On Sun, 6 Mar 2005 01:52:21 -0500, Ned Simmons
wrote:

In article ,
says...
Ned Simmons writes:

Tons sounds high, my SWAG is 1000# would be adequate for a Brideport
sized mill.

F = ma. The table and saddle weigh together 400 lbs or more. Add the
rotational inertia of the motor, pulleys/belts, handles, and screw. You'd
like the table to get up to a respectable slewing speed (for a hobbyist) of
100 ipm or better, in some fraction of a second.

But with a linear motor you don't have all that rotating inertia. If
you're looking for quick acceleration with a lead screw drive, the
torque required to get all the rotating stuff up to speed is usually
much greater than the torque required to move the load at a steady
velocity.

To get to 100ipm in 1/10 sec is only .04g , or 16lbf for a 400lb table.

Are the Mazaks with 3.5g acceleration not linear motor driven?


You must also exceed the
side cutting forces for a typical task by some multiple, from the
_Handbook_, at cutting speeds.

So say you're using the full 1 HP at 50 FPM = 660# at the periphery of
the cutter.

I backed into it from the other direction, assuming a reasonable force
on the table cranks and 50% efficiency for acme screws to get my 1000#
guess.


My smallish 0.1 HP PMDC motors at http://www.truetex.com/mcgpd34002.htm
produce about 800 lbs of linear force with 2:1 timing belt pulleys on
ballscrews on a freshly rescraped Bridgeport Series I with Teflon ways. It
is certainly adequate, but like a speedboat, you can never have too much.
Fun to watch at 100 ipm, but you wonder what 200 or 500 would be like.


Indicate your vice in 1/2 sec g

Ned Simmons