Choosing 3/4 or 5/8 screw was Re: Ballscrew question

Choosing 3/4 or 5/8 screw . Here is something you might find
interesting.

Stepper
Steps Per Rev 200
Torque in/oz 470
Torque in/lbs 29.375
RPM 300

Drive Ratio X to 1 1
Working Steps/screw rev 200
Working RPM 300
Working Torque 29.375


Ballscrew
Lead 0.25

Drive Force (Lbs) 663.8
Tw/.177x Lead

Max Travel (IPM) 75

Resolution 0.00125
Lead/Steps per Rev




Drive force is the big deal, which is 660 lbs max. When looking at
ballscrew, Rockford 5/8 single circuit ballnut is rated at 825 Lbs to
get max life out of it.

Changing that to a slightly larger stepper changes the numbers:

Stepper
Steps Per Rev 200
Torque in/oz 650
Torque in/lbs 40.625
RPM 300

Drive Ratio X to 1 1
Working Steps/screw rev 200
Working RPM 300
Working Torque 40.625


Ballscrew
Lead 0.25

Drive Force (Lbs) 918.1
Tw/.177x Lead

Max Travel (IPM) 75

Resolution 0.00125
Lead/Steps per Rev


Which changes the drive force to 918 lbs. When looking at ballscrew,
Rockford 3/4 single circuit ballnut is rated at 950 Lbs to get max
life out of it. Which makes it a good match.

When going with even a larger stepper such as a 1200 in/oz (the cost
difference between 650 oz and 1200 oz in minor) gives the following
numbers

Stepper
Steps Per Rev 200
Torque in/oz 1200
Torque in/lbs 75
RPM 300

Drive Ratio X to 1 1
Working Steps/screw rev 200
Working RPM 300
Working Torque 75


Ballscrew
Lead 0.25

Drive Force (Lbs) 1694.9
Tw/.177x Lead

Max Travel (IPM) 75

Resolution 0.00125
Lead/Steps per Rev


Now the drive force is at 1700 lbs, since a ¾ screw is the biggest
that will fit one can expect to get reduced life from the ballnuts.

Now I am not second-guessing the choice you made, it is a good match
for your application. And of course turning too much screw can be
just as detrimental as not turning enough, so you gotta get
everything matched up.

Thanks

Aaron Moss
www.IndustrialHobbies.com

--- In CAD_CAM_EDM_DRO@yahoogroups.com, "Paul" <chue2k@c...> wrote:
> Just wanna be sure ...
> The acme screw I have now is 1"
> Its a $117 diff between 5/8 and the 3/4 in my application..
(Ballscrews and
> doublenuts)
> Im on a super duper shoestring budget ..
> 117 is alot of beer money :O)
> Thanx ..
> ----- Original Message -----
> From: "ballendo" <ballendo@y...>
> To: <CAD_CAM_EDM_DRO@yahoogroups.com>
> Sent: Friday, February 27, 2004 3:46 PM
> Subject: [CAD_CAM_EDM_DRO] Re: Ballscrew question
>
>
> > Paul,
> >
> > Is 5/8 okay?
> >
> > Definitely.
> >
> > Ballendo
> >
> >
> > --- In CAD_CAM_EDM_DRO@yahoogroups.com, "Paul" <chue2k@c...>
wrote:
> > > Do you guru's think I could use the 5/8ths screw with 470 oz
> > stepper motors
> > > ??
> > > Or do I really need the 3/4" ??
> > > My main task will be cutting 1/16th deep channels in copper ..
> > > total area is about 3" square'ish..
> >
> >
> >
> >
> >
> > 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@a...,
> timg@k...
> > Moderator: pentam@c... indigo_red@q... davemucha@j...
> [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
> >
> >
> >
> >
> >