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Sound reduction for dust collector

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Forum topic by JohnMcClure posted 02-15-2019 07:46 PM 689 views 0 times favorited 20 replies Add to Favorites Watch
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JohnMcClure

622 posts in 1028 days


02-15-2019 07:46 PM

All,
I’m going to use this Rockler 3/4HP dust collector with my big new CNC:

Noise reduction is very important in this application. My thought (Recommended on the Axiom forum) is to build a thick, sound-dampening box around the collector and its dust bag, and put a household air filter on the box so the air can escape.
This collector can be wall-mounted but I think I’m going to lay it on the floor instead… I’d like to hear other’s thoughts on this. I’m disinclined to spend an afternoon making a sound-reducing box only to find that the air filter lets all the sound right out into the room.

Thanks for any and all constructive thoughts!

-- I'd rather be a hammer than a nail


20 replies so far

View HokieKen's profile

HokieKen

9502 posts in 1527 days


#1 posted 02-15-2019 08:19 PM

The key to sound-dampening is energy absorption. I don’t think a filter would be very effective at absorbing the vibrations and passing air too. If it were me, I’d build the box as suggested and have the walls cant out towards the base. This should (in theory at least) cause any rebounds/echos to be reflected towards the floor. Then I would make the ceiling of the box a baffled design. So the first layer would leave a gap of 1” or so at the front then the second, outer layer would have a gap the same size roughly at the back. This should aid in the sound that travels along the same path as the air getting attenuated between the panels.

Needless to say, the gaps in the ceiling need to be sized for the volumetric flow of air that the DC processes. I would probably use some 3/4” MDF to build the box because of its density. Maybe some foam insulation boards on the inside of it if necessary. Then seal the corners with some thick foam or caulking.

Disclaimer: This is my “gut” idea for good-enough. I would feel confident enough to build it if it were me. But, it would be simple enough to make a small scaled model with some MDF then put a phone or radio inside it to get an idea of whether or not it supresses sound sufficiently.

-- Kenny, SW VA, Go Hokies!!!

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HokieKen

9502 posts in 1527 days


#2 posted 02-15-2019 08:21 PM

Oh, forgot to mention…

I would also lean towards standing the DC up and putting the baffle (or filter if you go that direction) on the top. That way, sound that does escape via the air path will be directed toward the ceiling rather than out into the shop.

-- Kenny, SW VA, Go Hokies!!!

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therealSteveN

2812 posts in 962 days


#3 posted 02-15-2019 08:46 PM

Just like eyes and lungs, you only get the one pair of ears, treat them well.

I don’t care which you use, but the ear muff design goes on faster, and easier than most others, and you can get them in a NRR (noise reduction rating) of 30dB or more. Less and you are just kinda being proactive..

I would suggest a brand that is known to be checked, and legit for stated ratings. 3M and Howard Leight are tops there.

-- Think safe, be safe

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Scap

78 posts in 315 days


#4 posted 02-15-2019 08:52 PM



Just like eyes and lungs, you only get the one pair of ears, treat them well.

I don t care which you use, but the ear muff design goes on faster, and easier than most others, and you can get them in a NRR (noise reduction rating) of 30dB or more. Less and you are just kinda being proactive..

I would suggest a brand that is known to be checked, and legit for stated ratings. 3M and Howard Leight are tops there.

- therealSteveN

^^^this.
I will use Leight Orange ear plugs with over the ear Peltors for really loud situations. Glasses will cause ear muffs to bleed sound, and some sound is via bone transfer that plugs alone can’t stop.

View JohnMcClure's profile

JohnMcClure

622 posts in 1028 days


#5 posted 02-15-2019 10:26 PM

Thanks all. SteveN and Scap, thank you for the muff recommendation – I have some, and will probably upgrade for the reasons you suggested; I normally wear foamies; but the need for sound mitigation at the source a la kenny’s technique is important in this case. The garage shares a wall with the master bedroom, and much of my work is done at night while LOML and usually at least one baby iis asleep.
Even during the day, it’s hazardous because the kids are always coming out to “help”.

Kenny, I’m liking where this is going. I’m thinking it could even be standing, as you suggested, and even portable, about 18”x18” footprint, arranged such that exhaust air flows past the motor housing, and with a double AC filter baffle for the exhaust. Stuffed with mineral wool everywhere it can be. Double-walled where possible, maybe, but not trying to overkill on the footprint.
My home depot has 3” thick bats of 15” wide sound-dampening fire retardant mineral wool. Maybe I line the inside with that. Just gotta make sure there’s room all around the bag for easy air flow… A design is taking shape!

-- I'd rather be a hammer than a nail

View wingless's profile

wingless

34 posts in 130 days


#6 posted 02-15-2019 11:07 PM

There is lots of information on noise control.

