RE: [CAD_CAM_EDM_DRO] Force through ball screw based on stepper motor torque??

Hi Chris,

From page 113 of my Machinist Handbook 24th Edition. Assuming no friction,

Q = F x 6.2832 x R
----------
p

Q is the force of the screw.
F is the force on the end of the lever with radius R
P is the pitch of the screw.

In your example:

F is 200 oz-in
R is 1" since the F of the motor is rated in oz-in
P is 0.2"

Q is (200 oz * 6.2832 * 1 inch)/0.2 inch == 6283.2 oz

Divide by 16 to get pounds..

I calculate 392.7 lbs.

In real life it's less due to friction and your static friction to get it
moving from a stand still is more than the dynamic friction when it is
moving.

Page 113 also has the calculations if you know your co-efficient of
friction.

John Dammeyer

> Subject: [CAD_CAM_EDM_DRO] Force through ball screw based on
> stepper motor torque??
>
>
> 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.
>

<SNIP>

> 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
>
>
>
>
>
>
>
> Addresses:
> FAQ: http://www.ktmarketing.com/faq.html
> FILES: http://groups.yahoo.com/group/CAD_CAM_EDM_DRO/files/
> Post Messages: CAD_CAM_EDM_DRO@yahoogroups.com
>
> Subscribe: CAD_CAM_EDM_DRO-subscribe@yahoogroups.com
> Unsubscribe: CAD_CAM_EDM_DRO-unsubscribe@yahoogroups.com
> List owner: CAD_CAM_EDM_DRO-owner@yahoogroups.com,
> wanliker@..., timg@...
> Moderator: pentam@... indigo_red@...
> davemucha@... [Moderators]
> URL to this group: http://groups.yahoo.com/group/CAD_CAM_EDM_DRO
>
> OFF Topic POSTS: General Machining
> If you wish to post on unlimited OT subjects goto:
> aol://5863:126/rec.crafts.metalworking or go thru Google.com
> to reach it if you have trouble.
> http://www.metalworking.com/news_servers.html
>
> http://groups.yahoo.com/group/jobshophomeshop I consider
> this to be a sister site to the CCED group, as many of the
> same members are there, for OT subjects, that are not allowed
> on the CCED list.
>
> NOTICE: ALL POSTINGS TO THIS GROUP BECOME PUBLIC DOMAIN BY
> POSTING THEM. DON'T POST IF YOU CAN NOT ACCEPT THIS.....NO
> EXCEPTIONS........
> bill
> List Mom
> List Owner
>
>
> Yahoo! Groups Links
>
>
>
>
>
>
>
>