Re: [CAD_CAM_EDM_DRO] Servo Motor and Gear Reduction Calc Formulas?

Bill Kichman wrote:

>I hve seen bits and pieces of formulas, and was wondering where I can get a concise list of the formulas and general assumptions used in determining stepper and especially servo motor torque, required rpm, and resultant force calcs. I think I have it partially understood, but am missing a few things and want to be sure I ma headed in the right direction, converting my old Van Norman to CNC. For example, for travel speeds, am I reasonably on track believing that the z axis can run much slower, say 1 inch per second max, while it would be advantageous for the x and y axes to travel 8 to 10 inches per second for full speed travel? Any link to web sites or other references with example calcs, where folks have been there done that would be appreciated.
>
>

TEN inches/second? With Acme screws? Well, you'll be replacing those
in a couple of weeks,
then, I'm sure. 10 IPS = 600 IPM, which is definitely in the range only
done with ballscrews
or linear drives. I can get up to 120 IPM on my Bridgeport, but never
run it that fast for
safety reasons. Assuming a 42" table with maybe 30" of travel, maximum,
that would
allow you to get from one end of the table to the other in 3 seconds,
not figuring acceleration
into it. To actually accelerate to 10 IPS before it is time to slow
down at the other end
would require HUGE motors, enough to probably bend your Acme screws!

Yes, allowing for slower Z motion is reasonable, as the Z is a shorter
axis on most
machines, and is rarely traversed very far in any one move.

Anyway, out of experience and general guidelines, you should not push
Acme screws over
120 IPM or they will wear out extremely rapidly. If you went to 10 IPS
under load, I would not
be surprised if the screws seized and self destructed on the first move,
due to overheating!

Jon