Signs Of A Clogged Printer Nozzle

I’ve been fighting with my printer for a couple of days now because the nozzle keeps clogging. After changing out the nozzle and cleaning the hotend, it would run fine for a while and then start to plug up again. The printer has seen a lot of heavy use with different materials over the past six months, so I suppose I don’t blame it.

I think I’ve got it fixed now, but you can’t ever really have 100% confirmation that the crud is all gone. It may print well for the next one, two, or twenty prints, then clog again.

Signs that your printer is developing a clog:

  • You find you have to make changes to feed rate or flow settings that you didn’t before.
  • Extrusion (particularly first layer) doesn’t look consistent.
  • There is a roughness to horizontal and vertical skins that wasn’t there before.
  • Printed parts are more fragile than usual.
  • Lots of horizontal, “dotted” lines along the sides of the print.
  • You can hear an odd scraping sound coming from the extruder (the extruder gear is grinding plastic because it can’t push it in fast enough).
  • There is a lot more dust than usual around the extruder gear/motor (same reason as above point).
  • The motor driving the extruder keeps “thumping” or “popping” and jumping backwards because it can’t keep up with the electronics that make it turn.
  • The filament spool is not turning.

If you’re suspicious that there’s a clog, level your print bed and do a test print (you would be amazed at how many things can be fixed just by levelling the bed). If it’s still not printing properly, raise the nozzle from the bed (the further, the better), and extrude a bunch of filament, making sure to keep cutting it so it doesn’t touch the print bed and make the filament bend or twist. If the extruded plastic is pointed straight down, is consistent along its length, and is the appropriate thickness, things may be okay. Here are some samples from a test extrusion I did that showed there was definitely some junk stuck in there somewhere:

Filament with a lot of moisture in it can extrude like this. I dry my filament regularly and use a lot of dessicant so it’s probably junk in the nozzle.
This looks more like a clog.
Again, could be damp filament… could be junk floating around in the nozzle.
This is DEFINITELY a clog.

Another thing I do to help me keep an eye on things is mark one or two spokes on the filament spool with a colour that stands out (silver on a black spool, black on a white spool, etc). That way, I can note where the marked spokes are, leave the room, and come back later to see if they’ve moved.

I hope I’ve got it cleared out. If there is still any junk in there, it would be nice if it either melts or is small enough to fit through the nozzle. I have a spare (brand new) hotend, so if I need to I can swap it out and give the used one an even more thorough cleaning.

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