by mxk » Sat Apr 14, 2012 1:04 am
For bridges you generally want to stretch the filament a bit and/or cool it a bit so that you don't get the sagging shown in your photos. If you are using Slic3r, increase the speed for bridges under the Printer and Filament tab, and set the fan speed for bridging to 100% under the Cooling tab (if you have a fan).
If you are using Skeinforge to slice your objects, it's controlled under the Speed setting, look for Bridge feed rate multiplier and Bridge flow rate multiplier. Under Cool you can set the bridge cooling amount in degrees Celsius, but in my experience that only really works if you have a fan, the hot-end doesn't cool down quickly enough by itself to make a difference.