Originally Posted by
MechanoMan
I'd kinda assumed that going with a ballscrew on either side of the mill and stepping them together would be "the way to go" for performance in moving the gantry along the X-axis (the gantry's ballscrew being the Y).
The single screw underneath and in the middle looked problematic. When the Y axis is at the extremes, it's putting the cutting head far from the ballscrew axis, so there will be a torque on the guides with the ballscrew pushing the gantry assembly in the middle and the cutting force pushing back from the edge of the table. Seems like that force would result in some racking against the guides.
I was planning on a ~6ft x 5ft work area. Primarily to cut wood... although being able to cut aluminum would certainly be nice. I have a CNC Taig mill for that but it's limited to much smaller pieces.
And I started to wonder, since the ballscrews don't have a zero tolerance here. If the left and right sides are turned perfectly even at one end of travel with zero racking, and stepping them together, by the other end one ballscrew will have traveled more linear distance creating a small amount of racking- which could cause it to jam if the linear guides are tight.
But looking at builds I've seen so far, I didn't see where ANYONE went that direction. I guess it's not that necessary? What are the pros and cons here? This arrangement does cost more for ballscrews, motors, and drives.