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Solved Prints are blobbing with burnt spots of plastic

Discussion in 'Troubleshooting' started by Paul Arnold, Feb 10, 2017.

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  1. Paul Arnold

    Paul Arnold Member

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    I just repaired a major clogging issue, which was caused by the fan on the cooling fins of the cold side of the extruder assembly.
    Now that I am able to print again without clogging every five minutes, I am getting occasional blobs of burnt plastic. My guess is that the hot end is actually plowing through the plastic as it lays down fresh plastic, but I can't actually see this, and the finished product seems to be of correct dimensions, not squished as I would expect if the extruder wasn't raising the correct amount each pass.
    I have the bed set to 60 and the extruder set to 200. I use Matter Control.
    I've probably run about 10 spools of PLA though this printer and never had this problem.
    Any suggestions?
     

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  2. Spidematt

    Spidematt Member

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    you might still have old gunk burning in the nozzle you should try a cold pull.
     
  3. Rigmarol

    Rigmarol Well-Known Member

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    I got something similar once when moving from a dark filament to a light colored one. I changed my nozzle and the dark spots were gone.
     
  4. Paul Arnold

    Paul Arnold Member

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    I believe I may have figured it out, but as it is in the middle of an 18 hour print I can't test it yet. As you can see from the attached picture, there is a build up of PLA around the nozzle, and I'm thinking perhaps the PLA is leaking around the nozzle because the nozzle isn't seated fully. 20170211_121315.jpg
     
    #4 Paul Arnold, Feb 11, 2017
    Last edited: Feb 11, 2017
  5. Geof

    Geof Volunteer Moderator
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    Very possible, best course is to remove and reseat the nozzle to see. Have you calibrated your extruder ?
     
  6. Paul Arnold

    Paul Arnold Member

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    Geof, I've never calibrated my extruder. I have printed about 8 spools of PLA with virtually no issues, just some stupid things on my part, but this printer has been really phenomenal so far. I never felt that it needed any tweeking before. With all the clogs I cleared due to the cooling fan going bad, I'm assuming that I didn't get the nozzle seated properly, after seeing that blob of PLA on the side of the nozzle. I'll know in a couple more hours when it's finished. I have a spare hot end, I will just swap the whole thing out and carefully inspect the one I've been using.
     
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  7. Paul Arnold

    Paul Arnold Member

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    It looks like I am going to mark this as solved. I'm printing with my spare hot end now and all seems fine. This is what I found when I took the old hot end out, and got the nozzle out. It's pretty obvious that the PLA was getting around the nozzle. Thanks for the suggestions everyone. Hopefully this might help someone else someday.
    20170211_153836.jpg
     
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  8. mark tomlinson

    mark tomlinson ༼ つ ◕_ ◕ ༽つ
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    The trick with hotends is not that the nozzle needs to be seated to the heater block... (it doesn't) but that the nozzle needs to be seated against the end of the heatbreak :) They meet in the middle of the heater block and that is what seals. If not, you get leaks from the top or the bottom of the heater block.
     
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  9. Paul Arnold

    Paul Arnold Member

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    Thanks Mark. There was PLA on top of the extruder block also, so obviously I did not re-assemble correctly. I'll clean the darn thing up and try again when I'm feeling frisky
     
  10. mark tomlinson

    mark tomlinson ༼ つ ◕_ ◕ ༽つ
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    Had that problem with one of my printers recently. All my fault :) mess to fix but not a major issue

    Sent from my SAMSUNG-SM-G930A using Tapatalk
     
    Geof likes this.
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