How to Fix a Blocked Hot-End or Extruder on Your 3D Printer

By Kalani Kirk Hausman, Richard Horne

When you get a hot-end blockage or your extruder’s filament drive fails on your 3D printer, the signs are usually obvious: The stream of plastic starts to lessen, and then stops; the printer keeps trying to print, but extrudes layer after layer of nothing.

The first thing to do is stop the print and check to ensure that the heater block on your hot-end is still at the expected temperature. (Ideally, for maximum safety, you should use a non-contact temperature sensor.) If the heater temperature is significantly below 160 degrees Centigrade, it may have failed or it may have developed a problem in the wiring or the electronics controlling the heaters.

Unfortunately, it’s common for wires on home 3D printers to break due to the constant movement of the machine. Wiring should always have plenty of room to move around gently, with enough slack that it’s not tightly bent or yanked back and forth as the machine moves.

Using silicon-coated wire can help, especially with extra resistance to heat. Increasingly, newer machines use gently curved ribbon cable, (a ribbon of many separate, parallel wires instead of a thick wire). This tends to alleviate issues with cable strain and damage.

If your heater block is jammed but is at the expected temperature, here’s the general procedure:

  1. Keep the heater block turned on.

  2. Check to ensure that the filament drive hasn’t become blocked or that the filament is not buckled in or wrapped around your extruder drive wheel.

  3. Release the idler bearing and gently pull out the filament.

    It’s not common for a filament to become so jammed that it cannot be pulled out while the hot-end is at temperature. More commonly, the removed filament shows signs of being overly compressed — a little fatter where it melted inside the hot-end. Usually the action of pulling out the melted filament removes contaminants from the hot-end nozzle.

  4. Cut off the melted filament end and manually push it back down into the hot-end.

    If you can push down and material is extruded from the nozzle, you have cleared the blockage.

  5. If you can’t get the material to extrude, then allow the end of the material to melt and pull it back out again.

    Doing this several times should clear most blockages. If you still have a blockage, you have two more options to be done extremely carefully:

    • Push a pin or small drill bit into the nozzle end while pulling out the melted filament.

    • Allow your hot-end to cool down and when it’s cool, use a chemical solvent (such as acetone) to help dissolve any build-up.

    Before using any chemical cleaners, check with your supplier and mention the type of material that was last used in the hot-end when the jam occurred.

You may be starting to think that having a few different extruders is a good idea. Well, it usually is; in the event of a blockage, a backup extruder can get you printing again while you repair. Another reason for having a choice of extruders is that your machine becomes much more capable at printing different types of objects, which can widen your selection of available printing materials.