Re: [CAD_CAM_EDM_DRO] CNC router build

Dave,
 
This is primarily a precision cnc router for patternmaking, not a mill for machining metal, so coolant won't be an issue. 
 
I am aware of limitations of Dremel which is why I am looking for an alternative.  Yes, noise and heat come with high cutting speed.   I will probably be using carbide end mills exclusively.  Part of the plan is to build a sound enclosure but I don't know much about this.
 
One alternative I am considering is using a mini-mill head with belt drive retrofit.   This would allow me quieter belt drive and R8 collets but the max rpm would be about 4000.
 
I don't want to get into building a spindle so am looking for alternatives.  I am wondering if there is a die grinder or dremel type tool that has better bearings and might be quieter than a standard router motor.
 
Jack
 

--- On Mon, 3/30/09, David LeVine <dlevine144@...> wrote:


From: David LeVine <dlevine144@...>
Subject: Re: [CAD_CAM_EDM_DRO] CNC router build
To: CAD_CAM_EDM_DRO@yahoogroups.com
Date: Monday, March 30, 2009, 3:50 PM






Jack Mc Kie wrote:
> <SNIP>I have a router and a Dremel tool that could be used but I am
> considering some alternative hopeing to keep noise level down. Noise
> is a concern I'm not sure how to deal with. I'm considering making a
> box of some sort to house the router in and line it with some sort of
> noise absorbing material. Any cost effective suggestions on how to
> deal with noise supression would be welcome!

1. At high speed, everything gets noisy.
2. At high speed things get hot in a hurry.
3. A router or Dremel is not a good, precision spindle.

If you have machining available, consider that a good, fixed speed
spindle may be better for your needs.

Put something like a 5200 or a pair of 7200 bearings on the tool end
(angular contact preloaded bearings ensure good positional accuracy) and
a slightly loose bearing on the other (so the shaft doesn't bind.) A
7200 pair is rated for 29,000 RPM, IIRC. For higher speeds, ceramic
bearings work but are /*spendy! */Driven by a belt and an induction
motor, such a spindle will be quieter, more robust (last longer) and
more accurate, but heavier. Remember, lower speed is always better for
bearing life. Smaller bearings and open bearings (especially with oil
mist lubrication to remove heat) will run faster and last longer than
shielded or sealed bearings.

With a VFD and a 3 phase motor, you even get the variable speed
advantages, but with a weight penalty. You may need a cooling fan if
the VFD runs the motor slower than 75% of the rated speed.

--
David G. LeVine
Nashua, NH 03060



















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