2.85mm Filament Geared Bowden Extruder Feeder

(Deutsche Version) As promised, I will now explain all the single parts of my multi-material Ultimaker. Today, I will explain the feeder. Unfortunately, I did not find a good solution, so I had to build my own feeder. The feeder consists of several 3D printed parts.

The following parts are required for the extruder:

• 3D printed parts: https://www.thingiverse.com/thing:3703063
• Several parts from ebay or other shops (I suggest using the pictures below to buy the correct parts)
• A 1.75 mm metal feeder ("MK8 Metal Bowden Extruder" on ebay)
• A 4/6 mm bowden tube (PTFE, inner diameter 4 mm, outer diameter 6 mm)
• A bowden coupler (comparable to the original part at the Ultimaker 2+, "Bowden tube clip" on ebay)
• Extruder gear
• 2 x 26 teeth extruder gear
• 2 x bearings 625ZZ (16x5x5 mm)
• Nema17 motor, 1.7A, 0.9°
• Screws
• 3 x M3x10
• 3 x M3x30 (longer screws would be better, e.g. 35 mm length)
• M4x30
• Aluminum rod, 5mm diameter (I only found 5.3 mm, this is also fine)

At first, the motor is fixed on the main part.

Next, the feeder has to be adapted for 2.85 mm, therefore a 5 mm drill is used. Then the edges are rounded a bit.

Afterwards, the screw that holds the spring has to be shortened, otherwise the two screws will touch before the spring can build up enough pressure.

The next step is mounting the bowden coupler and bowden tube to the main part.

Now, the feeder is mounted with a M3x10 screw to the main part, from the other side a bearing is placed in the designated holder and both things are fixed with this screw. Important: The head of the screw has to be inside the metal part, otherwise, there could occur problems later.

Then, the arm of the feeder is built up (here you need the M4 screw) and mounted, therefore the three M3x30 screws are mounted in the other direction as the M3x10 screw. Afterwards, the spring is placed in the arm.

Now you need a 52 mm long piece of the aluminum rod. Mount the extruder gear with 7 mm distance to one end.

The large sleeve is placed on the rod, then the rod is placed into the bearing. You might need to push the arm a bit so it fits well.

If you fixed the M3x30 screws with nuts, you should remove them now. The second bearing is placed on the axis and the suitable holder is placed on top. You can fix this with the lower screw by placing the nut there, if you increase the pressure from the string with the M4 screw, the other screws will not fall out any more.

Afterwards, the large black clip is mounted, after this you can add the final two nuts to hold everything together.

Now we go to the other side of the extruder. The two extruder gears with 26 teeth are mounted in the big gears, you can use a small drop of glue to prevent them from sliding apart. The small sleeve is placed on the rod, otherwise the big gear will grind on the holder for the bearing and start to melt together. The gears are now mounted on the rod respectively the axis of the motor. Use some pressure from below on the axis to fix everything tight together.

Your extruder is now completed and can be used. Of course, you can use this extruder for any 3D printing issue that is not linked to multi material printing.

If I did not explain everything precisely or if I forgot to mention something or some material you need, please tell me so I can add this to this post.