Airtripper’s Bowden Extruder – Rostock 3D Printer BI

As part of our work for the construction of the Rostock 3D Printer BI Edition, we modified Airtripper’s original extruder. Our initial goal was to reduce the complexity of the extruder while maintaining the same functionality.

Our efforts were initially focused on replacing the idler/tensionner body strut with a printed part that would support it just as well.



After playing around with the design and testing the extruder, we ended up including other modifications:

Motor Shaft Support

We removed the motor shaft support since we did not have a miniature ball bearing on hand. After several hours of printing we haven’t experienced any problems with the removal of this part so we decided to leave it out of our final design. However, we would caution that a sufficient infill is required in order for this piece to be strong enough (we recommend > 40% infill).

Filament guide tunnel

We slightly elongated the filament guide tunnel. With Airtripper’s original version, we sometimes found that the filament would curve and fall outside of the effective gripping zone (between the bearing and the 5mm insert). Elongating the filament guide tunnel meant that the filament would remain straighter and eliminate these types of problem.

Embedded nuts

When the extruder is installed on the Rostock BI frame, there is little clearance to manipulate the nuts. As such, while trying to install them, it wasn’t uncommon for them to be dropped.  To solve this problem, we decided to embed the nuts and it worked nicely since we could press them into place and manipulate the extruder without having to worry about it.


Teflon Tube Adaptor

Finally, we decided to add a tube adaptor for a 4 mm outside diameter (OD) teflon tube.  This addition proved useful since we were trying tubing that had different ODs during the development stage of Rostock BI.


We would like to thank Airtripper for his original design. All the Sketchup models and .stl file for the BI edition can be found on Thingiverse.