Bracing a larger machine

I’m pretty sure this will work fine, but I’d just like some input for the build I’m planning.

If I build a machine approximately 2’x3’ with stainless steel rails I understand that I can get a machine perfectly rigid enough to mill wood. But what about small aluminum (or steel!) parts? I’m guessing that the rigidity starts to become a problem at that long of a Y axis.

My question is whether I can simply brace the 3’ long Y axis with another piece of ss tube/conduit and 3D printed brackets, temporarily making it a 2’x1’ machine? Would I be just as rigid as a machine originally built that small?

Sorry, one more question. I have an old 3D printer that I plan to cannibalize for this build. Can I use it’s KYSAN 1124090 Nema 17 stepper motors? I don’t know if nema 17s are rated for strength/quality or if they’re just generic parts.

No. You can not support the middle spans.


Yes, 42ozin or larger, these are 76ozin.

I understand that I can’t brace and keep the large build area at the same time, my intent would be to reduce the build area. But you’re saying I can’t brace the middle spans?

My idea was to simply print out extra sections of the right side of the machine (the brackets that support the outer frame and the gantry) and and plop that in the middle of the span temporarily, just for that project?

When you are making X and Y movements in concert with each other, both of the center spanning tubes have to be able to move. You can brace the tubing at the periphery but can’t brace the center. That means with that long of a span the center will tend to sag. If you brace as you suggest, the long Y axis will have to stay long so it can move.
Now, that doesn’t mean things aren’t going to work just fine, but be aware that your CAM skills are going to be called upon much more than they would be with a smaller build. 3’ spans with SS tubing doesn’t have all that much flex under these loads.
What you might investigate to help mitigate these types of issues is actually moving your corners. When you don’t need the full 3’, moving the corners in so the size is 2’ x 1’ would go a long way toward keeping things dialed in. Just do something to support the ends that are hanging out, or move all four corners to allow the same overhang on either side.

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I’m thinking that your idea of moving the corners inwards is a cheaper more reasonable solution. All I’d have to do is loosen some bolts and slide the legs over and re mount them. It seems like as long as I’m careful, I’d be able to get switch back and forth and still have a stiff, square machine.

Am I overthinking it in the first place? You’re suggesting that SS tubing is good enough to mill aluminum with a 3’ span, which sounds like good news to me. I know Ryan showed a video of him milling steel on what I think is a 2’x2’ machine.


You have to specify what that means. My machine is indeed about that footprint, with a smaller workspace.