Re: Formula? for determing torque of motors and leadscrews.

> > I'm starting with a large mill/drill (8"x24") and acme screws.
> > Hoping to upgrade to ballscrews and a fullsize b'port or the like.
> > But really only want to buy one set of motors. 740oi? 1070oi?
> >
> > -d
>
> doing the math, it seems that a 740 into a 10TIP leadscrew would
> deliver a theoretical 2,905 lbs.
>
> (2 * PI * 10 * 740 ) / 16 = 2,905
> 10 is tpi
> 740 is oz-in of motor
>
>
> 2905 * 90% = 2,615 delivered pounds for ball screws
> 2905 * 60% = 1,743 delivered pounds for ACME high eff
> 2905 * 30% = 871 delivered pounds for ACME low eff
>
>
> as a side note here, when talking about using all-thread or ACME or
> ball, considder that you would need a motor and driver almost 4

times

> as large to move the same load as a ball screw. talk about the best
> place to put your money !
>

I've casually started searching for ballscrews, stumbled over
some likely candidates that were 3 pitch.

3 pitch at 90% efficieny is the same as 10 pitch at 30% efficiency.
Still trolling for finer pitch ballscrews though, unless I'm totally
reading that wrong.

For the Watts calculation - it's done on power at the motor,
or delivered to the table ?

I played with this formula and here;s what I got.
1050oi steppers, 4100lbf * 0.30 (acme) = 1230lbs
watts: using 150 as a median value (PFA), ballpark top end for
a stepper system. 150W = (4100lb*20IPM)/531
[4100, not 1230,right????]
A 1050oz @150W will give 1230 lbs at 20 IPM.
A 740oi @ 150W will give 850 lbs at 28 IPM.
A 388oi @ 150W will give 460 lbs at 52 IPM.

Does this make sense? I would have expected the big motor to
be able to get a higher speed. At least it will outrun a
glacier :)

Math says going to ballscrews will give 3x force to the table,
but with no improvement in speed.

Gonna put down the calculator before I hurt myself!
Thoughts ?
-Damon (green!)