless I misunderstood.

Re: Are the spur gears involute?

etfrench — Mon, 02 Oct 2023 17:51:57 GMT

Yes, you have misunderstood😀 The initial design is simplified for display purposes only. The exported tooth shape is the precise involute shape.

Re: Are the spur gears involute?

nmakaroglouU36GX — Mon, 02 Oct 2023 18:08:19 GMT

Wait, before I misunderstand again 😅. What I am searching for is when I create the gears, they are involute ones and I can export the file to Ansys to continue. That way the process can be replicated by others with as few extra steps as possible.

For Ιnventor the gears I get after I create them are simplified and in order to get the involute ones I have to do the extra steps from the video and then export it, correct?

Now for Fusion 360, the gears I create are involute gears from the start with no extra steps involved, correct?

Re: Are the spur gears involute?

etfrench — Mon, 02 Oct 2023 18:11:03 GMT

Yes

Re: Are the spur gears involute?

nmakaroglouU36GX — Mon, 02 Oct 2023 18:23:12 GMT

Perfect! So, I will use the gears created from Fusion.

Thank you very much for your time and your help!