noise control - cnc router enclosure design

[mediaconvert]

I'm about to start the build of a 2x3 cnc router based on the FLA/CNCRouterParts design. see:
http://www.cncrouterparts.com/index.php or
http://www.finelineautomation.com/
or their threads in this forum.
I'm planning to use a Bosch Colt PR20EVSK-RT router as the cutter.
I don't have one handy, but I do have an old Rockwell 4620 Router.
It's noisy. My Radio Shack sound level meter reads 90-95db at 3ft
when running (no cutter, just running the router).
If I leave the router running in my basement I get readings of 60-65db
in the room above the router or outside the basement window
[poured concrete foundation, the noise is coming thru the cheap
basement window].

That's way too much noise to expect my SO to tolerate. I also don't
want to risk annoying the neighbors with the noise either.

I'm planning on putting the router in a (roughly) 3x4x3 box made out of
1/2 inch MDF. I might line the box with homasote for additional noise
deadening. I'll need to provide ventilation, but I'm planning on a dust
collection system anyway. That should suck in enough cool air to keep
the router cool.

has anyone built a similar enclosure or tackled the problem in a different way?

Frank Pirz
ps: yes. I also plan on blocking the window well with a sound absorbent
panel and might cover the ceiling with homasote to kill some of the
sound transfer to the upstairs rooms.

[FriendOfGhost]

I just finised my first cnc and faced with this annoying noise. I tried to make mdf closure but dont remcommend it. I beleive wooden materials let noise to outside. I tried a big cartoon box and adhesing agg carriages in it. these are low quality cartoon boxes to carry eggs. I saw them once on television, they used it for noise isolation in basement misic works.

these works fine and increadibily reduces noise as I can hear. but very huge noise also comes from bottom. metals and woods conducts noise so every table, table foot lets noise go to room. I tried to put cnc on soft plastic pieces to prevent noise go directly to table. you dont beleive but I could hear the noise reduction. (I dont have dbmeter). I will also put these plastics under the table. but even from a 1cm space between cartoon box and table there comes incrediaby high noise.

so these are for just ideas. if you find any solution please post here.
thanks.

[Jay C]

Most of the research I've done on this ... the answer was mass. I bought a kit of sound damping material called Dynamat. Got a great deal (IMO) on it at Amazon.


I lined my cabinet especially the doors. I recently added a vacuum. I built a box out of 3/4" MDF to house the vacuum and baffles for the exhaust. It was still too loud. I added some dynamat and it's much quieter.

FWIW,
Jay

[Jay C]

Another recommend is to use Green Glue and put drywall (5/8") on the outside of your MDF box. That is an elastomeric material that will absorb the vibrations. Home theater builders swear by the stuff.

[Jesse B]

Most of the research I've done on this ... the answer was mass. I bought a kit of sound damping material called Dynamat. Got a great deal (IMO) on it at Amazon.

Finally the car audio knowledge pays off

Sound deadening materials do *essentially* nothing but stop vibrations, which is not a bad thing at all. Any more than 25% coverage at the center of the panel is moot with this product; no more is needed, although having more won't hurt the performance in any way. One product I personally prefer over Dynamat is Damplifier, which is essentially the same thing, just higher quality imo. It can be found here: http://secondskinaudio.com/. There's another cheap product called Fatmat which will get the job done, but is lower quality.

On top of the sound deadener, it'd be beneficial to add something such as Mass-Loaded Vinyl or Closed-Cell Foam. This will help stop the physical sound waves themselves. Either of these products can be purchased from SSA, as well as numerous other places both online and locally.

