problem with maximum tooth thickness suggested by AGMA 2002? 2

[sabaa]

Hi everybody!
I have a problem with maximum tooth thickness suggested by AGMA 2002.
As a practical experience, I determined maximum tooth thickness of a pair of gear using that standard. Unexpectedly, after fabrication, many of gear meshing had interference and didn't rotate properly. However, the gear deviations were within the range of considered AGMA quality number, and there was no special error regarding center distance or axes alignment in the housing.
Then we reduced the maximum tooth thicknesses suggested by the standard manually and fabricated a new set of gears again. The interference removed in this case.
I think a type of error in root fillet had made a top-to-root interference that does not violate the gear quality grade, and nor the standard formula! Is it possible? How do you think?
the specification of gear pair are:
module: m=1.5
number of teeth: Zp=32 (pinion), ZG=95 (Gear)
profile shift coefficient: xp=0, xG=0
Gear Qaulity: Q12-D (AGMA 2002)
Maximum tooth thickness of pinion: tp_max= 2.356
Minimum desired backlash: B_min=0
So Maximum tooth thickness of Gear will be calculated from Eq. (1) as: tG_max=p-B_min- tp_max=tp_max=2.356
“p” indicates “circular pitch” that equals pi*m.

 

[gearcutter]

What is the actual mounting/centre distance of the gears that showed interference?
Also, what are the root & tip diameters of those gears?
There should be a theoretical clearance of (0.25 x Module) on both gears, in this case a total of 0.75mm.
Tooth thickness has nothing to do with root/tip interference.

 

[tbuelna]

A Q12 quality gear is very accurate, but I'd think you'll still want a minimum backlash greater than zero. Backlash is usually produced by thinning the teeth.

 

[sabaa]

Thanks to gearcutter and tbuelna.
The other data of gears are
center distance: a=(Zp+Zg)*m/2=95.25(-0.01 to +0.01)
tip diameters: do_p=Zp*m+2*m=51(-.02 to -0.05) , do_p=145.5(-.02 to -0.05)
root diameter (in theory, not checked): df_p=Zp*m-2.5*m=44.25, df_G=138.75
So the theoretical clearance of (0.25 x Module) have been considered.

I am not sure about the type and reason of interference. but I guess an old shaper cutting tool had been used (little amount of wear on tool tip).

 

[gearcutter]

You have mostly given us the calculated dimensions.
What I was hoping for are the *actual* dimensions.
Incorrect mounting distance &/or incorrect profile/tooling are the most common causes of tip/root interference.

 

[tbuelna]

You should check that your root fillet transition does not extend beyond the form diameter, which could cause interference with the mating tooth tip corner. There is a formula for max root fillet radius in the AGMA spec for standard spur gears.

Applying a controlled dimension tooth tip corner radius that smoothly blends to the active profile or tip relief surface is usually good practice, especially if you are going through the effort of making Q12 quality gears.

 

[mfgenggear]

Sabaa

I agree with Gear Cutter & Terry. don't worry about the cutter. build the cutter to the gears that are needed.
like said figure out the the Involute forms or TIF required with the gears at mess at the center distance that is required in the gear box. it is important that the contact area of the involute for both gears. and the radius and root diameter do not interfere with the mating parts. the cutter can be designed to cut the correct root diameter, root radius, and circular tooth thickness. and may even require gear grinding or honing.