Z-axis right side "droops"

Discussion in 'Calibration, Help, and Troubleshooting' started by W1EBR.Gene, Dec 19, 2016.

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  1. W1EBR.Gene

    W1EBR.Gene Well-Known Member

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    i am having a strange problem. I start with a bed that is pretty level. After running a print, the right hand side of the bed is now lower than the left hand side. It does this very predictably. Any ideas on why?

    Gene
     
  2. mike01hu

    mike01hu Well-Known Member

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    Missed Z-steps by the right hand motor is the likely answer, so increase the Z-driver voltage by a small amount to see if the problem disappears. A way to check this is the make a little twisted wire pointer attached to each Z coupler and align them so that you can see if there is any difference in their angular position after a Z move. You can try this with a LCD Z move but this may not be reliable, so do it with a simple test piece with retractions so that you are maximising the Z functions.
     
  3. W1EBR.Gene

    W1EBR.Gene Well-Known Member

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    Thanks, I will try that. I have turned up the voltage slightly already... I'll try again with the meter connected.

    I noticed a very strange thing. When the steppers are disabled and I turn the left hand z-axis stepper clockwise and counter-clockwise, the right hand stepper turns only in the direction that makes the bed go downward. Do you think this tells me anything useful or is it just a strange and unrelated phenomenon?
     
  4. Ephemeris

    Ephemeris Well-Known Member

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    Yes! Checking them by feel was smart. It sounds like one of the coils to the right z-stepper is either blown or not connected. Check your wiring of the right stepper.
     
  5. mike01hu

    mike01hu Well-Known Member

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    It is difficult to say because you are using one motor as a generator and that will send pulses to the other motor but it is not predictable how the other will respond due to manufacturing tolerances and the circuit they are connected to; this circuit will contain semiconductor switching devices that will also react in an unpredictable way.
     
  6. Jasons_BigBox

    Jasons_BigBox Well-Known Member

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    As Mike said, hand turning one stepper generates current which goes to the second motor and will drive that.

    I know it goes against what most people say but I had issues with skipping steps on the z and found that reducing the voltage helped.

    In my case both steppers were moving or not moving together. Greasing the bearings and screws always helps to keep the resistance down.

    I found that I also got the issue when using the LCD to manually move the bed downwards. It only happened using 0.1mm increments, using 1mm or 10mm seemed to keep it going.

    Worth checking the actual motion compared to what the LCD says too. A distance of 100mm is easy to check.........
     
  7. W1EBR.Gene

    W1EBR.Gene Well-Known Member

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    So Mike, I finally tried your pointer suggestion and sure enough, they are not both moving the same amount. I "think" the bed is trammed properly and I have tried increasing the voltage so I am looking for more ideas. Is it possible that one motor is not as robust as the other?

    I did check the wiring and it looks ok to me - the right hand side does step but maybe it is missing some of the steps????

    Looking for more things I can try... thanks all!
     
  8. Jasons_BigBox

    Jasons_BigBox Well-Known Member

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    A couple of things to double-check but not necessarily easy. Are the motors the same, maybe one is turning too much? To check, you'd have to take the bottom plate off the printer which is a big job. Maybe check all the others to see if one's different?!? The degrees per step should be on the motor.

    You'd see that show up when moving the bed using the LCD too.

    I'd check to see if one is sticking or just turning more slowly. I couldn't see it clearly during prints (you can only look at and at a time!). I videoed it and watched it back to see one was skipping steps.

    Did you try turning the voltage down? It worked for me!

    Good luck,

    Jason
     
  9. mike01hu

    mike01hu Well-Known Member

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    The only thing that can affect one motor and not the other, besides a mechanical misalignment, is the driver voltage and you may need to tweak that driver. The reason is that motors are not truly identical due to manufacturing tolerances and one motor may need a little more current to make it reliable.
     
  10. A Dragon In A Pie Costume

    A Dragon In A Pie Costume Well-Known Member

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    the connections on the dual motor thing are terrible, strip, solider alike and use the green screw clamper thing
     
  11. W1EBR.Gene

    W1EBR.Gene Well-Known Member

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    I will do that, thanks!
     
  12. A Dragon In A Pie Costume

    A Dragon In A Pie Costume Well-Known Member

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    this issue happened to me and 2 otjer people so far, so im 100% sure it's what's your issue is caused by
     
  13. mike01hu

    mike01hu Well-Known Member

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    DO NOT solder!!! This will certainly cause you problems sometime in the future due to the clamped wires loosening.
     
  14. W1EBR.Gene

    W1EBR.Gene Well-Known Member

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    I crimped a common connector together from the matching wires. I am also getting serious about converting over the z-axis to a stepper with integrated lead screw.

    While we are on this topic, does anyone know why the undriven end of the lead screw is free floating and not inside a bearing or sleave?
     
  15. mike01hu

    mike01hu Well-Known Member

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    I think it was assumed that the 4 corner rods would be sufficient to stop any bed movement but this has not been the case for some users.
     
  16. W1EBR.Gene

    W1EBR.Gene Well-Known Member

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    The bed may not move but I can see an eccentricity in the lead screw (i.e. the center of the leadscrew moves slightly as the screw turns).
     
  17. cez

    cez Well-Known Member

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    Did this solve your issue? Because I think I have the same problem
     
  18. W1EBR.Gene

    W1EBR.Gene Well-Known Member

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    Not completely. I tried applying a lighter lubricant to the lead screw nut (I think around NLGI 0; it is a mix of some Lithium NLGI-2 and Super-Lube high viscosity oil plus Teflon lube). That seemed to help some. I am going to convert over to the Dual IDEX design and will try again, however, if Greg's stepper with lead screw integrated is affordable, I may use those instead.

    BTW, Greg, if you see this, do you have a date and a price for the lead screw steppers?
     
    cez likes this.
  19. cez

    cez Well-Known Member

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    What issue did you have? And this totally resolved it?
     
  20. A Dragon In A Pie Costume

    A Dragon In A Pie Costume Well-Known Member

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    tr increasing the stepper driver to .70 or.80, try higher, mine is at .95

    bed was tilting to the right severely
     

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