Date: Mon, 4 Nov 2002 06:30:22 -0600
From: Ray Henry <rehenry@...>
Subject: Re: Re: Polar Coordinates CNC?
Well, yea. I can see the device but it seems to me that by the time you
build C with center bearings, drive, and some sort of support for
cutting forces around the outside of the suggested 4' diameter you'd have
more work into it than a conventional mill and all to save two slides, a
ball screw, and their supports.
A turntable with skate wheels around the OD sitting on a 1/4 thick, flat
rolled sheet would probably be flat enough for most CNC router work.
They usually are happy with a 6 inch Z travel. Remember the X is fixed
and technically it only has to go to the center. 2 feet of precision guide
ways to support an axis that in all other designs requires 4 feet plus
another 4 feet of support on each side. This is a major reduction in
complexity with very little loss of resolution, repeatability, or massiveness.
I did recently see a mega lathe with a C axis on the flat like this. The
turntable (spindle) had to be 10 - 12 feet across.
My interest was actually sparked in making a small bench top machine.
I'm thinking 12x12 inches rectangle (on the turntable), maybe less. 6
inch Z height. Rack and pinion on the X and Z w/B-W skate wheel guides,
and a large spur gear and pinion w/ motor mounted vertically, underneath
the turntable. disk overhang protects the moving parts from dust and swarf.
Angle Iron/channel frame. Might be a kick-butt kind of kit or entry level
machine with a router motor installed.
Best Regards, Fred Smith- IMService
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