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How do I troubleshoot filament loading problems?


Topic starter

Just fired up the Max3D and completed the following steps:

  1. preheated the extruder to 200c and hotbed to 50c. 
  2. Passed filament through the interlock and into the extruder opening. 
  3. Pressed "IN" in the tool\extrusion menu

Observed filament wheel moving and some take-up, but then nothing comes out and multiple presses of "IN" just increment the counter (I'm at 105mm).   It is not taking in the filament.    If I had to guess, I would say temperature is low or there is blockage.

Was I supposed to add parts to the hot-end?   I have a lot of extra stuff...  all metal tips, etc.



3 Answers
Topic starter

While troubleshooting the out-of-the-box filament feed problem, I found a small piece of black plastic blocking the top opening of the extruder.  This prevented the PLA on my spool from entering the extruder chamber and heating up.

Discovery required removal of the heater block.   I removed too many parts initially, so here is a disassembly instruction that I used the second and third time that works for me (absent any written instruction).  The warnings and workarounds are from my recent experience and missteps along the way.  (edited for accuracy) 

These instructions are for removing the hot-end to check for blockage in the feeder side or replacement with new extruder parts.   Disassembly is not needed for changing the nozzle only.

  1. Preparation
    1. If the filament has been heated, unload it first while hot.  Otherwise the solidified PLA will prevent easy disassembly.    Use tool>filament>unload 
    2. Raise the print head at least 10cm from the hot plate. Use tool>move>Z+, 10mm steps and ten presses on Z+, then turn the printer off to cool.
    3. Loosen the two set screws just behind the feed knob using the short end of the 1.5mm hex wrench.  Seat the wrench firmly in the set screw and loosen 1/2 - 1 turn.  Same on the opposite side of the shaft.   The knob will now come off easily.
    4. Remove the hot-end cover shield ( four black machine screws)
    5. Dismount the filament sensor to free the cable clamps (two screws)
    6. Cut the cable-tie at the end of wiring harness to free the heater and thermocouple from the level sensor.
    7. Carefully remove the insulator from the heater block to expose its mounting screws.  The insulator has a lip around 3/4ths of the top keeping it in place.  There is no lip on the side with the wires. 
      1. The front side can be folded down a bit and then it will slide off from the left (opposite the wires).  There is some friction keeping it tight on the fan side so go slowly as necessary. OR
      2. When folded down, the heater block mounting screws can be accessed and loosened a bit to relieve the friction if it is pinched against the fan (read details in the next steps before attempting this).
  2. Removing the Hot-End
    1. You may find it easier to position your printer on its side to get a better view during the next steps.  Note that these steps are for removing the assembly.   This is only necessary when an unknown blockage is interfering with the feed or when installing the "all metal hot end" (throat and nozzle).   
    2. Remove the two screws from the BOTTOM of the heater block that mount it to the feed unit.   You must loosen both first before removing them.  Warning: there is risk here of damaging the fasteners.  They may be difficult to break loose due to assembly torque and heat stress between the stainless steel screws and aluminum.   The provided tools work very well if used properly, the information here will guide you.  
      1. Carefully seat the short side (not the ball) of the 2.0mm Allen wrench fully into the head of the fastener.   It is a close tolerance with poor visibility as it is upside down on the bottom of the heater block.   You need to line it up properly and adjust the rotation of your tool until it begins to mate.  Then wiggle it while adding a bit of force in Z-direction to fully seat the tool.   
        1. You will know when this has happened because the wrench is now tightly locked in the fastener head.   
        2. Wiggle and push a bit more to be absolutely sure.  If it feels loose, check that you have the 2.0mm size and try again.
        3. If the 2.0mm tool tip fails to seat properly due to the close tolerance, or previous attempts have damaged the opening:  find a Torx T-8 driver and use it instead of the 2mm hex wrench to break it loose the first time.
      2. Consider your orientation to the screw and direction of applied torque required to loosen it up.  Loosen direction is always anti-clockwise when looking at the top of a fastener.  Lay the printer on its side if you are at all confused about this part.
      3. This is a potentially difficult step.  Cautiously apply increasing anti-clockwise torque to the wrench until the fastener breaks loose. 
        1. Torque in the rotational plane only.  I.E. keep the long side of the tool straight and parallel to the hot plate and the short side in perfect alignment to the axis of the screw. 
