I am trying to determine how to improve bridging over distances of about 30mm. What settings can I use within Cura LE to avoid stringing?
You asked about bridging … but then referred to “stringing”. These are a little different.
“Stringing” occurs when the print head stops extruding filament and performs a non-printing move to another area of the part… but some filament continues to ooze … resulting in a fine little “string” (sometimes like spider-silk).
There are numerous strategies to deal with this … retractions are the main way to deal with it. But there are some strategies in Cura such as wiping to the infill or wiping along a wall to allow any ooze to be deposited in an area where it wont effect the look of the part. You can search Thingiverse for a “retraction tower” to test various retraction settings and inspect how much stringing occurs between the two sides of the test part.
Some filaments types are notorious for stringing … and post-processing the part to clean it up may be the only realistic option. (TPU, for example, has a reputation for stringing and the elastic nature of the filament means it doesn’t respond well to retractions and still continues to ooze during non-printing moves. But this is an example where Cura settings to wipe along infill or travel along perimeters instead of open space can improve the part quality.)
“Bridging” is a little different. Imagine printing a model house and you need to include doors and windows. You’ll have gaps for each “window” or “door” until you get to the top of that door or window … and then you need to run filament across a gap. That filament along the top of the door or window may sag a bit. Printing in micro-gravity helps … but since we don’t live on the space-station… that’s probably not a realistic option. Filament tends to contract as it cools… that means the sagging filament may tighten up a little and sag less. Printing with the cooling fans on full will help. You may see mild sagging … but usually not too terrible. If you really need to avoid any sagging… consider adding some support material that you can break away later.
Yes I meant the sagging rather than stringing when trying to go across a gap. Just curious if supports cannot be used for some reason (like the lion with a “mane” that prints the hairs straight outward if you are familiar with this model) what settings would make the print possible? Reduce the speed down a lot with fans on 100%? There are a lot of speed settings so curious which would be modified and what the best values might be.