I’m getting ready to print my first MPCNC. I don’t mind spending the time or filament if it increases strength/rigidity. I’d rather do it now than wish I had done it later. So, for the folks that are looking to go above the minimum recommendations, what should I do? Does adding more perimeters help? Does increasing infill beyond the recommendations?
I’m using 1" SS tubing with .065 wall thickness, with the recommended Z height for a total work space is 2’x2’
As long as your 3d printer is dialed in with respect to size and extrusion, you stick with the recommended PLA filament, and you use temps that get you proper bonding between the layers, the recommended print settings should get you parts that are adequately robust. That’s why they’re the recommended settings 
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Many folks find they have some fine tuning of the printer to do if they haven’t tried printing parts engineered for tight tolerances. Squareness issues are not uncommon. Check out the Printer Tests and Calibration topic if you’re looking to ensure your printer is up to the task.
I agree with Tom. If you build it to spec, it will perform well. I did some research building my Burly and again when building my Primo to figure out ideal/better print settings. It turns out to be a complex problem with little data.
In the end I went with:
Both the extra perimeter(s) and the Cubic infill were based on videos I watched on the CNC Kitchen YouTube Channel including this video.
Since I finished my Primo, someone on the forum posted a link to this chart. I’ve mused a bit on whether carbon fiber filled filament with its extra stiffness would be worth the extra $20 of filament cost. Of course someone would need to build two identical machines with two materials to find out, and I suspect it would make little difference in the end.
from what i see on that chart, seems like HIPS would be a good choice for an MPCNC, unless i’m missing something? according to that data, it is stiffer & more durable and almost as strong as the Carbon fiber. plus it prints very well with ABS so if you had duel extrusion you could even use them in combination at key locations to increase the overall strength of components while still increasing the stiffness of the parts.
in my opinion if you want to try to make your prints stronger, especial if your not using good filament, i would add 1 perimeter, turn on an option called “alternating extra wall” witch helps firmly connect the infill to the perimeters. lastly i would increase the infill by 15% on stationary parts and 5-10% on moving components.
i personally feel the small amount of extra weight from the extra plastic wont have a huge effect while milling, but might be noticeable if you plan on putting a laser on the machine.