[abomb55076]

I am starting to design my second home cnc machine and I have many more resources to build this one than I did the first go around, so I would like to make this one much more robust and try and include everything I realized I had wanted in the first one. That being said there are still several things to figure out and I am looking for people suggestions. Im starting to design the gantry first and will build off of that. I have a set of 44" round rails for the gantry to ride along and I am trying to decide the orientation of the bearing blocks. I know that it is better to have the entire gantry ride on top of the rails but I also like the idea of having them mounted on the sides of the table because it cuts down on material and the height the machine ends up being (suggestions appreciated). Here is where I've gotten with it so far. The two upper horizontal beams are 2"x2" 8020 Extrusion, the verticals are 3/4" Aluminum, and the lower horizontal is a 1.5"x4.5" 8020 Extrusion. Let me know what you think! Attachment 232688

[wizard]

Criticism is a strong ugly word, how about calling this a quest for suggestions, advice and comments.

I am starting to design my second home cnc machine and I have many more resources to build this one than I did the first go around, so I would like to make this one much more robust and try and include everything I realized I had wanted in the first one.

That is good but as far as robustness goes, if this is your second machine go all out to make a stiff and strong machine.

That being said there are still several things to figure out and I am looking for people suggestions. Im starting to design the gantry first and will build off of that. I have a set of 44" round rails for the gantry to ride along and I am trying to decide the orientation of the bearing blocks. I know that it is better to have the entire gantry ride on top of the rails but I also like the idea of having them mounted on the sides of the table because it cuts down on material and the height the machine ends up being (suggestions appreciated).

The first thing that comes to mind is that if you are trying to make a much more robust machine you really need to consider profile rails on all axis. You didn't mention all of the machines dimensions but you might want to consider a fixed gantry solution as an easy path to robustness.

Here is where I've gotten with it so far. The two upper horizontal beams are 2"x2" 8020 Extrusion,

Go for a bit tube in steel or aluminum. Again you didn't mention span here but it wouldn't take much of a span to get poor performance from 2x2" 80/20. The gantry beam is a simple bit very important part of these machines, it really doesn't pay to skimp.

the verticals are 3/4" Aluminum, and the lower horizontal is a 1.5"x4.5" 8020 Extrusion. Let me know what you think! Attachment 232688

Personally for the verticals I'd go with box tubing with flanges welded on each end. Yeah an additional expense is incurred to get the parts machined and welded if you need that done, but you end up with a solid structure. You may need to play around with your design some to get the best layout possible.