Re: [CAD_CAM_EDM_DRO] Gantry Drive Topology

In my last email I said brass when I should have said bronze.
Here is a webbsite for you to visit:

http://www.keystonethreaded.com/prec.htm

John

----- Original Message -----
From: "john labutski" <kd6wd@...>
To: <CAD_CAM_EDM_DRO@yahoogroups.com>
Sent: Sunday, November 07, 2004 10:16 AM
Subject: Re: [CAD_CAM_EDM_DRO] Gantry Drive Topology


>
> John
>
> You might look at acme 12 foot long screws. One piece would handle the x
and
> y. I assume plasma cutting is only plus or minus about .020 and brass
nuts
> are easily available to make halfnuts. I don't think you need ball screws
> and they don't get along well with the metal spray and dust. Brass half
> nuts can be tweaked periodically for back lash of about .005 to .007. Or
you
> can spring load them to minimize this.
>
> If you attach to the halfnuts with a hook type bracket the screws can be
> protected from the splatter with U channel. Your prime concern is
> protecting what ever drive system you end up with from splatter. Also,
this
> would allow the x axis motor to be attached to one end of the frame. Less
> dangling control wires that way. Just use a bigger motor on the x axis.
> There is a lot of stored mass in an 8 foot long screw when you add that to
> the weight of the rest of the moving part of the gantry.
>
> This is just my opinion. I have not built one any near this big. There
are
> a lot of guys in the different cnc groups that have built this big stuff.
I
> suggest you just look at the pictures in each cnc group on Yahoo. Most
guys
> will be happy to return an email with their experiences.
>
> John Ocala Florida
>
>
> ----- Original Message -----
> From: "John" <johnhe-uk@...>
> To: <CAD_CAM_EDM_DRO@yahoogroups.com>
> Sent: Sunday, November 07, 2004 7:05 AM
> Subject: [CAD_CAM_EDM_DRO] Gantry Drive Topology
>
>
> >
> >
> > Hi!
> >
> > I am thinking of making a gantry for plasma cutting. I will
> > probably use something like Bosch Rexroth modular aluminium frame
> > for the travelling sections.
> >
> > I understand the difference between steppers and servos, and will
> > most likely be using servos to achieve a more dynamic movement on
> > thinner materials. However, I would like to ask for your advice on
> > choosing a motion system however.
> >
> > The table will be designed to take standard sheet metal sizes,
> > which means that a travel of approximately 1.5m by 2.5m is required.
> >
> > With the gantry being made from inherently light materials and only
> > spanning 1.5m, it shouldn't weigh very much at all.
> >
> > As I see it, I have a few options available. Lead screws, timing
> > belts or rack and pinion.
> >
> > I imagine lead screws are the first to go, but what would you
> > recommend I look at for the drive topology?
> >
> > Best wishes,
> > John
> >
> >
> >
> >
> >
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>
> 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
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> Yahoo! Groups Links
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