This page outlines the procedure for diagnosing and fixing a printhead that fails to extrude.
The first section gives background on the parts of the printhead and how jams can occur, or you can skip to the Troubleshooting Guide.
Parts of the Filament Path
Extruder
Filament feed starts with the extruder, where the Drive Gears powered by the Extruder Stepper Motor grip and feed the filament. If any part of the filament path experiences a jam, the Drive Gears will be unable to feed the filament forward and will grind a groove in the filament. After fully grinding away the filament, this means that if the jam is resolved the Drive Gears will no longer be able to grip the filament, and you will need to manually apply forward pressure on the filament to get the Drive Gears to grip.
Heatbreak
The purpose of the Heatbreak is create a sharp temperature transition between the cold end and the hot end. The filament in the Hotend is molten and flows freely as a non-Newtonian fluid. If the cold end fails to create a sharp temperature gradient, the filament above the Hotend could be above the glass transition temperature but below the melting point, causing it to jam within the filament path.
Common causes of Heatbreak clogs are excessive retraction, improper filament loading and unloading, or insufficient cold end cooling.
HeatBlock
The HeatBlock houses the heater and thermistor cartridges and melts the filament for extrusion through the nozzle. Since the HeatBlock filament path is a large diameter and reaches high temperatures it is unlikely for the HotBlock to ever be the cause of a jam. Keep in mind that when swapping filament types it is important to purge the HotBlock sufficiently as traces of the old filament may linger and feed down causing a jam in the nozzle.
Nozzle
The nozzle provides a precision orifice for the printhead to deposit molten filament. Since the orifice is small in diameter, it is the most likely part of a printhead to jam.
Common causes for nozzle jams are insufficient purging between material swaps or material impurities.
Troubleshooting Procedure
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Remove the filament elbow and inspect for broken filament or filament runout.
Preheat the printhead and select the “load filament” command on the printer screen. Check to see if the Drive Gears are spinning. If the Drive Gears are spinning but the filament does not feed, there is a jam in the Heatbreak or the nozzle. If the Drive Gears do not spin there is an issue with the Extruder in which case contact customer support.
Remove the nozzle using guide Replace a Nozzle . With the printhead preheated, select “load filament” and help feed the filament above the printhead manually as shown in the image below. If filament extrudes from the HeatBlock, the nozzle was jammed and you can install a new nozzle. If the printhead does not feed filament with the nozzle removed proceed to the next step.
With the printhead preheated, the nozzle removed, and the filament elbow raised, depress the tension lever with one hand and quickly pull up on the filament with your other hand. If you are able to remove the filament, trim off 20cm of the filament with side cutters, and try loading the filament again. If the extruder still fails to extrude, then there is Heatbreak jam and you will need to follow guide Rebuild The Hotend or contact customer support for a new Hotend assembly which you can install with guide Replacing a Hot End .
