Choices and Accuracy

I’m in the planning stages of an MPCNC build and I’d like to understand how well it might work. I would make it small to keep it stiff, with about a 12x12x2 inch work volume, use stainless one inch by 049 wall tubing, use a BLDC spindle motor and ESTLCAM to make gcode that was optimized for accuracy (trochoidal milling with an appropriate small carbide bit), with a final pass to clean it up. One piece I need to make has a 1.3 inch hole in plastic (PVC) about 1/4 inch thick. How circular might I expect this hole to be? What should I consider to make the MPCNC as accurate as it can reasonably be?

Thanks for your input.


That is very difficult to say, it depends on you you build and use it. You are saying all the right things but saying and doing…

How about you give some numbers that you expect and I can tell you if it is reasonable or not.

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Will it be as good as a 3D printer? I measured a couple of round objects and holes that I printed, with stock settings, on a common 3D printer. These measure over a range of about 0.008" total diameter variation in a 2.7" distance (measured with a quality digital caliper). Would we expect something similar for a properly milled hole from the MPCNC? Have others made simple measurements like this? What do other’s achieve?? I’m not expecting perfection here, but I would like to have some data to work with to understand what I could do with this tool.

Thanks in advance, AlanB

I went way overkill on my tubes but I have a are time thinking that you’d need to go SS at all at that required size. Ryan will know best on that though.

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I am pretty confident saying most people can get that sort of accuracy if you keep your build size reasonable. I approach this question with extreme hesitation. The machine can pretty easily do it, ask others what they are getting, but I make no promises to what your build will do.

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