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Reduced mass "direct drive' extruder with frame mounted motor

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Hello everyone,

I came up with this idea recently while trying to figure out how to reduce printer head mass.  I finally finished drawing it up yesterday, and just now realized that this design would be optimal with an ultimaker style gantry.


I'm getting ahead of myself a bit.  See my paste from the reprap forum below for better context.

Here's an animation I created to illustrate the concept:


It occurred to me that either of the "idler" shafts on the ultimaker gantry could be turned into an extruder drive shaft.  The idler pulleys could be mounted on bearings, decoupled from the idler shaft.  Then torque would be transferred to the print head through the connected cross shaft.  I need to learn ultimaker terminology.  What do we call either of the two X or Y shafts that pass through and move the print head?  One of those shafts would transfer torque to a filament drive gear located at the print head, directly above the hot end, much like a direct drive setup.  Heck, you could even drive two separate extruder drive gears (simultaneously, if you want) for multi color, by utilizing both idler shafts.

The reason this works so well with the ultimaker is that it does not contribute as much mass since there are already shafts driving the print head.

Heres what I posted last night over on reprap, before I realized this was ideal for ultimaker:



Please let me know if this has already been invented. I searched around a bit, but couldn't find anything like it.

I came up with an invention to mount an extruder motor remotely and stationary (to the frame for example), with the ability to drive filament directly at the print head. This would reduce the mass of the print head, like a bowden extruder, but with the advantage of direct drive (minus minimal backlash). It will only work with cartesian style printers.

It utilizes ball spline shafts and either bevel gears or worm gears to transfer the torque from the motor to the extruder drive gear.

I attached a fusion 360 rendered drawing to illustrate the concept. It's really only meant to convey the concept, so don't mind the lack additional necessary components.

And here's an animation:


Ball splines are currently very pricey, so I don't see this being implemented on a mass scale any time soon. But perhaps comparable components could be used, or perhaps prices will eventually come down.

No idea if this is usable or even a good idea, but just wanted to share in case it is.


Please let me know if this has already been invented!  And if not, I hope the 3d printer community finds it useful.



I'll get on Fusion and start drawing a complete ultimaker gantry system with this ball spline extruder system integrated in.  Might take me a few days since I can only work on this in my free time.

Edited by Guest

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Ideas are flowing in.

A superior option to the bevel or worm gear might be to use the same timing belts we already use, but with a twist ( i mean that literally, not figuratively).  This would virtually eliminate backlash from the system and would be much less expensive to produce without custom gears.  Does anyone have any experience with running G2 timing belt (or comparable) with a twist?  Perhaps it would wear the belts and cause premature failure?

Also, instead of a single X and Y cross shaft, multiple shafts could be used.  The torque they transmit could be used for anything from extruding multiple filaments, to swapping remotely stored filament/hotend combos.


Another idea,

instead of using expensive ball splines, perhaps precision ground square stock could be used.  The linear motion would be transmitted through small cartridge bearings rolling axially, along the shaft axis.  Since the shaft is square, torque would be transmitted tangentially through the bearings into whatever housing they are mounted on.

Edited by Guest

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