Layer Shifting or Misalignment issue - Where do i start?

Discussion in 'BigBox General Chat' started by AndyVirus, Aug 12, 2016.

  1. AndyVirus

    AndyVirus Well-Known Member

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    Hello,

    I have been playing with my Big Box Hybrid Dual for a few weeks now since i have built it and all has been relatively well. Lots to learn but i will get there.

    After many sucessful prints incuding a slightly oozey dual colour tree frog which i think is not bad for a first atempt i suddenly had an issue I have not had up until now and acording to S3D Troubleshooting this is ether a phisical nudge, a massive slip of the belts (seems unlikley) or a motor issue. I really hope it is not as i want to play more this weekend!

    Can anyone tell me where to start with diagnosing this issue (see image)?
    Timelapse:

    IMG_8244.JPG
    Basically at about layer 15 the whole print shifted to the right 14mm
     
  2. mike01hu

    mike01hu Well-Known Member

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    It looks like motor skip rather than belt or cog slip, so I would slightly increase the voltage on the X driver; try an extra 0.05V-0.1V from your current setting.
     
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  3. Old_Tafr

    Old_Tafr Well-Known Member

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    no pun intended? :)
     
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  4. AndyVirus

    AndyVirus Well-Known Member

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    Thanks! Ill give that a try. It has not happened again since but good to know where the issue may lay.
    Can AC power fluctuations cause this or is there some level of filtering when converting to DC? I know in the past my street has had some weird power issues causing my alarm to burn out once and lots of lights to flicker but happens less these days (maybe since i changed to LED bulbs). Im now wondering if this occurred during this print. I plan to get a UPS for this which would eliminate this issue somewhat but i do wonder if a spike/drop could have caused this on my MickeyMouse print :)
     
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  5. Old_Tafr

    Old_Tafr Well-Known Member

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    The answer on ac power fluctuations is a definite maybe! Power supplies have a certain amount of leeway or "regulation" so could withstand a decrease in supply (ac) voltage but it all depends on if the supply dropped to a lower voltage and for how long, or just dropped momentarily (for a moment that is). This depends very much on the design of the specific power supply in use, it may survive one brown out but not another. Input voltage dropping too far could result in too much current being drawn from the supply at which point the fuse would blow.

    As the Pi gets its power the same way then it could well crash too.

    So could motor power drop sufficiently to cause a flaw in a print.... yes.
    Could the Pi crash and not come back if it's supply dropped momentarily.... yes.
    Which would happen first who knows!

    I would say that it is worth checking the voltages on each driver to make sure they are correct, but increasing the voltage setting won't make any difference to a situation when the ac power varies, as if there isn't enough input power there is no way to generate output power; once the voltage out the capacitors (acting as a reservoir) drops that's it. A bit like your water supply, if the supply fails/pressure drops then opening your tap further does not make any difference.

    Only answer to power supply problems is a UPS.
     
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  6. GBR1

    GBR1 Member

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    As of today (and its done hundred of prints before with no problems) my big box pro with titan has just started to layer shift, no idea why. Anyway how do I increase the voltage as mentioned above?

    Regards

    GBR1
     
  7. Old_Tafr

    Old_Tafr Well-Known Member

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    In lieu of Mike answering on voltage..

    This page....

    http://wiki.e3d-online.com/wiki/Big...y_Process#.2827.29_Tuning_The_Stepper_Drivers

    Step 27 Tuning the stepper drivers.

    It is a must to have a ceramic or plastic screwdriver (Amazon do a plastic set of varying sizes) a slight slip with a metal screwdriver and the driver board is fried. Digital meter is handy but not totally essential as long as you have an analogue meter on a sensitive scale so easy to read 0.55 to 0.6 volts. Theories abound on setting the right voltage, but the e3d suggested voltages are a good start.

    If your mains voltage variation is sufficient to fry things as you mentioned, sounds like a brown out, then a UPS on anything you value is a good idea. Both your PC and the Pi in the BB wont like brown outs. The other thing you really need to avoid is equipment being repeatedly powered on and off if the supply voltage varies a lot/is applied removed repeatedly.

    Having a "contactor" type of power switch is good for this as the output power supplied to a coil holds the power button down. If the mains supply fails the coil releases the switch and power cannot be applied again until you physically hold the button down again.

    -----------------------

    It is very difficult to see if a pulley is slipping on a motor shaft, apart from the obvious of tightening the grub screws, make a mark across the pulley/motor shaft with an inedible pen so you can see if they have slipped in relation to each other.
     
  8. JonGillam

    JonGillam Active Member

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    Another possibility that I've ran across before that causes this, is over heating of the stepper drivers. Is your electronics cover fan in place and working? The next time it skips, place your finger on the stepper driver responsible, *careful* it may be surprisingly HOT. If for whatever reason you find this is your issue, you can pick up small aluminum heat sinks for them that help quite a bit.
     
  9. Tim

    Tim Member

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    Thanks for the tip Jon ^

    My BB suddenly started getting massive layer shift problems out of the blue (one print it worked perfectly, the next I started getting layer shift problems). I ended up sticking a 80mm fan directly over the RAMPs board, and that seems to have fixed the problem. Phue.
     
    #9 Tim, Aug 21, 2016
    Last edited: Aug 21, 2016
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