RE: [CAD_CAM_EDM_DRO] Re: Plasma table gear reduction - motors

Dave,

Right...large diameter rotors, pulleys, etc tend to have
higher moments of inertia. Many (not all) low inertia servos
are long and skinny as a result of this.

If we are optimising for COST we don't go for the very
lowest motor inertia though. We approximately match
reflected motor inertia and the load inertia. Motioneering
takes care of all that. You can google inertia matching
if you want more info.

By the way I should mention that the numbers I used will give
a VERY high performance machine. It can ramp from a dead stop to
240 ipm in 42 milliseconds. It can traverse a corner at full speed with
a 0.16 in radius. If you're gonna make one why not make it good?

I should also mention that this is for a low friction plasma with
essentially
no cutting forces. For a different machine like a mill or router the results
would be
completely different.

Leslie M.Watts
L M Watts Furniture
Tiger Georgia
(706) 212-0242

Main page:
http://www.lmwatts.com
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But, it seems one of your earlier posts mentioned flat and large
diameter motors are bad and long skinny ones are good. That makes
sense as the flywheel effect from the large motor would get in the
way of quick response. Ditto cast iron timing pullies vs. plastic
ones.

I do have the idea that a DC motor is rated on a somewhat linear
curve. and that generally speaking, a 100 volt, 10hp 4,000 RPM motor
is also a 50volt, 5hp 2,000 RPM or 25 volt, 2.5hp 1,000 RPM motor.

so, generally speaking, I can make a prototype axis a few feet long
and test the motors I have with different gear ratios to see the
acceleration.

Dave

Dave