Why not 2 extruder nozzles?  

RE: Why not 2 extruder nozzles?

patents?

RE: Why not 2 extruder nozzles?

I thought maybe, but Stratasys must be approaching the 21 year runout

RE: Why not 2 extruder nozzles?

Also, Ultimaker uses two nozzles/motors/materials

RE: Why not 2 extruder nozzles?

I'm hardly an expert, but from what I've read on dual-extruder printers:

• The extra weight is a problem on already-heavy cartesian printers, especially if you want both to be direct drive.
• It's difficult to get one nozzle leveled much less two.
• Loss of printable space.

Finally, Prusa already has an alternative with 5 available filaments in the MMU2, so what would the possible gain be? It can be difficult to get started with, but many users are getting undeniably excellent results.

RE: Why not 2 extruder nozzles?

speed, no purges, no waiting on purge tower printing

RE: Why not 2 extruder nozzles?

I have the MMU2s...not easy to get working (I found) and I consider myself fairly capable.  Waste tower is annoying, long print times are annoying.

Hard to imagine double the weight of the existing extruder assembly being a problem for existing structure.

I've heard of all the 'difficulties', but they were all solved many years ago by stratasys,and likely are available for use by anyone at this point.  Trickiest part seems to be moving the support nozzle up/down to clear material being printed.  Surely Prusa's smart engineers could figure this one out!?

I look forward to when they do!  🙂

RE: Why not 2 extruder nozzles?

Sounds like you've got it all figured out then. No real discussion to be had. 

RE: Why not 2 extruder nozzles?

Well, apparently you are out of ideas, so no need for additional comments, but glad you think I have it all figured out, I am flattered!

RE: Why not 2 extruder nozzles?

If you were to create a dual gantry machine, one carrying material extruder and the other carrying support structure extruder, seems like the structure would be unchanged (and not taxed any more since it is in OEM configuration), and the build tray is shuttled back and forth between them ?  Wouldnt you only need a longer tray travel to do this?  (and obviously software changes).  Wouldnt this eliminate need to raise and lower one nozzle to clear the other as on most dual nozzle setups?  Has anyone ever seen a dual gantry machine like this?

RE: Why not 2 extruder nozzles?

There are dual extruder machines on the market - I have one (Flashforge Creator Pro).  The ones I know of are not dual gantry though - just dual extruder.  There is a lot more weight on the dual extruder systems which mean more ringing etc.  Also, the effective width of the print bed is reduced by twice the distance between the nozzles.  And, of course, there is the leveling of the nozzles issue (not trivial on my machine).  For me, it became annoying enough and worth so little that I mod'd mine down to a single extruder system.  Dual gantry would address these issues for the most part (although the build size issue would still be present in the form of the deeper bed and extra movement.  But dual gantry would also mean 2 additional z steppers, an additional x stepper, and an additional extruder stepper.  That's a lot of extra hardware, not to mention the complexity of keeping the extruders out of each other's way.  All this doesn't seem any simpler that the current MMU which if Prusa could get to work reliably for people would solve all these problems more neatly.  So, I'd expect to see them putting most of their efforts into getting the MMU improved rather than some dual extruder approach.

RE: Why not 2 extruder nozzles?

Based on what I have seen, a dual-extruder nozzle that will let you spend more time printing than fiddling with it is likely to be a commercial/industrial grade printer that will cost over US$2000.

I bought a dual-extruder delta (HE3D K280) for my son's school. Big delta printer, huge build volume, great for printing props for school plays and such. They got the printer working, but they gave up on printing with both nozzles. It's just too hard to keep the effector level enough so the nozzles don't collide with the print.

I spent months looking for a reliable dual-extruder printer that fit my budget, and failed. So I bought a Prusa i3 MK3S (which just arrived yesterday) with intention to buy the MMU2S so I can print support material. I'm uneasy about that, though, due to all the posts I'm seeing about how much fiddling I might be expected to do to get it to work. My hobbies require me to print things, but I don't want my hobby to become tinkering with my printer. The MK3S was the closest thing I could find to a commercial printer that I could afford. I just don't know about the MMU2S yet.