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Unresolved Home command fail before Auto Level?

Discussion in 'Troubleshooting' started by Roger Worden, Dec 31, 2020.

  1. Roger Worden

    Roger Worden New Member

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    I am experiencing an intermittent failure of auto leveling at the start of a print job. I will post this on both the Simplify3D site and the Robo3D site. I do not know if it is a software, firmware, or hardware failure.

    Simplify3D version 4.1.2
    Robo3D R1+ with Marlin V1 firmware connected via USB through a simple USB-C adapter
    MacBook Pro running Catalina 10.15.7 (problem has occurred on earlier OS versions)

    I usually start with motors disabled, the print head roughly centered in X and Y, and about 30 to 60 mm up from the bed.

    Simplify3D starts by sending G90, M82, M106 S0, M140 S45, M190 S45 to set things up. Then:

    G28 to move to the home (0,0) position.
    G29 to initiate auto leveling. The head moves to about the middle of the bed, moves down slowly to probe Z, then moves to nine points to measure the height. The first point is near (0,0).

    When the failure occurs, it seems that the G28 move to home fails. Then when the auto level starts, the head is in the middle of the bed for the first point. Moving in X for the second point causes the head to hit the right side X stop and then the motor or belt grinds. Because the first point was not near (0,0), the whole auto level sequence is off. At this point I hit the Emergency Stop.

    I do not know what, if anything, triggers a failure vs. a success.
    • I have tried moving the head to (0,0)
    • I have tried Zero X and Zero Y in the software.
    • I have tried different starting Z heights.
    • I have turned the printer off and on (which does not shut down all power).
    • I have unplugged the printer from power and plugged back in.
    • I have started the print job before and after the print head is up to temperature.

    I have captured the Communication log entries from S3D for a success and a failure. In both cases I see G28 and G29 being sent, so S3D is not failing to send the Home command. Annotated log snippets are attached.
     

    Attached Files:

  2. mark tomlinson

    mark tomlinson ༼ つ ◕_ ◕ ༽つ
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    So you need to determine why the HOME is failing because if that happens then everything after will also fail.

    I would experiment by randomly moving the extruder somewhere and then sending a G28 in the Gcode console. Repeat this until it fails to actually home -- try moving the start position around randomly in case that matters.

    Once it fails to home (or even if it doesn't) after the G28 move is complete issue an M114 in the terminal to see where the printer is reporting the head at. It should be 0, 0 (X and Y) and if it is NOT actually at HOME then you have a problem. When that happens review how the head moved (if it moved). There is likely a sensor issue where one of the switches is falsely reporting HOME when in fact the extruder is not at HOME.
     
  3. mark tomlinson

    mark tomlinson ༼ つ ◕_ ◕ ༽つ
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    The printer firmware/software only have ONE position that is certain and that is HOME. Nothing else has sensors. Every other position is calculated from HOME :)

    The most common cause of the HOME failing is a false sensor reading. One of the switches reads triggered before the head actually reaches the home position. That can be a bad connection / wire or a faulty input on the RAMPS board -- or something gets in the way and triggers the switch before it should.
     
    #3 mark tomlinson, Dec 31, 2020
    Last edited: Dec 31, 2020
  4. Roger Worden

    Roger Worden New Member

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    G28 (plain) moves the head to the left, then the bed to the back. Then it moves both to near center, moves Z down to touch the bed. M114 then reports X:120 Y:127 Z:-1. This is consistent, regardless of starting position.

    G28 X moves the head all the way to the left (0,)
    G28 Y moves the bed all the way to the back (,0)
    M114 then reports X:0 Y:0
    This is consistent. If it was a sensor issue I would expect inconsistent results.

    Power-cycling does not change this.
    Zero X and Zero Y buttons in S3D software does not change this.
    Using G90 Absolute before G28 does not change this.
    Reverting to an original R1+ profile in S3D does not change this.

    It's as if something in firmware is redefining the meaning of the plain G28 to (120,127,-1) but not overriding the meaning of G28 with parameters.

    G28 X0 Y0 Z0 *does* move the head to (0,0,0). So I plugged that into S3D's process start script, in place of plain G28, for now. It seemed to kind of work OK on the first job. The head moved to (0,0) and maybe started to move down, but did not go all the way to Z=0 before G29 started the bed leveling, which proceeded correctly.
     
  5. mark tomlinson

    mark tomlinson ༼ つ ◕_ ◕ ༽つ
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    That is incorrect behavior for a Robo R1 series with stock firmware.
    The G28 should move the bed directly to X = 0, Y = 0.

    I suggest as a start you reload the stock firmware and see where that gets you. If not let me know exactly which version you loaded.

    The autoleveling (G29) will move the head to the center and then back to home for the first of the 9 points, but not the G28 itself.

    The C2/R2 are configured differently so that behavior does not apply to them.
     
  6. Roger Worden

    Roger Worden New Member

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    OK, I'll try that some time this weekend. I have not updated the R1+ firmware before. Is there a preferred stable version?
     
  7. mark tomlinson

    mark tomlinson ༼ つ ◕_ ◕ ༽つ
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