Irregular bottom object rafting?

Is there a recommended way to deal with objects that have irregular bottoms that need some kind of support or rafting before the actual bottom print layer is reached?

I have a basic cube with frames around all the edges. These edge extrusions on the bottom sit it higher off the bed and this leaves the actual cube bottom printing across a large span of air, a few millimeters above the bed. This of course leads to the first couple of layers having strand breaks and all kinds of issues like that - it looks less than polished on the bottom of the cube when finished. I thought maybe messing with support materials and rafting might fix this, building support layers underneath until the true bottom of the cube finally printed, but I have failed at every try and can't get support layers to infill the area underneath and between the bottom extrusions. Is there a setting I'm missing? I can't turn the cube on another sides as they all have this type of extrusion around the edges of the cube...

Slic3r 1.1.7
lulzbot taz 4
.35mm nozzle
ABS filament

It sounds like the shape of the object is not really suited to FFF printing as a single object. No type of support is particularly good at supporting a large bridged area in my experience. If you have multiple nozzles you could print a solid infill in soluble material.

My solution for printing such awkward designs is to print them in two or more sections and glue them together afterwards. I print with ABS, and a thin coat of acetone on the mating surfaces forms a very quick chemical weld that is stronger than the normal layer bonds and is invisible if done carefully.

Dave

Uncheck "Don't Support bridges" should help.

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