16 Extruder switch problem



  • Hi everyone,

    I am currently building a printer with the following spec's (components on hand or in shipping land somewhere):

    Frame: 1524mm x 914.4mm
    Build Area: 1219.2mm x 609.6mm x 596.9mm
    Build Plate: 1219.2mm x 609.6mm x 596.9mm x 12.7mm mic5 aluminum plate
    Z-Axis: 4 x 16mm ballscrews, 1 stepper
    Single Gantry carrying 2 steppers
    Print Head: 2 IDEX with 2 Kraken's each (16 water cooled heater blocks)
    Extruder: 16 titan extruders, bowden style
    Controller: Duetwifi + Duetx5
    Filament: only ABS

    Realizing that 12 is the maximum supported drivers, I reduced the IDEX from 4 to 2 so that 8 colors per print is available.

    My question:

    Is there a way to "auto-change" the extruder that is on a given driver? Even if it is manually wiring toggle switches? Or is there a better solution available?

    I appreciate any help that you guys can offer.

    This shows a partial assembly of the printer before it was disassembled yet again. Hopefully for the last time.

    https://drive.google.com/file/d/0Byg_-gI-koMTVEJSZEY0enNtV0U/view?usp=sharing


  • administrators

    A switch would work but you need to ensure the motors are powered down or you risk blowing drivers. There are more complicated solutions such as multiplexing the output signals but that requires electronics to be designed.



  • @llynch:

    …..................................................................
    Controller: Duetwifi + Duetx5
    Filament: only ABS

    Realizing that 12 is the maximum supported drivers,...........................................

    The Duetwifi has 5 drivers and the Duex5 also has 5. I make that 10 max, not 12 (unless I've missed something).


  • administrators

    David added support for two more drivers to pins on the CONN_LCD header - obviously requires external drivers.



  • Could make a stepper multiplexer like the Prusa MultiMaterial uses.

    For 16 steppers we're looking at 64 mosfets + connectors and passives 🙂

    Tony/ David - could the duet be made to output a binary signal (in this case 0-15 across 4 digital pins) so that a 4–>16 decoder code be used on the mux? This would have to be in response to the T0-T15 that it gets for the tool changes.

    @llynch Do you have 4 krakens, individually movable? Do you want to be able to print 1 nozzle max at once or be able to do ditto printing with 2 or more nozzles in play at once? The latter would involve multiple muxes, perhaps up to 4 muxes so that 4 kraken could be in play at once. Here we would be looking

    This was a kinematics concept I came up with I call IQEX (independent quad extruder).

    I originally wanted to do a full on "dual idex" with 2 IDEX y rails... which resulted in 11 motors, but this is before support for 12 was added so I whipped this up which brought it down to 9 motors.

    https://www.duet3d.com/forum/thread.php?id=1862

    Anyways… you can now do a full dual idex with 11 motors, I recommend using the 10 inbuilt drivers between the duet and the 5 expansion for everything except Z which I would do on 1 external driver.

    Electrically, with 8 free gpio pins (4 sets of a 2 pins on duet --> 4 channels decoder on the mux)

    All that said, I haven't yet thought about how to control 16 heaters and thermistors natively.

    I'm just working on straight up y splitters. I do have a kraken as well, but only one.



  • @Tony: Thanks, multiplexing is the word I was missing. I immediately found one method using a 8 relay module to control 6 steppers using to drivers.

    Schematic and Code: http://www.marlinkimbra.it/?p=698

    Automationtechnologiesinc 8 relay module: https://www.automationtechnologiesinc.com/products-page/cnc-parts/8-channel-dc-5v-relay-module-arduino-raspberry-pi-dsp-avr-pic-arm/

    At $10.00 US a piece, at first glance would appear to be the ideal solution for the steppers heaters and pt100's. Though I am not sure if there is enough io (duetwifi with duex5) to call each individual relay or if there are any other limitations that are escaping my notice.

    Would relays solve it?

    @raykholo:

    The Prusa solution uses the y-splitters right?
    If I understand correctly it would reduce the number of Kraken's but would increase time to switch to a different color depending on how far away the extruder/y-assemblies are. Is their circuit schematic open? I would like to see how the mosfets are used in their solution.

    I do have have 4 Krakens with 2 rails on a single gantry, each rail with 2 bearing blocks… 1 kraken per bearing block, but with enough room (I think) for 2 krakens per bearing block.

    The concept was to have them individually moveable and using only 1 nozzle at a time during a single print. But being able to switch to a different nozzle/color during that same print.

    My mind turns to mud when trying to hold the idea of 4 independent krakens printing at the same time.
    What are the challenges and benefits of that configuration during a single print?
    If it helps reduce print time I am all for it.



  • @llynch:

    The concept was to have them individually moveable and using only 1 nozzle at a time during a single print. But being able to switch to a different nozzle/color during that same print.

    My mind turns to mud when trying to hold the idea of 4 independent krakens printing at the same time.
    What are the challenges and benefits of that configuration during a single print?
    If it helps reduce print time I am all for it.

    Having been down the road of using separate hot ends/nozzles on my aged Mendel tricolour, and now using a Diamond mixing hot end, I feel qualified to have a stab at answering that. As well as the loss of X and Y travel which you've obviously thought about, I'd say there are two main issues that you'll be faced with. The first is getting all the nozzles at precisely the same height (within 0.1 mm or better). A single Kraken is pretty much a nightmare so 4 is going to be a real challenge. The second big issue is fighting ooze from the unused nozzles. The usual approach is to set a lowish standby temperature then switch between active and standby but you have to wait for the next nozzle to heat up. You'll need some sort of wipe mechanism but that shouldn't be too difficult.

    Have you considered the idea of fitting two Diamond 5 colour hot ends? That would give you the possibility of using 10 colours with a lot less complexity. That may be too many extruders, so if you can settle for 6 colour, you could use two 3 colour Diamonds. Of course, the ability to mix filaments in theory gives you many more colours, but the mixed filament comes out like stripey toothpaste. This can be negated by using transparent filament but not every object lends itself to that. There are other issues with Diamond hot end so it's not as straightforward as it sounds. One that I have learnt recently is that PLA does not like to be kept at print temperature for half an hour or more without moving, but then you'd likely have the same issue with the Kraken unless you set a really low standby temperature, which will of course make the print time longer while it waits to heat up. At least with the Diamond, all the filaments are loaded so there is no waiting for one tool to heat up while another cools down, and of course the single nozzle means there are no Z alignment issue or X offsets to deal with.


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