I based this in the coupling from here: http://www.thingiverse.com/thing:17021 I doubled the size of the coupling and then printed them in ABS at 0.2 layer, 30% fill, with Simplify3D on my Fabrikator Mini. Then I designed the base and funnel in Tinkercad and printed those on the DaVinci Jr in PLA using 0.3 layer height, 30% fill.
I connected the couplings by heating them up with a heat gun then pushing them together and let them cool. The Funnel was the same. The base was superglued to the bottom coupling.
The finished design was clamped to my table saw with the funnel positioned just to the side of the blade so it could not fall on the blade. My shopvac was connected to the base and then I gut some wood. It worked good but not great. It definitely reduced but didn't eliminate all the sawdust flying off the blade.