Shoot a Hole in My Crazy Idea: Dual-Extruder Mini (single hot end)
 

Shoot a Hole in My Crazy Idea: Dual-Extruder Mini (single hot end)  

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MKEMike
(@mkemike)
Active Member

I love my mini, but I'm yearning for a way to improve on color swapping.  I'd love to change colors / materials on the same layer, or at least automate the layer-by-layer color changes.   I could upgrade to a Mk3 and MMU, but a friend of mine with much more experience hasn't had the greatest luck with his.

Would it be possible to add a second extruder and run both extruders' bowden tubes to a Y adapter at the top of the hot end?  I'm thinking you could mount the second extruder on the right side of the Z axis upright so as to not add weight to the X axis arm.  We'd need to either add another stepper driver or multiplex the current extruder's one, since you wouldn't need to run them both at the same time.  We'd just need to change the load and unload lengths for the M600 command to shorten the retraction (just get the filament  out of the hot end and Y, not all the way out), and insertion (since the second filament will already be right up to the Y).   It would be nice to put flags to disable or timeouts on the insert/remove filament prompts and the "is this the right color" prompt before proceeding with the new filament, but that would take a firmware change and a new parameter added to M600.

So, what do you think?  Is there anything I'm missing that would make this harder or impossible?

Mike

Posted : 20/12/2020 6:21 pm
Robee Shepherd
(@robee-shepherd)
Estimable Member

I think there is a lot more to it than that, you would need custom Marlin firmware to control both extruders (meaning voiding your warranty), and it probably wouldn't work as well as a Mk3 and an MMU.

I do love the idea of multi-colour prints but the waste of filament for colour changes make me wonder if dual extruders are a better idea. But maybe the best idea of all is just to paint them!

Posted : 21/12/2020 7:56 pm
MKEMike
(@mkemike)
Active Member

@robee-shepherd

Well of course it would require customizing the firmware, but not by a whole lot.  And far as the warranty, anyone doing this would probably be on or more of the following:

1. A hard-core DIYer, with the experience and willingness to fix anything they break

2  Already have used the mini for a year,  so their warranty is up anyway.

3. Prusa, when they manufacture and sell the Super Mini Plus Dual.  🙂

I do think that it would be more reliable than the MMU, the both filaments would be kept loaded, with the working ends only pulled back a short distance at or in the Y, versus having to going back and forth through the extruder with each color / filament change.  There also wouldn't need to be the selection mechanism and cutter like on the MMU.  In my experience, any irregularity at the tip of the filament has only been a problem getting through the extruder, not into the fitting at the top of the hotend or the short piece of tubing inside the heatbreak.

 

I'm also thinking there could be a way to do it with just one stepper but driving two extruder gears on it's shaft and utilizing a solenoid on each of  two tensioner gears to feed each filament through its own bowden tube, up to a Y at the top of the hot end.  Only one solenoid would hold tension against a filament at a time so it feeds and retracts.  The other filament would be not have tension on it, so the extruder gear under it would spin freely.  This would keep the weight and mounting basically the same and having only one extruder,  being only slightly larger to have two filament paths through it.

Is multicolor wasteful?  Yes, especially when it is multiple colors on the same layer, and using a purge tower.  Layer-by-layer color swaps aren't so bad when you can just do a loose purge back in the corner of the bed, or even slightly off the bed into a "purge bucket" and swipe the nozzle over a brush to detach the purged filament.

 

 

 

Posted : 22/12/2020 12:30 am
Gordon W
(@gordon-w)
Reputable Member

I've got no experience of the product but https://www.3dchameleon.com/ might be of interest.

Posted : 24/12/2020 11:20 am
Robee Shepherd
(@robee-shepherd)
Estimable Member

There is also the Mosaic Pallette Pro 2 which is a lot more expensive: https://www.mosaicmfg.com/products/palette-2

Posted : 24/12/2020 3:23 pm
MKEMike
(@mkemike)
Active Member

Yes!   The 3dChameleon is almost exactly what a was thinking of, but with the bonus of having 4 colors and no modifications to firmware or electronics.  Having the Y carriage push a micro switch to change the filament is great for minimizing the modifications to the printer.  Also  having a section of 1.8mm inner diameter Bowden tube at the top of the hot end to re-form the blob back to size while it is still warm on retractions is brilliant.

Now I just have to decide to go with that or a second Mini.   Heck, maybe both, for the same price as a Mosaic Palette 2 Pro.

Posted : 24/12/2020 9:27 pm
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