X Axis Drive Design

[cxixer]

Hello all,

I've been searching for this for a while and can't seem to find exactly the answer I'm looking for. I'm designing a ~60" x 60" table and can't decide how to drive the x axis. The Y and Z on the gantry will be on skate bearings driven with acme screws. This will be a steel table, with a steel/aluminum/mdf gantry and because of the weight and useage, I wanted the X to be heavier duty. I was thinking these for the rails:

http://www.vxb.com/page/bearings/PRO...ystems/Kit7429

and I wanted to try to go with acme for this axis as well. The problem lies with where to put the screw. I have read not to drive it from the side like this:
http://www.cnczone.com/forums/attach...5&d=1178537140

I have thought of a setup with driving one acme screw on each side, like this: http://www.cnczone.com/gallery/showp...00/ppuser/6402

Or I could put it in the center underneith the table- but read not to do that either in one post or another. And I've never seen a bigger table like this driven from the center. Is there a reason for this?

I'm wanting to use the xylotex 3 axis kit with 425oz steppers. To somewhat control my costs, I would rather not use a lead screw on either side, each driven by it's own stepper, although I will if I must.

So...

1. What would be the best way to drive my X axis?
2. Is this 3 motor kit going to work for my setup?
3. Is there a reason not to drive it from the center?
4. Would 1/2"-10 acme screws be sufficient for this application?

[BobF]

Check this guys idea.
http://www.cnczone.com/gallery/showfull.php?photo=4652

[cxixer]

That's a really cool design, I didn't think of a dual rack like that. Now the question is - if this is the best option - Where can I find the R&P that will keep my budget in mind?

Any info is appreciated on whatever scenario.


Edit: OK, talked to stdsteel.com, they have great prices on racks but don't carry the gears. I'm thinking Mcmaster for those if I go this route. So now which way to go...

[BobF]

I think someone mentioned Boston Gear in another thread I saw.

[ger21]

4) use 2 start screws, either 1/2-8 or 1/2-10, and you'll get better performance.

[grahamshere]

I was just think about this and came up with an idea, I built the solsylva and having trouble with the x axis, so I thought, why not 3 lead screws for the x. have the the motor conected direct to the center lead screw then the other end have all 3 lead screws conected to the belt. that way it stays square and i dont need to buy another driver or motor. ill try to make a drawing to explain my madness . What ever you do dont hook the motor direct to a belt. It SUCKS. graham

[grahamshere]

Hey ppl, this is something ive been planning on my next machine for the x axis. so instead of 2 motors just the 1 and direct drive with a belt. tell me what you think and if this is would work. Graham