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A question about nozzles

Discussion in 'General Questions' started by Lance Weston, Feb 27, 2021.

  1. Lance Weston

    Lance Weston Active Member

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    I print the same objects on this R2 continually. When one roll is finished I put in another. I noticed that the print quality began to degrade at the end of a roll. When I loaded in the new roll it appeared that the filament loading was too thin coming out of the print head at 210C (0.49mm). I removed the filament and ran a 4mm needle up the nozzle and re-ran the filament load. This time the filament came out at .79mm.

    I have added a clip on filter to remove any particles from entering the nozzle with the filament. I am looking for anyone with experience in this. When it happens is it good enough to run a needle up the nozzle or is a short term solution with the nozzle needing to be replaced?
     
  2. mark tomlinson

    mark tomlinson ༼ つ ◕_ ◕ ༽つ
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    Well, I switched over a year ago to hardened steel and went from replacing nozzles every 1-3 months to ... I don't know yet. I still have not had to swap those. The brass ones are cheap, but they don't survive for miles of filament.

    I would not suggest ever putting anything up through the nozzle, but if you do make sure to not go far up the nozzle. The heat break internally is polished metal for a good reason... don't scratch it. You won't hurt anything as long as your probe stay well within the nozzle.
     
  3. Lance Weston

    Lance Weston Active Member

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    I did not give enough information. I only use hardened steel nozzles. I ream all of my throats with a solid carbide reamer to ensure they are smooth. The throats are all hard stainless steel. The 4mm needle met it's resistance at the filament exit point on the nozzle. I had to work the needle to clear this before I could insert it fully. If I do not insert the needle the nozzle diameter becomes smaller than 4mm which is why I was getting degraded quality prints. It is something that has happened before, I just do not remember if the needle is only a temporary fix. I also do not know why it happens. Maybe the filament carries enough particles that harden in the nozzle.

    More information:

    This morning I checked the finish print from the printer where I inserted the 4mm needle which resulted in the filament loading at 210C going from .49mm to .85mm and the prints had been restored to a high quality finish. The magic returned.

    I checked the finished prints on my other two printers.

    First printer I inserted the needle went from .59mm to .80mm extrusion at filament load @ 210C. The prints were okay but not as good as they should be. I am looking forward to see the results of the next print run in 14 hours.

    Second printer I inserted the needle went from .70mm to .77mm extrusion at filament load @ 210C. The prints looked perfect and I had run half a roll already. I am not expecting any improvement but will look in 12 hours when this print is finished.

    Results:
    The .59mm->.80mm had a minor improvement in finish
    The .70mm->.77mm showed no difference in finish.

    Conclusion:

    I am going to check my nozzle with a needle every couple of days because a restricted flow will print, but not give the same quality of finish an unrestricted nozzle will. All three machines are running GST3D filament at a printing temperature of 220C.

    I have been chasing print quality problems for years and I think I have finally found the first order problem.
     
    #3 Lance Weston, Feb 27, 2021
    Last edited: Feb 28, 2021
  4. DavidR

    DavidR Member

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    They make nozzle cleaning kits that are effectively just blunt tipped needles. A good way to prolong nozzle life is to use cleaning filament when switching materials, especially ones with drastic print temp differences. For instance, if you try to load Polycarbonate after having printed with PLA you have to heat the nozzle to 280 to load it. This is too hot for the residual PLA in the nozzle (the bit thats purged when loading the PC) and will cause some of it to oxidize (burn) and once this happens it is very hard to clean. Instead I load the cleaning filament in at the PLA printing temperature to clear out all the PLA and then heat to the PC print temp to load the PC and purge the cleaning filament.
     
  5. Lance Weston

    Lance Weston Active Member

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    I am not sure what you are responding too. Having found a gradual degradation of print quality, I identified the cause. A gradual reduction in the diameter of the nozzle out. I described a test for it and a verifiable solution for it with the hope that someone else would duplicate my testing and problem description. It does not seem that you have done any sort of qualitative/quantitative testing. You have posited a problem and defined a solution for that posited problem without any measurements of before and after. How can you know that you are accomplishing anything without testing?
     
  6. DavidR

    DavidR Member

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    What caused the reduction in diameter? That I think would be closer to the true cause you need to identify, and yes, my solution, in as much as it helps attenuate the buildup of oxidized filament in the heat zone is not something I have analytically attempted to test. It is rooted in subjective experience as opposed to objective measurement. If you think dust is your issue I tend to use dust-off on the circumference of the filament spool before using it.
     
  7. Lance Weston

    Lance Weston Active Member

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    I do not know why the nozzle diameter gets smaller. I do a filament load before and after inserting a .4mm needle into the nozzle. I can then verify that the diameter of the extruded filament gets larger after inserting the needle. I have inferred that the nozzle diameter is getting smaller. I have found that when the extruded diameter during filament load falls below .65mm the quality of the finish suffers, it does not change the amount of filament extruded. I know this by measuring the weight of the finished part with a lab grade scale. That is what I can measure and observe. The rest is conjecture. I have an oiler that removes dust, but who knows what gets through. I only use one brand and color of filament, GST3D black (made in the USA).

    I have modified the print head to use a dual gear extruder (picture below) that has much more grab and less distortion of the filament. It extrudes the same amount of filament regardless of filament temp, so I have fewer variables. I have other spreadsheet posts that show the Robo print head will extruded different amounts of filament depending on filament temp.

    I get excellent results right now by doing a filament load, pulling the filament, inserting the .4mm needle then reinserting the filament. My print times are about 10 to 14 hours and I try to do this with every print. Since using this procedure the quality of my prints remains consistently high, rather than gradually getting worse, and I have almost no rejects. I have three printers that run 24/7 printing the same 10 parts, so I am in a good position to evaluate how changes effect quality.

    Does this nozzle phenomena happen only with GST3D? Has anyone else tried to duplicate my experiment and results?
     

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    #7 Lance Weston, Mar 24, 2021
    Last edited: Mar 24, 2021
  8. mark tomlinson

    mark tomlinson ༼ つ ◕_ ◕ ༽つ
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    I have never (across 8 years and the 7 printers I have) seen that behavior. The nozzle invariably gets larger with wear and when printing it does not constrict in any way unless it is a clog. PLA does microclogs just because that is how it is material wise, seasoning and/or oiler sorts that out. What you describe -- I can't say I have ever seen. Whatever works is the correct approach so... don't sweat it.
     
  9. Lance Weston

    Lance Weston Active Member

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    Have you tried duplicating it? Do a filament load at the beginning of the roll and measure it. Do the same near the end of the roll and measure it.

    This is a very consistent result for me.
     

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