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Solved Y-axis grids and only move partway

Discussion in 'Troubleshooting' started by Frank van Gilluwe, Oct 19, 2017.

  1. Frank van Gilluwe

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    I've had about 20 successful prints since new, but now the Y-axis is acting strange. When I do a z-axis calibration, the extruder moves to home (good) and then moves towards the front. After moving about 2 inches it makes a non-metallic grinding sound and stops about halfway. Then the Z axis moves to the bottom and starts up. I normally turn off the power at this point, knowing the calibration will be wrong, since the extruder head is not at the full front position. I've done this now about 6 times in a row (checking and testing between runs), so it's not intermittent.

    With the power off both the X and Y axis move stiffly but smoothly. Both axis require about the same manual force over the total travel range. Both home microswitches are working (it does stop at home). Looked at all the rods and they appear in the proper locations and seated in the bearings. The two thiner x-axis rods also look correct and they are not binding on the case. Checked all 6 belts - and they look fine, no missing teeth. They are also straight (I had one rod out of the bearing out when I first got the C2, so I know what it looks like). Also confirmed each pulley's set screws are tight - on the rods (4 places) and the Y stepper pulley.

    Any ideas?
     
  2. mark tomlinson

    mark tomlinson ༼ つ ◕_ ◕ ༽つ
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    Well, something is binding mechanically. The gantry makes it a bit more effort to track all that down (more moving parts and belts/cogs).
    Could be many things from a shifted rod causing something to hit the case to a bearing. I would suggest manually moving the extruder around and see if you can feel what is binding.
     
  3. Frank van Gilluwe

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    As a follow up, even while it was happening during calibration, it would print fine. No noise during printing, but I was printing small items with limited Y axis movement. The binding/noise went away on it's own. From a Robo tech, it sounds like a tiny scrap of PLA might have got into a cog or the belt and worked itself out.
     
  4. OutsourcedGuru

    OutsourcedGuru Active Member

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    Yeah, that's what I was going to suggest given how many successful parts you've already printed.

    I had one job turn into the Flying Spaghetti Monster when the part separated from the raft and I had bits of spare/melted plastic here, there and everywhere, threatening to clog moving parts.
     
  5. Frank van Gilluwe

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    So far I've stopped a few rare problem prints as it happened. It would be tough to catch it a few of my 8+ hour prints! So far nothing serious.

    Maybe in a few years, we'll have cameras that can detect a print failure as it happens and shut off the print. Unlikely, but one can hope :)
     
  6. Geof

    Geof Volunteer Moderator
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    Google prusa mk3. Will be the "smartest" printer of.our standard to date
     
  7. OutsourcedGuru

    OutsourcedGuru Active Member

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    If you think about it, if the job has survived the first twenty layers then the success rate will climb rapidly from there.

    The exception for me currently is filament run-out since my sensors didn't work out of the box. But I'm fixing that.
     
  8. Frank van Gilluwe

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    I've been using my R2 for years now and had not solved the C2 issues that I started this thread with. I finally got back to my C2 as a friend wanted to use it. Still had the same grinding problems and would not place the head in the right start position. The print would work though.

    Solved the problem! On the screen: Utilities -> Options -> Eprom. Scroll down to Max Accelerations. Change the value of both X and Y from the default 3000 to 1000. (I tried 2000, but that didn't fix it). At 1000, it works great! This does not slow the print speed as it seems to only affect the speed moving from/to home at the start and end of the print.
     
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  9. mark tomlinson

    mark tomlinson ༼ つ ◕_ ◕ ༽つ
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    Excellent way to fix it and interesting that acceleration made the difference.
    Non-intuitive since acceleration is how fast it will speed up when it changes speed and direction.
    Lowering it will have a small impact on overall print time, but not usually a huge impact by any means.
     
  10. Frank van Gilluwe

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    The friend I'm giving the C2 to is familiar with stepper motors. He believes the noise was the stepper motors not able to overcome the power needed under high acceleration request, and they 'slip'. Zero harm to the motors or the belts, but the positioning is lost and the noise it makes is scary. Perhaps my belts are a touch too tight, but they seem reasonable. I can't tell any difference between my C2 and R2, although I have no way to accurately measure the tension. Anyway, hopefully, if someone else runs into this problem, it's an easy fix that has a negligible effect on the print speed. You can mark this "Solved"!
     
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  11. Geof

    Geof Volunteer Moderator
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    I’d imagine the issue is the gantry is not square or one of your rods is a bit bent. Slowing down the travel allows the stepper to overcome the resistance. Not square (even by a little) can cause some real grief with the motion system the R2/c2 uses
     
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  12. mark tomlinson

    mark tomlinson ༼ つ ◕_ ◕ ༽つ
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    My C2 arrived with the gantry knocked well out of square. I had to do some disassembly and reassembly to even use it the first time :)
    Pretty sure I have a thread on that unboxing...
     

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