New geared belt extruder

Hi Ormeroders and RepRappers

I am happy to present you my geared belt extruder based on ideas of fotomas, ianburny and drofarts.
This is one of the more complex designs from me.

I was not happy about the extruder performance for large prints of the Ormerod.
I had three things which I didn't like:

• grinding of the hobbed bolt
• wear of the hobbed bolt
• wear of the extruder plastic part due to filament
• no indication if printer is out of filament

After switching to the new dual extruder i bought just before Reprappro closed shop the reliability of my printer even turned to the worse.
Then when it was hot in summer the grinding of hobbed bolt turned more and more to a problem. So that had to switch back to the
single extruder to get my printer print extruder parts again.

I started on a extruder design with two hobbed bolts last year, even before my acute problems with extruding began. Then i saw
the belt extruder design by fotomas and improved on his work. And i am very happy about the result. My printer is reliable again!

But first an image of the geared belt extruder:


It has a lot of nice properties:

• sometimes it continued printing even with breaking filament (even if the prints didn't turn out to be pretty)
• depending how good your assembly is (my second print turned out a little to fat). So i had one running with 800mA
  power but it does no harm turning up the motor voltage up to e.g. 1100mA and regulate the pressure with the belt tensioning.
• there is a mount for a switch to monitor if there is still filament fed into the extruder (unfortunatly not wired up yet).
• design pretty reprap'ish: You only need a few bearings, three short metal rods,a belt and screws.
• much more reliable even with the problematic dual head from reprappro.
• steampunk like look

I had this extruder running since summer and the first design was a success and giving much better results than the stock extruder.
Still i had more and more ideas for improvement so this design is now roughly the third design iteration. So the only things i would improve
might be a larger big wheel (but with a need for a different belt and even more space) and a slightly different mounting of the large gear.

You can find the design at:
https://gitlab.com/tstone/things]Beltextruder[/url]

All parts are at the beltextruder/stls directory: They can all be printed in one go with your Ormerod. You just have to be careful about
the orientation of the parts. The all have been designed with printability in mind but only in one orientation.

I want to thank (in no ordering)

• freecad team for FreeCad and the improvements in the 0.16 release which made it much more reliable thus fun to work with!
• openscad team
• slic3r team
• fotomas for the design of the belt extruder. Even if after all the refinements no original parts of his design are left. Without his inspiration
  this design surely wouldn't exist.
• ianburny for his nice gears
• drofarts for his openscad library of parametric pulleys.
• dc42 for its ormerod firmware and distance sensor.
• everybody else working on the open source software stack.

I have also some photos of the assembly and the printouts (for the orientation of the parts). I can put them online if you are interested.

Have fun
Tim