rumbling Z axis

This topic contains 5 replies, has 2 voices, and was last updated by  michael 2 months ago.

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  • #100106

    michael
    Participant

    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!

    #100108

    Edward
    Participant

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

    #100109

    michael
    Participant

    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?

    #100112

    Edward
    Participant

    Try a new router bit and shallower passes

    1 user thanked author for this post.
    #100589

    michael
    Participant

    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.

    #100608

    michael
    Participant

    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.

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