Bridging, i.e. printing (more or less) long distances unsupported over thin air is tricky business. It requires different settings than regular printing, usually speed and cooling is key to the success.
Signs of poor bridging:
Saggy lines in the picture show poor bridging performance.
Explanation:
If you don’t have the correct settings for the bridging needed, then you will experience saggy lines and poor bridging.
How to fix:
Advanced slicer software detects when bridging is required and will allow you to apply different settings for the bridge.
Increase extrusion multiplier for the bridge.
Try different speeds, slower is usually better, but results may vary so experimenting is key.
Increase your fan speed for bridges. We want the material to harden quickly without drooping. May not be suitable for all materials, check with the manufacturer/seller.
Make sure your slicer is actually using bridging mode. If you’re using Simplify3D, make sure bridging of outlines is enabled.
More advanced bridging options like direction of the lines that make up your bridge or increasing the start and end zone of a bridge can help as well.
Better than trying to optimise bridging performance is trying to avoid bridges to begin with. If possible, reorient your part on the build plate so less bridges are required or add supports to your bridges. With supports under your bridge, it won’t be able to droop as much.
Reduce printing speed for support.
Use higher support density and if your slicer supports it – a different support pattern. If your slicer supports it, have a brim or a solid bottom layer added to your supports.