21 Jul 2021: This page is updated to include more details about the cleaning process and with photos showing how easy it is to do. The printer shown in the photos is an FLSun SuperRacer.


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:

  1. Heat the hotend to normal printing temperature. Doing this makes it a bit easier to remove the nozzle from the heater block.
  2. Remove the nozzle from the heater block. To do this, use a small wrench to hold the heater block, and a 2nd small wrench to unscrew the nozzle while holding the heater block still.

    Here is a photo of the top of my printer’s partially clogged nozzle. You can see there is a thin layer of fused yellow filament stuck to the inside of the nozzle’s opening. This layer reduced the amount of filament the extruder could push through the nozzle and this, in turn, resulted in under extrusion.

  3. Hold the nozzle with needle-nose pliers so you can heat it with a propane torch. I use the one in this photo, but any kind of propane torch should work. The clogged nozzle is just to the left of the torch.

  4. Heat the nozzle hot enough to burn and/or vaporize any filament inside it. This takes only about 30 seconds. You should expect to see some melted filament drop out of the end of the nozzle, as well as some flame emerging from both ends. Here is a photo of my nozzle after the torch process.

  5. While the nozzle is still hot poke around inside it with tools like these to make sure the inside has no tiny pieces of filament stuck in there.

  6. Cool the nozzle under running water (never let it go from the pliers once it is hot.)
  7. Before reinstalling the nozzle in the heater block I wrapped one layer of plumber’s teflon tape around the threads just to make sure there is a good seal between the nozzle and the heater block.

  8. Screw the nozzle back into the heater block using the same tools used to remove it.

    Yes, I took this photo without the hotend’s heater sock installed. But I didn’t forget to put it back on.

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: 27 Jul 2021