2019 3D Printer Extruder Guide – All You Need to Know

From the top to bottom, your typical 3D printer hot end comprises of a specific sequence of parts. There is a slight difference depending on if you are using a PTFE/PEEK or all-metal hot end. Here we explain the all-metal hot end — a breakdown of the differences between PEEK/PTFE and all-metal hot ends can be found in the section below this.

Firstly there is the filament feed tube (not pictured above). In both the Bowden and direct drive 3D printer extruder this will simply be the PTFE tube running from your cold end. Though note that not all direct drive 3D printer extruders feature this.

Sometimes you’ll see direct drive 3D printer extruders with the filament running directly into the print head.

On a Bowden 3D printer extruder, this feed tube inserts the filament directly into the heat break through the heat sink. The heatbreak, which is threaded into the heat sink, is often simply a threaded stainless steel (or other non-heat conducting metal, such as titanium) tube.

Divided into two parts (notice the two separate threads on the image below — longer for the heat sink,  shorter for the heater block) and featuring a treated interior surface, the heat break allows the filament to pass freely into the nozzle for extrusion.

3d printer extruder guide heater block, heatbreak and nozzle
Clockwise from bottom left: steel heatbreak, aluminum heater block, and brass nozzle.

But, since we’re dealing with accuracy and material that turns into a liquid to be rapidly re-cooled, the management of temperature is crucial. The heatbreak, in combination with the heat sink, maintains a specific boundary at which the filament is hit with high temperatures.

The upper portion, which is actively cooled by the heat sink and a dedicated fan (or water cooling system, in some extravagant cases), prevents heat escaping the hot end and weakening the filament before it is where it needs to be for extrusion. This undesirable phenomenon is known as heat creep.

The lower portion of the heat break sits within a heater block, along with a heater cartridge, temperature relaying thermistor, and nozzle.

Usually constructed from aluminum, the heater block ensures a seamless transition for the filament from the open end of the heat break tube, into the nozzle.

The temperature to melt the filament has to come from somewhere though, which is where the heater cartridge comes into play. Under an electric current, the heater cartridge gets hot, transferring heat to the nozzle via the heater block they are both encased in.

3d printer extruder guide heater block and its elements
Clockwise from top left: heating block, thermistor, heater cartridge, nozzle, heatbreak.

Power resistors are an alternate means to heat the hot end, but are less common these days.

Also housed within the heater block is a thermistor — a small probe that relays the temperature of the block to the 3D printer’s mainboard, allowing for the correct adjustments to be made. In layman’s terms (we’re not electrical engineers here — it’d be disingenuous to attempt to explain in detail), it does this by nature of its resistance changing in correspondence with its temperature, and thus the printer’s board can get a read on the temperature based on the resistance at that current point in time.

And then, at the raggedy edge of the whole system, there is the nozzle. A small nubbin of machined metal, the nozzle itself consists of a chamber — where the molten filament resides — that tapers to the nozzle’s opening.

This opening is a precise diameter, which is the measure by which you purchase it. Most desktop 3D printers ship with 0.4mm nozzles as standard, but there are many other sizes available.

3D printer nozzle guide
Nozzles! The larger opening on the right is where molten filament gathers inside the heater block, before being ejected through the nozzle opening.

Brass is the preferred material for factory-shipped default nozzles but, while fine for softer materials like PLA and ABS, filaments with tough additives such as carbon fiber will quickly wear away and deform a brass nozzle’s opening. For specialist filaments, 3D printer nozzle materials like stainless steel and ruby are preferred.

The 3D printer nozzle is a veritable world of options, so we’ll detail the popular choices and differences between them below in their own dedicated section.

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