Re: [CAD_CAM_EDM_DRO] Re: Z axis Thanks

> I thank you and Keith for your help.
> Like yourself I don't want to cough up 1200$
> for a prebuilt unit.
>
> In the interest of simplicity I may
> look at trying to drive the quill by placing a pully on the
> quill hand feed lever. Though I would still want to be able
> to use the machine manualy as well.

The problem with driving the quill feed handle is that there is
usually backlash in the rack. If all you are doing is drilling, that
is not a problem, but for 3 axis milling it is.

I have seen a couple of bridgeport-built cnc conversions. On one
they drove the quill with a bracket bolted around the bottom, going
more than a foot off the othe side where a ballscrew actuator drives
it. Even they recognize this as bad - it is only rated for drilling
3/8" in steel, although we sometimes use it for more. Another machine
drives the quill via the connection on the front that are usually the
depth stop. There is a sheet metal box put around these, containing a
small ballscrew.

Some bridgeport based cnc machines drive the knee instead. This takes
a stronger motor, and may wear out the vertical ways eventually, but
it also gives much more travel than the quill does. These machines may
use an air cylinder to null out most of the weight of the knee.

Purpose-built 3 axis cnc machines usually have a head that moves up
and down on vertical ways.

Chris Stratton

-------------------------------------------------
Christopher C. Stratton
Engineer, Instrument Maker, and Horn Player
ccs@... 617 628 1062
http://web.mit.edu/~stratton/www/brassbuild.html