One basic step is to eliminate an air path between the noise source and the quiet area. Even small gaps create a direct path for noise.

To that end, a solid wall / sealed door will create a barrier between noise and quiet. The exhaust air path would need to be ported to a don’t care area, like outside.

Other steps, like insulation and Mass Loaded Vinyl (MLV) will reduce the intensity of the noise coming through the wall.

View HokieKen's profile

HokieKen

9502 posts in 1527 days


#7 posted 02-15-2019 11:26 PM

Mobile is a good feature if you can swing it John. If you can eliminate contact with the shared wall, that’s half the battle. I’d be a bit careful about stuffing the box with insulation. There is heat to consider. I would start with just a box first with the baffles then start adding insulation as necessary.

-- Kenny, SW VA, Go Hokies!!!

View ArtMann's profile

ArtMann

1381 posts in 1204 days


#8 posted 02-16-2019 12:54 AM

The specifications for the dust bag filter on that unit say it is a 30 micron filter. That will certainly catch all the shavings but it will do very little to reduce the amount of 1 – 5 micron dust that gets in your lungs and isn’t expelled. I think putting the whole thing in a box and installing a decent pleated filter like a MERV 11+ rated filter is a good idea.

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JohnMcClure

622 posts in 1028 days


#9 posted 02-16-2019 01:08 AM

I’m headed to rockler tomorrow to pick up the 5micron bag. I bought 2 pleated filters at HD, it’s their finest rated filter (cant remember the number).


The specifications for the dust bag filter on that unit say it is a 30 micron filter. That will certainly catch all the shavings but it will do very little to reduce the amount of 1 – 5 micron dust that gets in your lungs and isn t expelled. I think putting the whole thing in a box and installing a decent pleated filter like a MERV 11+ rated filter is a good idea.

- ArtMann


-- I'd rather be a hammer than a nail

View Lazyman's profile

Lazyman

3409 posts in 1775 days


#10 posted 02-16-2019 01:26 AM

Will your CNC have a router or one of the quieter spindles? If a router, I have to wonder if you will even hear the dust collector over the noise of the router.

BTW, If you want make your own air filters for a custom application, you can buy filter media on Amazon all the way down to 0.5 micron. For example.

-- Nathan, TX -- Hire the lazy man. He may not do as much work but that's because he will find a better way.

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JohnMcClure

622 posts in 1028 days


#11 posted 02-16-2019 02:09 AM

Nathan,
Yes it has a quiet spindle.
Thanks for the tip, that is awesome. Didn’t know you could buy that so easily.

-- I'd rather be a hammer than a nail

View Lazyman's profile

Lazyman

3409 posts in 1775 days


#12 posted 02-16-2019 03:03 PM

I bought a Wen air filter a little over a year ago when the price dropped to about $90. When I started shopping for replacement filters, I was a little annoyed by the cost of the filters so I bought one set and some media to see if I could make my own stage one filters for less. 99% of the dust lands on the pleated filter so it is the one that needs to be replace more often, though I vacuum them off from time to time to extent their life. One of these days I will get around to actually make the frame to hold the media.

-- Nathan, TX -- Hire the lazy man. He may not do as much work but that's because he will find a better way.

View Lazyman's profile

Lazyman

3409 posts in 1775 days


#13 posted 02-16-2019 03:30 PM

Since we are talking about 650 CFM of (theoretical) air flow from that DC. I would think that would be enough to prevent any heat from building up inside the box so would it really be a problem to insulate the box? If yes, since the noise of the DC is primarily from the impeller, I wonder if you could mount the DC so that the motor is sitting outside the box?

A random thought…I wonder if you could use an auto or motorcycle muffler on the DC cabinet’s exhaust port to reduce the amount of noise exiting the box? Or do you think that would create too much back pressure? I suppose that they may be tuned for a different range and type of sound? Perhaps just making your own baffles similar to the way some mufflers are designed:

EDIT:
A little more research and apparently Bill Pentz has a design for a DIY DC muffler. Perhaps putting this on your DC cabinet exhaust will help.

-- Nathan, TX -- Hire the lazy man. He may not do as much work but that's because he will find a better way.

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JohnMcClure

622 posts in 1028 days


#14 posted 02-16-2019 08:39 PM

Thanks Nathan! Great suggestions.

-- I'd rather be a hammer than a nail

View Desert_Woodworker's profile

Desert_Woodworker

1805 posts in 1602 days


#15 posted 02-16-2019 08:44 PM



The specifications for the dust bag filter on that unit say it is a 30 micron filter. That will certainly catch all the shavings but it will do very little to reduce the amount of 1 – 5 micron dust that gets in your lungs and isn t expelled. I think putting the whole thing in a box and installing a decent pleated filter like a MERV 11+ rated filter is a good idea.

- ArtMann


+1

-- Desert_Woodworker

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