Re: [CAD_CAM_EDM_DRO] Sound proof box

Graham Stabler wrote:

>I have finally got my proxxon conversion fully up and running but and
>the only problem with it is the noise. My house ajoins another and
>there is no chance I can mill on an evening.
>
>I'd like to make a sound proof box for it and have already made a
>2.5" thick polystyrene cover for it that now just requires a "double
>glazed" door. However after trying it last night with some foam
>jammed in as a door it was anything but sound proof. Sitting the
>mill on some foam did help a little but is not ideal.
>
>Has anyone built such an enclosure? Would it be worth lining it with
>egg box foam? Should it be clad with a hard material like MDF as
>well? Is there a way of making a decent base for the mill that will
>not turn my bench into a sound box?
>
>

padding alone will only cut the highest frequency noise. For lower
frequencies, you need something stiff to "contain" the sound pressure
waves. A box made out of 2 x 4s and at least 1/2" plywood would
work much better. I made a "muffler" for an extremely loud oilless air
compressor that way, and it helped enough that I could run it in the
basement without driving the family out of the upstairs, screaming.

The most effective approach is a stiff barrier with some type of energy
absorbing padding that will damp the vibrations that will otherwise
turn the plywood into a sounding board. This can be tested by building
the box first, and observing the resonance by thumping on the box with
a hammer. You then add damping (one commercial material is lead
sheet with a material like sorbothane bonded to it - you then bond the
sorbothane to the wall to be damped) until the resonance disappears,
and all the sound that remains is a very dull thud. If the machine
makes a lot of high frequency noise, small openings at door hinges
and for wires, etc. will allow a lot of sound to escape.

If the problem is transmitted sound, foam or other isolation from
tables, etc. may be needed. No solid material, other than a ton of
granite, will prevent vibrations of the machine from being transmitted
into a bench or table. So, if the real problem is the machine vibrates
the bench, you have to use some compressible material to isolate the
vibrations. Placing the machine on a big sheet of plywood, and supporting
that with 3 or 4 small inner tubes is one way this is done. That may lead
to the machine dancing around, however. There may be a compressible
foam that works almost as well. I had some stuff a few years ago that
was sold for placing under typewriters and printers. It was a dense
black foam about 1.5" thick. 4 pieces about 6" square, each, would
probably support a minimill. (I'm not sure a Proxxon is that size, I'm
just guessing.)

Jon