Stargrove1 from the RoBo3D forums came up with this pretty sweet mod to his kickstarter RoBo3D.
He’s using a high strength servo motor to slide a stepper motor from side to side to achieve dual direct drive extrusion from a single stepper. He calls it the Dual Extruder Interfacing Single Stepper or D.E.I.S.S for short.
Overall it’s a really cool concept that may/may not have been done before. Definitely could be useful in compact applications such as dual direct drive with the Cyclops/Chimera.
Read more about it here: http://forums.robo3dprinter.com/index.php?threads/d-e-i-s-s-dual-extruder-interfacing-single-stepper.4361/
Or check out his Thingiverse Pager which contains a build guide for more pictures on just how this is accomplished: https://thingiverse-production-new.s3.amazonaws.com/assets/28/2f/a4/35/b9/Setup_guide.pdf
Oooh. That triggered a thought. What if you had a geared stepper motor that rotated a circular array of heads with a cam that pushed the selected head down a few mm into print space.
Wouldn’t need to push them down. Just have the axis of rotation at a slight angle, and rotate like the lenses on a microscope to bring the head into print position.
http://upload.wikimedia.org/wikipedia/commons/b/b1/Optical_microscope_nikon_alphaphot_%2B.jpg
I used to have a microscope like that, nice improvement to the idea. Now who can fabricate one for testing?
Very interesting. Although it seems that D3D is able to do this without a servo to move the motor, so not sure if their system beats this. Cost should also be considered.
This is a lot like what stratasys uses in the dimension/uPrint level printers. Its a single motor and the axis moves all the way to one side to trigger a cam that shifts the tension from one side of the drive wheel to the other. The motor switches directions based on which side the tensions from. So right nozzle it turns clockwise left counter. Works well. This is cool though.
Also, does the servo have enough torque to keep the drive gear pushing against the filament? Seems that the printer is printing fairly slow, so I’m guessing if you’d increase the speed, the drive gear will start slipping.
@Shai_Schechter D3D = Dimension 3D? Do you have any more info?
Not entirely sure how much pressure is needed but according to the specs I looked up the MG996 can supply between 9-12 kg-cm stall torque. Seems like enough but the RoBo is in general pretty slow and I’m sure once he gets more confidence in the design he’ll try moving faster. It’s certainly no delta in terms of speed 
@Joe_Spanier Man I really want to learn more about stratasys printers but it’s hard to find teardowns and the like.
@Shai_Schechter
The servo does only need torque during transition, the lever of the servo moves it by a slot hole and ends in 90° angle, the servo is even turned of by the firmware after reaching one of the two endpositions.
The print was fairly slow at max. 30mm/s, but as Mike said, the stock printer wasn’t much quicker. I am still playing around with the strength of the springs to find the best setup.
Brian and I have early drawings of a “six shooter” multi color head that uses one Extruder and one drive motor with a servo or stepper to rotate the head. It could use heavy retraction to escape the printing color back into theatricality cold end. Surprised no one has tried it. It would require a very slim, consistent path for the filament through the hotend, but Ubis metal has that. 6 cold ends would be required, or more likely, one big cold end with 6 positions/colors drilled out. Lots of cooling needed. Would love to start working on this if anyone wants to draw it up, we can work in public and open source from the beginning.
Engaging the drive gear will be tough but the drive motor could rock out of the way with a servo and engage a pinion on the drive mechanism. A cam or egg shaped barrel could engage a pinch to hold filament in 5 shafts while the drive position is open, allowing the main filament to push through freely.
Just ideas. Ideas are free… Making is hard!
Brook
