Heat Creep: What It Is and How to Prevent It

As a user of 3D printers, you may have heard of the term “heat creep.” Heat creep is the process of heat spreading irregularly throughout your hot end, disrupting the way filament must melt to extrude. This will often cause clogs, especially inside your thermal barrier tube.

What’s Really Happening with Heat Creep?

Your heater cartridge is attached to the heater block. The heater cartridge heats the heater block and disperses out from there. The heat goes up and down the thermal barrier tube, and that’s how you’re able to melt filament.

The filament swells as it goes through the tube. Only once in the area of the heater block, should it start to melt. Then, it becomes molten and gets extruded out the bottom of the nozzle.

But, when you cool down the extruder, the heat rises UP the thermal barrier tube.

If heat successfully creeps up the tube, the filament inside will start to swell too soon inside the tube. PLA especially will stick to these narrow walls much easier and that’s how you get a thermal barrier tube clog.

A Word on Thermal Barrier Tubes

Many thermal barrier tubes attempt to counteract heat creep. The notch you may see on your tube is intended to halt the spread of heat farther up by having less metal to conduct heat. The threads of the thermal barrier tube also act as somewhat of a heat sink.

The notch also denotes the spot inside the thermal barrier tube where the internal diameter changes. The diameter below the notch is wider than the diameter above it to allow space for the rapidly expanding filament to continue traveling down the tube toward the nozzle.

How to Prevent Heat Creep

Heat creep most frequently becomes a problem after you have finished your print and the printer begins cooling. Now the expanded filament that has softened and stuck to the narrow walls of the upper part of the thermal tube will harden and clog your extruder. These types of clogs are particularly difficult to remove because once the plastic in the top of the tube expands and cools, you have created too much mass for enough heat to creep to the top and soften that plastic again.

One way to avoid this consequence of heat creep is to always unload your filament when you are finished printing. For some this may be a reasonable solution, for others it may not.

Our tip for unloading filament once it is apparent to you that heat creep has caused a thermal barrier tube clog, is to “Load to Unload.” This simply means that instead of running the “unload” script on your printer to remove filament, perform “loading” your filament instead.

This is because if you attempt to “unload” filament, the heated and swollen portion of the strand of filament resting in the wider diameter will be forced to go up through the smaller diameter. This will probably be difficult, it may break off inside, or it might not come out at all. This does not work as well as heating the hot end normally, pushing the now softened filament down, and pulling it out. Clip off the uneven end and you’re ready to print again.

But like many things, the best prevention is simple due diligence:

  • Always use Ceramic Insulation Tape around your Heater Block
  • Don’t use low-end filament with filler and diameter issues
  • Avoid leaving your printer heated, but not printing
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  18. Leo 1 year ago

    The assessment is correct. When I pull out the residual filament after a clog, I notice a charred 5mm long bit of plastic that was resting straight in the throat section between heat block and cooling block. I’ve changed to full-metal from the original Ender version with teflon piping almost straight down to the tip, and have now changed back, to test if Creality had the correct thinking after all.
    Problem with the throat (a Micro Swiss precision imitator) is that it doesn’t seem to be conical, besides conducting heat.
    If you buy one of those, certify at least that this midsections internal channel is conical.

    Another warning is using hardened steel tip – the leakage will be tough to abolish completely. I thought “oh great, can use that both for ordinary PLA and fibered plastic”. A soft metal is malleable and with enough force the gaps will be shut. Not so with a hard tip. I think I will try putting a copper washer inbetween next time, if I can find one,

    Frankly, transition from throat to tip seem to be suboptimal, the ideal case is a smoothly conical reducement to final exit hole, but with that edging, plastic is bound to stop and stale in the corners, starting to form crystals.

    To cut a long story short, IMHO: the technology is not yet mature for common user. Most people will simply give up after a third clogging, because it’s tedious to pick it apart and then recalibrate. Some declogging mechanism is sorely needed. I think, a sidechannel with pressurised air pushing residuals out between prints. Or a ministepper sliding a needle down the channel. Automatics are needed.

  19. Kirk DeLucia 2 years ago

    I have a Creality CR-10 V2. it worked for a few months and suddenly now I cant stop the heat creep. I replaced the nozzle. on this model the bowden tube goes right up to the back of the nozzle. I replaced the nozzle with a hardened steel one and it didnt help. I trimmed off about 1/2″ of the bowden tube but that didn’t help. the last time i used it before the clog it finished the print ok and I left filament in it. should replace the bowden tube entirely? or could my thermistor have gone bad allowing too hot filament to back up?

