Inconsistent top/bottom surfaces with coarse layer height

[Marcz22]

Hello Everyone!

I am having a small issue with my prints' quality and I can't figure out why. When I'm printing high amounts of material, the surfaces become wavy, coarse, full of blobs. This happens at high wall counts, and high infill densities as well, but not just to the solid area, but everywhere on the print.

See this picture, the 1st layer on a 25% infill:

After a few layers, it clears up nicely:

On another model, printing simultaneously, infill is very unstable:

Since it usually clears up with 2-3 layers, it hasn't caused any major problems until now, but still, it massively decreases the quality of thin (low Z) parts.

The material you see on the picture is PETG, but PLA and ABS both produce the same issue. I have a different profile for different materials, they differ mainly in speed and temperatures, nothing else much.

I am printing at .35 layer height lately, so I have exclusively .35 examples to look at. Is it possible that I need to adjust something to print .35 stable? Is .35 viable with a .4 nozzle? I've found conflicting information biasing towards yes, but feel free to correct me.

I've tried to upload my factory and fff files, but couldn't. I can share my process settings if needed.
I have a Modix Big-60 V4 printer and this very print (on the pics) is happening at 240°, 8 walls, 8 top/bottom layers, and 25% infill, PETG, 2600 main speed.

Thanks!

[S3D-Jason]

It's somewhat normal in my experience that the first solid layer on top of the infill isn't perfectly smooth. That's part of why you print multiple top solid layers, to allow those defects to smooth out.

You could always try decreasing the solid infill speed, or potentially try higher infill percentages or a different infill pattern to see if those help.

[TheBum]

Another option along those lines is to use the Dense Infill settings to transition between your main infill and a fine enough infill to support smooth top layers. I always use at least 3 top layers regardless, sometimes more if I'm using Adaptive Layer Heights.

Speaking of which, it would be nice to get the option of specifying top (and probably bottom) thickness in mm, especially when using Adaptive Layer heights.

[Marcz22]

It's somewhat normal in my experience that the first solid layer on top of the infill isn't perfectly smooth. That's part of why you print multiple top solid layers, to allow those defects to smooth out.

I am not worried about the top solid layers, as you said, it does indeed smooth out, which I am happy for. I am worried more about the infill being so out of shape. It looks like it was molten way way too hot, and oozed randomly, but I don't feel 240° is that much for PETG. Or should I just not worry about the inner structure of the non-solid infill?

Also I have printed a few thin (6-8mm), flat, disc-like parts, and they came out with a really low quality top surface. The inconsistency, blobs, and random molten flows of inner infill and intermediary solid layers right below the top were having an effect. I entertained the idea of ironing such prints, but I have not tried that yet. Do you suppose that could work?

Another option along those lines is to use the Dense Infill settings to transition between your main infill and a fine enough infill to support smooth top layers. I always use at least 3 top layers regardless, sometimes more if I'm using Adaptive Layer Heights.

I thought dense infill was just basically another top/bottom solid layer, but I will look into it.

Thanks for the tips! I might post an update later; but I'd be glad to hear any other ideas.