Noise from gear Reducer 3

[sfsurfer]

Wondering why I have three of four Tigear2 right angle reducers driving conveyor that are much louder than one of them. One is about 72db the other three are 85 db. They are all new within 1 month old and are all driving the same type of conveyor.

 

[MikeHalloran]

Measure also the relative load on the conveyors, e.g. by measuring motor currents.

Look for differences in couplings and is mounting arrangements and availability of acoustic radiating surfaces.

Check the lubricant levels in the gearboxes.



Mike Halloran
Pembroke Pines, FL, USA

 

[BrianE22]

Alignment of the reducer shafts (to motor and to load) would be my first guess.

 

[sfsurfer]

It's more like a louder hum than normal. The louder reducers just hum much louder. The Tigear2 boxes are sealed so no way to check lubricant level. shaft alignment looks really good. Was more hoping someone had an experience where the manufacturer didn't adequately fill the box or possible tolerance issue with the manufacture of the gears.

Or possibly the quiet box is the aberration and the noisy boxes are the norm.

 

[MikeHalloran]

Reducers don't hum; motors do.

Look for an asymmetry in loads, as reflected in motor currents or motor speeds, if you have a good tachometer.

Either the quiet one is underloaded, or the noisy ones are overloaded, or if you are lucky, optimally loaded.

You may find a clue in the design/selection documents, if you can access them.



Mike Halloran
Pembroke Pines, FL, USA

 

[tbuelna]

I believe your Tigear2 right angle gear reducer is a worm gear design. While worm gear meshes are fairly quiet by nature, they also don't normally have the ability to be back-driven. It might be possible that your conveyor system operation is producing a torque feedback to the worm gear mesh contact that is causing the vibration.

 

[3DDave]

First up - swap the quiet one to one of the other positions. See if it is the gearbox or the location.
Second - What Halloran and TB. say.
Third - contact Dodge engineering to see if they know of conditions that cause these reducers to be loud
Baldor-Dodge Product Technical Support: phone: 864-284-5700 fax: 864-281-2317 brgpttechsupport@baldor.com

The guys at BD Tech support should have a backlog of thousands to tens of thousands of problem reports to go on.

I am reminded of a system that had the gear drive replaced with a belt drive to remove an obnoxious amount of noise. The result was no noticeable change in the noise. Turns out it was the PWM to the drive motor. An FFT showed the main contributor frequency, and an EE confirmed it as the PWM frequency.

 

[tbuelna]

When you get noise from a gear mesh, it is usually due to contact ratio. This is why helical gear meshes usually run quieter than spur gear meshes. And a worm gear mesh, which has a very high contact ratio, should normally run even quieter.

 

[maripali]

Also try to check how is mounted your reducer.
If there is available to bring some radial load from conveyor shaft to the reducers bearings it could be the main reason of the noise that also belongs from belt tension and coveyor load.

 

[sfsurfer]

I guess it's possible that the tension of the timing belt is putting that additional radial load on the output shaft of the reducer. I guess I'll try to take the timing belt off then check the noise level.

 

[tbuelna]

sfsurfer-

Usually when diagnosing these types of problems, a good first step is to verify the components are installed/assembled correctly. I took a quick look at the installation instructions for this type of gear reducer and there are a couple things you should check, the most obvious being correct installation of the motor shaft coupling.

Regarding your last comment about excess radial load on the output shaft from timing belt tension, this would likely only cause abnormal noise/vibration if it produced damage to the output shaft bearings. The tapered roller bearings on the output shaft are installed and preloaded at the factory, and the unit is sealed after being filled with lubricant. The only reason tapered roller bearings would produce the level of noise you describe is if they had suffered serious pitting/spalling damage. The easiest way to check for this type of bearing damage is to test a sample of the lube oil for ferrous metallic debris.

Good luck with your problem. And please post again when you determine the cause of the problem and how you finally resolve it. It might prove helpful to someone else in the future.

Terry

 

[Tmoose]

"timing" belts squirt air in puffs and sing a ~ one note song. frequency = shaft rpm X number of teeth on sprocket.
that wouldn't happen to be the frequency of what you are hearing, is it?

 

[sfsurfer]

Yes...it sort of sounds like that. My first thought was that the noise was being produced from the timing belt somehow. Might be the tension of the belt.

