Re: [CAD_CAM_EDM_DRO] Intro & Retrofit Questions

> I've had most
> of this for about 15 years, used for this
> and that including recumbent bicycle frame
> building.

If you're the same guy, I've spent quite some time looking at your
implementation of a bicycle power assist system using a small Honda string
trimmer engine (I saw your announcement on the power assist list). I haven't
built anything yet for myself, but I went through a long jag of late night
research a while back and I thought your setup was the nicest of all the
"roller drive" units out there. If I'm not mistaken, your web pages are
anchored at:

http://internet.oit.edu/~currinh/

I couldn't make this work at 1:30am EST, but perhaps the computer is down
just now.

> I'm planning to
> install steppers of about 550 oz-in using a
> 2:1 reduction through timing belts for X
> and Y. Z axis on the quill with a ball
> screw but haven't worked out any details.

Elrod Machine makes these, but they're about $1200-$1500:

http://www.elrodmachine.com/quill.htm

Jon has a nice homebrew version. I think he bootstrapped his by retrofitting
X and Y first, then milled the parts for the Z axis:

http://www.artsci.wustl.edu/~jmelson/CNCconv.html

You'll also want to look at these:

http://www.artsci.wustl.edu/~jmelson/Machining.html

http://www.linuxcnc.org/

(Shameless self promotion):

http://users.erols.com/mshaver/

> Half stepping (400 step/rev ?) would then
> give (800 step/rev at .2 lead) .00025" per
> step. Should give reasonably smooth curves?

Yes, maybe not good enough for bearing bores, but good enough for most
anything else.

> I want to covert to ball screws. I suspect
> the SuperMax isn't a close enough copy to
> use a Bridgeport retrofit package. So this
> will take some doing.

Well, you could check your current screws against this drawing:

http://www.hiwin.com/ballscrew/bridge.html

These guys also sell XY kits (but there's not much on their web site):

http://rockfordballscrew.com/

Nice having you here,

Matt Shaver