Hope this helped a bit


- Jesse

[mediaconvert]

Thanks to all who replied. I just got done building a home theater so
I've seen some of the products a few of you have mentioned. I decided
to run a quick test to see how effective the box approach would be.
I built a 14 inch cube out of OSB (Oriented Strand Board) used for
siding and roofing. I had it available. It's not as dense as MDF.
With the Rockwell router on a foam pad sitting on a concrete floor
I read 93 db at 3ft from the router. Placing the OSB box over the
router (I left one side open) cuts the sound level to 82 db. I was hoping
to get more, but realistically it's not bad for something I cobbled together
in under an hour. MDF will most likely be a few db better. It's clear that
I'll have to pay attention to sealing the box and putting mufflers on any
air intake/exhaust openings. I'm hoping to get a few more db by putting
an additional layer of sound treatment either on the inside or the outside.
Haven't decided what to use yet. Looking for something cheap.

Frank Pirz

[Pplug]

What about regular fiberglass insulation sandwiched between layers of osb with a small air gap on the outside layer? Or you could insulate the basement ceiling like me to reduce the sound as well as the heating bill!

[mediaconvert]

Pplug asked
"What about regular fiberglass insulation sandwiched between layers of osb with a small air gap on the outside layer? Or you could insulate the basement ceiling like me to reduce the sound as well as the heating bill!"

For soundproofing the fiberglass needs to be compressed. You are better off
using boards made from fiberglass that are meant to be stuck to the sides
of exposed air ducts in unheated spaces. They usually have one side covered
with aluminum foil. I was going to try Homosote instead as it's less of an irritant
when you cut it up. A sandwich of MDF-Homosote-Sheetrock might work well.

I think part of the way 'green glue' works is to create a small gap between
two layers of (usually) sheetrock. The glue is resilient, so it damps vibration
between the layers.

I plan on insulating the ceiling. Note that most of the sound transmission
to the upper floor is thru the exposed heating ducts. So those should be
wrapped with something like Dynamat/Damplifier/Fatmat products mentioned
in an earlier post. The basement walls are already insulated/finished.
Had to do that to keep it warm. If your basement walls are not insulated
you are loosing heat thru them. Do that first. A warmer basement means
warmer floors upstairs!

[mediaconvert]

I just got the Bosch Colt router that I'm going to be using as
the cutting head for my cnc router.
For reference, here are the noise figures for at it's various
speed settings:
1 ~16k rpm - 71 db
2 ~18k rpm - 75 db
3 ~20k rpm - 78 db
4 ~22.5k rpm - 81 db
5 ~26.5k rpm - 86 db
6 ~35k rpm - 92 db

Measurements were made under the same conditions.
No router bit installed. Router sitting on a rubber mat
on concrete floor. Sound meter at 3 ft from the router.

At it's fastest speed it's just as noisy as the bigger Rockwell
router I used for my previous noise tests. The only saving grace
is that I have the option of running the Bosch at a slower speed
[but a slower ipm cutting rate] to keep it quieter.

I'm still planning on enclosing the router.
Next step is insulating the two hvac ducts that feed the upstairs
bedroom and determining if that helps reduce the noise level there.

Frank Pirz

[diecutter]

I got lucky and got some free insulated panels from a Food Lion warehouse that was being remodeled. The panels have aluminum skins on both sides and 4" of foam in between.

I run a Hitachi M12VC router and even during heavy cuts I can hardly hear anything on the other side of the room. In the next room I can't tell if it's running even at the doorway.

This would be a good low/no cost option if you could find some surplus panels.

[mediaconvert]

Diecutter - thanks for the posting!
Sounds encouraging (no pun intended).
Did you build an enclosure out of those panels, or use them
for your shop walls?
If you build an enclosure, what did you use for a door?
If you built a room was there any special treatment for the ceiling?

Frank Pirz

[diecutter]

This is the only picture I have handy. You can see the thickness of the foam at the bottom of the photo.

Yes, I did build an enclosure with the back wall being my cinder block basement wall, the "ceiling" and side walls and front wall are foam panels. The top half of the front is removable (has two handles) and has a large acrylic viewing window.

The panels are held together with steel l brackets and the seams are caulked to prevent dust from escaping.

The enclosure went together quite fast and easily.