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Solved Terribly Inconsistent Printer!

Discussion in 'Troubleshooting' started by Ender, Mar 1, 2017.

  1. Ender

    Ender Member

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    Well I am back, with the same problem.
    I printed about four things yesterday with all of them having great adhesion to the bed at a z offset of 0.12 mm. I changed filament and started a print. And now it was to high off the bed, nothing crazy, but not what it was the day before. So now I had to change it to -0.03 mm and it could go just a little bit more negative, to get it to what it was the day before. This is very irritating.

    On another note, I have noticed when the printer does its autoleveling the microswitch on the right side is always triggered, but on the left side the switch is activated when the nozzle touches the bed. Seems like the weight of the motor is to much for it to lift up off of the switch.
     
    #1 Ender, Mar 1, 2017
  2. mark tomlinson

    mark tomlinson ༼ つ ◕_ ◕ ༽つ
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    Sounds like one of your switches is not positioned correctly.
    Adjust the position on the Z rod until they both trigger as close together as you can get them with the crossbar in the middle of the bed.
    They have little nuts you can loosen to adjust them...
     
    #2 mark tomlinson, Mar 1, 2017
  3. mark tomlinson

    mark tomlinson ༼ つ ◕_ ◕ ༽つ
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    This is what people mean when they talk about "dialing-in" or adjusting the printer to work at its best. There are a lot of little things that may need tweaking.
     
    #3 mark tomlinson, Mar 1, 2017
  4. Ender

    Ender Member

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    They are seated correctly, as far as I can tell. But the nozzle doesn't touch the bed on the right side, but does on the left. And it has to be like this to get a level print.
     
    #4 Ender, Mar 1, 2017
  5. mark tomlinson

    mark tomlinson ༼ つ ◕_ ◕ ༽つ
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    Then you need to do a manual leveling across that axis. What we call a "paper leveling" because you normally use a sheet of paper to manually level the carriage from side-to-side so that the nozzle is just touching a sheet of paper.
     
    #5 mark tomlinson, Mar 1, 2017
  6. mark tomlinson

    mark tomlinson ༼ つ ◕_ ◕ ༽つ
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    #6 mark tomlinson, Mar 1, 2017
  7. mark tomlinson

    mark tomlinson ༼ つ ◕_ ◕ ༽つ
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    Those nuts on the side allow you to loosen the mounts and make sure the switches are snug up against the carriage with the nozzle off of the bed. On both sides.
     
    #7 mark tomlinson, Mar 1, 2017
  8. Ender

    Ender Member

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    When I level it on both sides with a piece of paper, then it won't print level. It is too close on the right side and no filament will come out.
     
    #8 Ender, Mar 1, 2017
  9. mark tomlinson

    mark tomlinson ༼ つ ◕_ ◕ ༽つ
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    That is because the switches have to be adjusted :)
    You can't just spin the rods. you have to make sure the two switches are correctly positioned on the crossbar or they will trigger at different heights...

    The switches are the physical Z home indicators. When they trigger it is ON THE BED as far as the printer is concerned. You want them to both trip as close to the same place as possible.
     
    #9 mark tomlinson, Mar 1, 2017
  10. mark tomlinson

    mark tomlinson ༼ つ ◕_ ◕ ༽つ
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    #10 mark tomlinson, Mar 1, 2017
    Last edited: Mar 1, 2017
  11. Ender

    Ender Member

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    I adjusted the micro switch mount, which seems to be held very tight around the nut even when the screw is loose. Now the right switch will trigger when the nozzle is on the right and the left switch will trigger when the nozzle is on the left, and they both trigger when it is in the center.

    Now I can make the X axis level with the bed and it will print level. However, I am not totally convinced that this will fix the inconsistencies of the z offset. I guess time will tell.

    Thanks for the help!

    EDIT: I did some more calibration circles and it seemed like the left side was printing higher up so I kept turning the screw to lower that side with little to no effect. I ended up lowering the z offset to -0.02 and it was so close to the bed that it would print on the right side. After adjusting the rod on the right side and trial and error with calibration circles, I finally got it printing level.

    But now the micro switch on the right side will only trigger when the nozzle touches on the right side during the bed leveling procedure. There is also a lot of play in the threaded nut/rod assembly, I don't see it being possible to get both switches to trigger reliably at every point during the bed leveling procedure.
     
    #11 Ender, Mar 3, 2017
    Last edited: Mar 3, 2017
  12. WheresWaldo

    WheresWaldo Volunteer ( ͠° ͟ʖ ͡°)
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    The design actually only needs one side to trigger, while it was a clever way to introduce Z endstops by using the nozzle itself as a probe, the actual implementation is a bit suspect. As long as you are getting even prints all around the bed don't worry too much about which endstop switch triggers first.
     
    #12 WheresWaldo, Mar 3, 2017
  13. Ender

    Ender Member

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    Well then I won't worry about that.

    It still doesn't explain why I keep having to change my z offset every few prints. Any ideas?
     
    #13 Ender, Mar 4, 2017
  14. mark tomlinson

    mark tomlinson ༼ つ ◕_ ◕ ༽つ
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    Something is moving.

    Z offset is defined in mm (usually a fraction of a mm) and is the mechanical offset left over after the extruder is used to probe the bed with the switches to sense it. Think of it as the mechanical "slop" left over from the probing. The probing determines where the "bed" is and that "slop" is the offset from that you need to print the first layer correctly. All other layers are defined in the slicer and based on the first layer position.

    If your Z offset is changing then mechanically you have slop in the "detector" -- which in this case is the extruder itself and the X axis crossbars that are lifted to sense the bed (and obviously the Z switches and mounts).

    It is usually a switch or a mount. Test it (tell it to do an autoleveling run) and watch the switches and mounts for movement. It does not have to be MUCH movement to matter when you are dealing with fractional MM layers.....
     
    #14 mark tomlinson, Mar 4, 2017
  15. Ender

    Ender Member

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    So I have inconsistent slop. I will try to tighten up all the screws in the area and see if that helps, Even though I think I got most of them if not all of them when I was trying to adjust the height of the switches.

    Would a video help?
     
    #15 Ender, Mar 4, 2017
  16. mark tomlinson

    mark tomlinson ༼ つ ◕_ ◕ ༽つ
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    Possibly. It can't hurt :)

    The best approach is to force it to do an autoleveling move (G29; gcode) and carefully watch the switches on both sides. Make sure they are not moving up/down any, just opening and closing as needed. The mounts they have those switches in can sometimes work loose and then the switch (mount and all) will move slightly when the bed is being probed. That is bad.
     
    #16 mark tomlinson, Mar 5, 2017
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  17. mark tomlinson

    mark tomlinson ༼ つ ◕_ ◕ ༽つ
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    One other thing, but far less usual is that there may be a loose connection on one of the switches. Since the Z axis ones are normally closed and they go open for a Z home indication, if you have a loose wire/connection it will present a false HOME.
     
    #17 mark tomlinson, Mar 5, 2017
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