How to unclog your extruder barrel and nozzle

Nozzle and barrel apart

Nozzle and barrel apart

Here’s the process I used to unclog my extruder barrel and nozzle without a lot of extra equipment.  Obviously you should take all reasonable safety precautions with goggles, gloves, tongs, with a fire extinguisher, etc.  Plan ahead and be safe.

1. Materials:

  • Clogged extruder
  • Yarn
  • Q-tips
  • Heavy iron hook
  • Wrench
  • A big rock
  • Ethernet cable
  • Wire strippers
  • Blow torch
  • Safety equipment
  • Drill bits
  • Thick rubber band
Cleaning the inside of the nozzle - kinda gross

Cleaning the inside of the nozzle - kinda gross

2. Process:

  1. Disassemble the extruder
    1. Since PLA had gotten into the threads I had to leave the extruder warm as I unscrewed the PTFE insulating barrier.
    2. Unwrap the heater – taking off the ceramic tape, thermistor, nichrome, and Kapton tape.
  2. Remove plastic from the extruder
    1. I wrapped the unsharp end of my smallest drill bit in a thick rubber band to give it a grip.
    2. I then rotated the drill bit into the barrel by hand.
    3. Extruder barrel and thick yarn

      Extruder barrel and thick yarn

    4. When I had gotten as much out as I could, I switched to a slightly larger drill bit (again wrapped in a rubber band for grip) and drilled out as much as I could.  I repeated this until I had gotten to my largest drill bit that would fit in the barrel.
    5. I used a precision flathead screwdriver to follow along the threads of the extruder barrel and chip out plastic.
    6. I used the same precision flathead screwdriver to follow the threads inside the PTFE and chip out plastic.
  3. Heat the barrel
    1. This prior post has pictures for the entire setup.
    2. I was unable to remove the nozzle from the barrel.  Don’t worry if you can’t either.
    3. Put the extruder nozzle and barrel inside the large washer so the barrel is hanging down through the washer with the nozzle keeping it in place.
    4. Place the washer on a big iron hook or some similar piece of large thick heavy metal.
    5. Weigh down one end of the hook with the rock.
    6. With all reasonable proper safety measures in place and with adult supervision, heat the barrel and nozzle with the blow torch until it emits black smoke (which you should NOT breathe) and then keep it hot until it stops emitting smoke.
    7. Flossing the nozzle with copper wire

      Flossing the nozzle with copper wire

    8. Use the wrench to pick up the assembly and check if you can see through the nozzle.
    9. If you can’t see through the nozzle, keep heating it.
    10. Once you can see through the nozzle, it’s time to clean the extruder again
  4. Clean the extruder
    1. Once the barrel and nozzle had been heated, I found the nozzle came off very easily.
    2. Clean out the large cavity of the nozzle with the Q tip.
    3. Clean out the barrel with the yarn by inserting the yarn and “flossing” it.
    4. I happened to have pieces of an ethernet cable lying around.  I cut open one of the wires inside and pulled out the thin copper strands.  I took two of them and fed them through the 0.5mm nozzle.  I “flossed” the nozzle until it felt reasonably clean.
  5. Reassemble!

Playing with fire

Well, not really playing.  But, I suppose not really “working” either.  Here’s how my experiments in unclogging a clogged extruder barrel went:

You can see where there is some minor plastic residue left over from the PLA in PTFE insulator which oozed into the threads.  I had used a precision screw driver to follow along the threads and chip out plastic.

PTFE insulator, mostly clean

PTFE insulator, mostly clean

Here’s the clogged barrel.  I had chipped out plastic from the threads using the same precision screwdriver.  You can see some of the scar marks from my brilliant idea to use a wrench on the smooth part of the barrel at one point.  (FYI, that was sarcasm – don’t use a wrench on the barrel.  It was, in fact, a bad idea).  I was totally unable to remove the nozzle from the barrel.

Extruder barrel, clogged

Extruder barrel, clogged

This was my idea for the setup so that the flame/heat would not discolor everything.  You can see where the nozzle has gotten a thin layer of black ABS fused to it.  Again, you can also see the marks on the nozzle where I tried to use a wrench.  And, again, not a good idea.  All I managed to do was just scar it up.

