I had a problem bridging with my UM1 so I decided to experiment with variables such as extruder temperature, print speed, extrude rate, fan on/off, and separation between threads in the first layer.
The model used was a simple box with no lid. The bridging threads are approx 46mm in length.
Cura 13.11 was used to generate G-Code for the box and a spread sheet was used to generate code for the bridging layer.
The material used was ABS. For normal printing I have been getting good results with