There are several reasons the filament in your extruder may become jammed or fail to feed. Today, I’ll cover 3 causes I have encountered with my 3D printers.
The jam most encountered on my list tends to be caused when the heating block tube (small nylon tube inside of the heating block) becomes clogged. This can be caused by various reasons and precautions should be taken to prevent them. One of the causes of this is if the filament becomes restricted or tangled around the spool holder while the printer is running. This prevents the extruder motor from pressing filament into the heating block. Another situation you may encounter is if the filament has been to tightly rolled onto the spool and therefore will not unwind as easily as it should. Sometimes, if you are printing from the computer (USB cord) rather than the SD card you may experience a jammed extruder because the extruder motors just stop turning (bug), however, the printer continues to print. The extruders continue to heat the plastic in the heating block, but the plastic filament does not move through the system. Hence, the plastic just cooks inside the heating block and hardens inside the plastic tube. This is a good reason to always monitor you printer when printing a design.
Another reason I have seen for a jammed extruder is not truly a jammed extruder. It appears as if the extruder is jammed, but what has really happened is the filament has jammed inside the feeding mechanism above the heating block. I have generally seen this jam in conjunction with one of the clogged tube jams previously discussed. I usually discover this jam after I have cleared the previous tube clog and then still have problems loading the filament.
The final reason for a jammed extruder may actually be a clogged nozzle. Sometimes old plastic will cook too long inside the extruder. I have rarely seen this, but it warrants discussion as it is easily fixed with a straight or safety pin.
Removing The Clog or Jam!
One of the first techniques I employ to clear an extruder jam does not require any tools…YEAH! I call this technique the “Stuck in the mud” technique…I use the Load/Unload Filament utility to try and work loose the jam similar to the way you would try to get a truck unstuck from the mud…back and forth… load and unload.
If that fails to free your filament, I then apply the “Get a bigger hammer” technique…I adjust the preheat option on the jammed extruder to 250C and preheat the machine. To do this just use turn on your machine and arrow down on the display until you see <Info and Settings>. Next select <Preheat Settings> and then select the extruder which is jammed…Left or Right. Then run up the temperature to 250C. Return to the main screen and enter the preheat sequence. Once the extruder reaches 250C I run the machine through Load/Unload sequence again. If that does not work, I resort to pulling out my trusty tools…they always work!
- Small metric wrench (9mm)
- Needle Nose Pliers
- Tool to hold both heating blocks together
- Small needle
- Included tool kit
- Small knife or Xacto hobby knife
- Thin metal rod that will fit down into the heating block ~1.75mm diameter…slightly less than filament diameter. Might be able to use the smallest hex key included in your included tool kit.
Okay, we are now down to the procedure I dub…”Oh crap, I have to get my tools” technique. So, first things first lets go for the most likely culprit…a clogged heating block tube.
Remove the nozzle
Heat the extruder which is clogged, you can do this by using the Load or Unload utility. If you fail to heat the extruder the nozzle will likely be extremely difficult to loosen and you may damage the nozzle or heating block.
Using your pliers, grasp the heating blocks being careful to not tear the Kapton tape which surrounds the heating block as in Figure 1. You want to prevent any movement of the heating blocks while trying to loosen the nozzle. If you break loose the heating block you will need to retighten it from the back and you will need to remove the extruder from the carriage as well as remove the feeding assembly. One other way to prevent the heating blocks from moving is to use an object that fits tightly between the heating blocks the runs from the front all the way to the rear of the blocks. I use a small pocket knife to hold mine in place (see Figure 2).
Using your small wrench (mine is a 9mm, but yours may be different) loosen the extruder nozzle which is clogged. This will likely be very tight and you must be careful to not turn the nozzle in the wrong direction.
Use caution because the nozzle and heating block are VERY hot. Remove nozzle and plastic heating tube from the heating block (see Figure 3) and set them on the build plate. Do not handle them until they are cool. The nozzle tube may be difficult to remove from the heating block and you may need to remove it with needle nose pliers. If so, be careful to not squeeze the tube enough to deform its shape.
Once you remove the nozzle you can use the needle to unclog the small hole in the nozzle.
Examine the plastic tube to see if any filament is jammed inside. If so, you will need to remove it. Use the small metal rod mentioned above or the smallest hex key that came with your tool kit. Once the tube is cleared, you can reassemble the extruder. I recommend that you reheat the extruder block when you reassemble it and DO NOT over tighten the nozzle. You will need to be quick when you screw the nozzle back into the block as it will heat up quickly once it touches the heating block… (that’s experience talking…Ouch!). Remember, the plastic tube will fit inside of the top of the nozzle.
Once reassembled try to unload and reload your filament. If you are unable to get the filament to load you will need to disassemble the extruding assembly above the heating block.
In Part 2 of Unclogging Jammed Extruders, I review how to unclog an extruder by removing the extruder to clear the filament.
– Dave Weas, Imaginator3D Team