Basics: Cleaning out a clogged nozzle!

As you 3D print more and more frequently, clogged or partially blocked nozzles actually get rarer as you learn how to avoid them. But if you do manage to get yourself a blocked nozzle, here’s how to fix it!

We’ve all been there: A hotend that just doesn’t seem to let any filament through. While there are a few different things that could cause your printer to behave that way, a clogged nozzle is a likely cause and one that you take care off easily. So today i’ll walk you through how to identify a blocked nozzle and how you can easily fix it, often even without taking your 3D printer apart at all.

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A clogged or partially blocked nozzle is usually fairly easy to make out: If your extruder motor is struggling to push material through the hotend or you’re getting prints that are mostly air with only very little material making its way down, then it’s a good idea to check the nozzle. While disengaging your extruder form the filament by pushing the idler lever back, try and push filament through the heated hotend by hand. You might get an initial amount of material making it through, but you’ll find that it’s either impossible to push or that the extruded material curls heavily right after leaving the nozzle or extrudes much thinner than what you might be used to. This can indicate a small particle stuck in the nozzle bore, which we’ll need to get out. Somehow. One of the easiest, but also least reliable ways is to grab a wire or an acupuncture or hypodermic needle that is small enough to fit up the nozzle and try and get the blockage unstuck. Obviously, you’ll need a needle or wire that is small enough to fit your nozzle bore, typically 0.4mm, and while some users recommend using a drill bit instead, i’d actually say not to use one, since they are expensive, break more easily than a solid needle, and worst of all, can permanently damage the nozzle if you’re not super careful. So as a first try, preheat the nozzle to your regular printing temperature and get cracking with that needle. Still being careful not to burn yourself, your goal is not to extract the blockage, but only to break it up enough so that it slips through the nozzle the next time you push filament through. You might have to go through the cycle a few times of fiddling with the needle and pushing through a bit of filament by hand to check if you’ve broken up the blockage enough.

Another way that I personally prefer over pushing needles up the hotend, is to use a cold pull – Ultimaker calls this the “Atomic method”, which is similar in concept. A cold pull works best with slippery, soft materials – so, Nylons, like Taulman’s Bridge filament. Again, heat up your hotend to the working temperature of your Nylon or Polyamide filament, push it through the hotend as far as possible, ideally, until your previous material is cleaned out, which obviously is going to be somewhat hard if your nozzle is, like, completely stuffed, and then have the hotend cool down. Now, what i like to do after that is to set the hotend to 110, 120°C and just keep on pulling on the filament while the hotend is heating until the filament plops out in one piece. This should leave you with a perfect negative shape of your hotend’s and nozzle’s bores and you will be able to see the contaminant on the end of the filament. Then cut off the contaminated end, fully heat the hotend again and repeat the process until the pulled end of your filament comes out clean and you’ve restored good flow through the nozzle. Usually, two or three passes should be enough.

Now, what Ultimaker recommends is actually setting the hotend to a fixed temperature, 90° for PLA, 110° for ABS, waiting until the hotend is at temperature and then yanking the filament out. This works fine for Ultimakers, but the keep in mind that both ABS and PLA aren’t flexible enough to be pulled out cold from many other hotend geometries, including the common E3D v6 setup. Nylon works fine for this.

Now, if both of these methods don’t get your nozzle unclogged, you can always go a step further and clean the nozzle outside of the printer. Click up here to learn how to remove your hotend’s nozzle safely, but if you’ve got the option to, do a cold pull first to empty out as much material from the nozzle as possible.

With the nozzle removed, you have the choice of either removing the gunk mechanically or by using solvents. For mechanical cleanup, it’s the same idea as with the nozzle installed – heat it up, e.g. with a hot air gun set to low, and then carefully scrape out as much of the contaminant as possible using needles or other pointy tools. When using hardened nozzles, be very careful not to overheat those, as they will lose their hardening if you do. What also works for many materials is simply burning out the nozzle with a blowtorch. However, if you’re unlucky, you might end up with a nozzle that is completely FUBAR, so i’m not going to recommend this.

But if you’re using ABS or PLA, you can actually chemically dissolve most of the plastic remainder in the nozzle. For ABS, acetone or more aggressive solvents work well, and PLA somewhat dissolves in ethyl acetate. So leave the nozzle in those for a few hours and you should be able to much more easily clean out out the bore. If you can, go for a squeaky-clean look with the bore completely freed up.

Now, if these methods didn’t get your extruder working perfectly again, you should also check the teflon liner inside the hotend if your printer has one, and give the extruder a good staredown to see if it’s grinding through filament because the hobbed gear is clogged up, dull or from the filament being kinked and crooked inside the extruder.

So now that you’re left with a functional hotend, how do you prevent it from clogging up again? My printers have been running blockage-free for many years now, and it’s just a few simple things:

First off, use decent filament. There’ve been reports of steel balls contained within dirt cheap filament, and those, of course, are guaranteed to completely block a nozzle in a heartbeat. Also, better filament is usually made in a cleaner environment, which means it’s only going to contain components that will actually melt in your printer’s hotend.

The same goes for your 3D printer’s environment: Keep it clean and dust-free. If your printer sucks in dust or other particles, those can accumulate and easily clog the nozzle over time. If you’re uncertain about whether your workspace is clean enough, you can simply use a bit of foam with a hole punched through to wipe off any dust before it enters the printer – you’ll be surprised how much that actually catches over time!

And lastly, don’t cook your filament inside the nozzle. If you leave the hotend heated up for an extended period of time, chances are the filament is going to slowly decompose into an unextrudable mess. So simply turn off the hotend when the printer is idle. Some machines actually do this on their own.

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