Noise is not the same in both direction 1

[robindbois]

A couple of month ago I started a topic concerning a set of a small pinion and an internal gear assembles in parallel axis. I had to explore many setting in order to reduce noise. There is almost no load to transfert.

Choice was to use plastic internal gear so I made one in 6061 and another one in plastic. The other choice was to explore the helical type of gear set. I designed and ordered straight and helical gears in both plastic, stainless and 6061 to explore all possibilities.

I have in my hand all gears excepts the internal helical gears. I installed the straight set made of a stainless pinion (12 teeth 48 dp offset of 50%) and the internal gear (244 teeth, no offset) made of 6061 (I have one in plastic too).

The strange thing is that the noise is different if I move by hand the gears in one or the other direction. What can be the cause? Is it possible that the cutter do not do the same quality in both face of each teeth?

Robin

 

[diamondjim]

Robin,
The slip ratio is not that high,
anytime the gear od approaches near
the base diameter the ratio get high.
I have seen 14 and the gears seem to
mesh well in slow applications.
Just decrease the od of the gear by
a small amount and see how quickly this
ratio changes.
These are such small gears that you
could probably deburr by hand with
a diamond emery board to see if that is
the source of the noise. You might try
running it in at a slow rpm for an hour or
so and gradually increase the rpms.

 

[GearmanPE]

Assuming teeth in internal are shaper (Fellows) cut, it is quite possible to have better quality in one direction than the other.

Best analysis is by single flank testing, or analytical inspection.