rumbling Z axis

I completed my mpcnc about a week ago, and i cabribrated the whole thing yesterday. It's really accurate, but i have one small issue: when cutting from right to left ( cutting towards the top ) the whole Z axis starts to rumble.

My machine's specs are:

1m wide 1m deep, 10cm legs, 30cm Z axis conduit & leadscrew length, 200w spindle, ramps 1.4 +3 drv8825 drivers ( x & y in series ) and single flute 3,175mm bits. The voltages are adjusted as told in the guides, and i use the ‘official’ mpcnc firmware.

I suspect it has something to do with the larger Z height, but before i start cutting the leadscrew, i would like to know for sure if this is likely to be the issue.

I tried changing speeds ( higher speed = less rumble, i only cut mdf at the moment ), i also tried less & more tension on the belts, but the problem is still there.

Has anyone experience with this issue? I’m fine with cutting the Z length ( i don’t need it that long anyway ) but if it’s not needed, i prefer to keep the rod as is.

Thanks in advance!

Is it climb cutting in that direction? the router bit might be pulling the machine along in that direction.

With climb you mean, cutting in the same direction the spindle moves? I think it is indeed. I watched the machine for quite some hours, and it seems it also overshoots in that direction, and then the spindle sounds like it slows down a bit.

So the Z axis height probably has not much to do with this issue, it’s just a weak motor for this job?

Try a new router bit and shallower passes

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Allright, i made some progress:

It’s caused by ‘overshooting’. Climb cutting is off ( im using estlcam ), im using conventional milling for all tests. What did help hower, is adding a finishing pass with 1mm roughing tolerance. The result was a lot better! However, i still have some overshooting ( cutting too far ).

I tried a couple of things:

  • x / y acceleration to max 100 ( instead of normal 400 ) > helped a bit
  • cleaning all the pipes, loosening all bolt with bearings a bit ( i had them quite tight ) > helped a LOT! The extreme rumbling stopped, but is still overshooting a bit.
  • less deep passes ( 0,5mm - 2mm ) >better, but still some overshooting.

What could the final issue be?
Is it okay if i make a video and post it so you guys can try to find the cause of the problem? I honestly tried so much already, but i just can’t seem to figure this one out.

On a sidenote: i did not buy the kit from v1engineering because of shipping costs ( i was on a tight budget because i had no job ).
I will do a donation however because i’m extremely satisfied with the machine! Just have to wait for my paycheck to arrive ( just got a job ) and then i’ll send a donation, regardless if you guys can help me with the issues or not.

Edit: i think i found the issue…
I have the belts on both sides attached with a gap, instead of just one and the other one tight to the plastic. I’m going to adjust this now, and will post my findings later.