        2. Keep the wrench fully seated into the fastener head by pushing on the short end where it is inserted.  For example, you can turn the wrench with your left hand and keep it seated with a small force from your right hand thumb and index finger that are pinching the short end.
        3. Stop immediately if the tool tip begins to rotate and the fastener does not.  You are about to strip out the head of the screw and create an enormous difficulty for yourself.   Even so, it can be saved with either a Torx T8 or T9 bit depending on the situation.  If the T8 bottoms out and wants to strip the head further, try tapping a T9 into the fastener gently with a very small hammer and the smallest necessary force.
      4. Once the first screw has moved, break the second one loose and then remove both of them to free the heater block.
    3. Carefully wiggle the hot-end out from the feeder.  It extends about 2cm into the filament feeder.  You need to get a bit of slack in the wiring harness by pulling it down a bit, then, grasp the heater block and wiggle it a bit while sliding  the hot-end out from the feeder.  Check the slack on the wires if it seems stuck and make sure the cable tie has been removed.
  3. Inspection
    1. Check if there are any obstructions in the extruder assembly.  It should be clear of filament from Step 1.  Shine a small led flashlight (eg. a keychain light) in the top and see if the chamber is clear.  Then check if any light comes out the bottom through the nozzle.  If all is well, you are done.  Continued disassembly is not necessary. Use the provided needle wire for a final check by inserting it from the top and observing a bit of the point coming out the other end.  After that, a shot of canned air from the nozzle end while the unit is inverted will remove any microscopic debris before reassembly. 
    2. Decide on replacement.  If your goal is to clear a blockage only and you are still in doubt, consider that a very small (<0.05mm) bit of anything other than filament can clog the nozzle, and it would likely be removed when the semi-solid filament is withdrawn from the hot extruder in Step 1.  Thus, the absence of a clear beam of light coming out the nozzle end with the flashlight test means there might be other damage to the nozzle. Choose a replacement and you can fuss with the suspect part later.
    3. Continue from here to change out either of the extruder parts, otherwise go to "reassembly".  
  4. Disassemble the hot-end components
    1. Detach thermocouple and heating element.  Observe that the extruder is hanging from the heater core and thermocouple wires.  You may want to take the safe route and unmount them prior to wrenching on the extruder nozzle.  The heater has one small set screw (loosen 1/2 - 1 turn) on the bottom and the thermocouple has a small hex head bolt snugged against its wires that can be loosened or removed to free the wires.  Both parts slide out easily from their respective recesses in the heater block.
    2. Remove the nozzle.  Use an adjustable wrench to secure the heating block and a 7mm box wrench to loosen the nozzle.  The provided wrench is inadequate to crack it loose the first time.  There may also be some melted filament that leaked into the threads that make the tip difficult to unscrew from the aluminum heater block. 
    3. Remove the top piece . The stock extruder must be removed with locking pliers while holding the block with an adjustable wrench or other means.  Definitely remove the thermocouple and heating element before attempting this.  All the soft parts will be out of harm's way.   Latch the locking pliers tightly on the shaft and support the heater block with an adjustable wrench to avoid nicking it up.  Otherwise you can mount the block in a vise or use channel-lock pliers if nothing else is available.  
  5. Clean the threads and mating surface
    1. If the same nozzle is to be re-installed, the threads must be cleaned of frozen filament.  Otherwise, little bits debris including metal shavings from simply unscrewing it can wind up inside the chamber and jam it up again.  Chase the threads with an M5 1.0 die (if you have a tap and die set) to clean the bulk of the crud.  A dental pick works almost as well. Use a hand-torch, or gas-stove, to soften any stubborn bits (hold the hex part of the tip with pliers and heat the threads with the torch for 5-10 seconds, stop if it starts smoking).  It should look perfect when finished, otherwise replace the tip.
    2. Clean the threads on the throat.  The threads on the extruder throat must be perfectly clean before reassembly.  Use the M5 1.0 die and/or dental tool as before.  
    3. Inspect the heater block. The threads in the heater block must be perfectly clean before reassembly. Again, any tiny bit of junk on the threads can end up inside the throat and clog up the nozzle.  This is an aluminum part and the threads may begin to shear off the inside of the bore if the hot-end parts are overtightened.  If you observe small shavings of aluminum stuck in the threads of the harder material or clinging inside the bore, there has been a bit of damage.   Just be careful to clean them off completely and re-tighten with caution. 
