Unfinished draudi, ground filament..

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    Trying to get familiar with the sigma.

    my first larger print – the hollow draudi at 175% – just as in the demo video from BCN.

    sliced in cura, printed in BCN yellow PLA at 200C. middle in the print it stopped extruding and then i found the filament was ground and the bowden tube pulled out from the hotend.. i cleaned the nozzles with Nylon but there was no clog in the nozzle…

    any tips before I print this beast again?


    Lower the print speed, retraction distance and retraction speed. What happens it that the feeder retracts lots of times on the same length and grinds the brittle PLA. It is typical for perforated models.


    Hi EmvioEng, can you give more specific details and values – it happens quite often with our Sigma as well.
    Can you take BCN PLA profile as a base and advise how one should change these values in case of perforated parts?


    Hi there
    First if you should apply thermal paste on the hotends ( if they don’t have it already ) following this guide (http://www.bcn3d.com/forums/topic/improve-the-hotend-performance/)
    Then I would also make sure that the extruder feeders are clean and then teeth that grab the filament are clear of any ground filament, I made a guide on how to do this (https://emvioeng.com/blog/)
    My retraction settings for retraction intensive parts is Speed:25 and length 3.5 – 3mm. Now to make the retraction effective with these settings you cant be extruding a lot of material so either print at very fine layers 0.1mm for example, or reduce you print speed to about 30mm/sec for 0.2mm layers
    There is also the Bondtech extruder upgrade for serious users which grips the filament from both sides and overcomes all material extrusion – feeding issues


    Thanks EmvioEng.
    We applied thermal paste for our 0.4 mm hot ends, but it seems like working the same way without improvement. We also received 0.6 mm hot ends which didn’t work at all, we need to test them more to draw a final conclusion.
    Today for example the new print just broke down while removing support in the middle in the thinnest section of the part. The bottom part (left) is good, but the top half definitely had problem with traction for a couple of mm, then it went well.
    All the speed and retraction parameters are from BCN’s default PLA profile.
    Retraction speed – 40 mm/s, distance – 4.
    I don’t really understand how we should change these parameters to improve printing.
    I would change infill speed from 60 to 50 mm/s.
    Can you please advise other changes we can make?


    Ok if you get failures with the 0.6 nozzle on non retraction intensive parts then it might be spring tension on the feeder. If it is too tight the teeth bite the filament very deeply and grind it fairly fast, also the side that is pushed against the bearing gets flattened. If the tension is low then the feeder cannot grip the filament enough to push it. Maybe unscrew the tension screw a a bit to see if it helps. Share a picture of the part of the filament that has been ground if you want
    Lastly I also recommend using a filament filter to ensure that the filament if dust free when it enters the hotend, I think it is a good principal for maintaining the extrusion system well.

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