3D Printers: Remote Direct Drive Extruders overview

in printing3d •  7 years ago  (edited)

Hi ! Any FDM Printer has either a direct drive or a bowden extruder.
There is a third way: the remote direct drive extruder.

Quick Recall

A direct drive extruder has its name implies pushes the filament with a gear hob driven by a stepper motor in the heat throat of the hotend.
Reprap-Prusa-i3-3D-printer-no-motor-1-75-mm-all-metal-direct-drive-Extruder-hotend.jpg_640x640.jpg

A bowden extruder has a so called bowden tube that is directing the filament pushed from the gear hob driven by the stepper motor.
Geeetech-GT7L-Assembled-Bowden-Extruder-J-head-for-Reprap-Kossel-Delta-Rostock-3D-Printer.jpg_640x640.jpg

Direct drive

Pros:

  • Very short and More constrained filament path: sharper reaction, improving print quality
  • Print flexible filaments
  • Short retractions
  • Less oozing improving print quality

Cons:

  • Weight, Inertia: Difficult to accelerate fast
  • Vibrations affecting print quality

Bowden

Pros:

  • Weight, Inertia: Easier to accelerate fast
  • Less vibrations improving print quality

Cons:

  • Long and less constrained filament path: lazy reaction, reducing print quality
  • Cannot print flexible filaments or very slowly
  • Long retractions
  • More oozing reducing print quality
  • Difficult to really implement it correctly (any source of play is introducing hysteresis and longer reaction)

The Remote Direct Drive Extruder

The Remote Direct Drive Extruder is using a constrained cable that connects the stepper motor to a driven gear reductor (worn gear) that is pushing the filament directly in the heat throat of the hot end.
The stepper motor is outside of the gantry just like a bowden extruder, the gear/assembly and the hob driving the filament is on top of the heat throat.
Yes, it looks like a remote Dremel or something like that.
Full package.png

It seems to be as good as the Bowden for the weight, inertia but also allowing a very short and constrained filament path that is needed for sharp reaction and to enable to print fast enough flexible filament.
Is it so good ? I think it is interesting on the paper, but as usual the implementation makes the final decision.

There are two options:

Both products are very similar: compact, lightweight and using a worn/gear.
The Flex3Drive has a 40:1 reduction and the Nimble has a 30:1 reduction.gear-set_2000x.jpg
They have both good reviews.
The weight is around 30 to 60 grams.

Pros:

  • Weight, Inertia: Easier to accelerate fast
  • Very short and More constrained filament path: sharper reaction, improving print quality
  • Less vibrations: improving print quality
  • Print flexible filaments
  • Short retractions
  • Less oozing improving print quality

Cons:

  • Input torque limited for the driven cable (reliability and hysteresis issues)
  • Max speed limited by the stepper motor (high gearing): low inductance/low inertia stepper motor, high voltage (cheap stepup voltage circuit is an option), probably moderate microsteps or even none.

Others:

  • Backslash is not an issue, lot of people are using geared steppers for Bowden.
  • Limited Acceleration of the retraction due to the high gearing: it is not a good idea to have a huge acceleration on the extrusion part if you want to go fast.

Personally, I think I will give a try to one of those

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I didn't understand how this new drive should work. Isn't that like a motor again on the print head or where to you position the remote drive extruder ?

Sorry I should have put an image, it will be more clear.
The worn/gear assembly is attached as a regular direct drive extruder on the hotend, but instead of having the stepper motor, you have a cable that is driving this gear assembly that goes to the stepper motor attached to the chassis

I edited the post to add the missing photo

Thanks now I got it :) nice design gonna be interesting to see it in a prosumer printer.

They are doing custom designs: the case is 3D printed for both companies.
For instance: https://flex3drive.com/flex3drive/f3d-range/

Cool they also have it for UM2+

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  ·  7 years ago Reveal Comment
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