Re: [CAD_CAM_EDM_DRO] My Next Router

Re router noise

The Porter Cable 3 1/4 hp series of routers are good machines but notoriusly
noisy. I use them and actually wear earplugs in the shop.

There is a Hitachi router now being made that is 82 dbA at one meter.

I work some with portable power tool noise reduction. I gave an engineering
seminar for a group of manufacturers a while back in Chicago. So I have
some interest in quieting down routers. (I have not worked for PC but want
to)

I have not done a vector sound intensity map of the PC routers yet but
will next time I have the stuff set up for another job. So I can only give
educated guesses as to why it is so loud.

I do not think it is the bearings.
I think these are abec-1 electric motor grade (quiet running) conrad
type with grease and shields that have increased internal clearance.
Certainly the bearings make some noise, but I think not the major
amount.

I suspect two things: Brush noise (frome arcing and sparking) contributes
a good bit. This creates a correlated harmonic series (the whine sound).

But I think most of the noise is the fan system. Although the outer parts
are a moderate subsonic mach number I think the air flow is reaching
sonic velocity in some areas. That and vortex shedding seem to be
making the very loud random component of the sound.

This is very similar to the noise from shop vacs etc.

Puting the thing in a box will certainly help, but take care not to restrict
air
flow. The air ports need to be tuned absorbers.

Work noise (from the tool) will always be there but the PC motor
noise is much greater than the typical work noise as I use them.

There is really no reason a router or shop vac has to be that noisy.

Leslie Watts
L M Watts Furniture
Tiger, Georgia USA
http://www.alltel.net/~leswatts/wattsfurniturewp.html
engineering page:
http://www.alltel.net/~leswatts/shop.html