    • Anonymous 1 year ago

      if you aren’t printing an abrasive or tremendously high temperature filament, the hardened steel nozzle can actually be a significant detriment due to steel’s low thermal conductivity value

  20. James 2 years ago

    I have a BIBO Touch 2 dual extrusion printer. I run one extruder all the time and never have issues. However, the other other extruder is a source of constant headaches, disassembly and wasted time. It continues to clog, no matter how many times I swap the nozzle. Even when I can push filament through it manually, it is extremely difficult.

    I must have some sort of heat creep issue. How do I fix this? I appreciate the prevention side, but how can I unclog the throat?

  21. John Schneider 3 years ago

    This is a test comment. Just to see how awesome 3D-Fuel filament is.

  22. Tori Raddison 3 years ago

    It’s good to know that you should always unload your filament when you’re done printing so that your printer works well. My dad just got a 3D printer and he’s so excited to try it out! I’ll have to warn him about this when he does finally use it. Then he won’t have to worry about heat creep.

  23. George H. Barehenn 3 years ago

    I have a maker select V2, and also have jams in the teflon throat tube. I even still have a teflon throat tube with a piece of PLA well and truly stuck in it. Not an easy thing to do.
    I have resolved this problem for ≈ free. I added teflon tape around the threads that attach the throat tube to the hot end. And, I added heatsink grease between the throat tube and the cold block, and between the cold block and the heatsink/ fan.
    What I find now is that only the bit of filament in direct contract with the extrusion nozzle melts.
    If more that the last 2~3mm of the filament are heated substantially, the pressure from feeder, causes the filament to shorten and become thicker. If the heat is confined to the heater block, and can’t travel further up, only the filament in contact with the extrusion nozzle is soft, and the filament doesn’t shorten or widen appreciably.
    Although this solution is nearly free, and seems to work, a better solution would be a ceramic or glass throat tube. Sadly these aren’t available.
    One more note is that if I’m going to get heatsink grease on me, I might as well grease the heater to heater block interface, and the thermistor to heater block, and the nozzle threads to the heater block. The latter should be avoided for an all metal hot end, as the grease may contaminated the filament.
    The result is that things heat up faster and are more stable when printing. However, I did need to recalibrate my print settings as the optimum temperature seemed to be 10 ~ 15 degrees cooler.

    • otis 3 years ago

      I don’t think a glass throat tube is a good idea because if someone inserts something like metal into it and should it break the glass -that could be a really bad day. A ceramic throat tube with a slick teflon-like internal surface sounds like an ideal solution though.

    • Marcelo 2 years ago

      Hello George, I my mind you are tottaly corect in you concept. I´m thinking abou some days for analising the termodinamic concepts inside the heat block. I wwil test exactly this in near future. Congratulations

  24. Stephen Mackay 4 years ago

    Thanks for sharing useful information on heat creep and I really like the way you have explained. Good job.

  25. Albano 4 years ago

    Thanks for the explanation of the heat creep. I think I got that on my Smart Extruder but my fillament jut don´t come out and it broke inside. Is there a way of taking it out? I tried “load to unload” but as it is broken inside i can´t push it nor pull it out. If you have any ideas or advices i will apreciate it a lot.


  26. matt 4 years ago

    sounds like old filament, buy a new roll

  27. Jack 4 years ago

    Could the heater cartridge be bad? ive had my 3d printer (a monoprice maker select v2) for a while now and have not printed anything for over a year. Ive tried everything to fix it, from adding new ceramic insulation tape, slowing down the print, heating up the extruder, unclogged the nozzle, and cleaned the gears, but it still will not work. It almost looks like the outer walls have a wavy pattern, and it can no longer print small objects, like its under extruding. I would like to return it, but the warranty wore off. do you have any suggestions on what is should do?

    • Wilfred Ramsley 4 years ago

      Hey Jack,

      Ive been using the Maker Select V2 for a few years. If you’re getting a wavy pattern on your printer (a problem ive have if we’re thinking of the same thing) then try slowing down the outer shell speed or maybe print it with 2-3 shells. If that doesnt fix it make sure your frame is solid and the belts are tight enough.

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