Brand new KMG is LOUD

Stacy E. Apelt - Bladesmith said:
And the new grinding rooms will be double walled and soundproof.
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I would always vote for that but it's not necessary. Grinders are above 2kHz so a simple barrier is enough. Few years back I tested the influence of a simple thin door. Grinder was screaming at 15kf/m and behind the door it was OK. Nobody was bothered with it. Inside was unlivable.
 
the sound of 36 grit belts going full tilt, doing what they do best (hogging material off S90V) is music to my ears....but to be fair, I have partial hearing loss in one ear from an IED, and tinitus from...well...Navy stuff.
 
100dB is normal. If it's too loud for the surroundings, go slow with high pressure. When I grind Ti after midnight, no-one hears me. I'm in a buildings basement. 4 pole 3 phase motor @10Hz with a 4" drive wheel.
 
Maybe this is too dangerous. If somehow you could put a load on the drivewheel no belt. Those DBs seem high to me compared to my gas blower rating.
 
When I initially set up my grinder (2hp workhorse motor) I wired it wrong and it got really loud under load. Should be very quiet with no load.
 
Gilbert M said:
When I initially set up my grinder (2hp workhorse motor) I wired it wrong and it got really loud under load. Should be very quiet with no load.
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Yeah, that's what surprised me, and I thought the belt might be rubbing on something, because the motor itself is relatively quiet and even with the drive belt connected to the pulleys it was quiet, like normal indoor voice quiet, and then when I put the first belt on (36-grit shredder) the noise difference was huge. I checked over the whole machine and couldn't find anything wrong so I got worried.
 
OK, I'd never thought much about measuring the noise from the grinder. Since you've got a belt driven grinder thru 3 step pulleys I think you might be about right. A direct drive runs a good bit quieter than the belt drive. My first grinder was a 3 step pulley KMG clone. Never thought about the noise, it only ran around 3,000 SFPM or so? I don't remember exact speed. After I built the direct drive grinder I was amazed how much quieter it was than the belt driven grinder.

I just checked noise level on my 2X72 direct drive at 3600 SFPM so it would match your numbers. I used a new X weight 36 grit AO belt and noise level was around 90 db at my head level. Cranking up to max of 5,000 SFPM it was around 95 db at head level. It seems the tracking wheel was the most noise at 100 db with phone held 6" or so away from tracking wheel. By holding phone 6" away from each wheel I could check the db level at each wheel. This is with platen putting light pressure on the belt.

to the OP I'd say your noise are about right for that setup with the Combat 36 grit ceramic belts and the belt driven grinder with 3 step pulleys. As I said, I never measured noise level from the old 3 step belt driven grinder, but it was a good bit louder than the current direct drive.

I remember back when all I had was the 3 step pulley belt drive I didn't see why anybody paid the money for a VFD direct drive grinder. Heck I had 3 speeds, what more did I need? After building the direct drive with VFD, WOW - what a difference, so much smoother and quieter. No way I'd think about going back to a pulley driven grinder.
 
Mine is loud. I have not tried an add-a- link belt but it might help. They do last forever.

My Ameribrade is not loud at all, I'm not really sure why but maybe because it is a variable speed.
 
Another reason to like my Northridge grinder. I just installed the app and tested with a Norton Y weight 36 grit belt with plenty of tension over a flat platen. Holding the phone on the edge of the rest, about 6-8" from the moving belt, much closer than my head would be. At my common 35% speed I get 77db and ramped up to hogging speed it's 83db. It's louder than light weight belts, but never uncomfortable.
 
That sounds like a direct drive grinder? Worlds of difference in noise level between a belt drive and direct drive grinder. And, what is your "hogging" speed in SFPM?
 
One good way to make it less noisy is using 3" idlers. 4" are even better. Few days ago I have printed 2" idlers to test will nylon work. It does. Now after this thread I'll make them bigger. Probably will go with 4" tracking and 3" idlers.
 
Ken H> said:
That sounds like a direct drive grinder? Worlds of difference in noise level between a belt drive and direct drive grinder. And, what is your "hogging" speed in SFPM?
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Yes direct drive. I haven't calculated the speed. 60% on the dial is about as fast as I ever go. I just go by feel.
 
Good idea JoeB, I'd never thought about printing the wheels. Are you using Nylon filament? what about ABS? I've been running 3" longboard wheels so they're not so expensive either.
 
Richard338 said:
Yes direct drive. I haven't calculated the speed. 60% on the dial is about as fast as I ever go. I just go by feel.
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Here's the formula (courtesy of Contender Machine Contender Machine )

SFPM = motor speed (eg 1750) x drive wheel size (eg 5 inches) / 3.82

So using the EG numbers the sfpm would be around 2300
 
Ken H> said:
Good idea JoeB, I'd never thought about printing the wheels. Are you using Nylon filament? what about ABS? I've been running 3" longboard wheels so they're not so expensive either.
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Nylon 6 with 20% CF. ABS should work if your belt is not heating up. ASA should work, too. Nylon is heat resistant above 150°C so it's the best of all (non aerospace filaments). And it's one of the toughest.
Printing smaller contact wheels is also a good idea. Nylon base and TPU outer layer. Can even choose the groove design.
 
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