[wizard]

Thanks for the input wizard. Here's a few pics of the current design.

Interesting, the gantry is improved significantly? However I'd still consider a large square steel beam for the gantry. Yes it is harder (somewhat) to work with but you do gain some positives

As for side access I will once again suggest at least thinking about orienting the gantry the other way. With your current design, using extrusions, you would gain a stiffer gantry and a better mechanical arrangement of the parts. Now I understand the importance of side access to the machine, however you can simply make the machine longer giving you access to the same space. That is if you need a 4 foot table for your normal workloads make the machine 5.5 feet to 6 feet long and park the gantry out of the way when doing setups.

Having lots of time and little money I've actually have considered building a machine as you describe. That is a long gantry and a short X axis. In my case the goal eventually is to have a multipurpose machine to handle up to light metals. The long gantry would make designing for stiffness more difficult while still keeping the machine compact. I've actually thought seriously about going moving table here.

In the end the machine only needs to be good enough for your needs. I just think you are taking the hard way here. Not impossible mind you but your approach will require at least two lead screws for the X along with driving electronics.

I definitely DO appreciate your input. You sound like a logical guy. Using the current basic design, what do you think I could do to increase rigidity across the gantry (and the whole machine for that matter)? Thanks.

Justin

Big square beams are the easy solutions for gantry beams. The more Z clearance you want the bigger beam you need. The key to understanding gantry beams is that they are unsupported except at the ends.

Beyond that the supports for the gantry need to resist any rotational torque that the beam may apply. This requires spreading the bearings out further along the X axis. This is where your design looses it a bit as you have to compromise the spacing on the X axis saddles to avoid wasting a lot of usable area on the table top.