RE: [CAD_CAM_EDM_DRO] Re: Is this motor workable?

I did some calcs to try to figure this out...

Assume:
30 in-lb @ the lead screw
5 TPI screw
The "lead" of the screw is 1/5 inch per revolution

From my Machine Design Book (Shigley & Mischke) the linear force produced by
the screw is:
2 * pi * 30in-lb / (1/5 in)* Efficiency


Or 283 lbs using a 30% efficiency which is guestimate for an ACME screw.

Since I am a complete armature haven't-done-it-since-highschool machinist I
have no idea how this force relates to those required to push the work in to
the cutter. It does sorta feel like the 30in-lb torque is the torque
required at the lead screw and not the torque required at the motor side of
gear reducer.

I'm on the right track here???




-----Original Message-----
From: FJ62 [mailto:fj62@...]
Sent: Friday, February 04, 2005 6:38 PM
To: CAD_CAM_EDM_DRO@yahoogroups.com
Subject: RE: [CAD_CAM_EDM_DRO] Re: Is this motor workable?



That makes sense, but what I want to know is if the 30/40lb-in torque is the
required input at the leadscrew. i.e. with a 2:1 ratio do I need 15/20lb-in
motors to get 30/40 at the screw or do I need 30/40 motors to get 60/80 at
the screw? Thanks, Vortec62


-----Original Message-----
From: cnc_4_me [mailto:cnc4me@...]
Sent: Friday, February 04, 2005 6:28 PM
To: CAD_CAM_EDM_DRO@yahoogroups.com
Subject: [CAD_CAM_EDM_DRO] Re: Is this motor workable?

--- In CAD_CAM_EDM_DRO@yahoogroups.com, "FJ62" <fj62@s...> wrote:
>
> Are these numbers for a 1:1 ratio?
>
>
> >Well many bridgeport retrofits are using 30lb-in or so servos for
x
> >and y and 40lb-in or so on the knee...But there is a lot of
confusion
> >on this spec as to if it is continuous or not...
>
> >Wally


Most people use a 2-1 or 2.5-1 ratio....Depends on your servo
rpm...You want to use most of the servos rpm range to get the most
power out of it...

Wally