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How Does a 3D Printer Hotend Work? Facts Explained

The hotend is one of the most critical parts of your 3D printer. However, it can be pretty mysterious since all the components are so small and hidden away in a casing. So, what goes inside a hotend? 

A 3D printer hotend works by melting the filament so that it can form shapes. The hotend needs to have a consistent temperature to work. You want a hotend that won’t clog and reach your set temperatures accurately. Otherwise, burned plastic can become an issue. 

The hotend is one printer part, but it’s full of other components that process and heat your filament as you run your 3D printer. In this article, I’ll go over all you need to know about 3D printing hotends and what they do, so stick around! 

How a 3D Printer Hotend Works

The hotend has a few essential jobs that allow you to achieve excellent results with your final printed piece. It melts filament and extrudes the material in even layers, giving the object structure. 

You may also refer to the hotend as the nozzle on your printer. However, the nozzle is just one small part of the hotend. 

The hotend connects to the extruder, which supplies the filament. Depending on your printer, it may also connect to the mounting or Bowden tube. The metal hotend also reaches very high temperatures with help from the heater cartridge. 

While the idea of a hotend is straightforward, they can be complex pieces of machinery. 3D printer technology is still developing, so companies might set up some newer printers differently from older ones. 

This YouTube quick video covers all the parts of the hotend: 

In short, a 3D printer hotend works just like a hot glue gun. I’ll break down all of the parts of the hotend, and what they do below so you have a better idea of the entire process. 

3D Printer Hotend Parts

There are six main parts of a hotend. Each component performs a different function, allowing the 3D printer to create layers of plastic. These six parts include: 

  • Nozzle 
  • Heater block 
  • Heater cartridge 
  • Heat break 
  • Thermistor 
  • Heatsink 

To understand how the hotend works on your 3D printer, you should first learn about all the different parts. Knowing what the main pieces do makes it much easier to understand the hotend. 

Nozzle 

Let’s start with the most critical piece of the hotend – the nozzle. 

Nozzles are usually metal since they can get very hot during a print job. The nozzle has a precise, tapered angle allowing the melted filament to flow through without clogging. High-quality 3D printers also have nozzles with flatter tips, which help the material lay better and form a strong bond. 

You can change out your 3D printer’s nozzle as you wish. Nozzles with larger diameter openings can print faster. On the other hand, a nozzle with a small diameter opening will offer more detailed prints with shorter, narrower layers at the cost of speed. 

You’ll also want to use nozzles to match your printing material. Some nozzles start to deteriorate when you print with a filament that requires very high print temperatures. So, you’ll likely need to upgrade your nozzle if you want to work with a material like PEEK or polycarbonate. 

This short YouTube video covers how to change the nozzle on your 3D printer: 

Heater Block

Next, the heater block contains a material that conducts heat well, usually copper or aluminum. The heater block connects the nozzle with the heat sensor and the rest of the hotend, allowing all parts to work together. 

The heater block also conducts heat and passes it to the nozzle as additional heat storage. That way, the temperature of the nozzle doesn’t fluctuate, giving you consistent printing layers. If the nozzle’s heat fluctuates, the plastic won’t bond well and can appear lumpy or uneven. 

Overall, the heater block acts as heat storage for the nozzle to draw from if it starts to cool down too much. This feature keeps the nozzle at a consistent heat at all times. The heat block also acts as a connection between the nozzle and the other printing parts. 

Heater Cartridge

The heater cartridge performs several essential functions in the hotend. It uses a heating coil and electricity to become hot, then transfers heat to the other parts of the hotend that need it. 

Suppose you want to print at very high temperatures. In that case, you’ll need to find a heater cartridge that can safely reach those temperatures without failing

Additionally, the heater cartridge makes sure that the hotend reaches the correct temperature. You can swap out your heater cartridge, but you should make sure it fits correctly into the printer. If the carriage isn’t a perfect fit, it can’t spread heat to the hotend, and it will fail. 

The number of watts your heater cartridge uses matters. Heater cartridges of 20W or less are weak and won’t work well in most 3D printers. Instead, choose a 30W heater cartridge – it’s the standard today in many machines. 

A 30W heater offers excellent results while being very safe. Plus, a 30W cartridge will get your hotend to about 572°F (300°C), allowing you to print all common plastics. If your hotend doesn’t seem to reach temp, then upgrading to a 30W heater cartridge should help you drastically. 

Heat Break

Next, I’ll explain the heat break. The heat break consists of threaded metal that separates the cold and hot sides of the hotend. Most of the time, your heat break will be stainless steel. 

The heat break has a cold and a hot side. The one side remains cold by dropping heat into the heat sink part, while the hot side connects to the heater block. When the filament moves inside the heat break, it melts. 

