Re: [CAD_CAM_EDM_DRO] has anyone built a 4x8 CNC router?

In a message dated 8/8/2004 2:25:54 AM Central Standard Time,
mjmautoinnovations@... writes:
Has anyone built a 4x8 CNC router?<<
I did a 5x10. NEVER again! TOO Much work, and NOT enough money! There are
"store-bought" X-Y machines that size for less than MY cost for materials and
parts, NOT including my "labor"!
I am hoping to build one cheaply.<<
This would be akin to building a new luxury automobile at home for $5000.
I have a pretty good idea if what I want to do. But, I am unsure about a few
aspects. For example leasdscrew sizes, stepper sizes" &". <<
Only 4x8? "Professional rapid-traverse rates", or slow as a box-turtle? It
MAKES a difference! If you use preloaded ball-screws, one with at least
1.3" major dia. would be needed for the 8' axis, if not 1.5 inches. To turn
that and move a gantry of the size/weight I'd expect you would be doing, you
would need a good Size-42 stepper with "chopper drive". For the "Y-screw", I'd
STILL use at least 1.3" dia. A triple-stack bipolar "KML-093-nnnn" stepper by
Superior Electric would possibly do if your machining is fine, and you use
proper bearings, well-aligned. For the longer X-axis, that goes without saying!
Do NOT expect to support "the motor-end" of the screw by the
motor-shaft/bearing! Use DUAL "fixed" angular-contact bearings at both ends of BOTH screws,
and a proper "no slop" (aka "no backlash") coupling connecting one end of the
screw to the resp. motor.

Take it from me: When you go to the Stepper and Driver store, take MONEY!

If you think you can do this with ACME screws and preloaded Turcite bearings,
one or both of TWO things will come to your attention: You may need LARGER
motors (to overcome the friction) than you expected, and/or your SPEED of
traverse will be reduced.

Sounds all negative and nasty, doesn't it? Lotsa luck. HOPE you can prove
me wrong. Been nearly two decades, now, since I had finally discovered what it
means to say, "Been there; DONE that!"

Jan Rowland


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