PLA isn’t particularly strong, especially in small sections under high stress:
I tried solvent-bonding + clamping the break, didn’t expect much, and wasn’t disappointed.
It adds a festive touch when done up in orange PETG:
The attentive reader will note the missing head of the screw anchoring the mount to the left Z rail. Apparently a #32 drill was a bit too small to let the randomly chosen self-tapping screws thread themselves into EMT; they probably anchored a PCB to the plastic case of a long-forgotten lump of consumer electronics.
It should last long enough for something else to let go …
Many of the pieces of the MPCNC look pretty trivial to mill out of aluminum when they inevitably succumb to stress. Are you thinking about doing that?
Ryan designed the shapes specifically for 3D printing, so they’d be awful to chew out of solid stock with a simple milling machine. A guy on the MPCNC forum showed off his lost-PLA aluminum cast parts, although IIRC he didn’t do much in the way of post-casting cleanup.
Bulking up the existing shapes seems the least-awful way of reinforcing them, although the screw fittings on the circumferential clamps still look like the weakest parts.