Why does my PLA filament form a spiral shape and clog my extruder?

  • I'm using brand new PLA filament and am getting frequent clogs in my extruder.

    I've had this problem with 2 different filaments from 2 different vendors.

    It will be print just fine, then clog up. It doesn't ever seem to go more than 5 minutes before clogging. When it clogs, and I pull out the filament, it is always twisted in a spiral (helix) shape like a corkscrew. I have put a picture of 2 clogs below.

    I have tried using temperature of 220 all the way down to 180 in increments of 5 degrees and seem to get the same result. it prints the base layer GREAT on the 70 degree heated bed. No warping or peeling off. However, after a few layers, it clogs up and stops extruding.

    I am using an HIC PRUSA I3 printer with a single extruder head. I've only had the printer for a couple weeks. It had been printing fine with ABS, but the ABS would peel up from the heated bed, so somebody suggested that I use PLA and hairspray. Hairspray is AWESOME !! It sticks really well and removes easily as well (once the bed cools a bit).

    Please let me know if you've had the same problem with the extruder just clogging up and twisting the filament into a corkscrew shape.

    By the way, pay no attention to the black marks on the green filament below. That's just me marking every half inch or so with a sharpie marker to see if it's still being extruded.

    Filament Helix

    I think I figured out the problem. Now, to figure out a solution...
    Take a look at the image below. There is a 1 inch tube that goes from the heat element to the heat sink. This 1 inch of tubing is REALLY hot and larger than 1.75mm. So, the filament goes through that tube on its way to the head and gets soft in the tube because the tube is so hot all the way down to the head. When the filament gets hot, it melts and bends and curls which makes it NOT push itself into the heated tip and out onto whatever I'm printing.

    The solution would be to find some way to cool this 1 inch shaft between the heat sink and the heated head so that the filament inside of it won't melt.

    Any ideas???

    Extruder Assembly

    Here is a picture of my heat tip. Note the shaft has about 1 inch sticking out of the heater. The top of that (above the white arrow) is inside the heat sink. But 3/4 inches of it are bare and uncovered. There is also no teflon tube inside the metal throat.

    enter image description here

    Another picture of the extruder

  • darth pixel

    darth pixel Correct answer

    6 years ago

    The shape you get is quite easy to explain. It's the shape of the lowest energy possible in your situation. Simple but it doesn't explain the issue... or does it?

    It does. The filament cannot be put into the extruder as it becomes plugged. This leads us to some obvious explanations. You can read this post.

    So how is that possible that there is enough room to form such corkscrew? My bet is you don't have teflon pipe inside the extruder heatsink. So filament goes into the heatsink and everything is ok until the heatsink itself warms up to the temperature when filament becomes soft, then there is no enough force to push the filament out of the nozzle so above the nozzle filament bends and forms the shape of the lowest energy as said.

    Options to check:

    1. Take your extruder apart. See if there is a teflon pipe. If its length is proper.

    2. Check if cooling fan is working well, if it's pushing air to the heatsing but not sucks from the heatsink.


    Looking closer to your photos I'm pretty sure you don't have such teflon pipe. Your spiral has flat external (virtual) surface... it looks exactly as it would be pushed into hot pipe with diameter of 4mm.

    please take a look on the picture
    enter image description here

    Either missing PTFE tube, or using parts designed for 3mm filament.

    @RyanCarlyle yup... good point.

    Nailed it. No tephlon in tube. One end of the tube has a metal lip so 3mm won't fit. Other end has no lip. Just bare metal tube. Another problem is of a heat sink does not press up against the heat shield. The screws are too long so it dangles there next to it. I put 2 nuts on the head end of the screws. Now the heat sink is very tight up against the heat shield . That should keep the screw shaft a little bit cooler.

    @Curtis but why there is such long pipe out of the heatsink? Something's not ok. at the hot end of the Hotend :) there should be not more than 2..3mm gap between heater and heatsink. This is a heat barrier. It lowers heat transfer from the heater to the heatsink. Definitely the gap is too wide. Could you show your HE without a cooler fan?

    Take a look at the picture above in my posting all parts are labeled. You can see the fan. The bottom of the fan is level with the bottom of the heat sink. The tube goes directly into the sink there. It's about 1 cm from the heater to the sink. I think the problem is that there's no plastic tube inside of the metal throat leading to the head. The other problem was the heat sinks were not tight together I have fixed that and I'm waiting for the new throat parts to arrive that have the plastic tube inside them.

    @Curtis I noticed you did add picture but please take a photo without cooler fan. it would help me to figure out your settings. I'm askig for this as it's hole wrong to have such long heat barrier. Whole thread should be inside heatsink... i suppose heatsink can be mounted upside down :)

    @Curtis see edit2 in my answer

    I've updated my original post with a couple more images. I'm away from my printer, but found good pictures online of my exact setup. There is no way to move the tube up higher into the heat sink as it would be in the way of the extruder. I guess I could shorten the tube by 7/8". I have ordered replacement tubes that do have Teflon inside them. Hopefully, that will help. Bottom line is that HIC has a TERRIBLE design with their extruder/print head assembly. Incompetent and lazy.. Like an 11 year old kid with random parts hacked it all together. (which is probably how they designed it)

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Content dated before 7/24/2021 11:53 AM