Retraction Issue?

So I have a Mini2 and I’ve been seen gaps in horizontal, flat surfaces appear (see attached). Is this a retraction issue?


How many top layers are you using?

When you print a part with infill, you’ll get hollow pockets in your infill and the size of the pockets depends on the infill percentage. When the printer puts a “top layer” over the infill, the first top layer may sag into those gaps and leave holes. A second top layer will usually look better than the first, but usually still not seamless and smooth. By the 3rd of 4th top layer, things are usually starting to look pretty good. I’ve never needed more than 5 and typically number 4 looks perfect.

As I look at your part, I see what appears to be the infill pattern through the top-layer … and this is making me wonder if the issue is caused by not having enough top layers.

As for retraction… retraction is followed by a re-prime of the same amount as the retraction. An over-retraction can allow the nozzle to pull in air – which gets hot, expands, and can spit when re-primed. A direct-drive printer usually doesn’t require much retraction for most materials (e.g. 1-2mm is usually enough for things like PLA, ABS, PETG, etc.). Some materials require more.

So I’ve been having retraction issues. I printed cubes and got big, blobby strings at 1.75mm. So I upped it to 2.25mm and 60mm/s travel speed and they got better. Then, these gaps started appearing. I turned the settings back to 1.75 / 40mm/s and the gaps got worse.

Currently printing 4 top layers.

There’s several other retraction-related settings in Cura, but the only advice I can find online seems to be about adjusting retraction distance and travel speed. And apart from printing retraction cubes and tweaking those two parameters, I really don’t have a methodical approach to sort it out.

It looks to me like under extrusion. Best thing you can do is find a small part that exhibits the issue so you can adjust parameters and see results. My advice is don’t adjust too many parameters at once so you can see the results of each change.