Inventor What Does Unit Correction Calculate? Export Bevel & Helical Gears?

[Anonymous]

Hi I designed a couple of gears in Inventor and there's a feature called Unit correction and I have no idea what does it do. Can you please tell me what does the unit correction feature do, what does it calculate and how to use it?  Also can somebody tell me how to export bevel gears and helical gears?

kelly.young has edited your subject line for clarity: Gears

[ToddHarris7556]

I'm no expert with the Gear generator, but I do know that unit correction has to do with profile shifting. From what I understand, it only applies when one gear gets small (<17 teeth?). When this happens, the tooth profile would begin to show undercut, which is weak. In order to avoid the undercut, the profile gets shifted (corrected) toward the larger gear. 

That's the extent of my understanding - when I get to that level, I call my power transmission guru 🙂

Re: bevel and helical gears.... I've noticed the bevel gear generator in Inventor, but not used it. I'm not aware that there's a helical generator. 

[jhackney1972]

I will try and deal with your question about "export".  You did not specify what you meant by export.  It you are going to export the gear so someone can manufacture it then the model that Inventor generates will not be enough to cut the gears.  The tooth form that Inventor generates for their gear representation is not exactly correct.  They give you a method of exporting the correct tooth form for spur gears but, as far as I know,  not for bevel gears.  I show this is the screencast. 

If you just want to export a gear "representation" as a file type, I show that process in the screencast.  I only show a helical spur gear but the same is true for a bevel gear.

[Pavel_Holecek · Accepted solution]

Hello,

Yes, I can confirm that exact tooth shape is available for Spur Gear generator only. Other Gear generators have simplified tooth shape.

Regards

[Pavel_Holecek]

Hello @Anonymous,

could you send me a screen capture of your unit correction failure. The sum of unit correction should equal to 0.

Thanks

[plecorp]

Profile shift is also carried out sometimes to balance the gears strength characteristics between contact and bending or contact between mating gears.

In addition, profile shift can be adopted to correct for center distance so as to ensure correct meshing occurs

Given this is an AGMA calculation Autodesk should stick to the correct terminology. See example below how the center distance is corrected.

[craig.ballou]

The unit correction should really be called profile shift coefficient. It is the profile shift divided by the Module. (or multiplied by the DP) If you input a standard Module with zero unit correction there is a value calculated called df. This is the root diameter. If you change the the unit correction, it will change the the root diameter. What ever the difference is between the standard df and the new df is the profile shift. Take that value and divide by two to get the shift per side and then divide by the Module and it will equal the unit correction.