    4. Inspect the heater block threads.  If the threads look clean and shiny and sharp with absolutely no visible defects, tap the part on the desktop and see if anything falls out.  If not, hit it with a shot of canned air and skip the next step.
    5. Clean out the header block threads.  Best to use an M5 1.0 tap, running it in and out of the bore once or twice.  Go slowly with left and right turns, one forward, half backward the first time through. It will bind up a bit where the trouble is found and restore any bent threads.  If you do not have the handy tap and die set, there are other options.  A dental tool, a sewing needle with a bent tip, compressed air, a tiny bottle-brush with isopropanol, also WD-40 will all work for debris removal with a bit of patience.  Be sure to rinse out any remaining cleaners/oils with isopropanol and give it a shot of canned air after you are done.
    6. Check the mating surface of the throat and nozzle.  The flat end of both parts will mate together inside the heater block.  They should be free of defects, crud, etc., and look perfectly flat.  The point here is that anything that prevents full contact of the mating surfaces will cause a leak during extrusion.  If you found frozen PLA in the threads, it came from here.  If the crud cannot be scrubbed off, or if there are surface defects like nicks and scratches, touch up the faces with very fine sandpaper (600 - 1000 grit). 
      1. Put a 50x50 piece of sandpaper on a completely flat surface (the aluminum bed of the printer will do) and balance the part on the paper.  Keep the part in exactly this orientation while twisting or sliding it back and forth a bit, with gentle pressure, into the paper. 
      2. Do it gently until you have the feel of it.  The face must remain completely flat on the sandpaper while polishing. You can tell when it goes off-axis because the resistance changes.  The greatest resistance is felt when th
      3. Look at the end after a few strokes and check the work.  Rotate the part 60 degrees and then repeat the steps until the face is perfectly flat (tiny scratches are ok, but raised up gouges or dents must be flattened out).
  6. Reassemble the hot-end 
    1. Check the fit of the cleaned parts in the heater block.  They should thread smoothly in and out without using any tools.  Repeat the inspection steps above if they bind up while assembling.
    2. Install the nozzle first.  Orient the block for assembly to get the positioning correct.  The bottom has a set screw for the heading element and the right side has a port for the thermocouple.  The nozzle threads in on the bottom, next to the set screw.   Thread it in by hand to finger tightness, it will be tightened against the heating block in the finished assembly. 
    3. Install the throat next, threading by hand until it mates snugly against the nozzle.
    4. Place the tools at each end of the assembly.  A 7mm nut driver (or provided open-end wrench, or miniature socket driver) on the nozzle and an adjustable wrench on the throat (the all-metal piece has flat sides for this).  Use locking pliers for the stock throat. 
    5. Tighten to moderate torque.   7NM is typical for aluminum parts if there is a handy torque wrench.   Without one, tighten to an average hand strength with the nut driver, a bit less if using a short wrench.  In any case, there should be no rotation of the parts when tightening.  The ends are mated together and cannot turn further.  Thus the torque applies a load on the threads of the aluminum block and will separate them when over-stressed.  If you feel the torque diminish in the slightest while tightening, back off immediately. You are past the limit for the condition of the part. 
  7. Remount the extruder onto the feed unit  with the two stainless screws. 
  8. Remount the thermocouple and its wires.   The retainer screw does not need to be tight.
  9. Remount the heater core and tighten the set screw.
  10. Reinstall the insulator and tuck the trim back into place with a thin wedge as necessary to get it exactly right.
  11. Use one of the extra wire ties to secure the end of the wiring harness where the previous one was cut off.
  12. The heater wires tuck in between the heater block and level switch.
  13. Remaining parts go back in the order removed.
  14. Happy printing!
This post was modified 10 months ago by RobertM

I attempted to follow this very well laid out guide and was stopped cold at step #5. Dismount the filament sensor to free the cable clamps (two screws)
The top screw came out easily but the head of the bottom screw was stripped when I tried to remove it. As this is the first time I've tried this, it obviously came that way. As you can tell by the picture, a pair of small needle nose pliers wasn't much help either. Any suggestions?


I found the same - there was what looks like a remnant of red filament stuck in the top of the hot end.  Tried once I found that and everything worked as expected.



moi aussi j'ai eu du mal à mettre le filament ça bloquait , j'ai passez la petite tige pour déboucher la buse (fournis) et après plus de problème