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Experimental Bridging in 4.0 causes big blobs in slicing


bradjshannon
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Posted · Experimental Bridging in 4.0 causes big blobs in slicing

Hey folks, I'm looking for help with the issue shown here:

 

AHRQ2rQ.png

 

My bridge settings are to slow down massively, to the minimum print speed, while printing bridges. But this appears to lead to massive squirts of plastic on my prints.

 

What you see above in the sliced view is a good representative of what the printer really does -- it squirts a jet of plastic when it reaches those gigantic polygons, which are basically extrusions with a line width of, I don't know, several millimeters.

 

Am I just doing the settings totally wrong? Should I not slow down the print so much for bridges? I do find it helps a lot in other prints, but perhaps the difference between normal and slow speeds in this case is just too much.

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    Posted · Experimental Bridging in 4.0 causes big blobs in slicing

    Hi @bradjshannon. Those blobs are being generated because the bridging code tries to stop the underextrusion that normally occurs after a bridge segment by overextruding for a short distance to recover the extruder pressure back to what it should be for the non-bridge lines that follow. I have to admit that I did not imagine that people would use such a huge difference in speeds between the bridge and non-bridge line segments. Sorry, the only workaround is to use a higher speed for the bridge wall segments. I will modify the code so that it limits the amount of overextrusion in cases such as yours. Unfortunately, the fix won't appear in Ultimaker's Cura for many months but I will put a fix into my own releases right away. You can find them at https://www.dropbox.com/sh/s43vqzmi4d2bqe2/AAADdYdSu9iwcKa0Knqgurm4a?dl=0

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    Posted · Experimental Bridging in 4.0 causes big blobs in slicing

    Hi @bradjshannon, I just realised looking at your project that you don't need bridging enabled anyway as you are using support. Just disable the bridging and the big blobs will go away. I'm going to fix the problem anyway, but for this print, it's a non-problem.

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    Posted · Experimental Bridging in 4.0 causes big blobs in slicing
    10 hours ago, burtoogle said:

    Hi @bradjshannon. Those blobs are being generated because the bridging code tries to stop the underextrusion that normally occurs after a bridge segment by overextruding for a short distance to recover the extruder pressure back to what it should be for the non-bridge lines that follow. I have to admit that I did not imagine that people would use such a huge difference in speeds between the bridge and non-bridge line segments. Sorry, the only workaround is to use a higher speed for the bridge wall segments. I will modify the code so that it limits the amount of overextrusion in cases such as yours. Unfortunately, the fix won't appear in Ultimaker's Cura for many months but I will put a fix into my own releases right away. You can find them at https://www.dropbox.com/sh/s43vqzmi4d2bqe2/AAADdYdSu9iwcKa0Knqgurm4a?dl=0

     

    10 hours ago, burtoogle said:

    Hi @bradjshannon, I just realised looking at your project that you don't need bridging enabled anyway as you are using support. Just disable the bridging and the big blobs will go away. I'm going to fix the problem anyway, but for this print, it's a non-problem.

     

    Thanks so much! I figured the difference in speed was the issue, since it is so extreme (an unnecessary). I'm just playing around with settings for different materials and discovered this unexpected behavior along the way. Happy to hear it'll be patched eventually. Thanks again

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