Bowden extruder
On the other hand, the indirect extrusion or bowden type consists of removing the filament pusher motor from the moving parts and placing it in the structure of the printer. So that the filament does not pass directly from the motor to the hotend, as in direct extrusion, but with this technique the filament is guided to the hotend through a tube. This tube is usually made of PTFE (polytetrafluoroethylene, better known as Teflon) and usually has an internal diameter larger than that of the filament to compensate for manufacturing tolerances that the filament may have and to prevent jamming.
Bowden extrusion has the advantage of reducing the weight of the moving parts, which means being able to print at higher speeds. But it has the disadvantage of being a system susceptible to jamming and more difficult to control shrinkage. In addition, given the complexity of pushing a flexible filament through a tube, from the bowden to the hotend, it is very difficult to print with flexible filaments. The greater the flexibility of the material, the greater the probability of jamming in the tube.
That is why we know many myths about the impossibility of printing flexible filament in 3D printers with extruder and bowden tube. But there are multiple solutions that will allow us to print flexible and even very flexible materials on these machines, which we will see below.