Re: [CAD_CAM_EDM_DRO] Why don't gantry systems "twist"

If you look at the major router companies the gantry is very rigid and the
bearing spacing at the 4 corners are far enough apart that even withe servo
off and you push the gantry bothe sides move the same distance.

Harko

On 11/20/06, Jon Elson <elson@...> wrote:
>
> James Washer wrote:
>
> >I've been looking at photos of gantry based routers, etc. and I cannot
> see why the gantry doesnt twist (i.e. varied travel on one side as opposed
> to the other).. Are they generally "ganged" using timing belts, or is there
> a motor on each side driving the gantry in lock step, etc?
> >
> >The designs generally don't look stiff enough to mechanicly resist
> twisting..
> >
> >
> Large machines, like gantry bed mills, vertical boring mills, etc. use
> "tandem" axes, where a pair of
> servo drives are kept synchronized by the CNC control. These do not
> have a stiff linkage between the
> gantries, but a swivel bearing. This allows the machine to be slightly
> out of alignment before
> the axes are homed. After that, they should be in perfect alignment.
>
> This prevents damage to the machine's structure if the two gantries do
> ever get out of sync.
>
> Jon
>
>


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