What am I looking at here? (Top layer bumpy lines)

As you can hopefully see in the attached images, the smaller areas and the TARDIS shape are smooth and not shiny. But large portions of the flat area around are shiny and oddly rough.

The bed is as level as it can be, bottom layers are smooth and and fully adhered.


I'm using Cura to slice (4.1.0), on a Mendel90 Dibond, 0.4mm nozzle. I'm printing on a sanded pertinax surface (similar to protoboard material or FR4). Material is PLA.


Weirdly enough, I used to print on an unleveled glass bed with glue stick all over the place, where the bottom layers were absolutely horrible, but the top layers were pristine.

Any ideas or suggestions please?

How many top layers are you using? It looks like the infill is 'shining' through.

Can it be the extruder is skipping sometimes? Maybe the gears are filled up.

Did you try new filament without reconfiguring flow in Cura? Could be just a too low flow.

Maybe the last option would be the hotend might be skewed somehow? Is it upright in a 90º angle to the print surface on both axes?

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http://www.marinusdebeer.nl/

4 top layers, infill is 100%.
Thing is, it used to print near perfect top surfaces on the other print bed. The bottom was horrible, though, half torn up, wildy varying adhesion, etc.
I seem to have thicker lines in between the flat ones, so I'm rather guessing it may be overextrusion, not under? I reduced the flow by 2% now and am testing again.

Quote
Arakon
4 top layers, infill is 100%.
Thing is, it used to print near perfect top surfaces on the other print bed. The bottom was horrible, though, half torn up, wildy varying adhesion, etc.
I seem to have thicker lines in between the flat ones, so I'm rather guessing it may be overextrusion, not under? I reduced the flow by 2% now and am testing again.

You could also try to add ironing the top layer in cura. It adds print time but should make for a nicer top surface finish. However, it seems that would only be fixing a symptom while there is probably an underlying issue. Are you sure nothing else changed after changing the printbed surface?

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http://www.marinusdebeer.nl/

Check the end of the nozzle is square to the bed.
Doesn't look like 4 layers as you can see the previous layer ridges at about 5% spacing.