SOLVED z-axis making grinding noise, couplers turning unevenly during auto homing

Discussion in 'Build Help' started by kevclarx, Aug 16, 2016.

  1. kevclarx

    kevclarx Active Member

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    Just got to the auto homing step and electronics look good but when I auto home it started making some straining/grinding noises when it was raising the bed. I noticed when I move z-axis manually from the LCD usually only the left side coupler will turn and the bed starts to go crooked, then the right side will turn a bit and level out some.

    Should I go back to reinstalling the whole bed or is there a quick adjustment to be made here? I turned the couplers by hand a few times and tried retightening them so feel like it is all probably out of whack now.

    Any advice appreciated.
     
  2. Stian Indal Haugseth

    Stian Indal Haugseth Well-Known Member

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    When you rotate the Z couplers by hand are the smooth? Any uneven resistance?

    I would check wiring and see if it might be a bad connection. Maybe swap over a stepper driver and see if the problem moves on. What's the voltage on the driver?
     
  3. TimV

    TimV Well-Known Member

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    Did you check when installing the motors, that you took 2x a 1.8° (or 0.9°) motor?
     
  4. Old_Tafr

    Old_Tafr Well-Known Member

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    I would remove the coupler on both sides and then operate the "bed" from OctoPrint. If the motors both move in sync then you are good to move to the next stage. Add a pointer made of cardboard stuck with Blu Tack to the top of the coupler sans threaded rod to observe the movement.

    If they don't turn in sync then investigate the wiring, I think that both the Z motor connections go to the same driver board on the Rumba so if one motor turns correctly then the board must be doing something right (other than maybe not adjusted to the right voltage?)

    You could even remove the connections for one motor then test, then connect just the other motor and test again.

    There are a number of posts where the connections are not made correctly.

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    With the couplers removed from the motors then rotate the threaded rods by hand an equal amount on each side and see if they turn smoothly (lots of grease on the rod/coupling in the bed is GOOD, you can always wipe some off afterwards) If one side is more difficult than the other with motors not connected then you have a purely mechanical problem which is probably putting more strain on the motor that fails to start turning.

    Lack of grease or the fastening/support/bearing at the top of the threaded rod too tight could be a problem, I think that they are only tightened during commissioning? Bent rods are probably not bent, just the way the rod fits in the coupling can offset it slightly so the top describes a circle rather than turning on it's own axis, try rotating the rod 90 degrees at a time in the coupling to fix this.

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    So try and isolate it to a mechanical or electrical problem by disconnecting the coupler as described above, then troubleshoot whichever problem you find.

    Typical problems are mechanical misalignment, no grease, support at the top too tight before commissioning, wrong voltage on motor driver board.
     
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  5. kevclarx

    kevclarx Active Member

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    Thanks all, I will remove the couplers tonight and test the motors as suggested and then go from there. I did not grease anything yet so I will do that as well.

    crossing fingers
     
  6. Jasons_BigBox

    Jasons_BigBox Well-Known Member

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    Basically I'd backup everything old_tafr said.

    I had a similar issue that came down to a couple of things but mainly one of the stepper plugs wasn't seated correctly in the motor. One motor was moving but the other wasn't turning correctly until the bed motion drove it.

    Good luck!

    Jason
     
  7. Old_Tafr

    Old_Tafr Well-Known Member

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    Jason's comment about one motor moving the other is particularly relevant. I think the term is "servo motors" that work in the same or similar way, turning one turns the other without any external power applied, so there is scope for any number of odd things to happen if one of the plugs is on slightly wrong as they should be connected in parallel.

    Grease is an absolute must ! Not only on the threaded parts but also on the smooth rods where it will be sucked inside. Also mentioned in various posts is once things are working it is good to run the bed fully up and down ten or twenty times to run the bearings in.
     
  8. 3DogModeling

    3DogModeling Active Member

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    so was there ever any resolution for this? I'm having a very similiar problem. Ive moved stepper drivers-no change, tried different motors-no change. All I can think of is that it is the split cable that came with the kit, one side works and one side just causes the stepper to vibrate or move with what sounds like a grinding sound, but moves very little. when the motors are disconnected they both move with equal force and smoothly, and that goes for the second set I tried also.

    any help would be greatly appreciate. Oh and I also tried adjust the stepper voltage up and down- no change.
     
  9. Paul Begley

    Paul Begley Well-Known Member

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    Check the motor cable, mine was badly crimped at the RUMBA end, I soldered the broken wire on to the crimp and all good.
     
  10. Chris Toast

    Chris Toast Well-Known Member

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    I would seriously take a look at the motor wire to RUMBA connection (re-seating them). Verify you have the leads inserted into the proper connector terminal.

    Every time I flip over the box and noodle with my innards, I've managed to dislodge one of those buggers and have to reinsert a loose connector into the terminal. Typically the same symptoms you guys describe, and the axis is not performing correctly (such as going the opposite way commanded from the interface).
     
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  11. Jasons_BigBox

    Jasons_BigBox Well-Known Member

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    Double-check your stepper driver voltage too.

    I found I was skipping z layers recently. I regreased everything and tried turning the voltage up a little but that made it worse.

    I'm running my z-axis at 0.45v currently which should be too low but it's working well.
     
  12. A Dragon In A Pie Costume

    A Dragon In A Pie Costume Well-Known Member

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    i had a similar problem, its the connection between the motors and the board, the connector isn't the greatest, id suggest cutting the wires and feed them through that green bar thing with the screws...
    the noises is the bed getting uneven, the stepper motor skips steps
     
  13. 3DogModeling

    3DogModeling Active Member

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    This is exactly what I did and now it moves smoothly and quietly.

    Thanks for the replies all!
    :):D:):D:)
     
  14. kevclarx

    kevclarx Active Member

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    Sorry for the late reply, been out of town for awhile. In my case I did as mentioned and isolated my testing to the stepper motors and sure enough one of them was sort of shuddering back and forth while the other turned smoothly. Dug around in the innards a bit and found my blue stepper motor cable to the Rumba had shaken loose. Popped it back in and they are in sync again - now to put the zaxis back together(again!) and do levelling test.
     
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