Bowden Cable Coupling for RepRap
by Erik, published
Description
Its use is shown in this video:
youtube.com/watch?v=cSBqBW1w2wE
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:
blog.reprap.org/2009/04/bowden-extruder-concept.html
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:
thingiverse.com/thing:3775
Recent Comments
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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/thi...
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Instructions
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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See this derivative that is tuned for the Mendel X carriage. http://www.thingiverse.com/thi...
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.
Do you have a picture of what you mean by "turning a nut into the PTFE tube"?
Essentially you thread it onto the PTFE. I've added the picture. I've added the part number that Adtech.co.uk currently uses.
Here's a video by profounddevices that pointed me to this: http://www.youtube.com/user/pr...
Very interesting, however, I am trying to get my M6 nut on the PTFE tube for 3mm ID and it's not going on!!