Need Help!- Gantry design options

[cnczoner]

Designing a gantry system, but no experience doing one before, so looking for general info. I'd appreciate any thoughts you have on these...


(1) For a light duty, but high precision application, what are the pros cons of the following gantry styles:

(a) Y axis has 2 linear rails or shafts/pillow blocks, but only one side is driven.

(b) Y axis has 2 linear rails or shafts/pillow blocks, but both sides are driven.

(c) Y axis has 2 linear rails or shafts/pillow blocks, but center driven.

I expect the answer will involve racking, but not sure how relevent it is for a light duty application.


(2) Why would I choose linear rails over shafts/pillow blocks? Suprisingly I can't much on this comparison here or via Google. Also, I've seen some designs that use bearings mounted at "triangulated" angles against a shaft. Any good for precision use?


(3) Over a 2-ft run, what diameter of shaft should I use? Or should I use something small but continuousl supported ?

Thanks,
-Neil.

[ger21]

1)
a and c would depend on the rigidity of the gantry.
b takes that out of the equation.

2)Linear rails are smoother, and can carry heavier loads.

3) Supported is a must. 1/2" should be adequate.

[cnczoner]

It's my ability to build very precisely (with my existing equipment) that has me leaning towards (b). The extra cost to drive a second side (assuming belts) is not that much.

Thanks,
-Neil.