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Layer shifting Y-Axis

Discussion in 'Troubleshooting' started by Lazytron, Jul 11, 2024.

  1. Lazytron

    Lazytron New Member

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    Suddenly getting some pretty severe irregular layer shifts (several mm) on the Y axis.

    Just checked and all of the gears seem tight, they're just friction fit with the set screws on the rods, correct? I did notice one of the sliders looks like it's separated at the snap-together underneath, but everything still seems to be sliding smoothly (not sure where i'd get a replacement anyway).

    Any suggestions? Trying to reduce speed and see if I can make it through the current items to print, but im at a bit of a loss for what other issues to look for.
     
    #1 Lazytron, Jul 11, 2024
  2. mark tomlinson

    mark tomlinson ༼ つ ◕_ ◕ ༽つ
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    On an R2?
     
    #2 mark tomlinson, Jul 12, 2024
  3. Lazytron

    Lazytron New Member

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    Yep
     
    #3 Lazytron, Jul 12, 2024
  4. mark tomlinson

    mark tomlinson ༼ つ ◕_ ◕ ༽つ
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    Need picture of the "sliders looks like it's separated" but there are no belts to stretch so if the layers are shifting it is going to be:
    1) Bad bearing causing "stickage" while that axis is moving. (The bearings should last darn near forever, but they are likely using the cheaper Chinese LM bearings as they did on the R1 and those don't last as long.)
    2) Stepper driver for that axis (part of the main controller board on the R2/C2) is failing*
    3) stepper motor for that axis is failing OR needs the stepper driver current adjusted**

    * there is no way to replace just the driver on the R2/C2 so the entire control board would need to be replaced. PartsBuilt.com may have those.

    ** I don't remember for sure, but I am not certain the stepper drivers are adjustable on that control board either -- but I think they can be.
     
    #4 mark tomlinson, Jul 12, 2024
  5. Lazytron

    Lazytron New Member

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    Here's what I was calling the slider, looks like the plastic tab just gave up but it seems otherwise intact. Is that what you mean by "bearing" or is there somewhere else I should be looking at?

    Tried a gantry alignment this afternoon that seemed superfluous, but maybe it will help.
     

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    #5 Lazytron, Jul 12, 2024
  6. mark tomlinson

    mark tomlinson ༼ つ ◕_ ◕ ༽つ
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    Yep, inside of that little plastic shell is an LM8UU (LM6 for the C2) bearing that rides the rails. Looks like this: https://www.prusa3d.com/product/linear-bearing-lm8uu/
    They are (the good ones are) permanently lubricated. The Robo ones are not the best and you can try using a bit of lithium grease to lubricate them. The real solution is to replace the bearings (if the lubrication does help). They are not expensive, just a hassle to replace.

    LM6 example: https://makerstore.cc/product/us-bear-lm6uu/
     
    #6 mark tomlinson, Jul 12, 2024
  7. mark tomlinson

    mark tomlinson ༼ つ ◕_ ◕ ༽つ
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    If they wear enough they can score the smooth rods and that is much more of a pain to fix :)
     
    #7 mark tomlinson, Jul 12, 2024
  8. Lazytron

    Lazytron New Member

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    Awesome, I'll grease the rails and see if that helps.

    Any STLs or suppliers for the housings? If I'm going to have to pull them anyway I'd like to replace the cracked parts as well.
     
    #8 Lazytron, Jul 12, 2024
  9. mark tomlinson

    mark tomlinson ༼ つ ◕_ ◕ ༽つ
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    #9 mark tomlinson, Jul 13, 2024
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  10. Lance Weston

    Lance Weston Active Member

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    Get yourself a 3mm button head screw set. Button head for clearance. Where the block has separated drill a hole in both corners of the block. Select a screw that just fits through the block and secure with a nut. You have now repaired the block and fixed your problem. I have to do this with every block, eventually they break.
     
    #10 Lance Weston, Jul 29, 2024
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