The extruder has two different types depending on the drive. These are Direct extruder and Bowden extruder.
In direct extruders, the hot end and cold end are simply attached together. In this setup, the filament goes straight down through the cold end and into the hot end.
One of the main benefits of a direct extruder is the very short distance between the drive mechanism and the hot end. This means that it more responsive to extrusion and retraction. As a result, it can produce clearer prints with less stringing and oozing.
Moreover, the shorter distance between the drive mechanism and hot end can make printing with flexible materials a lot easier.
However, because direct extruders are directly attached to its hot end, there is also a possibility that its mass will be moved along with the hot end. This means that as more mass are moved around, it will likely to backlash, overshoot and frame wobble.
In Bowden extruder, the hot end and cold end are not directly attached to each other. Instead, there is a tube that extends from the extruder to its hot end.
With this setup, the printer will be able to print faster, more accurately and more precisely than 3D printers with direct extruder.
Nevertheless, the most common weakness of Bowden extruder is that it is prone to retraction and stringing. Additionally, since the idler/gear pinch point and hot end are far from each other, there is a chance that the hysteresis (lag) of the system will increase.
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