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Gaps in bottom solid layers (infill)

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I realise this problem has come up a few times before but since this is on a UM3, I thought I'd post it here.

I'm more curious as to what causes this rather than being worried about solving it.

So, the bottom layer prints fine, the 2nd layer prints with gaps in the infill (pictured), the 3rd slightly improved and then I think then it was the 4th / 5th that printed perfect (also pictured) and from then on, no problem at all. It's almost like the nozzle is slightly too far and everything levels out over time. I don't believe this is underextrusion as the problem cures itself with the same temperature and even faster speeds.

Relevant Settings:

Active levelling ON

Layer height: 0.2mm

Top/bottom speed: 35mm/s

Temperature: 210 degrees

Colorfabb PLA/PHA


2nd Layer


4th / 5th Layer



Edited by Guest

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Probably is the high differences that Cura profile sets for infill and top/bottom layers. If you unhide the speed options you will see that there are many different speed settings for each kind (outline/infill/etcetc). So probably this top layers over a bottom are printed at a different speed. Also the line width has many different settings for each kind of part, so probably a change of flow for that area causes that holes.

Btw I saw the same too on my prints until I did some hard mods.

Other thing that affects that is the automagic acceleration/yerk control. All that fluctuations on the extrusion flow can cause that. But anyhow the profiles give a nice finish in the end.

Edited by Guest
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