Unsupported Areas in Recessed Top Surface

I’ve got a model to print, it has short insets in the top surface. When I slice it, the bottom of the insets become floating islands since they don’t line up with the infill. A higher infill isn’t an option, neither is changing the orientation of the model. I tried slicing the model in Prusaslicer and it expands the bottom of the insets until they touch the infill.
Is there a slicing option in Cura that does the same thing? I’d prefer to stick with Cura.

I have attached some simple model images that should show what I’m doing. Imagine the top surface of a die. If you print with low infill, the bottom of the inset pips won’t be supported.

Hi there,

What if you tried rotating the model so that the side with the insets was touching the build plate. This way they would be connected to the walls of the inset?

Hopefully this helps,

I appreciate the option, but the actual model I’m printing can’t be reoriented. I clipped the really simple “dice” example to try to explain what I’m seeing as best I can.

In the new picture (book dragon), you might see the inset writing on the top surface pages. That is causing a mess in the actual print. I suppose I could try printing it upside down but I think the print quality of the dragon will suffer.

Thanks for your swift response!

I’m just curious what is stopping you from printing at a higher infill rate? In my opinion this would be the best way to remedy the situation, you shouldn’t have to raise the value by very much in order to fill the space a little more.


Try the support infill setting in Cura. That might work for you.

A higher infill might be only solution in Cura. I was hoping to save some time and money. PrusaSlicer detects the problem and expands the area until it touches the infill. Maybe it’s time I learned more about PrusaSlicer.

Thanks for the suggestion of “Infill Support”, I tried it. Maybe I didn’t use it correctly, or it just isn’t ready for “prime time”. It creates infill islands that aren’t going to work, even in my super simple “dice” test.

Have you looked at lighting infill?

Or gradual infill steps?

Thanks again. I tried Lightning and Gradual Infill (set to 4 steps from 80% down to 5%). Here is what I see in the slices.

First, with Gradual Infill, I see the same problem as I got with “Infill Support”. The slice ends up with floating islands of infill. I think this will end up creating a spaghetti mess.

Lightning infill looks more promising. I was able to get 80% infill support under the top surfaces with the least amount of material in all of my trials. A lot less than going with a 25% to 30% grid.

I think I’ll try running with Lightning (91g / 14 hours for Lightning @ 80%, 140g / 18:30 hours for Grid @ 25%).

Lightning infill worked out really well. Shaggy printing from the poor quality wood-fill PLA aside, I’m pretty happy with the end result.
Thanks everyone for your ideas and help.


Hi there, thanks for the update!

The print looks really nice, great job!

Happy printing,