What to look for when diagnosing a jam

There are several potential ways that filament can get jammed on the H-Series machine.  A jam is most often identified when the filament assist motor or extruder motor starts skipping against the filament and stops advancing.  The first step is to identify if the jam is coming about from trying to extrude filament or retract filament.  

Jam while retracting filament

If you are experiencing a jam while trying to extract your filament, several things could be happening. For soft filaments, it is possible that the filament has buckled at the backside of the drive rollers. This can happen if the filament assist has built up pressure in the line and the extruder is pushing against this pressure to retract material. 

If this is the case, first cut off the filament that is protruding from the rollers as close as you can to the exit point. Next, remove the PTFE tube from the back side of the extruder. To do this, remove the blue collet clip, then push down on the black plastic collet while pulling out the tubing. After this, use the web control, extrude a small amount of filament (5 to 10mm). This should force the material back into the normal drive path.  Then retract 100mm while pulling on the filament by hand. (Pro tip: a small square of sandpaper can be very helpful to get a grip on the PTFE tube when removing or reinstalling).

When inserting the PTFE tube back in, check for damage to the end. Make sure the end of the tube is unobstructed and the edges are not folded over. Also, make sure that the tube is in the proper orientation. The 60 degree Vee of the end should align with the nip point of the drive rollers. Looking closely between the rollers and the extruder arm, you should be able to see the PTFE in contact with the rollers when it is fully inserted. If the tube is not properly aligned with the rollers, this likely a cause of the jam.

A second way that a retraction jam can occur is if the retracted filament has a bulged or misshapen end.  This often happens when filament is retracted so quickly that hot filament reaches the drive rollers and is compressed into an abnormal shape. In this case, first try extruding until you get consistent flow out of the orifice, then attempt retraction again at a slower pace. If this does not work, follow the same procedure as above to remove the PTFE tube from the back side of the extruder. Cut off the bulged region of filament and reinstall as above.

A third way that an extruder jam can occur is if the retracted filament has strings or globs that break off when it is pulled through the drive rollers. This usually comes to light when trying to load the next filament into the extruder. In this case, you will need to remove the extruder spring-loaded arm. First, release the extruder torsion spring by grasping rightmost end with a pair of needle nose pliers. Pull this end off of the tab on the extruder arm and lift the leg of the spring up 90 degrees.

After this, remove the M3 shoulder screw holding the arm in place while squeezing the arm toward the drive roller by hand (squeezing in this way prevents the last thread of the shoulder screw from being damaged by the remaining spring force).

After this, clean off the drive roller and reinstall the arm being very careful not to trap the rear leg of the spring against the motor pilot face.  To avoid this, place the extruder arm up and to the left of its final location and press it against the motor face. Then slide it down and to the right until the shoulder screw can be threaded into the tapped hole. 

Jam while extruding filament

If the extruder is stalling or slipping while trying to extrude filament, this could be caused by a clogged nozzle, damaged hot end PTFE tubing, or improper positioning of the arm of the extruder.

The easiest way to clear a clogged nozzle is to either replace the nozzle with a new one, or by performing multiple cold pulls to clean the inside of the nozzle.

The PTFE inside the hot end will need to be replace over time as it will start to wear down along the edges or degrade chemically from long periods at high temperatures. If you are experiencing any extrusion issues, then follow the guide for replacing the hot end PTFE tube.

Refer to 4.2 Repair/replace an FDM Hotend for guides on replacing the numerous components of the H-Series Hotend.