Ideal dual material setup?

Hi,

I am trying to decide which dual material setup is the most useful one for my situation. My main area of interest will be printing objects with soluble supports. I am not that much interested in dual color printing but dual material printing could also be interesting.

My actual setup uses the Y splitter commected to the hotend, driven by 2 Titans. If it is setup nicely, it can print nice 2 color objects and even support material. However there is a problem with this setup: Even with a big purge tower, I can't prevent a small amount of material mixing between thw two filaments. If you print in color, it slightly changes the color of both filaments, which is visible and a nuisance but not very very important. If you print with soluble supports, that becomes a huge problem because when the support is dissolved, the object's layers also start to separate as there is a small amount of support material mixed with the main material and it creates gaps and structural instability when dissolved. I also don't really like the Bowden setup required by this system. It is hard to control the filament flow.

The alternatives are:

A dual direct drive setup using 2 hotends. It will require some design change but it is doable .Using remotely controlled extruders (Flex3drive or Zesty Nimble), the weight could be kept to a minimum. The down side for this setup is that It seems that people have problems with leveling the nozzle heights and also oozing and scratching of the printed object by the inactive nozzle.

A Chimera or Cyclops with a remotely controlled extruder. It seems that Chimera is more suitable for support printing. It is a more compact design but I assume it has the same problems with the 2 hotend solutions, namely scratching and oozing.

A dual X carriage solution with remotely controlled extruders. Right now I am inclined to think that it is the best solution for dual material printing. The X carriages are moving independently and there would be no oozing, as the inactive head would be parked outside. Scratching could still be an issue bu should be a minor concern. This would require a majör design change on the printer, including a daughterboard for controlling an additional X motor, another GT2 belt, new X carriage design and probably chaning the entire aluminium extrusions to be able to preserve the same printable area. Is it worth it? I haven't seen many comparison videos or articles about how successful dual X carriages are.There should still be a problem with leveling nozzles and I have no idea if this setup is compatible with bed leveling solutions (BLTouch).

Any ideas / comments / suggestions are welcome.

The IDEX (dual X carriage solution) is probably the best solution, but also the most expensive. You don't need to get the nozzles exactly the same height unless you want to print 2 identical parts simultaneously using both hot ends, because each hot end can have its own Z offset. You can use bed probing and bed compensation.

There is quite a lot of discussion about this type of machine in the BigBox forum at e3d-online.

Edited 1 time(s). Last edit at 04/11/2017 09:40AM by dc42.

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

The one solution that would help you to avoid the second nozzle scratching is the autolift hot end by D3DGlass or so.

There the inactive nozzle is retracted automatically when the pressure of the filament is removed by retracting the filament.
That way you avoid a low nozzle scraping. They also have a way to set the height of the nozzles correctly.

And of course I warmly support your idea of using Remote Direct Drive extruders. :-)

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Lykle
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Co-creator of the Zesty Nimble, worlds lightest Direct Drive extruder.
[zesty.tech]

I have build a dual x printer and it is working just fine. It is not yet ready for release as open hardware, but as soon as the second prototype works as expected this is planed. You can find info on it on my website and youtube channel.

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[www.bonkers.de]
[merlin-hotend.de]
[www.hackerspace-ffm.de]

For me currently have parts flying in from china for a y splitter. Cost-benefit seems balanced with this setup however I think I have to give up PLA for that and start buying more PET/PETG

I just finished putting together a dual system with a filament splitter. It works quite well and so far the only problem I have had is adjusting the prime tower size to get good purging. I made my Bowden extruders using 5:1 geared stepper motors. They work extremely well.

Why not extend/retract direct drive extruders using a solenoid or short travel Z stage?

I'm not seeing any advantages of dual x stages over such a system. Splitting the weight across two X carriages does not provide any advantage because the Y axis still has to move the entire load and you want acceleration to be symmetrical across the XY axes or your prints will look different depending on orientation.

Quote
dc42
The IDEX (dual X carriage solution) is probably the best solution, but also the most expensive. You don't need to get the nozzles exactly the same height unless you want to print 2 identical parts simultaneously using both hot ends, because each hot end can have its own Z offset. You can use bed probing and bed compensation.

There is quite a lot of discussion about this type of machine in the BigBox forum at e3d-online.

Would it be possible to use 2 BLTouchs with Duet Wifi? I normally use a BLTouch for Z leveling and I also have a spare one in case one fails. In an IDEX configuration, I assume one could be used for bed leveling, while the other is used only to determine Z offset. I checked the wiring scheme for the BL Touch on Duet Wifi but there is no mention if it is possible to connect 2 of them (which is understandable, as it isn't common to have 2 Z probes). If not, what would be the alternative to the second BLTouch?

Also, that part where you are told to add a 240 Ohms resistor to the BLTouch wire in parallel: I am inexperienced with electronics so it is confusing a little bit: Do I have to take a 240 Ohm resistor, remove the plastic sheet around the wires, and solder one leg to each wire? Does it make a parallel connection?Which part of the wire should I use (I know that it doesn't matter but would it be easier if I wired it close to the connectors?).

The Duet WiFi can support two Z probes, but one of them must be able to sink about 1.2mA of current because it will be connected to an endstop input. I don't know whether the BLtouch can do that, it's closed source. In any case, you would still need to calibrate the trigger height of the second Z probe, so I don't think having two probes would gain anything.

Most people who build IDEX machines use a Z probe on one carriage only, and configure the Z offset of the second nozzle manually. If you want to be able to do ditto printing (i.e. print 2 copies of the same object at once using both heads), then you need to get the two nozzles at the same height anyway. So it's a good idea to design the hot end mounting system to make the height of at least one of the hot ends easy to adjust. The alternative hot end mounting system that E3D is prototyping may help with this.

I read that the later versions of BLtouch have a trace to cut for 3.3V operation instead of having to solder a resistor on.

HTH David

Edited 1 time(s). Last edit at 04/14/2017 07:36AM by dc42.

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

Quote
dc42
The alternative hot end mounting system that E3D is prototyping may help with this.

Do you have any link for that?

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drmaestro

Quote
dc42
The alternative hot end mounting system that E3D is prototyping may help with this.

Do you have any link for that?

[forum.e3d-online.com]

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

or use a cheap16mm rod support, people just need to have holes in the right place.
Though if the collar had some sort of internal cooling channels for fluids?
Got me thinking of trilobyte rework hmm, a water cooled block with 3 throat holes.

Edited 2 time(s). Last edit at 04/16/2017 12:01PM by MechaBits.