Why does the nozzle get clogged?

Sometimes the nozzle of your printer gets clogged, it may be due to a too low heating temperature, an upstream cooling in the hot-end not efficient enough, a build plate located too close to the nozzle or the quality of your nozzle.


The filament’s heating temperature depends on its constituent material. Sometimes, you have selected the correct temperature in the printer settings but, because tolerances of tool are not perfect, it has varied by plus or minus 5 ° C. Further, if you have increased the speed of printing without increasing the temperature, it is possible that the filament does not heat up fast enough compared to the extrusion speed and it is blocked.

We advise you to adjust the heating temperature of your printer manually to find the right one for your filament. For more details on the choice of heating temperatures according to the filaments, read our article about this.

Hot-end and heat-sink

The hot-end is used to ensure the filament’s fusion, to do this, it maintains a thermal barrier so that the filament can move in its solid state until it must melt. If the filament heats up and melts too early, it settles on the walls of the heat-sink, blocking the passage to the nozzle. This happens when the heat-sink does not cool this part: the radiator can be dirty and less efficient than normal, in which case you can try to clean it regularly. If you do not see improvement, it is possible that the hot-end is poorly designed, in which case you should consider changing to a more efficient.

Otherwise, if you turn off your printer before the temperature goes down, the radiator can not work, so the filament expands, blocking the extrusion path for the next print.

Build plate

The setting of the build plate is quite complicated to elaborate because it requires a great precision (tenth of millimeters) with the help of not very precise tool (often the adjustment must be done with the eyes in three point on a plate which is probably not uniformly flat). It is likely that it is imperfect and therefore, in some areas, that the distance between the nozzle and the tray is not good enough. The problem that arises is that the filament has no place to go out but the extruder pushes it anyway, so it accumulates it-self at the exit and forms a kind of plug. In this case, you need to remake the calibration of your build plate, possibly change it if it is damaged.


When your nozzle is of low quality, chances are it is damaged in addition to being blocked. The inside of the nozzle may have deformed with time by heating for example. It is also possible that the nozzle does not allow to heat the filament fast enough because it is not well designed. In these cases, if you unclog it and put it back, chances are that you will have to repeat the operation very soon, you will certainly benefit from replacing it directly, possibly for a better quality material that would allow you to do not reinvest from here.

Of course when your nozzle is of high quality, replacing it would cost you a lot, and there is little chance that it really is the problem, clean it well and check the other points, and try to solve it before starting a new print.

Technique to unclog the nozzle

  1. Heat the printer in a vacuum to expand the filament
  2. Remove the filament from the extrusion line
  3. Using a tool, unscrew the nozzle
  4. Remove the excess molten filament with a needle as an acupuncturist needle and screw the nozzle

The tools in step 3 may depend on the printer you are working on. For Prusa printers for example, you can find tools to remove your nozzle without damaging the electronics.

Caution: some printers are not designed to allow the possibility to remove the nozzle, you will need to proceed otherwise like for example change the hot-end for a version that can change the nozzle. Osmoz 3D offers tailor-made hot-end for some printers concerned.

To reduce the risk of clogged nozzles, we advise you to choose your filament according to the needs of the printing and the printer.