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Unanswered Auto bed level question

Discussion in 'Troubleshooting' started by Printrrnoob, Jun 15, 2015.

  1. Printrrnoob

    Printrrnoob Member

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    This might be a really stupid question, but I was wondering if the auto bed leveling also automatically controls the z height for the first layer. I figured it would because it has to hit the bed to level, so I'm assuming it knows when it hits the bed, so I would think it knows when it's perfectly above the bed to begin the first layer.

    Or does it just babe the usual switch to that we have to adjust?

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    #1 Printrrnoob, Jun 15, 2015
  2. WheresWaldo

    WheresWaldo Volunteer ( ͠° ͟ʖ ͡°)
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    I am working with the Marlin developers to help them "fix" auto-level for the Robo. the way it currently works, once the 9 point auto-level dance is complete the extruder head is sitting at the Z Axis Probe trigger point not at the top of the bed, depending on how much your build plate flexes this number fluctuates just a bit from machine to machine. You must correct for this minor discrepancy. On my particular Robo, I know that I have 1.18 mm between the location of the extruder just a touching the top of the bed and when it has triggered the Z minimum endstop(s). You compensate for this in the Robo firmware with an M565 command. The difference between the probe location and the extruder head is a negative number and should be entered as such. Most start-up G-Code will include an M565 Z-1.18 (in my exact case, your number may/will vary) somewhere near the beginning usually before the home all G28 command and the Auto-Level command G29.
     
    #2 WheresWaldo, Jun 15, 2015
    Mike Kelly likes this.
  3. Mike Kelly

    Mike Kelly Volunteer

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    What sort of correction are you looking to make?
     
    #3 Mike Kelly, Jun 16, 2015
  4. Printrrnoob

    Printrrnoob Member

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    I think I'm confused. So it doesn't have a z endstop right?

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    #4 Printrrnoob, Jun 18, 2015
  5. Mike Kelly

    Mike Kelly Volunteer

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    The Z endstops are under the idlers and they activate after the nozzle touches the bed
     
    #5 Mike Kelly, Jun 18, 2015
  6. Printrrnoob

    Printrrnoob Member

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    Oh okay, but you don't have to move them around to get the perfect height. Honestly, that and the auto bed leveling were the main reasons I bought the Robo. I can't tell you how many times I had to reposition that endstop on my old i3. Sometimes it would take me well over an hour to get it perfectly positioned so the hot end wouldnt smash into the bed or it be way too far off the bed.

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    #6 Printrrnoob, Jun 18, 2015

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