operation cnc

[kingcreaky]

this really is like a mind boggler. ive spent pretty much every waking moment, reading posts, writing notes but mostly thinking. Oh, and getting frustrated with google sketchup.
I have made a final, firm decisions on a few things.
*It will be around 1.5m by 1m
*after reading the pros and cons, and weighing them up in my own head, Im using chai's supported bearings SKB16, maybe 20's for the gantry to slide along on(is that the X some people call it X some people call it Y)
*The first version, Il use the 1610 ballscrews I think that is what Irving is trying to suggest in his above posts) , and although maybe not recommended il spin the ballscrew not the nut. I may eventually re-think this once ive learnt from my mistakes. As Il be driving the ballscrews with timing belts I can gear it so they for optimal reliability not speed.

I am very confident with steel. I can weld well, (although I understand the issues over warping) so please see my gantry design.

Ive read thread after thread explaining the importance of keeping the gantry supported to stop flexing. I also appreciate the ultimate goal is keeping the cutting tip as close to the center of the gantry as possible through organising the Y and Z axis /ballscrew configurations.

With the comment over confidence in steel and no experience in extrusion or ali whatsoever, please see my current gantry plan (attached?)

as you can see, ive used two peaces of 50x200x6 I intend to triangulate the back for extra support and place the Y bearings one at top and one at bottom (top marked in red)

In terms of fixing the material together, I think im going to carefully weld it.

I need your thoughts now, Ive heard Jonathon banging on about steel box not being 'straight' and I should probably be using ecocast ali. or even extrusion like some of the builds here. Without entering into yet another full on discussion over gantry design. is carefully welding the steel going to distort it that much the z unit wont slide the length of the gantry without binding?

should I use extrusion?

With extrusion... how do you know the t-slots or slots in the extrusion are going to line up with the pre-drilled holes int he supported rail?

where do I buy extrusion?

totally consumed in this, and seeking some support!

m@