This is the dumbest question anyone will see all day. It's an .stl file I downloaded, and I'm wondering how on earth it would print.

Slic3r seemed perfectly happy to slice it up, but I can't believe it would actually print without supports. I've never tried to print something that isn't relatively simple and flat. It looks like there are overhangs on every conceivable orientation of this object, so I can't see any way to rotate or flip it that would eliminate them.

What would a smart person do if s/he wanted to print such an object?

I would flip it 90 degrees to lay flat before slicing.

If you haven't already done so, get the latest version of Slic3r (1.1.2), and enable support.  Set it like this:

overhang threshold  =  15°
Pattern spacing        =  2mm
Angle                        =  45° (or anything you want, since this object is round, it won't matter)
Interface layers        =  3
Patter Spacing          =  3

Uncheck Support Bridges.

Also I would suggest you put a brim on this (4-5mm), since you have very little base surface (just a ring).

Alternate Method:

if you are printing using ABS, you can always cut the model  using netFabb.  Simply rotate it as previously discussed, then cut the bottom ring off, so you have the main piece with a nice flat bottom, and a separate ring.  Once printed you just glue the ring back on.

I would rotate it with mouse ears pointing up and then slice it with KISSlicer. Load the gcode in Repetier to print. It does a much better job than Slic3r for supports and it has a better tool path which usually gives a superior print.

+1

I see that this is one of those can-of-worms questions. Slic3r's "generate support" options seem to have been a headache for a lot of people - so far, I can't get it to do anything. Apparently as of version 1.0 it's different; I got 0.99 in the download of the mac software from the solidoodle store last week. Any reason not to go ahead and upgrade slic3r to 1.01, the current stable release? Is the distributed version from solidoodle tweaked in any solidoodle-specific way that will break if I replace it with the generic download from slice3r.org?

Long story short, there are compatibility issues with later versions of slicer. You can get it working, but sometimes it is troublesome.

There is nothing we do to customize slic3r save for the ini files.

Use supports.

Fair enough. So does that mean hauling it into Blender, for instance, and adding them manually? I assume there's no computational / automated way to do this? Is there a guide anywhere on how to judge where they're needed / what dimensions they should be / how far apart, etc?

This is the dumbest question anyone will see all day. It's an .stl file I downloaded, and I'm wondering how on earth it would print.

Slic3r seemed perfectly happy to slice it up, but I can't believe it would actually print without supports. I've never tried to print something that isn't relatively simple and flat. It looks like there are overhangs on every conceivable orientation of this object, so I can't see any way to rotate or flip it that would eliminate them.

What would a smart person do if s/he wanted to print such an object?

Use supports.

Slic3r seemed perfectly happy to slice it up, but I can't believe it would actually print without supports. I've never tried to print something that isn't relatively simple and flat. It looks like there are overhangs on every conceivable orientation of this object, so I can't see any way to rotate or flip it that would eliminate them.

What would a smart person do if s/he wanted to print such an object?