Extruder barrel with nut partway on

Extruder barrel with nut partway on

This is similar to the setup I settled on for trying to unclog the barrel.  I’m going to cut the suspense and let you know – this doesn’t work and you shouldn’t try it.  This setup did not work for two very important reasons you can learn from.  First, it was too low to the ground and the blow torch kept going out when I tilted it to get to the heater barrel.  Second, it relied on kitchen tiles – which is a terrible terrible idea.

Kitchen tiles - good intentions, bad idea

Kitchen tiles - good intentions, bad idea

Here’s the next part of the setup:  blow torch, flint, wrench for picking up hot things, and fire extinguisher.  Off camera right is a garden hose.  Again, this setup relies on kitchen tiles – which will actually shatter when this kind of heat is applied.  So don’t do it.  Oh, and it turned out I did have a blow torch – but it was empty.  :)

Setup - empty propane tank, bad kitchen tiles

Setup - empty propane tank, bad kitchen tiles

This is a better setup – with a brand new propane tank – but still a terrible idea with kitchen tiles.

Setup - FULL propane tank, bad kitchen tiles

Setup - FULL propane tank, bad kitchen tiles

This was a good setup.  Friend nearby with a garden hose and fire extinguisher, no nut on the barrel so it sits in the washer and is easier for me to heat the entire barrel, suspended in air by a metal hook, held down by a big rock, high enough that I didn’t have to tilt the blow torch.  Here you can see the scorched and shattered kitchen tile in the pile on the right.

GOOD setup with extruder barrel suspended in air by metal

GOOD setup with extruder barrel suspended in air by metal

Since I was in charge of the blow torch and my friend had the fire safety equipment I really only pictures of stuff as it was in a relatively cool state.  This means I did not get a picture of the barrel as I was heating it – I had gotten it glowing red hot which was pretty nifty.  I also missed out on getting a picture of flame spewing from the nozzle as the ABS inside ignited.  It was like a mini flame thrower tossing out a thick black smoke.

I was expecting some of the ABS to leak out of the bottom – but the barrel was essentially clean.  I could see all the way through the nozzle with no problem.

Things I learned while trying to unclog my extruder barrel

I learned a lot this morning!  And now you don’t have to learn, as they say, the hard way.

  1. Never ever ever use tiles. I thought I was being very clever with the tile idea.  Apparently leftover kitchen tiles can shatter and fly apart when you heat them.  Who knew?
  2. Instead, use a big piece of metal to hold the barrel. I ended up using a piece of metal I had laying around to hold the extruder barrel and weight it down with a rock.  This worked perfectly.
  3. Don’t tilt your blow torch too much. Probably an elementary thing for most people.  My torch kept going out when I tilted it too far – probably a safety feature.  This meant I had to change the set up so that the barrel was somewhat elevated so I could keep the torch mostly vertical.
  4. Keep a friend handy. This was one of my few ideas/preconceptions that actually worked out.  Thankfully I didn’t need him to use the fire extinguisher or garden hose, but I very well could have.
  5. Don’t leave a nut on the extruder barrel. At the last minute I decided to screw a nut part way on the barrel.  I figured I could prop the extruder barrel up in the washer, heat it, and not discolor the nut or washer.  This didn’t work out because I needed to apply more heat to the barrel to get the clog out.

Printed Dinos!

Don’t get me wrong – I like the acrylic dinos I have.  But what if you want to replace yours with a printed set?  Or what if you want to print up a full extruder kit for a friend?  Well, now you can!  I just uploaded some designs for a printed set of dinos.  Depending upon your batch you may have Big/Little dinos or Weird/Big dinos.  These should work in place of either, assuming that the placement of the bolt holes in the Z stage haven’t changed. 1

I’ve uploaded the sketchup files to make it easy to play with the designs.  As I was mocking these up I was tempted to turn them into bunnies instead of dinos.  Or to give the dinos some more features.  Since I was so torn about which route to take I decided to upload the bland models and let others embellish if they want.

So, print up printstruder and a few dinos for an authentic fully printed printruder.

Update:  Try out Zaggo’s printed dinos instead.  His is a much cleaner more elegant design.

