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Help troubleshooting an odd problem  

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Dave
 Dave
(@dave)
Eminent Member
Help troubleshooting an odd problem

I did a filament change and after several attempts, couldn't get material to extrude.  When I unloaded the filament, the piece that had entered the extruder wasn't even slightly melted.  When I reloaded the filament, it was pulled in about 3cm, then the gears sounded like they were skipping.  As if the filament couldn't be drawn in any further.  The filament itself is notched slightly by the gears, so I know they're gripping it well.

I heated the hotend to 270° for a bit, thinking that any PLA in there blocking the nozzle would ooze out.  No such luck.  Reloading the PLA resulted in the same issue; no material coming out and the filament not even being melted.  I replaced the nozzle, thinking it could be clogged, but no luck there either.

I'm guessing there's a blockage between the feeder gears and the hotend itself.  This is a situation I've never encountered.  Can anyone suggest a way to troubleshoot without having to disassemble the extruder?  I want to upgrade to the MK3S (I have an MK3 now), but haven't printed the parts yet.  I'd really like to not have to rebuild the extruder 2-3 times.  🙁

Help?

Best Answer by bobstro:

Before you replace anything or tear apart your extruder, give this a shot:

  1. Heat the nozzle to 285C.
  2. Remove the nozzle.
  3. Open the extruder door.
  4. Insert a 15cmx1.5mm rod down through the filament feed on top, past the (open) extruder gears and down into the PTFE tube below. Press until you encounter resistance.
  5. Apply steady pressure while bracing the extruder mechanism to see if you can dislodge the stuck material. Be sure not to twist or damage the extruder.

A 6in/15cm length of rod is ideal. You can find this at a hobby shop, or a stiff piece of wire laying about might work. Polish the ends so as not to nick the PTFE tubing.

I had something very similar happen and was able to clear it this way.

 

 

Posted : 24/05/2019 3:25 pm
tom.s33
(@tom-s33)
Eminent Member
RE: Help troubleshooting an odd problem

One thing I would try is opening the extruder idler door so you can see the filament you are manually pushing through (once you're heated to 240 c - I rarely ever need to heat PLA higher for this procedure - any hotter and you run the risk of cooking the plastic into a hard chunk), making sure the filament enters the PTFE tube correctly AND is aligned with the Bondtech gear, and try to force the filament through.

If that doesn't work, you may have to take the assembly apart to see where the block is.  But maybe before resorting to a teardown, you might want to use a nozzle declogging tool, such as https://www.amazon.com/gp/product/B074HRPB2H/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1.   It has helped a couple of times on another printer I use every so often.  I hope this helps.

This post was modified 3 years ago by tom.s33
Posted : 25/05/2019 4:26 am
Dave liked
Dave J
(@dave-j)
Trusted Member
RE: Help troubleshooting an odd problem

I've have this problem on my MK2.5S. When loading a filament I keep pushing the filament down (very little effort needed) until I see hot filament coming out of the extruder.

I have a feeling that when I installed the IR sensor as part of the S upgrade, the extruder body may have become misaligned when I was putting it back together, so I think all I need to do is partially disassemble and reassemble the extruder again, and this time doubly rechecking the parts are aligned.

If you do the S upgrade, you will also be able to check and adjust the alignment. So sorting two items with only one partial disassembly and rebuild

Cheers,Dave Jackson"Enthralled Nooby (not so much maybe, ~58 years old)... If 3d printers had been around 40 years ago... "

Posted : 25/05/2019 3:55 pm
Dave
 Dave
(@dave)
Eminent Member
Topic starter answered:
RE: Help troubleshooting an odd problem

Thanks for the suggestions, guys.  @Tom, I think you're right about the PLA fused into a chunk.  While trying to do a nozzle change, I accidentally jacked it up to 260 C for a minute or so before I realized it was that hot.  Betcha that fused the residual PLA into a nice plug.

On that note, would it be easier to find a 6" drill bit to drill out the plug, or to just replace the hot end altogether?

Posted : 26/05/2019 2:53 am
tom.s33
(@tom-s33)
Eminent Member
RE: Help troubleshooting an odd problem

If it was me, I'd probably just go for the new hot end, David.  I would be a wee bit nervous drilling into such a small orifice and not nicking something else in the process.  Also, a drilling might loosen the chunk, but it could also shred it into many smaller chunks and remain in the hot end anyway.  If it can't be heated and pushed through the nozzle, then it's probably time for a bit of surgery.

This post was modified 3 years ago 2 times by tom.s33
Posted : 26/05/2019 3:50 am
bobstro
(@bobstro)
Illustrious Member
RE: Help troubleshooting an odd problem

Before you replace anything or tear apart your extruder, give this a shot:

  1. Heat the nozzle to 285C.
  2. Remove the nozzle.
  3. Open the extruder door.
  4. Insert a 15cmx1.5mm rod down through the filament feed on top, past the (open) extruder gears and down into the PTFE tube below. Press until you encounter resistance.
  5. Apply steady pressure while bracing the extruder mechanism to see if you can dislodge the stuck material. Be sure not to twist or damage the extruder.

A 6in/15cm length of rod is ideal. You can find this at a hobby shop, or a stiff piece of wire laying about might work. Polish the ends so as not to nick the PTFE tubing.

I had something very similar happen and was able to clear it this way.

 

 

My notes and disclaimers on 3D printing

and miscellaneous other tech projects
He is intelligent, but not experienced. His pattern indicates two dimensional thinking. -- Spock in Star Trek: The Wrath of Khan

Posted : 26/05/2019 4:05 am
Dave liked
Dave
 Dave
(@dave)
Eminent Member
Topic starter answered:
RE: Help troubleshooting an odd problem

@Bobstro...HAHAAAAAAAA!  Got it!  The 285C trick did it.  A bit of goo oozed out and doing a standard filament feed pushed the rest out.  Brilliant!  Thanks so much for the help.  Saved me a butt-load of time and energy.

Posted : 26/05/2019 4:31 am
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