Re: Servo motor selection

Jon,

Thanks for the reply. Now for the question: what about acme screws
at 10 threads per inch? Do you feel that I should preform a ball-
screw retrofit before I go on to the CNC?

I know there are backlash issues and such, but for the short term I
think that backlash correction should be suffcient to help me. I
eventually want to do the ballscrew conversion anyway, but the CNC
project is really what I'm itching for.

With the added friction of acme screws vs. ball screws, is this 600-
peak, 50oz-in/amp still sufficient? I don't know the pitch diameter
so its hard for me to calculate the efficiency... Any "rules of
thumb"?

By the way, I've seen your site before, and sadly it confused me
terribly. I'm going to try to work through it step by step tonight.

(if you promise not to tell anyone, I actually got through high
school, college, and grad school without ever taking physics...
shh!...hehe. After all, us computer scientitst don't need any of
that.. hehe)

Jake

--- In CAD_CAM_EDM_DRO@y..., Jon Elson <elson@p...> wrote:
> With a 2:1 belt reduction and 5 TPI ballscrews, it will probably
have
> enough force to break any tool you can put in the spindle. Stepper
to
> servo is meaningless. Steppers have a fall-off in torque with
rising speed
> that depends on the power supply and motor inductance, mostly.
Servos
> generally have full torque up to the max speed limited by the power
> supply. So, a 100 Oz-In servo may be able to outperform a 600 Oz-In
> stepper at moderate speeds like 600 RPM! These motors should be
> quite adequate.

...snip...

> I've got a calculation here http://206.19.206.56/motor.htm
> I'm running a Bridgeport with 73 Oz-In (cont) motors, which gives
about
> 300 Oz-In peak. It is fine for me, and I can deliver about 1000 Lbs
> linear force to the table.