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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