Making STL Shells solid

I have a couple of STLs that are essentially just the outside mesh. I would like to get this to print as a solid object with infill, but slic3r will not fill them.

Does anyone have any suggestions? I’ve tried using Solidify in Blender, but I can’t get it to fully fill without generating odd geometry, so I have to leave a void. However, Slic3r picks up this void and thinks it’s an exterior perimeter and tries to print it free-floating. I’ve downloaded netfabb, 123D, and Meshmixer, and haven’t found a solution yet.

Any hints would be fantastic! I’ve attached one of the original shell STLs and my attempt at using Blender to solidify the part.

ajford (43.2 KB)

The outside mesh should be all you need. Solid objects are defined by their boundary surfaces as far as slic3r is concerned. “IvarTest” in the files you uploaded is the one you want to use I think.

Here is a screenshot from that shows a layer about halfway up through the print. The yellow lines are infill.

You will need support material to print this, or you might want to chop it in half and print both sides and then assemble them afterwards, depending on your application.

You might find this thread useful:


Hey Kent,

I think I may have something misconfigured on my Slic3r then. If I slice the IvarTest.stl file, the gcode generated does not have infill, but I have 30% honeycomb infill set.

Perhaps you can share your slic3r config for me to compare with? I’ve attached my slic3r config and the gcode generated. I’ve also attached a screenshot of the gcode rendered in
ajford_slic3r_config.ini (3.32 KB)
IvarTest.gcode (741 KB)

I was fiddling with the settings in slic3r and lo-and-behold, if I set a layer thickness of less than 0.18mm the infill disappears. I now have gcode with infill. I don’t know if this is a slic3r bug or something build in that I don’t understand.

– Anthony

I just used the first config i could find to test, which happened to be the config for the bed corners in production:

I’m not sure about the missing infill. What version of slic3r are you using?

Not sure if you are still having issues or not.

I imported this into SolidWorks as a conversion.

It is indeed solid!

Here is the SolidWorks file converted back to stl form…

Good luck

IvarTest sw.STL (39.1 KB)