So, starting from the top of the extruder, the filament has to go through the cold side, which keeps the material solid. Then, it passes through to the hot side, where it becomes a liquid plastic. The filament begins to melt in the middle area of the heat break where the cold and hot sides meet.

If you have the temperature settings correct on your 3D printer, the plastic softens drastically and can take any shape that you want it to. High-quality 3D printers prevent clogs by having a shorter middle space where the hot and cold sides meet.

Lastly, the hot and cold sides create pressure on the melted filament, allowing it to flow from the printer’s end. The tension builds as the melted plastic forms a wall in front of the solid plastic in the cold end, making it easier for the solid filament to force the melted filament out. 

Thermistor

The thermistor is the heat sensor on the hotend. It reads the temperature of the heater block and then decides whether it needs to heat more or cool down to keep the temps consistent.

For example, the thermistor will turn it on if the heater block isn’t up to temp. Likewise, the thermistor switches the heater cartridge off if it’s getting too hot. This process is entirely automatic, so you don’t have to monitor the temperature of the hotend on your own. 

Heatsink

Finally, the heatsink is part of the cold side of the hotend. It redirects warmth away from the filament, keeping it solid. The heatsink has a larger surface area, which takes longer to heat up. 

Most printers also have a fan that blows on the heatsink, dissipating any warmth that the part collects. This process ensures the hotend’s cold side doesn’t overheat. 

There are also other types of heatsinks that you’ll find in high-quality 3D printers. While the metal coil is the most common option, you can also find liquid heatsinks. The liquid also transfers the heat away from the hotend’s main parts. 

Heat creep can be a huge problem in some 3D printers. This issue can cause heat transfer to other areas of the hotend, causing clogging. Ensure the heatsink is clean and add cooling fans if needed to prevent it. Incorrect print settings can also cause heat creep. 

How To Deal With a Clogged Hotend

Clogged hotends can become a huge problem, especially if the printer doesn’t turn off right away and keeps trying to extrude material. Eventually, you’ll probably run into a clog, so it is best to know what causes them. 

Clogging happens when something blocks the inside of the hotend, causing the filament to get backed up. You can use two methods to deal with a printing clog: 

  • You can clean the hotend with nylon, also called a purge filament. You can find nylon cleaning kits online – you’ll want to use them occasionally to ensure your printer doesn’t clog.
  • You can “purge” the printing filament. Start by opening the purge menu, then raising the temperature. Give the printing machine a few minutes to heat up, and you’ll see the filament start oozing out. After turning the temp back down, reload the filament and see if this fixed it. 

What Hotend Is Best for PLA?

PLA is one of the most widely available types of plastics that you’ll run through your 3D printer. Some types of hotends work better with it than others. You can always upgrade your hotend if you want to get better-looking prints. 

The hotend that’s best for PLA is one with a brass nozzle. It provides ample heat transfer and should be cost-efficient. While brass isn’t durable, it will give you the most consistent layers in PLA prints. 

Many people don’t recommend using all-metal hotends with PLA. While it might seem like an upgrade, you’ll receive better results and have fewer clogs if you choose one with a brass nozzle on the tip. 

Overall, there are so many different kinds of hotends out there! Make sure you do your research to know you’re getting the best option for your printer model. You can likely find the specs for your current hotend in your owner’s manual or online. 

What Makes a Hotend Good?

A few different factors can make a hotend good, although you need them to be reliable. You shouldn’t have to unclog the hotend every time you make a print. 

A good hotend comes with high-quality materials and construction. A hotend should reduce print failures and have measures to prevent clogging. Likewise, your hot end should be able to print the filaments you use the most often. 

You can swap out parts to create a hotend that suits your needs. For instance, you can remove the current nozzle and swap out for one that’s a different material and has a larger diameter. You can also change the heatsink and the heater cartridge. 

Speaking of the heater cartridge, it significantly impacts how hot your hotend can get. You’ll want to make sure your hotend comes with a cartridge that reaches temps hot enough to print with your specific filament. You may need to upgrade yours if it doesn’t seem to be reliable enough. 

In short, you want a reliable hotend that doesn’t clog. However, you can always upgrade it by replacing various parts in the one you already have instead of buying an entirely new one. Hotends can wear out with age and use, so make sure you replace yours when it starts to degrade. That way, your prints will always turn out stunning. 

Final Thoughts

The hotend has six main parts that allow it to work. Its main goal is to warm the filament and make it soft enough to travel out the nozzle. These parts need to work together flawlessly for the printer to run at its best. 

Overall, the hotend works much like a hot glue gun. It can reach over 500°F (260°C), so you should never touch it right after finishing a print! If you need to change the hotend nozzle, let it cool down for a few hours before handling it.