November 27th, 2023
If you’re relatively new to 3D printing, or even an old hand, you may wonder what a heat-break is and what function it actually performs in your 3D printer. Then there’s the bi-metal aspect which again you may not be sure of. Well, there’s a couple of questions that obviously need answering so let’s first take a look at what a heat-break is.
What is a heat-break?
The heat-break is basically the connecting part between the "hot" zone and the "cold" zone of the hot-end. That in itself doesn’t seem to make sense as how can you have a cold hot-end? Well, as you probably know the hot-end is a generic term for the part of a 3D printer that melts and extrudes the cold filament. The filament is fed into the hot-end and heated so that it can be extruded onto the build plate. This then continues and builds layers to form the printed model.
The heat-break is therefore used to form a transition area between the molten material and the solid filament that is fed to the nozzle. In basic terms, if it wasn’t there then the heat from the nozzle would extend backwards to the extruder and cause all sorts of issues with clogging. This is known as “heat creep” and can be the source of a lot of frustration in the world of FDM 3D printing.
You could therefore look at a heat-break as a kind of firewall which protects your extruder and hot-end from clogging and the filament from melting or softening at the wrong point in the process.
Most standard heat-breaks are made of metal with a PTFE tube fed inside which then stops at the top end of the heated nozzle. This tube thermally insulates the filament before it reaches the nozzle. The PTFE lined heat-break is well suited for use with PLA filament as it doesn’t require high temperatures to print. However, an all-metal heat-break allows you to print at higher temperatures without worrying about the PTFE tubing or dangerous fumes.
So, let’s now move on to looking at the bi-metal aspect of heat-breaks.
Bi-Metal Heat Breaks
As we’ve mentioned, an all metal heat-break is pretty standard and what comes with most 3D printers from the factory. However, a bi-metal heat-break is an easy upgrade that will improve the reliability of your printer and allow you to print at higher temperatures.
A bi-metal heat-break not only improves on the fundamental problems that a PTFE tube hot-end has, but it also has advantages that an all-metal stainless steel heat-break can't match.
For example, a bi-metal heat-break consists of two metal components with different thermal conductivity. These are usually copper alloy and titanium alloy but other metals are also used occasionally. While the titanium alloy reduces upward heat conduction (heat creep), the copper accelerates downward heat dissipation. It therefore allows you to print at a temperature of up to 500°C if required and effectively prevents the filament path from clogging thanks to its smooth inner wall.
That’s the differences explained then but why choose one over the other?
Why and When to Choose a Bi-Metal Heat-Break?
Firstly then, let’s look a little bit more into the “why” aspect of a bi-metal heat-break choice.
As we’ve discussed, the bi-metal construction of the heat-break provides much better heat conduction but also in the right areas. Instead of having a single heat flow through an all metal heat-break which can be a bit hit and miss, you’re giving your prints the best opportunity of success and quality. You’re also avoiding as much as possible the issue of heat-creep and the inherent problems that can cause.
The next question though is “when” and this may not be as obvious as it seems. A bi-metal heat-break, as mentioned, can handle temperatures up to 500°C but the average printer that you might buy as a beginner doesn’t have the capability to deal with printing temperatures of this magnitude.
If you take the example of a Creality Ender 3, which is probably the best selling 3D printer around, it’s maximum working hot-end temperature is around 255°C. You may then think that adding a bi-metal heat-break is a waste of time as the temperature range is incompatible.
However, you’ll remember what we said about quality and reduction of heat-creep etc. The maximum temperature then doesn’t become an issue because you’re adding the bi-metal heat-break as an upgrade to improve quality and not to work with higher temperatures.
That then moves us nicely onto those printers that can handle the high temperatures we’re talking about.
Most FDM printing users will have worked with PLA (Polylactic Acid) filament at some point or other and will know it’s working temperature to be around 190-215°C. Therefore there's no need to worry about having a printer which can handle higher temperatures unless you want to use different filament types or work at much higher speeds.
Say though you do want to work at higher speeds and higher temperatures but don’t want to necessarily spend out on a new printer. Without digressing too far from the point of this article, you can upgrade your existing printer to use a new hot-end/extruder setup, update the firmware accordingly and last but not least, upgrade to a bi-metal heat-break.
Not Just an Upgrade
Of course you may already have a bi-metal heat-break and therefore don’t so much need to upgrade but may need to replace or improve slightly on the quality of the piece.
As we’ve mentioned when talking about all metal standard heat-breaks on “from factory” printers, you’ll also sometimes find that the quality of bi-metal heat-breaks may not be so great on what are supposed to be more “high end” models.
Therefore it may be wise to change the stock heat-break out as soon as you can so that you get both the best performance from your 3D printer and improve the success and quality of your prints.
So, whether you want to upgrade to a bi-metal heat-break, replace an old one or just improve on the quality adding a bi-metal heat-break is a good way to help with all of these.