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Filament Blob at the end of prints

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I am a middle school teacher having students use Tinkercad for their design, printing to Ultimaker 2+. In recent times, some students at the end of their prints have the printer bury the nozzle in the print, squirt out filament into a small blob. When this happens, the feeder also chews up the filament and it needs to be cut and re-threaded. This issue seems to be happening more and more frequently on three of my six printers. 


Things I have tried:

  • updating printer firmware
  • Re-exporting stl files from TinkerCad and re-slicing them
  • Using new, reformated SD cards

If anyone knows the answer to this question of what is causing this issue and how I can get it to stop, I would greatly appreciate this.


Looking forward to the expert community chiming in.




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Have you tried comparing the g-code between prints that work and prints that don't work? I would take a look at the end of the g-code file and check if there is unexpected stuff at the end of the file - e.g. from a plugin or a garbled Cura installation/printer profile?

The file should end with something like this:

M107 ; Stop Fan
G10  ; Retract
G0 F9000 X136.470 Y90.649 Z10.000 ; Move back to home position - different values since it is relative to the end position of the print
M25  ; Stop printing from SD card


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Thanks for the quick reply. I suspect the gcode is somehow corrupted. I just viewed the gcode and I don't see the text listed above. When comparing successfully printed gcode files with non successful, there doesn't appear to be any noticeable difference (from a non-coding person). I suspected some of the misprints from students were coming from their settings errors from Cura. When it started happening to me I suspected maybe my changing profiles (I change nozzle settings, etc. for student prints) was causing it. Also, I notice that stl files exported out from Tinkercad are not especially good. I think the internal structure of the files are not so good comparing files from other programs like Fusion 360, etc. School is out today but I will investigate. I thought maybe it had something to do with multiplying the same object more than once. It was creating the blog on the last item of the print. I added an additional piece, and scaled it way down just so the printer would go to this 'dumby' piece and squirt the filament blob rather than on my desired piece. It actually squirted the blob on the last piece then went to the tiny dumby piece. Thanks in advance to all responders..

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Since there is so many ways to get from STL file to a moving printer, maybe if you explain your process in more detail somebody has an idea where to check in addition?

What comes to my mind is:

  • Check in Cura: Manage Printers... --> Machine Settings --> Printer tab --> Gcode flavor. should be Ultimaker 2
  • Chech in Cura: Manage Printers... --> Machine Settings --> Extruder Tab --> Extruder Start Gcode and Extruder End Gcode should both be empty

Depending on the way you print - SD card, Octoprint, seriall connection, etc. there might be more that influences this.

You said that this happens when you multiply the same object? Do you do this in Cura? If so, maybe you could test it with a different Cura version once? I still use the old 15.04.6 for most of my prints and have used the multiply function there successfully before.

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Thanks for the follow up. As I mentioned, today was the last day of school and I was slated to get an upgraded laptop so I didn't bother to download/install the latest version of Cura. I decided to purchase the computer and keep it as a second hand computer at home so I downloaded the newest Cura. I opened the profiles and deleted old ones and double checked settings. I printed a file that had the blobbing issue and it didn't happen on the print. I suspect it had to do with the printing profiles. Again, I have a bank of six Ultimaker 2+  printers that I print to using SD cards. Files are sent to me from my tech students and others that often require me to change the speed, density, nozzle settings, etc. I suspect I didn't discard a profile or something wasn't correct there. It appears to be fixed for now. Not sure what students if students had somehow messed with their printer profiles as well that was also causing the problems because periodically, I would print files from their laptops directly onto the SD card and into the printer. At any rate, I appreciate the prompt replies and at this point I will say case solved. If I have issues with this in the future I will know to  discard profiles and set up new ones.




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