Steps on facing operation

Guys, i’m out of guesses right now.

Tried to face some aluminium as a test, mounted in a vise pretty high up, i think about 1/2" /12-15mm below max z wich should give it plenty strength.

Cut data: 480mm/min, .5 DOC, 1mm stepover, 2 flute 1/8" endmill @ 12krpm

As you can see (and clearly feel) there are some nasty steps. i tried aliging the spindle wich i pretty much failed at since there are no really good reference surfaces to measure of and even if, i dont exactly know how to adjust for it. wich screws do i need to touch? is it the tool that is not aligned with the machine? is the machine itself misaligned? i really dont know where to search the reason for the problem.

in wood, its the same thing but way less pronounced, i tried cutting either and both directions wich didnt make a difference. if i’m rotating the work 90° (using the x instead of the y axis to feed) it gets a little bit better but still nowhere near what you’d expect. i’m fully aware that you will always see milling marks, but in my book you should not be able to feel them?

please correct me if i’m wrong and its totally normal to feel steps when using the mpcnc. it certainly wouldnt matter for the stuff i do, but i want it as perfect and capable as i can get.


Thanks for helping!

I what direction was that cut? Finishing pass? That is a very shallow cut and a low step over, a bigger bit could be better.

You have a slower spindle so the two flute might be okay but typically a single flute works amazingly.

How big is your build, spindle type, end mill type?

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its 376x376x70 travel range. direction was using the x axis to move across the workpiece and the y axis to step over. i’m using the 500 watt chinese spindle motor and the endmill is a carbide one from banggood that i stuffed into the collet all the way to leave it short as possible. i do also have single flute with 12mm flute length that i could try tomorrow.


do you think its a problem with the cut itself or misalignment?

i think i got there, used the single flute 12mm flute length with the same exact gcode and it was waaaay better. it seems like my machine takes conventional milling orientation way better than climb milling, so i might limit it doing that. with downmilling the machine got loud and it vibrated quite a bit, but the finish is now much better. the milling marks are still there but you can only just barely feel them with the finger, so its definitely good enough for the girls i go out with.


thanks for your input ryan, appreciate it!