ABL issue with play in the rollers

  • Hi @admin,

    I have a very technical question about the ABL (auto bed leveling) feature.

    The nozzle is applying a downwards load on the build plate until the strain gauge registers a certain force. As I watch the procedure, the build plate also deflects downwards when the nozzle is pressed into it. This happens more on the left and right sides of the plate and I assume that it is due to play in the y-axis wheels (rollers) and slight flexibility the whole build plate structure. This would cause the measured z to be lower than it actually is. And since the nozzle never actually presses down on the plate during a build, the error should remain.

    I could imagine that a sensor like the BL Touch has a very light probe so that it wouldn't deflect the bed at all.

    What is the actual load (programmed into the firmware) that the ABL strain gauge is picking up? Can this value be tweaked so to reduce the possible deflection error of the build plate structure?


  • Hello @admin,

    I followed the suggestions in the forum to tighten the rollers and I did that. Now me bed and X gantry have no slop in them.

    But still when I ABL, the plate still deflects more on the left and right sides than in the middle.

    The best way to see this is to watch the opposite side of the bed. When the nozzle pushes down in locations 1–4, the right side of the bed raises. And when the nozzle pushes down in locations 13–16, the left side of the bed raises. The bed doesn't move for locations 5–12.

    Can we adjust the sensitivity of the strain sensor?

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