Extruders
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A 3D printer extruder (with FFF) is the part of the printer that pushes filament through the heated nozzle. There are multiple types of extruders as well as some ambiguities to avoid.
An example of a simpler extruder is a single drive gear extruder, such as the one used on Creality machines. The tension on the filament is also not adjustable. The spring pushes out the idler arm, which in turn pushes the bearing against the filament and provides tension to keep the filament against the drive gear. When the drive gear turns it pushes the filament through either the bowden tube or the hotend depending on whether a direct extruder configuration is being used.
Dual Drive extruders have two gears on either side of the filament, as opposed to a single gear and bearing. This allows the extruder to grip on the filament more reliably, making it less likely to slip.
Extruders that have the drive gear directly attached to motor shaft are known as Direct Drive extruders. While this term is often shared with an extruder mounting configuration, the two are unrelated. Some extruders are geared and have an extra reduction gear in between the drive gear and motor, allowing for higher torque and finer extrusion control.
Some extruders allow you to increase and decrease the amount of tension that is exerted on the filament. Being able to adjust this is useful for flexible filaments, as too high tension will crush or squish the the material. Flexible materials aside, it is useful to have for standard filaments, as sometimes an extruder with pre set tension is not satisfactory.
Many extruders have gaps and spaces where the filament is not constrained as it passes through. While not an issue for harder materials (like PLA, ABS, and PETG), flexibles can jam into, and squeeze through these gaps. A well constrained path is necessary to print flexible materials well.
The term "direct drive" is widely misused. Increasingly commonly it is used to refer to an extruder/hotend combination where the extruder is mounted with the hotend on the same carriage, such as the hotend/extruder combination that Prusa or Artillery use. Technically, this usage of terminology is incorrect.
According to industry definitions from outside of hobbyist 3D printing, a "direct drive mechanism" is one that "uses the torque coming from a motor without any reductions (such as a gearbox)". This also aligns with definitions within 3D printing itself from years ago.
A "direct drive" extruder refers to an extruder where the filament drive gear is mounted directly on the motor shaft, i.e an ungeared extruder, such as the one that a stock Ender 3 uses. The anthithesis, then, of a direct drive extruder is not a Bowden extruder but rather a geared extruder, such as the Bondtech BMG or the E3D Titan. Instead, the extruder configuration that many refer to as "direct drive" nowadays should more accurately be called a "direct" extruder.
A "direct" extruder is one where the filament drive mechanism is mounted in close proximity to the hotend, eliminating a long Bowden tube. The antithesis of a "direct" extruder is a "Bowden" extruder. Consequently, you cannot have a "direct Bowden" extruder, but you can have a "direct drive, direct" extruder. Additionally, and perhaps confusingly, a "direct drive Bowden" extruder is just as valid. Given the confusion between the terms and the fact that "direct drive" is so commonly used to mean "direct" nowadays, the suggested usage of terms is to simply eliminate the term "direct drive" from your vocabulary entirely.
True "direct drive" extruders can be just as accurately referred to as "ungeared" extruders with much better distinction. Meanwhile, "direct" extruders should be called "direct" to avoid confusing the definition of "direct drive" in 3D printing compared with its actual definition.
- Direct Extruder
- Dual Drive
- Geared Extruder (3:1)
