Is this under extrusion?

[Thadote 0]

This happens from time to time. it mostly happens on the first layer after some infill.

Is this under extrusion? if so, what can I do to helt it? if not, what is it then?

The outher (and inner) surface looks good, there are no string, no deposits from oozing, I don't think there are any problems other than this, and it bothers me.

I had one time where the printer was printing in the air, this was due to a knot on the filament, but can this still course problems? because of the knot, the drive wheel was dirty, so I cleaned it, thus there should be no problem there.

The printer have (only) been running for a week, if that have anything to say..

[Nicolinux 288]

Hi,

this doesn't look like under extrusion to me but rather the first "bottom" layer after some infill. If the photo depicts the finished object, then it is a huge problem. But if it is just printing one layer and then another few over that one, then it should be fine.

However it could be that the nozzle is a bit clogged. Check out this guide about the atomic method:

https://ultimaker.com/en/support/149-atomic-method

[JohnFox 25]

Had printing stopped when you took the photograph?

It just looks as though it had only printed a single layer for the top. What were the layer settings and top and bottom thickness?