Direct drive extruders are combined with the hot end to form a single printhead and push the filament directly into the nozzle.
Bowden extruders have a Bowden tube (PTFE) connected from the extruder to the hot end, through which the filament is pushed into the hot end.
What are the advantages and disadvantages of both extruders?
In a FFF(Fused Filament Fabrication) printer, the extruder is a part that pushes an exact amount of filament into the HotEnd, a combination of a heater and a nozzle that melts the filament.
There are two types of extrusion systems. If the extruder is in direct contact with the HotEnd, it is a Direct Extrusion. If the extruder is separated from the HotEnd, it is Bowden extrusion.
Now let's take a closer look at the Direct extruder and the Bowden extruder and determine the pros and cons of each method.
< Direct Drive Extruder and Bowden Extruder >
Direct Drive Extruder
Direct extruders are attached with a hot end to form a single print head. The extruder pushes the filament directly into the nozzle. The advantages and disadvantages of this are:
Due to short distance between the extruder and the nozzle, the extruders motor can easily push the filament through the nozzle.
Because the extruder is closer to the nozzle, it is easier and faster to retract the filament.
Due to short distance between the extruder and the nozzle, a large torque is not required from the motor to extrude the filament.
Various filaments available
Since the distance that the filament must travel from the extruder to the hot end is short, it can be fed stably regardless of the filament material. Direct extruders are recommended, especially for flexible or abrasive materials.
Printhead weight increase
It will be much heavier than if the printhead had only a HotEnd. This requires more power to operate the printhead and also reduces the print speed. It also causes more shaking when changing orientation while printing.
Maintenance, such as cleaning the nozzles, can be more difficult.
The Bowden extruder is attached to the frame of the 3D printer and does not move. Bowden Tube (PTFE, Teflon) connects from the extruder to the HotEnd, and the filament is transferred to the HotEnd through this tube.
Both the Direct Extruder and Bowden extruder can be connected to the filament spool via a tube, so tube existence doesn't necessarily mean Bowden extruder.
Because the Bowden extruder mounts to the printer frame rather than the printhead, it puts much less weight on the carriage. The result is faster, quieter, and less printhead vibration, resulting in high-quality printing.
Required a more powerful motor
Bowden extruders have to push and pull the filament through a long tube. PTFE tubing also has some friction, so a more powerful motor is needed to properly control the filament.
Slow response time
Friction between the Bowden tube and the filament further increases the delay between the extruder and the nozzle. Therefore, in order to deposit efficiently and avoid stringing, the extruder needs a faster acceleration in extrusion and retraction.
Material is limited compared to a direct extruder due to the long filament path. Highly flexible materials such as TPU do not slide well over long distances, making it difficult to pass through the tube. Highly abrasive filaments can easily cause tube wear.
Which extruder to choose?
Many manufacturers still prefer Bowden extruders. First of all, there's no reason to change it since it's been working fine so far, and effective extrusion and retraction control of the extruder is possible by using your own slicer.
On the one hand, the number of direct-drive extruder machines continues to grow. The main reason is that modern stepping motors are much smaller and lighter than conventional motors, so the weight disadvantages can be considered as much smaller compared to the benefits gained.
As always, each option has its pros and cons. The choice will depend on the user's need, taking into account the stability of the motion system, the required print speed, and the material to be used.