I've got a direct drive extruder printer, that I have equipped with a Bowden-tube to give it a nice and defined filament path from my spool and to protect it from moisture when it exits my drybox. I've noticed that this 1 m Bowden tube adds quite a bit of friction to the system. I am keenly aware of it as feeding filament form the drybox into the tube by hand is quite a chore already, especially with high friction materials like PETG. Also I notice that I can sustain only lower volumetric flow without skipping or underextrusion after adding the tube.
So I figured, why not have a motor on both sides of the bowden tube? A big and heavy one at the entrance, providing a baseline pressure on the filament. And a comparatively light one on the other end, adding that fine control you want for your retraction, rather than trying to implement that via a 1 m wet noodle full of static friction.
Seems like it would give you the best of both worlds. Not quite as light as a full Bowden system, but you could have all the control of a direct drive system, with much less of the weight/flow rate tradeoff.
Anyone aware of this being done before? Or any good arguments as to why it is a stupid idea? Seems like a fairly straightforward mod; in the simplest implementation, just add an additional extruder of the same spec on the other side of your Bowden tube, and split the control signal to be the same amongst both motors.