Enable bridge setting on entire unsupported cantilever beam wall

[leedav11 0]

Hello,

 

I'm printing this using PETG on at 255deg with a 0.8 nozzle. Print speed is 50mm/s. walls are printed at 25mm/s. For most of my print, I keep no fan on for most of the print and my print is already not as hot as I'd like to make it.

 

Cura is slicing the unsupported cantilever beam using bridge setting all the way. it looks like Cura is only applying bridge setting on the crossing portion(bridge portion?) of the cantilever and the entirely unsupported edge is printed at normal setting. This creates at problem where the print without the 100% fan cooling will sag badly, and I could not keep the fan on for the rest of the print, so i really need the entire unsupported wall portion to be printed using bridge setting where fan is turned on 100% and print speed slowed down to 10mm/s

 

 

With bridge setting enabled - red circle identify incorrect print speed/ slicer setting applied to unsupported wall

Bridge wall should be printed at 10mm/s and the slicer is not slicing the entire unsupported wall using the bridge setting.

 

[GregValiant 1,488]

I believe that is because the end isn't considered part of the bridge.  It is considered part of an abutment that on that particular model does not exist.  A "bridge" exists between two abutments and you only have one.

I don't believe that shelf would print at any rate as there is nothing for the plastic of those movements to stick to and so the extrusions would simply loop back around to the main body of the model and hang vertically as they solidify.  Cantilevers happen all the time and always require support.  An alternative would be to add a chamfer to the model on the underside of the feature so it would not require support (or bridging).

All that being said, when you have situations that aren't covered by the "normal" software settings then hand coding some things can help.  You can find that area in the gcode and kick the fan up to 100% with an M106 S255 and lower the feed rate with M220 S20 before the movement and M106 S0 and M220 S100 after the movement.

I still think it's going to sag though as no matter what you do with feed and fan - it's still air printing.

Edited December 31, 2021 by GregValiant