Bowden Cable Coupling for RepRap

by Erik, published

Bowden Cable Coupling for RepRap by Erik Feb 24, 2010
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Bowden Cable Coupling for RepRap by Erik is licensed under the GNU - GPL license.

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This is only for people who want to print really fast ;)

Its use is shown in this video:

This is the filament drive mechanism end of the Bowden extruder. The same coupling could be used on the other end (the extrusion, or hot end), or a special purpose (smaller) coupling could be designed to fit your specific extruder (one that also clamps the heater insulator).

The idea of turning a nut onto the PTFE tube comes from profounddevices. I really liked it so much that I replaced my previous design to incorporate this idea.

I\'m thinking of using the nut as part of an electrical switch to get feedback of when the pressure is fully released. This way you can put reversing functionality in the firmware without needing to configure it per material.

The concept of using a Bowden cable as guide was suggested and pioneered by Ed Sells. See his post here:

If you can print to high tolerances or don't mind some trial and error prints, you can use a 'push to fit' variant of this coupling:


  1. Start printing the part.
  2. Screw nuts onto the ends of the PTFE tube (see parts list). If needed, cut a little material away from at the end of the tube to make it fit.
  3. If your filaments do not run through easily anymore, run a 3mm drill through the end where you have the nut.
  4. If you want it to be able to stand more force, put a drop of super glue on the PTFE (above the nut) and screw the nut a bit further. Then truncate the PTFE to be flush with the nut.
  5. Push it into the printed part.

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Very interesting, however, I am trying to get my M6 nut on the PTFE tube for 3mm ID and it's not going on!!

what inner diameter PTFE do you recommend for a 3mm filament?

See this derivative that is tuned for the Mendel X carriage. http://www.thingiverse.com/thing:2221http://www.thingiverse.com/thi...

Modified Bowden Cable Coupling

Pardon my ignorant question; I'm a total noob at this stuff. It looks like part of this would be hanging over empty space no matter how you orient it, so I don't see how it could be printed without support material. Is this not intended for Cupcake/RepRap?

You're right. One of the pictures was different and this showed a version that could not be printed without supports. I had already changed this, but an old rendering got uploaded with the rest.

I've created a new version. The old one worked pretty well but the holes were very tight for M5 bolts. I printed the new ones while using the first couplings I printed and they work fine.

It still looks like it would need support - all that overhang in the center. If you turn it upside down, there's the bevel near the center.

Upside down works fine. The overhang is chosen to be 45 degrees, for most machines (depending on nozzle shape, layer height, speed, filament, etc.) this is on the safe side of what can be done. You can go further by choosing a low-layer height, or extrude an inner shell first and then pasting the outline against it.
I've been able to makes some 90' overhangs, gravity hardly has an impact on what can be built, it's more how the nozzle tends to push material outward.

Do you have a picture of what you mean by "turning a nut into the PTFE tube"?

Erik - in reply to tbuser

Essentially you thread it onto the PTFE. I've added the picture. I've added the part number that http://Adtech.co.ukAdtech.co.uk currently uses.
Here's a video by profounddevices that pointed me to this: http://www.youtube.com/user/profounddevices#p/u/3/ELcNOBYtsQ0http://www.youtube.com/user/pr...