Top Layer Issues

Hey All,
I have a very simple print that is driving me nuts because I cannot get it to have a smooth top layer.
It appears the infill is collapsing and causing holes in the top layer.
I have attached the stl file.

I have tried setting the nozzle temp down from 270 to 240 to 245 (I’m printing with ABS)
I have tried adjusting the filament diameter from 2.85 to 2.87 to 2.83 made no difference.
I have tried adjusting the printing speeds for the Infill and top layer currently running at 15mm/s

The only way I was able to get a successful test print was to up the infill to 85% (It was at 40).

Cura 21.02 3.5mm nozzle 40% infill 270C 100C bed. 2.85 Dia filament

Cura 3.04 3.5mm nozzle 40% infill 270C 100C bed. 2.85 Dia filament Irioning enabled.

Cura 21.02 2.87 and 2.83 filament dia Printing speeds decreased.

Cura 3.04 3.5mm nozzle 85% infill 245C 100C bed. 2.85 Dia filament Irioning enabled.

Its a little hard to see in the photo, but the top layer of the plastic drops between the outside perimeter and the inside perimeter of the fat part of the E.

I’ve never had the printer have issues with the top layer before so I’m a little stumped as to what to do. When examining these parts under magnification you can see the extrusion has a zigzag edge, and that it doesn’t appear to touch the edge of the previous extrusion.

I’ll also add the walls are perfect, no missing spots or bulges.
Dimensionally the prints are coming out correct also.

I’m stumped.

For some reason, the Forum keeps deleting my attached pics.

Earl.stl (70.4 KB)

Try increasing the number of top layers. I don’t use Cura, so not sure if the setting exists or something comparable.

I forgot to mention that.
Nozzle .35mm
layer height 0.2
Walls/top 0.8 (so 4 layers)
infill normally at 40% with using the lines type.

Yeah, more top layers and additional shells may be the way to go there. Or if it’s a small enough part just keep the high infill. Turning cooling fan on for the last layers (it’s basically a bridging operation) would also help.

So I went back and tried printing an old file that works from a few weeks ago. The only difference in my setup for the one that worked was I was using a Red colored ABS and now I’m using Black.

But it did the same thing with a crappy top surface.

Filament can have an affect on your overall print quality. Is this an old roll of filament? Filament can absorb moisture overtime becoming much more difficult to print with. I would recommend you try switching back to the red ABS using the new model and see if you are still seeing the new model come out poorly. If not it will almost certainly be something going on with the filament.

Sorry for the late reply on this.
The Black ABS was a brand new roll just opened from Village Plastics.

I found some other parts that I had printed before switching to the Red ABS with the old roll of Black ABS and they were showing issues with the top surface also. So I guess for some reason my printer doesn’t like printing decent top surfaces when using Black ABS unless you run it close to 100% infill.

Ok, I think I might have figured this out.
Just for giggles, I ran this file through a really old version on slic3r (1.2.9 for those playing along at home)
It printed just fine with a good top surface. (It had some adhesion issues to the bed but the top surface is 100% better than my other attempts)
Digging through the slicer profile I noticed the Default Extrusion Width was set to 0.25mm, Infill was 0.24mm, and Top solid Infill was 0.25mm (Print settings/ advanced/ Extrusion Width settings)
Checking Cura 3.0 it has all of these settings set to 0.35mm (These are under the Quality setting)

Looking closely at the attached pictures especially the pic of the bottom of the part. It appears that the 0.35 spacing is to much for the printer and is leaving a gap between each extrusion.
I don’t know if its common for the Extrusion width to always match the nozzle size? If it is I guess I’m underextruding then?

Posting an update here.
I removed the nozzle and soaked it in Acetone for a few days to dissolve all of the ABS.
This is supposed to be a 0.35 nozzle that I got when purchasing the hexagon upgrade.

I can’t get a piece of 0.25mm wire to pass through it. So either this nozzle has a partial clog or it is the incorrect size. I’m leaning towards a clog due to the erratic way the plastic emerges from the nozzle. It wants to curl around and up back to the nozzle instead of dropping down an coiling up on the bed.

I got some drill bits coming, so I’ll see what I can fish out.