I’m trying to print what will end up looking like a pile of rocks. There are crevices between the rocks creating steep valleys in the middle. It built up the bottom half with the hex infill pattern. When it got to the bottom of these crevices, it started laying a flat base to build up from. The problem is that the edges of this base don’t align with the walls of the infill, so they are just dropping down in to the cavities. Is there a way to tell the slicer that it needs to over-extend this support layer to the edges of the infill walls, then build up from a spot that is supported on all sides?
Post gcode? Not obvious to me what you’re describing. Sounds like that could be normal behavior and you’re having underextrusion issues preventing bridging from being successful.
It’s still in the middle of this print. I’m going to let it finish and hope it comes out fine. My guess is that it will. But this is what I’m seeing as it progresses. Seems like it should have just capped off the whole top of the hexagon instead of laying irregular splotches that aren’t supported. Some of them are falling in, so the next layer has nothing to land on. I’m sure it will fall in as well. Makes me wonder what the final will end up looking like. For this specific print, I suspect if there are gaps, I’ll just fill them in post cleanup rather than trying to print it again. So, I’m more asking for a longer-term solution that benefits the next version of slicer.
Nope, that behavior is intentional. It will only build a skin starting 3ish layers down from the top skin (or whatever # of layers the slicer is configured for).
If there’s inadequate support for your particular model’s geometry causing them to fall in you need to increase the infill density.
Errors like this can be avoided by previewing the gcode in a viewer like ncviewer.com to ensure nothing is getting printed over thin air, and tweaking the slicer parameters as needed.
Using Cura directly instead of using Luban as a restricted interface to Cura will make the tweaking and previewing process a lot faster and easier.
Just for discussions sake’s the first solid layer above infill can be a tricky one. It looks like your model has smooth curves meaning there is a very small contact patch on the infill which is the root of the problem. You could increase the number of top and bottom layers to increase that contact patch. You could also use different parameters at different Z heights and change the infill. Other slicers other than Cura have their own methods for solving issues like this.
I definitely didn’t think it was unintentional. I was just hoping to suggest there might be a more elegant solution than just throw more plastic at it.
The slicer can tell outside the model if it needs support, but it doesn’t seem to be applying that same login inside the model. Adapting whatever routine generates the supports so they are also generated in between the infill definitely would eliminate potential problems.
Changing infill density for just a specific layer to two would have solved this. I didn’t think that was possible. I assume I have to get out of Luban and use a different slicer for that.
But again, I’m not looking for ways to work within existing software. I’m trying to propose features for future versions that would keep this coming up at all.
To be perfectly transparent and honest, Luban is not a slicer, it uses Cura, which has its own support forums and feature improvement recommendations process. You have a good suggestion, and to see it submitted into a feature candidate you would need to report it here: Issues · Ultimaker/Cura · GitHub
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If you do give Cura a try, I think the setting you’re looking for is minimum infill area, or skin expansion:
Infill settings – Ultimaker Support.
There’s also the gradual infill setting, which might be closer to what you want, you can have less infill in the less dense parts, and it steps up as it approaches a ceiling.
If you use gradual infill, definitely check the layers, at least in the old version of cura, gradual infill really liked to try printing in the air (this might be fixed with the latest version where they completely redid the slicing engine though).