My 3D Printer Is Jamming

A number of factors can cause your 3D printer to jam. This article is written to systematically diagnose and troubleshoot a 3D printer that is jamming. We will investigate the following components in order to determine the cause of a jam:

  1. Filament Spool
  2. Guide Tube
  3. Extruder
  4. Hot End
  5. Print Settings

You may need the following tools in order to perform this procedure from start to finish

  • 4mm Allen Key
  • Needle nose pliers

Filament Spool

The first area of the printer feed system to inspect is the filament spool. Verify the following:

  1. Spool contains filament: The end of the spool may have a bend in it that prevents it from loading into the guide tube. Furthermore, if there is no filament present whatsoever then no material will extrude from the hot end.
  2. Spool is not tangled on itself: unwrap the spool ~10' and respool. A tangle should be obvious in the form of a knot in the filament wrapped around the spool.

Guide Tube

Issues with guide tubes are fairly uncommon, but the following should be verified before proceeding to the next section

  1. Verify that there are no sharp kinks in the guide tube. This is generally not an issue for most filaments, but stiffer filaments (stiff plastics, carbon fiber filled, glass fiber filled) may require significant force to move around bends in the guide tube. Ensure that there are no sharp kinks in order to check this. This can be verified by pulling a length of filament through the guide tube to check there is no significant back force.

Extruder

The extruder pushes the material. If no material is being pushed through, then there may be an issue with your extruder. The following conditions must be verified for successful extruder function:

  1. Tension is set correctly: the tension on the hobb of the extruder must not be set too high or too low. If it is set too high then the extruder will carve through the filament and cause a jam that must be cleared If the tension is too low then the extruder will slip over the filament and apply no pushing force. The tension should be set to the minimum amount that will catch the filament and push it while holding the filament from above the extruder. This is particularly important for more flexible filaments.
  2. No filament obstruction: broken off filament may be within the extruder. Follow the extruder clearing procedure if this is the case. This will generally prevent loading of the filament.
  3. Motor is functional: you should be able to see the hobb and tensioner wheels of the extruder spinning. You may have an obstruction or a bad motor / wire if the extruder is clicking as if it is trying to spin but not actually advancing.
  4. Teeth of extruder clogged: If a jam has occured ,the teeth of the extruder may be clogged. Clean these out with a brush. Furthermore, fiber load materials can quickly wear down components, especially brass hobb wheels. If the teeth are worn down then the hobb should be replaced.

Hot End

The hot end is the next component to inspect after the spool, tube, and extruder. Verify the following to ensure there are no hot end issues.

  1. Hot end barrel is not clogged. You will need to use an allen key to free the hot end from the print head. Ensure that there is no visible obstruction in the hot end.
  2. Nozzle is not obstructed. You can verify that the nozzle is not obstructed by removing the extruder from the print head, heating up the hot end to the recommended filament temperature, and manually attempting to pass the material through the hot end. If material emerges, then the nozzle is not obstructed. If the material cannot be pushed through or if it does push through but comes out kinked sideways rather than flowing straight out then you likely have a partially or fully obstructed nozzle. The nozzle should be replaced if this is the case.
  3. Cooling fan / liquid cooling loop is turned on. If the liquid cooling loop or the fan on the fins of the hot end are not running then material will soften in this zone and cause a plug preventing material from advancing. Check that this are functional and running when hot end is above 50°C.
  4. Hot end heats up. No material will flow if the hot end does not heat up.
  5. Nozzle is not too close to bed. If the nozzle is too close to the bed on the first layer then the material will have no where to go. If the nozzle is dragging on the bed, then perform a Z levelling of the printer.

If all machine components above are checked and good, then you may be impacted by your print settings. These are usually the issue if the printer works for the start of a print job but fails in the first 10% of the job. The following settings are most significant in preventing jams:

  1. Temperature: Ensure that your temperature is within the manufacturer's recommended range. If the temperature is lower than this range then it will likely not become molten and be able to extrude from the hot end. If the temperature is higher than this range then heat may creep up the hot end, soften, and cause a plug. It is recommended to use the minimum recommended manufacturer temperature for printing.
  2. Print Speed: If print speed is too high then there will be an excessive back force causing failure of the print. Dial down speed to increase reliability. It is important to remember that this more significantly maps back to the volumetric flow rate: if your speed is reasonable but you have extremely thick and/or wide layers then you will still experience significant back force. You can reduce these settings also to reduce your flow rate. A less likely case is that
  3. Layer Height: Low layer height below 0.2mm especially for fiber filled materials can cause an excess in back force on the print head and may cause a jam if flow rate is too high. Increasing layer height will help if this is the case.