  1. Doubtful []

An idea for checking the temperature of an extruder at the barrel entry

Several people have suggested that the temperature at the entry of the barrel is very important to printing with PLA.  This makes sense.  If the temperature at the barrel entry is above the melting point for PLA, it can melt right there and ooze down around the threads.

Maybe I should assembly my extruder with just the thermistor on the barrel entry, and heat it until it is just below the melting point of PLA – then check the temperature at the nozzle.

Or, I could get a second thermistor and use it at the top of the barrel while keeping the original thermistor at the nozzle.  I could only use one set at a time (since I don’t know how to hack the electronics/extruder board), but that shouldn’t be an issue.

MakerBot extruder clog experiment

DO NOT USE THIS extruder unclogger setup

DO NOT USE THIS extruder unclogger setup

UPDATE: DO NOT USE TILES!!!  THEY WILL SHATTER!  READ LATEST POST!

The bad news is this is my first clogged extruder.  The good news is I have all the spare parts to whip up a new extruder, no problem.  That means I can experiment with wild abandon!  My backup plan is to slice and dice the PTFE insulator into washers.

Having drilled out most of the plastic clog from the barrel, it’s mostly empty.  The PTFE is in pretty good shape with the threads intact, if a little worse for wear.  My plan to get the remaining plastic out of the nozzle is to put the nozzle/barrel assembly into the large washer upside down and prop it up on some ceramic tiles.

My hope is that by applying a heat source to the nozzle the plastic will just drip/fall out.  The suggestion for using a blow torch to clear out the barrel and nozzle comes from Rick Pollack / MakerGear.  Thanks again Rick!

By the way, wicked Google Sketchup skillz, no?

Plastic oozing into threads – is that the end of my insulator?

I don’t know, but I’m about to find out.

I’ve managed to clear out the PTFE insulator pretty well.  I pulled the entire heater out of the extruder, turned up the heat a little, held the barrel lightly in plyers, and unscrewed the PTFE without a problem, and then turned the heat off.  I then used a precision flathead screwdriver to follow the threads, popping/chipping the plastic out as I followed I went.  However, I don’t know to what extent the threads are still intact.  Since the PLA oozed into the threads, I have to think they’re messed up to some extent.

As for the barrel, I used a drill bit with the unsharp end wrapped in a rubber band.  I rotated the bit using the rubber band as a grip to drill out the plastic.  It actually worked really well for clearing out the barrel right to where I can see the barrel entering the nozzle.  The inside is reasonably clean, but I still can’t put a filament into it freely.

I also had to take a precision screwdriver and follow along the threads on the barrel to chip out plastic.  This went reasonably quickly.  Once I was done the nut was able to screw on and off freely.

Now I’m left with a slightly discolored PTFE and a mostly clean barrel.  I’ve got a spare PTFE insulator, but I’m hoping this one is salvageable.  It still has threads and the barrel will screw in nicely.

Rick and Spacexula have suggested I use a torch to heat up the nozzle and let the plastic burn/fall out.  But, this is a trick for another day with proper safety equipment.

Oh, and before I forget, Spacexula suggested keeping a ruined PTFE barrier to slice into insulating washers.  I’m hoping I might be able to re-use the PTFE insulator, but this is certainly my backup plan.

PLA Woes

My adventure with PLA has ended in heartbreak.  It wasn’t working very well so I switched back to ABS – which was fine for a few prints.  Until I found it just wasn’t extruding and stripping the filament.

So, disassemble time.  My filament looked like it was getting shoved into a jam and splitting apart like a banana – with the center making it down to the nozzle through a small aperture.  I found I couldn’t remove the insulator – and upon looking closer found that a very small amount of PLA had oozed down and around the nut above the insulator/ washer.  I removed the extruder assembly from the ‘bot, and the heater assembly from the extruder, heated it back up and slowly removed the PTFE insulator.  I found the barrel was clogged with ABS as was the insulator.

I’ve managed to clean out most of the insulator, the nut, and the threads of the barrel using drill bits and precision screwdrivers.

I’m going back to ABS, I would rather deal with warp than the heartbreak of PLA ooze into the threads of my heater assembly.