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tinsoldier

First layer oozing, excessive extrusion (Cura issue?)

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I've finally dialed in most all of the settings on my Ultimaker/Cura nicely but the first layer gives me trouble. It sticks fine, has for a long time, but the amount of material extruded in this layer is overkill. It seems like it is extruding 150-200% as much as needed and the nozzles forms grooves in (smears across) the excess material that has oozed out. Every other layer lays down nicely. I've seen references to how well "Cura stitches the first layer," and other comments that seem to suggest that the first layer is intentionally laid down extra thick so I suspect this is a software issue (or a user issue with the software ;) )

A couple other observations:

 


  • [*:3uvyu979]manually twisting the z-axis about 3-4 notches (Z+) produces a more pleasant first layer fill but very thick still. Incidentally, my Z-limit is set to a few thousdanths of an inch above the table (thickness of piece of paper).
    [*:3uvyu979]adjusting first-layer thickness does have an effect but doesn't solve the issue; seems like there is still excessive extrusion
    [*:3uvyu979]this doesn't ruin the print by any means but it makes the bottom surface ugly and when printing the second layer, the sprung table rocks underneath the nozzle as it rams through the ooze piles. That seems bad.

 

Googling for this issue has been difficult but since it seems like a configuration/software issue I thought I'd quickly chime in here to see if this was by design. If that were the case, I'd be curious what my options are to control that mechanism and if this isn't a known issue, I can go back to my machine tonight and get some pics and example gcode.

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try printing something that has a larger flat area, i.e. 8x8cm (it doesn;t matter what it is, you are stopping the print after 2 layers anyway). and slice in cura with the initial layer set to 0 (assuming you try printing 0.2mm layers, just for this test).

once the print starts (with 3x outline, just to be sure the nozzle is properly primed), lower the bed by a couple of clicks, and watch the infill extrusion for a couple of lines. they should form small ridges at the point of return, but be somehow flat in the center (some small ridges are preferred, since the first layer should be slightly overfilled. if you see large ridges, lower the bed more, and make sure you count the clicks, until the first layer looks decent. each click/notch is about 0.06mm (I can count 50 clicks for a full rotation), after which you can calculate how far off your measurements of the table hight are, and you can adjust, either the hardware stop, or your gcode header.

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Most likely it's the "first layer thickness" feature that you're not expecting. Cura is printing the first layer thicker then the other layers. This really helps in getting the first layer to stick properly to the tape, without sticking it so well to the tape that you cannot remove it. If your first layer is oozing all over the place, then your start height is a bit to low. You can manually turn the bed a bit down during printing of the first layer to see if it goes better. (just grab the bottom of the Z screw, and turn it, don't worry, you will not damage the machine)

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