Since FDM printing involves melting polymers and feeding them through a very small hole, Nozzle clogs are one of the most common and one of the most annoying problems to occur with a 3D printer.  Repair can be as simple as pushing a hard alan wrench through the barrel, some can be as Nozzle Clogtime consuming as dissambling the carriage and torching the material out.


Heat Creep

As mentioned in our Cooling chapter, a barrel fan is needed for almost all FDM printers to succeed without heat creep causing a nozzle clog.  While feeding material out of a hot nozzle, the heat will often creep up the filament.  This causes the filament to expand inside the barrel, often creating a lump.  This lump will cause a clog and will make the removal of the filament from the barrel near impossible without disassembly.

PID Tuning

PID refers to a proportional integral derivative controller that is used in 3D printing to control the temperature of the nozzle.   When the PID settings are off, a fan can drastically change the temperature of the hotend.  The barrel fan or the active cooling fan can drop a hotend from 210°C to 160°C if the PID settings are off.  This rapid cooling will make the nozzle too cold for the filament to feed.  This means that the extruder gear will slowly grind into the filament until it snaps.  You can update your PID settings by reflashing your firmware.

Tips to Avoid Nozzle Clogs

Keep Everything Clean – Cleaning a bed and wiping down a nozzle after and before each print can go a long way to preventing a clog.

Feed Filament Down Roughly 1/2 inch before pulling out – When filament is just sitting in a barrel, some minor heat creep can occur. While not enough to cause a clog while printing, it can be extremely difficult to remove. This can be prevented by feeding the filament past this point, and then pulling it out.

Use only one material in each printer -This can be very difficult for those with only 1 or 2 printers, but switching materials on a printer can lead to clogging. Switching from ABS to PLA may not get rid of all of the remaining ABS material, which can clog during the print.

Proper Printer Speed – Printing too fast on a material can cause grinding until the filament snaps, and printing too slow can increase the heat creep risk.


Continue to O - Orientation of Print