Octoprint affects/influences homing

Discussion in 'Calibration, Help, and Troubleshooting' started by wfredette, Dec 4, 2016.

  1. wfredette

    wfredette Well-Known Member

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    Hi, all. I took a long (several month) mental health break from my printer, but came back to it this week. I had been having terrible trouble with Z homing, and the behavior of the Z axis in general, which I thought might be at least partially due to some interaction between Octoprint and the printer. Conventional wisdom here was that it was probably a mechanical problem. After replacing the Z axis bearings, switching to spider couplers and recommissioning the Z axis a few times, I got to the point of repeatable, if not perfect, results.

    So, I decided to connect Octoprint again. And all my problems returned. Z homing became completely unpredictable. OK one time and then driving the bed into the hotend the next. And the Y homing behavior changed, too. Though that had never been a problem before. I had to back out the Y endstop screw quite a bit. I think I probably contributed to the unpredictability by power cycling the printer in my any attempts to reposition the IR sensor, so probably sometimes the Octoprint had established a connection, and other times no.

    I disconnected Octoprint this morning, and spent an hour or so recommissioning the Z-axis and am printing again. So while my original question was "Can Octoprint affect the homing behavior of the BigBox?" I'm now pretty certain that it can, and my question becomes, "If yes, then by what mechanism?"

    EDIT: I should add that I was using Octoprint only for the camera. I entered the parameters provided in the e3D build documentation, but was not using Octoprint for any kind of machine control.
     
    #1 wfredette, Dec 4, 2016
    Last edited: Dec 4, 2016
  2. Dr Jeep

    Dr Jeep Well-Known Member

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    It's interesting but I can't see how it would. Is octoprint even connected at this stage (over USB), if you are just using it as a webcam then you don't need the USB plugged in and then some freak electrical interference issue aside there is no way it could interfere

    I'm the other way around (all my prints go through octoprint) I have noticed it interfering with SD card prints when I was first setting up the printer and trying to run the calibration prints. Never had a Z height issue though.

    When you get a Z homing issue what actually happens. the sensor fails to trip or the settings for the offiset in Marlin get changed by something ?
     
  3. wfredette

    wfredette Well-Known Member

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    As of now, the USB to the Pi is disconnected, and I am using the Pi only as a webcam to monitor the printer. I suspect that the IR sensor is failing to trip when Octoprint is connected, but cannot confirm this. When I autohome while the Pi is connected via USB, and Octoprint is running (though may not have established a connection to the BigBox), autohome typically results in the bed continuing to rise, driving it into the hot end.

    I guess I'm going to give up on Octoprint, as the printer is now working reasonably well, though still with some random ribbing/banding. I know that others have theirs really dialed in, but I'm not convinced I'll ever get good prints from this thing.
     
  4. Dr Jeep

    Dr Jeep Well-Known Member

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    It is possible, it does take a great deal of effort to get it fully dialled in but to it's credit mine once dialled in did stay there. My prints have room for improvement but now are better and far more consistent than my old K8200. The main issues are a bit of sag on the X/Y axis which is countered by bed levelling and though that 4 point guide for the bed was a good idea to prevent bed sag, it takes a lot of patience to get it trammed just right.

    I think E3D discovered the hard way why nobody else was doing a 4 point fixing like that, it is more rigid but any miss-alignment causes binding. I want to rid mine of couplers full stop (I aim to get some of those steppers with the built in Z screw when I can find them with a compatible pitch)
     
  5. Henry feldman

    Henry feldman Well-Known Member

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    Try covering over the red light on the camera. It may cast similar colors confusing the sensor?
     
  6. wfredette

    wfredette Well-Known Member

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    Hmm... interesting idea!
     
  7. Stefan

    Stefan Well-Known Member

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    normally when the IR Sensor is triggered the red LED on it will light up.
    So does it light up when homing with octoprint and it is crashing in the head?

    I cannot imaging the g28 from octoprint is processed different than from LCD or SD.

    One thing I can think of that that the IR sensor can get confused with the black and white of the heated bed, so a strip of single colored (black) tape under the glass where the sensor homes may help.
     

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