Mini-Mill ball screws/nuts AND CNC Router project

Mini-Mill

I converted my Griz Mini-Mill to cnc using Ron Steele's plans (with
minor mods) and Xylotex controller/steppers. The Z axis is a ball
screw/nut but the X/Y are the original screws with modified nuts.
Building the retro was easy except for the Z axis which would have been
easier to make if I had a boring tool. I used the mini-mill in 2 axis
cnc mode to build the Z axis and accuracy wasn't what I would have
liked. Everything was a bit sketchy on how to attach the cog pully to
the ball nut and I had some minor problems with concentricity.
Having a Bridgeport would have been a lot of help!

I'm using Rhino/Rhinocam/Mach3 with this set up and am very pleased with
the results. I think this software combination is the most "bang for
the buck" though I wish I could afford the Rhinocam-pro. The cnc
mini-mill is used to make patterns for spincasting and is saving me many
hours.

All that said, I'm not happy with the conventional screws/nuts on the
X/Y axis. Backlash is the major problem along with the occassional
stall during rapids. The modified nuts are difficult to adjust and, as
expected, wear quickly. Has anyone had experience with "shoe-horning"
McMaster/Carr 5/8" ball screws w/square ball nuts in a mini-mill?
These are such a bargain that I am hoping to use them.

Router

The mini-mill retro has been sucessful enough to prompt me to build a
small cnc router. I am in the process of gathering parts and hope to
build the router in a few weeks. The travel will be - X48" Y16" Z 6".
All the bearings will be linear ball type and the screws will be
McMaster 5/8 ball screw/nut. Steppers will be 425oz + - . The main
purpose of the router will be to carve wood model ship hulls and
wood/plastic patterns for cast parts. I am also wondering if I will be
able to cut brass? Main concerns are being able to level/align
everything.

I need a four axis controller, two of the four will be used for the X
axis with one stepper slaved to the other. I haven't decided what
controller to use but am considering Geckos. I have heard that Gecko is
coming out with a low cost controller and wonder if anyone in the group
knows anything about these? Will I need a opto-isolated breakout board
or are these Geckos opto-isolated?

Any discussion/insight on the above appreciated!

Jack







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