today is May 24, 2022

There’s an old joke about the Thermos bottle that keeps things hot and cold, so someone loaded it with soup and ice cream. That joke is a little close to home when it comes to FDM 3D printers.

You want to melt plastic, of course, or things won’t print, so you need heat. But if the plastic filament gets hot too early, it will get soft, expand, and jam. Heat crawling up the hot end like this is known as heat creep and there are a variety of ways that hot ends try to cope with the need to be hot and cold at the same time. Most hotends today are air-cooled with a small fan. But water-cooled hotends have been around for a while and are showing up more and more. Is it a gimmick? Are you using, planning to use, or have used (and abandoned) water cooling on your hot end?

Heat Break

The most common method is to use a heat-break between the heating block and the rest of the filament path. The heat-break is designed to transfer as little heat as necessary, and it usually screws into a large heat sink that has a fan running over it. What heat makes it across the break should blow away with the fan cooling.

From Thomas Sanladerer’s review of the Copperhead hotend. Heat break in the middle.

High tech solutions include making heat-breaks out of titanium or even two dissimilar metals, all with the aim of transferring less heat into the cooler part of the hot end. More modern hot ends use support structures so the heatbreak doesn’t need mechanical rigidity, and they can make very thin-walled heatbreaks that don’t transmit much heat. Surely, then, this is case closed, right? Maybe not.

While it is true that a standard heat-break and a fan can do the job for common 3D printing tasks, there can be problems. First, if you want to print fast — time is money, after all — you need more power to melt more filament per second. If a heatbreak transfers 10% of the heat, this increases demands on the upstream cooling. Some engineering materials want to print at higher temperatures, so you can have the same problem there as well. If you want to heat the entire print chamber, which can help with certain printing materials, that can also cause problems since the ambient air is now hotter. Blowing hot air around isn’t going to cool as effectively. Not to mention, fans that can operate at high temperatures are notoriously expensive.

There are other downsides to fans. Over a long print, a marginal system might eventually let enough heat creep up. Then there’s the noise of a fan blowing during operation. True, you probably have other fans and noisy parts, but it is still one more noise source. With water cooling, you can move the radiator outside a heated enclosure and use larger, slower, and quieter fans while getting more cooling right where you want it.

Water Water Everywhere: Nothing New?

High-performance computers have long relied on liquid cooling. A heat exchange block has an inlet and outlet for a liquid that absorbs heat better than air. A pump circulates the liquid and another heat exchanger allows the liquid to cool before it is pumped back to the hot part of the loop. Why not apply that to 3D printing hotends?

Why not, indeed. There are several entries in the field, going back a few years. None of these have become super popular for general use. We’ve also seen renewed interest and products lately. If you want to do it yourself, we’ve looked at a very easy way to water-cool an E3D-style hot end.

It is somewhat surprising how long ago these first started to appear. The Titan Aqua from E3D was hardly the first entry in the field and its intro video is from December 2017.

[DIY3DTECH] looked at a cheap eBay-sourced water-cooled hotend about a year later, although we didn’t find a follow-up video, so we wonder if it sat on the shelf or if it just sprung numerous leaks. Dyze Design had water cooling back in 2015. So it isn’t new, it just isn’t that widespread. At least, not today.

Modern Times

Even the newer hotends can participate. Slice Engineering has a liquid version of their Mosquito hotend. Trianglelab has the Arethusa, and there are still custom projects like the one in the video below.

Of course, adding a heat exchange block and a quantity of water can add weight to a hotend and that’s not desirable. However, in practice, the tubing and fittings don’t weigh much and there shouldn’t be that much water inside the heat block at any given time. However, if you are doing your own design, you should be mindful of adding too much weight.

The other problem you may worry about is leakage. Today, a failed extruder fan might lead to a jam. But spewing water all over your printer is probably going to be worse. You want to use connectors that are unlikely to fail. In addition, you might think about the liquid you use. Any additives or chemicals in the liquid should probably survive contact with your nozzle without disastrous effect.

As we’ve seen before, homebrewing a liquid-cooled hotend doesn’t have to be a big undertaking. Most hotends already have some heatsink so you only need to flow water over it. The video below shows a self-described “janky” method, but it proves the point: this can be a fairly simple modification to many printers. On the other end of the spectrum, the Blackbox printer uses it right out of the gate — no modification required.

Your Turn

Do you have any interest in water cooling your 3D printer? Or have you done it? How did it work for you? Let us know in the comments.

If water is too simple for you, and cooling with oil isn’t messy enough, we’ve also seen people opt for peltier devices to cool their hot ends. There are a few problems with this, though. First, they do take a lot of power. Also, while one side gets cold, the other side gets at least as hot, and that heat has to go somewhere. So now you might be back to a fan or — yep — water cooling.