There should be a separate parameter for number of bridge perimeters
I've been making prints with Perimeters set to 4 (and 'Ensure vertical shell thickness' set to off) as a way of getting stronger, more precise, and more opaque parts. This has been working great (and probably warrants reducing the fill rate on many models but I haven't experimented with that) but it causes a problem with some bridges. It's particularly acute with this model, but happens for many others.
The issue is that the perimeters on the bridge get so far in that they aren't even anchored to the outside and come off. Setting Perimeters to 3 seems to be a happy medium which is both fairly strong and doesn't cause bridges to fail, but why do we have to choose? Why isn't there a separate Bridge Perimeters setting? If that were an option I'd set Perimeters to 4, Bridge Perimeters to 1 or 2, and have the best of everything.
RE: There should be a separate parameter for number of bridge perimeters
I have found that Bridging is better with higher levels of cooling. I am not tracking a bridging parameter.
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Chuck H
3D Printer Review Blog
RE: There should be a separate parameter for number of bridge perimeters
To clarify: The linked file prints fine with the default of perimeters=2, and most models work great with it set to 4, but the linked one has an issue with 4 because on the underside of bridges the perimeters go so far in that the bridge infill doesn't get properly anchored at the ends. This seems to be entirely a software problem which could be fixed by extending prusaslicer to have a special 'bridge perimeters' parameter which only applies on the underside of bridges.
RE: There should be a separate parameter for number of bridge perimeters
@bram
Why wouldn't just use a (HRM) height range modifier to extend the Infill/Perimeters overlap for the bridged layer?
The Filament Whisperer
RE: There should be a separate parameter for number of bridge perimeters
A height range modifier is poor match for what's needed. It's possible to modify exactly the height of the bridge but that modifies other parts of that layer where the change is unwanted. It's also possible to use a modifier mesh to get the one area but it's hard to keep that from hitting other layers. Either way it's a lot of painstaking work for something which should be a single parameter to set which then works properly everywhere.
RE: There should be a separate parameter for number of bridge perimeters
I've never encountered the issue your describing, this to me is a perfect candidate for a modifier (Something that doesn't happen often but you have a need) It's available and allows you to target the problem areas with a mesh. as for the pain staking part, I would normally create my modifier meshes in my 3d program, then import them with my mesh and just set the properties for the modifier in slicer, if you have multiple places that need these settings you can literally copy and paste them. This is super fast to do.
Anyway Sorry I couldn't help.
Swiss_Cheese
The Filament Whisperer