Re: [CAD_CAM_EDM_DRO] Ideas for matching drives on a YY axis design?

I have seen quite a few gantry drives with one screw down the center under
the table. This presents two problems. First, the table must be supported
at the corners which limits stiffness. Second, the moment loads developed
when the head is at either end of the gantry cause wracking of the gantry
(and deflection of the limp table caused by the first problem).

The usual solution to these problems seems to be overbuilding the table and
gantry. Neither work very well. A more effective solution is to design the
gantry so it can be driven from one side. This works surprisingly well,
though it requires some unconventional thinking to accept. I would choose
this approach if I were doing it again.

Another approach is to use two screws and link them together with belts to
the motor, which will then have two pulleys. The motor is placed at one end
of the table between the screws. Any loss of accuracy from the long belts
will be insignificant compared to Abbe errors, thread drunkenness and
thermal stratification in a sub$80K machine.

Doug

----- Original Message -----
From: Jim Brown <jagco1998@...>
>
> Just curious............
> Why cant you just space out the linear bearings on the z/y axis' so it
will have less of a chance of binding when traversing in the x axis, and
drive it from the center with the ballscrew/leadscrew?
> I realize that this will be a big feat to perform, being the width of the
gantry. But It can be done, cant it?