The Complete 3D Printer Extruder Guide

3d printer extruder

Fused deposition modeling is a 3D printing technology within the wider material extrusion category. It is in this category as FDM 3D printers extrude melted plastic filaments, layer-by-layer, to create a finished part. Therefore, today we’re taking a closer look at 3D printer extruders and what they are, their parts, the Bowden and direct extruder types and differences, and more in our 3D printer extruder guide.

3D Printer Extruder Definition: What is a 3D Printer Extruder?

Though extruder is the name that stuck, a 3D printer extruder is actually more of a ‘feeder’. This is because the 3D printer extruder is responsible for pushing the correct amount of filament to the hot end where it is then melted and extruded.

The extruder is commonly confused with the hot end, though they are separate parts. The extruder is not involved in the actual heating process and merely sends the correct of filament to the hot end for 3D printing, thereby earning its nickname of the ‘cold end’.

3d printer extruder process
The 3D printer extruding process (extruder denoted by ‘cold end’)

3D printer extruders need to be made according the size of the filament being used with the 3D printer. In the past, 3mm filaments dominated the marketplace, and 3D printers were commonly fitted with 3mm extruders to compensate. However, now 1.75mm filaments are more common, extruders are usually built to accommodate 1.75mm filament.

How to convert a 3mm extruder 3D printer to 1.75mm extruder?

If you have a 3mm extruder you can easily convert it into a 1.75mm extruder with a few simple tools, a TPFE tube, and a 1.75mm hot end. For more details on how to do this, check the video out below:

3D Printer Extruder Parts

There aren’t actually too many parts to a 3D printer extruder. The few main parts are firstly the motor (usually a NEMA17 or similar), a filament drive gear, and an idler (holds filament against the drive gear so it can be extruded through the hot end).

Though these are few pieces, slight changes in these pieces can result in large discrepancies in 3D printing results. For example, the idler’s teeth need to be neither too fine or too thick, as each extremity can cause clogging of filament during 3D printing. Most idlers are made specifically for this purpose however so you are unlikely to need to worry.

3d printer extruder E3D titan
The disassembled parts of an E3D Titan 3D printer extruder.

3D Printer Extruder Types

There are two main types of 3D printer extruder. These include direct extruders, and bowden extruders. There are also dual extruder 3D printers, which aren’t mechanically different except there are two of them.

Dual Extruder 3D Printer

Dual extruder 3D printers allow for two different print heads to operate simultaneously, opening up a variety of new possibilities.

Firstly, two materials can be printed concurrently in each extruder. This can help for example as you can print supports in a different, soluble material to improve surface finish. Moreover, having a dual extruder means you can print objects in two colors, for those who enjoy colorful builds.

Dual extruders aren’t a different type of extruder however, just the option of having two of them. The main two types explained below are direct extruders and bowden extruders.

3D Printer Direct Extruder

Direct extruders are called direct because, literally, they are directly attached to the hot end. Used in 3D printers such as the Lulzbot Mini (featured in our best 3D printer ranking), most plug and play 3D printers are direct extruder 3D printers. They often incorporate gears, especially in DIY 3D printer kits.

direct 3d printer extruder
A direct 3D printer extruder.

Direct Extruder Strengths

  • Firstly, since there’s a shorter distance to the hot end, you are likely to experience better responsiveness to extrusion. Moreover, this results in less force being required to extrude filaments. This better responsiveness means cleaner prints and better surface finish overall.
  • Direct extruders are known for being far better for printing more delicate, flexible materials such as TPU.

Direct Extruder Weaknesses / Limitations

  • Since direct extruders involve the extruder being connected to the hot end, this combined part has a heavier weight overall. This larger mass can create slight issues and mistakes during 3D printing from vibrations in the 3D printer’s frame leading to slight overshooting.
  • This heavier mass also generates more heat on motors.

3D Printer Bowden Extruder

Bowden extruders differ from direct extruders as they are not directly attached to the hot end. They instead have a PTFE tube which connects the extruder to the hot end, sometimes called a ‘bowden tube.’ This 3D printer extruder type is used in printers such as the Ultimaker 3, known as one of the best 3D printers in the world.

3d printer extruder bowden
A bowden 3D printer extruder

Bowden Extruder Strengths

  • Having the extruder decoupled from the hot end means there is less weight  to carry, as the heavy extruder body can be mounted on the printer body instead of moving around whilst printing. This means 3D printers featuring a bowden extruder can print more quickly, accelerating and decelerating much faster.
  • Less mess as there is less overshooting as a result of the larger mass on the extruder which occurs with a direct extruder.

Bowden Extruder Weaknesses / Limitations

  • Filament has a longer distance to travel between the idler and hot end before being printed, which can result in a slightly less refined print. Since there’s extra lag, this needs to be countered in your slicing settings before printing.
  • More friction on the filament due to this further distance for the filament to travel. This makes 3D printing with flexible filaments such as TPU far more difficult.
  • It can be difficult to switch filaments with a bowden extruder 3D printer as less force can be applied to filaments as with a direct extruder.

Best 3D Printer Extruder?

There is no right answer to this question. The answer depends on your printing needs, the size of your filament, or whether you intend to use flexible filaments or just basic ones like PLA. The good news is there aren’t any terrible 3D printer extruders out there. This means that for a DIY 3D printer extruder, you’re fairly safe as long as you follow the instructions and take care with installation.

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