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Getting rid of the bowden tube completely and coming up with an elegant solution for getting filament directly to the head is a good thing.

I don't know if anyone thought of this one but the primary challenge with putting an extruder with motor is too much mass.

I brought this idea up to Brian Van Diepenbos at MRRF....I was going to go ahead and develop it and probably protect the idea from the big boys but here it is:

What if on one end, the motor to the extruder was hooked up to a flexible drive shaft and on the other end of the shaft, an extruder?

Would this eliminate the bowden tube? What about lash? Increase it or no? Perhaps a really small extruder?

Perhaps carbon fiber components might also reduce weight (shaft casing) - of course, maybe the shaft doesn't need casing!

This could also work for Cartesians!
Any thoughts here?

Replace bowden tube and filament with loose filament and flexible drive shaft. Replace bowden connector with drive gear assembly. Given how long that drive shaft has to be to accommodate motion, the weight gain might be as bad as just putting the motor at the extruder.

The other concern would be torque exerted on the extruder. If the arms or joints move/bend/twist at all, it's going to move the nozzle and affect the print. That concern comes up no matter what angle you bring the power in (could be from the side rather than the top). You can beef up the arms and joints of course, but then you're defeating the purpose.

The idea has been suggested and implemented in various ways on conventional Mendel style printers, I don't think anyone has decided it's a big win, and it's a hell of a lot easier to implement when your printhead only moves on one axis. You also introduce a set of new problems with the solution not least of which is backlash in the extruder drive mechanism.
The reprap forum is a great place for a treasure trove of ideas that people have tried, most never seem to make it to the Wiki and the forum is not the easiest place to find things.

Yeah, just saw the stuff. I guess it's true: Nothing is ever new.

I think the only thing to avoid conjecture (well, maybe just endless guessing) is to try it. I think it will be a fun, doable trial project - without tons of parts.

The Zero-lash extruder gear thingy seems to be a good idea to counter the lash challenge - but we'll never know unless we try it out!!!

Under a post entitled the Remoter. (Yeah, that's searchable...)

http://forums.reprap.org/read.php?14,26 ... msg-266572

Of course, while I posted this, I just noticed that I'm on the 6th loop of a skirt instead of putting the loop out six mm...crap. If I get the hard stuff, the easy stuff fades away...