Help with top layer print quality issue?

I’m having a new issue that I can’t figure out – my top layers have messy zits and burps on them.

My first layers are coming out beautiful; no warping or un-sticking, and the strings and blobs are under control on the sides of the prints. I’m still working on getting the Z-hop setting optimized, but things are generally looking pretty awesome…except for on top. It only happens on fairly large, horizontal surfaces with fill underneath them. It doesn’t happen on slanted surfaces, only flat ones, and on these pieces, the thinner solid areas don’t have the problem; only the ones where the piece was thick enough to have some fill layers. So it’s something about the fill, but that’s as far as I can get in figuring it out.

Here’s a photo to show you what I mean. If you look close, the larger “burps” even look like they’re discolored, although I think maybe that’s a trick of the light, since it doesn’t seem likely the filament would actually discolor like that. I didn’t go through any major nozzle-cleaning stuff when I started this filament, but I printed two fairly big prints with it before this one, and it’s feeding smoothly, so I doubt there’s any residue of anything else in the nozzle.

I’m using a Taz 5, 0.5 mm nozzle, Hatchbox ABS. Print temp 230º, bed temp 110º, using Simplify3D with default ABS “medium” (0.2mm) settings except that I’ve tweaked the retraction distance and speed, Z-hop, increased top and bottom layers to 4, and slowed the print speed. (Okay, maybe not so default any more… :wink: )

This photo is of a print of one of the Settlers of Catan border pieces from http://www.thingiverse.com/thing:26979.


Any ideas?

This may not be the answer, but I’ve noticed that if your infill is like 30% or lower that this issue comes up more prominently, but can be fixed by adding additional solid layers to the top of the print in the settings. I bet if you’re watching it print, the first top layer is really ugly with more holes, then the 2nd top solid layer is more solid but still has holes. Adding more layers can fix the rest. If you’re using 2 solid layers, try 4. Also you can try increasing your infill % so they are closer together so when it’s adding the top solid layers over that there is less sag and more surface contact.

You might want to turn your flow down like 4-5% as well. You might be extruding too much.

This may not be the answer, but I’ve noticed that if your infill is like 30% or lower that this issue comes up more prominently, but can be fixed by adding additional solid layers to the top of the print in the settings.

Thanks, that does make sense. I’m using 20% with 4 top layers, right now. I just looked back at Cura, because I wasn’t having this problem with it, and it has a 1 mm top layer setting, whereas with my Simplify3D settings, 4 layers would only be 0.8 mm. I’m off to try another print!

P.s. Does your username relate to your location? If so, we might be neighbors. :slight_smile:

I’d definitely increase the top and bottom layers to be greater than 1mm… so 5-6 layers at .2mm.

Might be a little overextrusion happening also… I know we went through the whole estep validation in your “rant” thread. But some filament colors may need a little tweaking on the multiplier setting in S3D. Another tip in S3D is to set a .2mm coast… does wonders for prints.

Another tip in S3D is to set a .2mm coast… does wonders for prints.

I saw that setting, but didn’t understand its purpose, and am still floundering when it comes to finding stuff on their website. (There’s no search function; what’s THAT about???) What does it actually do?

Coast turns off the extruder the specified distance before it normally would, to drain what would have oozed at the end of a line because of pressure. This can help with ooze-induced blobs at the end of lines, but, if turned up too high will lead to gaps in your print walls. You should be able to see changes to this setting visible as “gaps” in Simplify 3D’s g-code preview.

DougZ is spot on.

The tooltips in S3D can be seen when hovering over the parameters. More training can be found in their Youtube channel.

Coast probably won’t help your current problems, but is a nice parameter to turn on to get good prints. I suspect adjusting the number of top layers will help the most with your the current problem.

Let us know how the new print turns out.

Yes coast really only helps where a line meets another line and stops extruding just before they meet and won’t really affect the middle of a surface, but it is a great feature and I use it all the time.

I think adding an extra top layer has fixed the problem! I printed a smaller object with a similar configuration, and it didn’t have any “pillowing” in the flat area, which is promising. I still need to re-try the larger print to make sure, though.


I haven’t attempted that yet, because (as you can see) there were also some retraction problems that needed nailing down. I think I’m almost there! The ones on the right are near-perfect, but my OCD nature is compelling me to continue tweaking by seeing how far I can back down the more radical setting changes I used to get there. :wink:

Dang, guys, I might get good at this yet! :slight_smile:

That’s quite an improved progression!

That’s quite an improved progression!

:sunglasses: