Hello,
I'm having trouble bridging the flat top of a small box-like structure. The rectangle is 70mmx32mm - so the distance to be bridged is 32mm. Cura chooses to do it at an angle which makes it just over 45mm. The lower part of the model prints very well including quite a bit of fine detail and overhang, but the bridging makes the model not useful.
The first bridge filament adheres at both ends and looks great -- then the extrusion head moves back across the gap putting the second filament close and parallel to the first. This melts the fist thread in the middle and leaves an impressive looking second thread standing alone with two short pieces of number 1 hanging from the walls. This continues to happen with only an occassional drooping thread surviving in one piece.
I'm using a UM1, ABS, V2 0.4mm extruder at 245C, Print speed 100mm/s, SD card with Ulticontroller, recent Marlin, Cura 13.10, Heated bed with Kapton on Basalt and Bed Temperature 110C.
Can anyone suggest a way to overcome the difficulty please?
I've turned the fan on (during the preceeding layer) and that has a small effect but not enough. I assume that the heat radiated from the nozzle is able to melt the single strands in the middle but not near the walls where the cooling has been greater. Lowering the nozzle temperature would reduce the radiated heat but would probably lower the quality of the rest of the model.
If Cura were to enable the initial bridging threads to be much further apart, I think the isolated bridging strands would not get the heat from the nozzle and would survive unscathed. The gaps could be progressively filled - one strand per gap at a time, so the earlier strands would be revisited by the hot nozzle when they were significantly cooler. I guess its easy to say but may be hard to implement.
Any suggestions/comments would be greatly appreciated please.