Direct or bowden – how the filament gets to the hot end?
Why did the chicken cross the street? Never mind. Why did the FILAMENT go to the hot end? Scrap that. The real question is HOW?
During printing, the filament is driven into the hot end by a mechanism and there are mainly two ways this can happen. That’s why we distinguish the Direct (feed) and the Bowden Extruder.
First of all; There isn’t such a thing as The Best Extruder Type. Both of them have pros and cons and under given circumstances a printer has to make the best of the chosen solution, and with the right settings, and some fine tuning, both can produce excellent prints.
But what are the main differences between these two types?
The filament can be driven directly into the hot end by a stepper motor sitting on top of the extruder, or we can take this mechanism off the carriage of the printhead and place it somewhere on the frame of the printer, and push the filament through a tube (the “bowden”) to the hot end. Some prefer the bowden-based solution because the weight of the stepper motor doesn’t have to be carried around by the extruder, allowing it for smoother and sometimes faster motion during printing.
These extruders are best used with a 3 mm filament, because they are a bit more rigid and can be pushed through the bowden, more precisely, but note, that a cheaper, uneven filament, or one swollen by moisture, or sometimes even a flexible one might jam the tube, not to mention, that retractions can be a bit laggy.
On the other hand, the carriage of a direct feed extruder might have to carry a bit more weight which can cause some wobbly edges, since the printhead cannot stop at the right point because of inertia, but a good, stable frame can easily resolve this problem, and a direct extruder can provide a nice continuous filament feed, with rapid retractions, and both 1,75 mm a 3 mm filaments can be used, as well as flexible ones.