 

[Tmoose]

The siren effect is strong regardless the tension. the belt teeth essentially fill the sprocket tooth gullets, pumping air out in precisely timed puffs.

10 minutes work with a PC microphone and free FF software would likely make it quite clear IF the "noise" is a tone, and IF the frequency of the tone is shaft rpm X sprocket tooth count ( either shaft would be the same).

http://www.cns.nyu.edu/~david/courses/perception/lecturenotes/ear/sound slides/Slide12.jpg

The FIRST think I'd do is identify the frequency content of the "noise." Without that, I'd be guessing about any cause and effect, which makes a solution a big old guessing game.

The variation in noise level/loudness between "identical" machines can sometimes be attributed to stuff like reflection and reverberation and other "room effects."

 

[Tmoose]

http://www.pfeiferindustries.com/troubleshooting/timing-belt-unusual-excessive-noise.html

http://www.pfeiferindustries.com/troubleshooting/timing-belt-unusual-excessive-noise.html

 

[tbuelna]

What Tmoose describes about air being displaced as the teeth of an elastomeric timing belt mesh with the sprocket grooves is basically true. But the sprocket grooves are usually designed to provide clearance between the tips of the belt teeth and the groove roots, and this should provide adequate space for the air displaced by the incoming belt teeth to escape without creating high velocity noise. I've never personally seen this type of problem with a timing belt drive that used the correct type of belt and sprocket, but I suppose it is possible if there is an incorrect fit between the belt teeth and sprocket grooves. It should be easy enough to check for this type of problem by seeing if the belt teeth tips or sprocket roots show evidence of excessive rubbing/contact.

You might also double check that you are using the correct type of belt for the sprockets. Every manufacturer makes different proprietary types of timing belts that each require sprockets with a specific matching groove profile. They can appear very similar and it would be very difficult to determine if you had the correct combination of belt and sprocket just by looking at them. Hopefully there are part numbers on the belt and sprockets.

 

[Tmoose]

Hi Tbuelna.

I hope the OP gets some real info about his noise problem rather than making big decisions based on my synchronous belt comments.
//If// he can determine the noise is being radiated from the flat walls of the gear housings, or the frequency of the noise is NOT belt tooth mesh, then another approach should be taken.


"Noise generation from synchronous belt drive systems has been an on-going issue in the
Industrial Power Transmission Market. " But then the report makes a bunch of comparisons ( 10dBA lower, etc) without once mentioning how loud they are.

https://www.google.com/url?sa=t&rct...8YCYAQ&usg=AFQjCNFnvKR6a1ANKL3h85wHLfRWMuBxhw

==================
Looks like his drives are max 28 HP, and maybe much less.

http://www.baldor.com/support/Literature/Load.ashx/FL1611?LitNumber=FL1611

We sold a bunch of variable speed 50 HP big torque belt driven machine tool spindles. The straight tooth synchronous belt drive (with sprockets over 3 inches wide from memory) came right out of the engineering department of one of the big belt manufacturers. The belt noise level at higher rpms was so loud ( I seem to recall over OSHA standards) and annoying they fabricated enclosures to try and knock it down, which brought on a series of other problems, among which was violating belt drive requirements for ventilation.

The Goodyear herringbone timing belt brochure proudly makes this claim.
"Up to 19dB quieter than straight tooth belts"

http://www.goodyearep.com/productsdetail.aspx?id=3400

Quieter ain't the same as quiet, so I believe what is implied about the other guys' drives and even their own is worth noting.

http://gatesbeltsandapplications.blogspot.com/2010/11/minimizing-noise-in-synchronous-belt.html

In the above Gates link they kind of pussy-foot around the noise issue in any quantitative way.


little teeth pump small amounts of air. The various profiles of automotive timing belts running on 1 inch wide sprockets in enclosed cases are not easily compared to
Large teeth on industrial size drives pump big puffs of air. A teeny groove or 20 thou of tip clearance is not going to change that materially.

If the tooth mesh frequency happens to be around 1000 - 3000 Hz (1000 rpm and 60 teeth, 1800 rpm and 33 teeth, etc) then the siren tone will sound even louder.

http://read.uconn.edu/PSYC3501/Lecture12/audiogram.jpg

A mosquito's ~ 600 Hz buzz isn't very loud. But because it is ~ a tone, and in the sensitive valley around 1000 Hz, it quite audible and attention getting.

http://hypertextbook.com/facts/2000/DianaLeung.shtml