Bridging is a term for printing layers over thin air without the use of supports. It may sound like an impossible feat, but with our MK2 and MK3 printers, it’s not that difficult. Keep in mind that the best results are achieved only over short distances because the printer’s fans need to cool the extruded plastic mid-air in order to create a solid connection. There are three key settings for printing good looking bridged layers: Slic3r settings, speed, and cooling.
The typical problem of bridging layers is sagging or drooping as seen in the photo above.
How to fix poor bridging:
Bridging flow – the best way to prevent the layers from breaking in bridging mode is to change the “Bridging flow” setting in the Slic3r. The first bridging layer should be done with a lower flow of the material. Open the settings in Slic3r by right-clicking the model, then go to Object settings – Advanced – Bridge flow ratio. We recommend using lower speed for printing bridges and also lower bridging flow. The idea is to “pull” the string of extruded filament behind the nozzle, so it drops less. The ideal approach is to download bridging test models, for example this one, put it in the slicer several times, and set up a different flow for every model. This should be a relatively quick way how to find correct settings for a your printer / material without the need to perform many test prints.
weak the fan speeds in Slic3r: In Slic3r PE, double-click the object to open the Properties window. Then click the Plus button, choose Speed – Bridges and tweak the speed for printing bridges.
Obviously, the best solution is to change the orientation of the object (rotate it) until you get rid of the bridges completely and you don’t have to worry about bridges or supports. It won’t be possible in many cases, but the rule of thumb here is to try to avoid bridges and supports completely.