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

The math is correct except I doubt that he is getting the 200 oz in torque.
While running he uis probably getting 50 oz torque
Thus F= 50X6.28X5X.9( efficeincy of the ballscrew)/16=88lbs which is about
what he was reporting .
Dan Mauch
low cost stepper and servo motors.
cases for Gecko drives
kits and assembled 3-4 axis drives
www.camtronics-cnc.com
www.seanet.com/~dmauch

----- Original Message -----
From: "John Dammeyer" <johnd@...>
To: <CAD_CAM_EDM_DRO@yahoogroups.com>
Sent: Tuesday, May 16, 2006 10:40 AM
Subject: 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
>>
>>
>>
>>
>>
>>
>>
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> Addresses:
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> Post Messages: CAD_CAM_EDM_DRO@yahoogroups.com
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> 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
>
>
>
>
>
>
>