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Solved Strangeness on bed leveling

Discussion in 'Troubleshooting' started by David Lockwood, Jul 18, 2017.

  1. David Lockwood

    David Lockwood Member

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    I have embarrassed myself so many time asking silly questions on this forum I guess one more won't do me any worse. I replaced my stock extruder (Robo3d R1+) with a Titan from E3D. I finally got it all back together after figuring how to reverse the direction on stepper motor. When I try to print now my G29 puts on quite a performance. After doing a G28 it begins the 9 point check. When it gets to the first point it goes up rather than down. On the second point it functions properly the same for the third. It then goes through a random mixture of up and down at the remainder of the check points. I checked the level of the X carriage thoroughly and thought I might have done some damage (I don't know how) to the end stops so I replaced them (both). I am mystified. I reversed the stepper in firmware. Could I have accidentally messed something up?
     
    #1 David Lockwood, Jul 18, 2017
  2. mark tomlinson

    mark tomlinson ༼ つ ◕_ ◕ ༽つ
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    That is almost always a Z switch (there are two, one on each side) triggering in the wrong place. They are N/C switches held open by the crossbar. In proper operation when the extruder hits the bed, one will trigger (change from being held open to closed) and signal Z HOME. If that happens due to a switch being loose, out of position or whatever... same result. Arduino thinks Z is homed and will ONLY go up.
     
    #2 mark tomlinson, Jul 18, 2017
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  3. David Lockwood

    David Lockwood Member

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    I thought I had summarized the fact that I had checked out the items you mentioned. I'll tear it down and do it again to see if I can discover the problem.
     
    #3 David Lockwood, Jul 18, 2017
  4. mark tomlinson

    mark tomlinson ༼ つ ◕_ ◕ ༽つ
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    Yes, but the code is the code :)

    (All of the following refers to the stock Marlin firmware, anything you have changed is not a known quantity, but you know what you changed in the configuration file. )

    The autoleveling is a set sequence and if at some point it would not go down, the reason is that it sensed it was already at Z home.
    There are only the home switches for sensing.

    There is nothing really mysterious that happens in the autolevel sequence. It is preset to sample at a number of fixed points, but beyond that the extruder will behave as normal (meaning if it thinks it is on the bed it will only go up).

    It may be a bad switch or it may be a switch slightly out of position or it may be a bad wire or a bad RAMPS, etc.
    What you can take away is that the Arduino thinks a Z home switch was tripped.

    All that said I am leaning towards a switch issue simply because if happens only at one sample point if I read that correctly.
     
    #4 mark tomlinson, Jul 19, 2017
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  5. David Lockwood

    David Lockwood Member

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    Finally found my own solution. Turns out that the springs that return the X axis to the proper position after contacting the bed are hanging up leaving the axis out of wack. The problem is when it moves to another point it either straightens itself out or move the other way. If i simple press on the axis bars it returns to normal. I must have an excess of grease, cheese or other foulness in there. I'll clean it out. Weirdness abounds.
     
    #5 David Lockwood, Jul 21, 2017
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