Full Y Range is not being used, top left corner distance too far from print head

Discussion in 'Calibration, Help, and Troubleshooting' started by srd, Apr 16, 2016.

  1. srd

    srd Member

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    So this morning I've tried printing my first thing with large-ish dimensions (15cm on the X axis, 11cm on the Y axis). I've noticed that while the first layer printed really nicely towards the home position, the print head distance grew ever farther from the bed the closer it got to the top left corner. In that corner I had poor layer adhesion and poor infill behaviour because the fillament just dropped down to the layer instead of being deposited there directly. I'd guess around 1 to 1.5 mm more than near the bottom of the bed.

    So I tried auto-levelling the bed, and printing again. And I'm still getting the exact same behaviour after the auto-levelling (yes, I stored the new auto-levelling values to memory before trying to print again). And again I had the print head being noticeably further away from the bed in the top left corner. This time I had to abort the print because the PLA for the first layer didn't even properly reach the bed and was just pushed up against the print head so that the print head as pushing around a viscous mess of PLA.

    What may be compounding this is that my Big Box Pro does not seem to use the entire Y range when auto-levelling. The print head travels to just shy of the 160 mark instead of all the way to the 200 mark. I can move the entire range using the "Move axis" menu entry without problems and the print head finds the ooze bucket as well when running the calibration program.

    Any ideas on how to fix that pesky top left corner? The bottom left corner is fine by the way, and while the top right corner could be better it's not that bad that the print material can't reach the bed itself.
     
  2. R Design

    R Design Well-Known Member

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    I have a Pro and the autolevelling does a good - but not perfect - job.

    Obvious things that might upset it include:

    a) something very dirty going on on the surface (normally it reflects off the PCB);

    b) a sagging PCB underneath;

    For these the ultimate cure (if you read the maker's blog) is to paint the bottom of the glass with barbeque black paing!

    (I shoved some foam under my PCB to stop it sagging).

    Everyone who does it seems to prefer 9 point mesh levelling which you can activate in firmware (I haven't).

    This MAY be because it could compensate for any sag in the RODS.

    ps during autolevel the IR sensor (not the nozzle) is over about 40 and then 190 on the Y.
     
  3. srd

    srd Member

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    Rod sag may be the thing here. The PCB looked fine when looking at the bed from underneath.

    For now, I just stuck 3 more washers under the PCB for that corner screw, trying a print now. And there is no perciveable difference between the top left (previously worst) and bottom right (previously best) corner in the deposited filament.

    While doing a mesh levelling seems tempting, I'll hold off of a firmware update until we get a non-RC version for the Pro.
     

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