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  1. #1
    Hi all..

    One day, in the dim and distant future, I will finally kick all the bugs outa this cnc build, but not today it seems...

    When I am jogging the x axis (dual drive nema 34's, slaved together in Mach3) it moves freely, until I try to also move the y axis simultaneously.. Then an awful grinding noise and the x axis completely stalls (no movement)... First picked this up last week when it was cutting a circle and it was rapid moving (G0) to the next cut, it stalled the x axis and therefore did not move to the right place..

    I have since redone all the wiring and triple checked all mechanical movement which has made no difference, in fact I would say it has got slightly worse if anything..

    I am using a Uniport controller, 2 x PM752 drivers (x-axis) and a PM540 driver for the y.. I have wired it all according to the plan shown here..

    Click image for larger version. 

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    Anyone encountered this before? Any ideas? Wanna lend me a really big hammer..?

    Last edited by fasteddy; 03-10-2011 at 01:22 PM. Reason: wrong pic..!

  2. #2
    Just to mention, I have reduced the motor tuning speeds and accelerations in mach3 until it now crawls at snail speed, no difference...


  3. #3
    Is the power supply man enough as your simultaneously driveing 3 motors when you move both X and Y.
    Just a thought as I assume each drives well on their own.


  4. #4
    If you'll forgive my ramblings, do you get the same problem with X and Z?

  5. #5
    Hi guys..

    In order..

    PSU has plenty of power, am using a 55v 5amp for the nema 34's, and a separate 24v 2.5amp for the nema 23 (y axis, 3Nm)...
    Dont get the same prob with the z and x... Only the x is stalling... And only in rapid, regardless of what I set the motor tuning to...


  6. it could be the psu? can you measure the DC voltage on the driver and see if it drops when you move the other axis? Also are you daisychaining the DC or comming back to a star point?

  7. #7
    what current setting do you have the drivers set to?


  8. #8
    Hi again..

    Just gonna pop my lad to bed then will check what you guys have asked/suggested..


  9. #9
    Hi again..

    Bit more info on the problem.. It only seems to happen when moving x and y in full rapid, if one or other of the axis is not moving at full speed it does not happen i.e. it happens when rapid at 45 degrees, but not 30 degrees... If that makes sense... Sorta guessing both motors are at full throttle when moving at 45 degrees rapid..

    Some more info on my setup..
    X axis is a pair of SY855TH80-5504B steppers driven by a pair of PM752 drivers.. The settings on each driver is;
    3200 microsteps

    Y axis (and z) is a 3Nm nema 23 (from Zapp) on a PM540 driver, settings are;
    3200 microsteps
    2.5 amps

    Got my specs wrong on my PSU's earlier, should be;
    X axis run by a single PSU (separate outputs) which delivers 65v 8amps..
    y and z share a 24v 4amp PSU..

    Will test voltages tomorrow when I can get a new battery for my multimeter...
    Am 99.9% sure it is something electronic as I have torn apart and rebuilt every mechanical part and everything is freely moving.. Also, I am a decent engineer and a crap electrician with only slightly more knowledge of electronics than my cat...

    Last edited by fasteddy; 03-10-2011 at 09:57 PM. Reason: oops

  10. #10
    Just a thought...

    Have been roving around all the cnc forums trying to find another with the same probs... I have seen an awful lot of posts about earthing, but I have to say, as a complete burp at electronics, I ended up more confused than when I started... Cant get my head aound the myriad of different advice being handed out, and much of it was american.. Do they use different terms for all that common,starpoint,earth,neutral,-ve supply/rail,0 volt stuff? Damned if I can work out what they are in English without even more varying terminology.. I ramble..

    Does seem to be a big cure-all for a lot of electronics issues so I was wandering if there is a good post/guide to earthing for us feeble minded noobs? From what I have read, I ought to do this as a matter of course, if only to eliminate several potential problems...


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