How to Clean Your 3D Printer’s Nozzle With a Cold Pull

Learn how to perform a cold pull to clear partial nozzle clogs and prevent future clogs.

The complexity of 3D printing is only surpassed by the sheer number of things that can go wrong during a 3D print. Of all these 3D printing challenges, nozzle clogs rank the highest in terms of their disruptive and destructive power.

What if we told you there is a relatively simple way to prevent nozzle clogs from occurring in the first place? What’s more, the same solution can also resolve partial nozzle clogs.

Read on to learn the art of performing cold pulls, and how this 3D printer maintenance hack can make your life easier.

Contrary to its name, the cold pull technique involves subjecting a 3D printer nozzle to systematic heating and cooling cycles to clean unwanted debris and burnt material off the nozzle and filament pathway using nothing but a strand of 3D printing filament. The nozzle is cleaned by a small section of semi-molten filament that adheres to particles clogging the nozzle.

The filament is then physically yanked out of the nozzle from the extruder end. That’s the pull part of a cold pull. The nozzle cleaning technique gets the former part of its name because the filament must be near its glass transition temperature (point of softening) before it’s pulled out of the extruder. This is significantly lower compared to the usual extrusion temperatures.

Unfortunately, "glass transition temperature pull" doesn’t quite roll off the tongue, which makes cold pull a much better name for this nozzle cleaning technique.

In the ideal world, you’re expected to use different sets of nozzles for materials printed at significantly different temperatures. That’s because printing nylon at 290 °C after a batch of PLA parts extruded at 190 °C is a recipe for disaster. The massive temperature difference between the two filaments would cause extant PLA residue within the nozzle to solidify as burnt particles. And that’s how you get nozzle clogs.

Performing cold pulls between such printing material swaps is a great compromise to avoid the impracticality of swapping nozzles often. In addition to clearing partial nozzle clogs, regular cold pulls also go a long way toward preventing them from occurring at all. This is especially important when printing exotic materials such as wood filaments. The wood residue left in the nozzle by such filaments can also cause full-blown nozzle clogs due to the flammable nature of the material.

But if you do experience a total clog, our guide on how to unclog 3D printer nozzles will save the day.

The cold pull technique is also quite effective at clearing partial nozzle clogs which often ruin prints. Unlike plain-vanilla nozzle clogs, the partial variety can cause your 3D prints to become brittle, exhibit surface defects, and outright break during printing.

The usual recourse of poking a needle through a heated nozzle is futile in this case. A cold pull is your only way out of this mess.

Performing a cold pull is quick and easy once you get a hang of it. Until then, it pays to exercise caution and follow these steps precisely to avoid damaging your extruder assembly. We recommend keeping a pair of pliers, flush cutters, and some nylon filament handy.

Prepare a small section (about 30cm) of filament (preferably nylon). Snip a bit (diagonally, as illustrated in the photo below) off the end of the filament with a pair of flush cutters. The resulting sharp point makes it easy to pass the filament into the nozzle past the extruder gears and heat break.

Make the filament pathway in the print head accessible by removing the Bowden tube connected at the nozzle end.

This applies to all printers with Bowden extruders, except ones equipped with direct drive extruders that don’t use Bowden tubes. However, some 3D printers featuring direct drive extruders (all Voron variants and Bambu Labs printers) use reverse Bowden tubes. You must remove the Bowden tubes in these cases to access the filament.

Raise the nozzle from the bed far enough to allow the purged filament to extrude without obstruction.

We must now remove the existing filament from the hot end. Heat your nozzle to the appropriate extrusion temperature of the loaded filament. Once the nozzle has reached operating temperature, you can manually pull the filament out of the hot end. However, this method only applies to Bowden extruders.

If your printer has a direct drive extruder, you can use the unload routine in your printer firmware to extract the filament. Disabling the extruder stepper motor (through the user interface) also allows the filament to be unloaded manually. Alternatively, the tensioner arm in most direct drive extruders can be manually disengaged, which allows the filament to be pulled out by hand.

While the nozzle is still hot, raise the temperature of the nozzle to the extrusion temperature specified by the manufacturer of the nylon filament. This can be anywhere between 250 °C and 280 °C depending on the composition of the material and the size of your nozzle.

Insert the section of nylon into the hot end, pointy end first, once the nozzle is at operating temperature. Push a few centimeters of the nylon filament through the nozzle.

Switch off the nozzle heater. As the nozzle cools down, maintain constant downward pressure on the filament, such that a tiny amount of it continues to ooze out the nozzle. Continue maintaining downward pressure until the filament ceases to ooze out the nozzle. Keep up the pressure for another 20 seconds.

When done right, this compacts the molten nylon and fills up the entire nozzle cavity with the molten material. This makes the filament adhere strongly to burnt debris clogging the nozzle.

Wait for the nozzle to cool down to 50 °C.

Direct drive extruders continue to grip onto the filament and make it impossible to pull the filament out. Ensure that the extruder stepper motor is disabled at this juncture. Alternatively, you can also manually disengage the extruder tensioner arm while pulling the filament out in the subsequent steps.

Set the nozzle to heat up to 120 °C.

While it is heating up, grip the filament and maintain constant upwards pressure, like you’re trying to pull it out.

The filament is too hard to be pulled out of the nozzle while it is cold. However, as it heats up, it might become too soft to remove the debris stuck inside the nozzle. That’s why maintaining a constant pull on the filament allows it to be extracted from the nozzle while it is still in the Goldilocks zone—where it has softened just enough to let go of the nozzle, while also being hard enough to hold onto the debris.

For most nylon filaments, this can occur anywhere between 110 °C and 120 °C. You’ll hear a distinct popping sound when this process is performed successfully. Being able to see a near-perfect imprint of your nozzle cavity is a visual confirmation of success.

It’s easier to spot burnt residue extracted from the nozzle if you use white or transparent nylon filament for this procedure. Repeat this process until you can no longer see any filament residue after subsequent cold pulls.

By carefully using this technique, one can not only clear partial clogs but also prevent total clogs from occurring. This is especially true for those who print with exotic materials, or otherwise use a lot of different 3D printing filaments.

Nachiket has covered diverse technology beats ranging from video games and PC hardware to smartphones and DIY over a career spanning 15 years. Some say that his DIY articles serve as an excuse to pass off his 3D printer, custom keyboard, and RC addiction as “business expenses” to the wife.