Re: Force through ball screw based on stepper motor torque??

Neglecting screw efficiency:

Lbs = pi * TPI * in-oz / 8

Mariss


--- In CAD_CAM_EDM_DRO@yahoogroups.com, "lcdpublishing"
<lcdpublishing@...> wrote:

>
> Hi guys,
>
> This problem (if it is) has been bugging me for some time now. On
> my CNC router, I can only get about 70-80 pounds of force on any of
> the 3 axes. I am using the cheapo rolled ball screws 5/8 diameter -
> .2" pitch and they are attached to the ball screws - direct drive.
>
> The static load on any of the axis is less than 5 pounds of force.
> In other words, to move any axis and overcome it's friction, it
> takes less than 5 pounds of force.
>
> I have two different brands/types of motors. Only one of them
> is "modern" and it is a chinese made uniplolar 200 oz-in motor

rated

> at 3 amps. It is a six wire motor and does run real "zippy" - much
> more responsive than the motor it replaced - an older round style.
>
> Anyway, even though this machine is working good, I am using it as

a

> basis for determining the specs for some other machines I am

planing

> on converting to CNC. When I did the original calculations for
> thrust force, I came up with much higher numbers than what is
> actually showing up on the machine.
>
> I am wondering if someone can run the calculations and tell me what
> they come up with as to what force I should get on an axis with the
> following:
>
> Unipolar 200 oz in motor @ 3 amps, 5/8" x .2" pitch screw, direct
> drive.
>
> Oh, and the driver is running at 40 volts & 3 amps
>
> Thanks folks!
>
> Chris
>