Comparing Bowden Extruders and Direct Drive Extruders

The extruders of a 3D printer can be divided into two types according to their different feeding methods: Bowden Extruder and Direct Drive Extruder. The following will compare and contrast the two types of extruders.

Bowden Extruders

3D printers with Bowden Extruders have the extruder and stepper motor installed on the printer outer shell. The filament is fed remotely through the Teflon tube to the nozzle.

Two common 3D printer brands that feature the Bowden Extruder are Ultimaker and Delta 3D printer.

Advantages of a Bowden Extruder

1. The extruder is lightweight, with small inertia giving it precise movement and positioning
2. The moving speed of the extruder can reach 200~300mm/s, resulting in fast printing speed
3. The nozzle and extruder can be separated for easy maintenance

Disadvantages of a Bowden Extruder

1. The feeding distance is relatively long, the resistance is high, meaning the stepping motor of extrusion is required to have a higher torque.
2. The extruder and the nozzle need to be connected with a Teflon tube and a pneumatic connector. This design is more likely have a failure than the Direct Extruder.
3. Both the filament and the Teflon tube are elastic. Additionally the pneumatic connectors has a certain amount of movement space. Therefore, the required retraction distance and speed are greater, which is not as accurate as the Direct Extruder.
4. The distance between the extruder and the nozzle is long, so the filament in the feeding tube is more difficult to use up.
5. It is not very convenient to change the filament, especially when replacing the old filament with new filament without pausing the printing process. The printing process must be paused because the head of the filament cannot be withdrawn when it is in the feeding tube.
6. Because the feeding distance is too far, once elastic filament is used, the filament cannot be fed normally. Therefore 3D printers with Bowden Extruders generally cannot print elastic filaments.

Direct Drive Extruders

3D printers with Direct Drive Extruders usually have the extruder and stepper motor installed on the nozzle and the filament is fed directly to the nozzle.

Examples of 3D printers with Direct Extruders are Raise3D’s E2, Raise3D’s Pro 2, and Raise3D’s Pro2 Plus.

Advantages of a Direct Drive Extruder

1. The Direct Extruder has more precise control of the loading amount than the Bowden Extruder, and the retraction is more precise. This results in a better surface on the printed model.
2. The torque requirement of the extrusion stepper motor is relatively low.
3. It is easier to change the filament.
4. It has a better printing performance for elastic filaments.

Disadvantages of a Direct Drive Extruder

1. The hotend of the nozzle, the extruder, the stepper motor, the cooling fan are integrated, making it inconvenient to disassemble and maintain
2. The extruder is heavier, especially for dual-nozzle printers, which have large inertia when moving. It is relatively difficult to accelerate and decelerate, so the printing speed is generally lower than that of the Bowden Extruder

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