Direct Extrusion vs Bowden
One of the most fundamental parts of any 3D printer fdm is the extruder, the mechanism responsible for pushing the filament to the hot-end to be melted.
There are two main extrusion systems, the direct and the bowden.
Today in the blog we are going to break down both extrusion systems and see the advantages and disadvantages of both systems.
|Direct extrusion system|
The direct extrusion consists of placing the motor that pushes on the filament directly on the hot-end, in the own mobile piece of the printer. This system is commonly used in most printers, being the first to be developed together with the Rep-Rap printers.
The direct extrusion has evolved a lot in these years, optimizing the system to be able to work with a wider range of materials.
|Greg's Wade extruder|
Of the first systems of direct extrusion and one of the most famous we find the mythical extruder Greg's Wade used years ago almost in all the Rep-Rap printers. One of the biggest drawbacks of this extruder was the use of a bearing to push the filament, which often caused it to slide down.
Today we find direct extrusion systems that already have more compact gear reduction systems that in addition to minimizing the size of the extruder allow greater control of traction on the filament.
The advantages of this system are that when pushing the filament near the hot-end it is easier to calibrate it to achieve a good control of the retractions of the material, which will allow us to obtain a better finish in the pieces. In addition, it will allow us to work with flexible materials such as eFil or eFil +.
The main weaknesses are the weight added to the moving parts of the printer, which when printing at high speeds could suppose problems of vibration, but we'll talk about that later.
|Bowden extrusion system|
The bowden extrusion consists of removing the filament thrust motor from the moving parts and placing it in the structure of the printer. In this way we will guide the filament to the hot-end through a PTFE tube. This tube usually has an internal diameter greater than that of the filament to compensate for manufacturing tolerances that the filament may have and that jams do not occur.
Bowden extrusion has the advantage of reducing the weight of moving parts which means that we can print at higher speeds. As main drawbacks we find that it is a system more susceptible to traffic jams and that it will be more difficult to control the retraction. In addition it will be more difficult to work with flexible filaments.
The printing speed
As we mentioned earlier, the advantage of bowden extruders is that reducing the weight of the moving parts when printing inertias is also reduced, which will allow us to print at a higher speed.
However, with the printing speeds that are usually used in most applications and with the components of increasingly high quality printers, spindles, bearings ... These effects are going to be practically imperceptible.
Having worked with both systems, from 3Dfils we recommend using direct extrusion for most applications. This will reduce calibration problems and open a wider range of available filaments to use.
We recommend using bowden extruders on printers that use multiple print heads. In this case the weight if that can be an important factor, especially when we move from the two print heads. Also in these systems the use of direct extrusion can directly affect the printing area.
We see ourselves printing.
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