A fairly common 3D printing problem is a jammed nozzle. When the nozzle jams it stops melted filament from being added to the current print, but the printer knows nothing about this, so it just continues as though it was printing OK. The net result is “printing in air” – nothing is actually printed, but the printhead keeps moving just as though everything was OK.

The good news is this kind of jam is easy to spot – just looking at the printer shows that filament is not being added and something needs to be done to fix this.

A partial nozzle jam is different. This happens when the nozzle is only partially obstructed, resulting in an insufficient amount of filament being printed as the printhead moves around. Consequently a partial jam is far less obvious than a full jam.

Here are 3 closeup photos of the same part of the same print that show the difference between a partial jam and an unjammed nozzle. The first 2 show what the partially jammed nozzle produced, and the 3rd one shows the unjammed print.

Outside surface showing when the partial jam occurred
Inside surface higher up on the print
Outside surface after clearing jam

Finally, here is a photo of the finished print after I cleared the partial jam:

Nice and smooth

The STL file for this part and more pics are here: https://www.thingiverse.com/thing:4544066

There are many ways people use to clear nozzle jams. After trying several of those I decided it was time to revert to something that was easy to do and that actually worked. It falls into the category of a “brute force” technique, and I recalled the ancient military dictum “Victories are won by the application of overwhelming force.”

The method I use is very simple and quick – the entire process takes only about 5 minutes and works every time. Here are the steps:

  • Heat the hotend to normal printing temperature
  • Remove the nozzle from the heater block
  • Hold the nozzle with needle-nose pliers
  • Use a propane torch to heat the nozzle hot enough to burn and/or vaporize any filament inside it. This takes only about 30 seconds.
  • Cool the nozzle under running water (never let it go from the pliers once it is hot)
  • Screw the nozzle back into the heater block

That’s it. Heating the nozzle may change it’s color and/or appearance a bit, but otherwise the nozzle will print just fine.

Last Update: 16 Jul 2020