Using two extruders on a long Bowden tube one assisting the other…

  • Using two extruders on a long Bowden tube one assisting the other…

    Basically we have a large printer with a very long Bowden tube about 5mt i have been using a single driver the one that would normally be for dual z axis motors with good success but of course after a few minutes printing the extruders would slip (2x E3D Titans) each 2 meters roughly apart wired in series on the dual output for the z axis just mapped as an extruder instead. The solution i had was to shorten the tube and extend the wires for reference we are using shielded igus 4 core but then the motors started acting rather strange they would intermittently work or stall or you could change direction with manually counterrotating the motor mid process my thoughts were this was due to the higher resistance and differential currents for the motors as they were effectively further awn in terms of wire length so i tried turning up the feed power to no avail. so i then wired them up as separate drives i.e. each motor has a mapped drive for the same tool or hot end 2 or 3 extruders for one hot end... but an error popped up when i was on the print screen that looks as follows

    ! M120
    G1 E-10 F2400

    Wrong number of extruder drives for the selected tool: G1 E-10 F2400

    But when i checked on the tool library in the online menus the controls reflect 2x active drives and the hot end heats up and shows correct temps etc so I'm stumped

    i followed the guideline in the documentation

    M563 P0 D0:2: H1 ; create a tool using extruder drives 0, 2 and heater 1

    Please can someone let me know whats going on ?

  • administrators

    You will need to enable mixing for that tool and set the mix ratio to 100:100. See the M567 and M568 commands.

  • Thanks DC42 so in my example above i should add in the Config.g

    M568 P0 S1

    M567 P0 E0.0:0.2:100:100

    ? and where will this need to be placed in the config near the top or near the extruder config section again thanks

  • administrators

    The mixing command needs to be:

    M567 P0 E100:100

    because the mix ratio refers to the 2 extruder drives you have configured for the tool. Put this and the M568 command somewhere after your M563 command.

  • Just out of curiosity, as I understand it from your description, you have a roll of filament some unknown distance (presumable short) between that and the first extruder, then around 2 metres of Bowden tube feeding into a second extruder, then around 3 metres of Bowden tube to the hot end. Is that Correct? So my question is, why do you need the first extruder? Is it because there is too much resistance through the 3 metres of Bowden tubing from the second extruder to the hot end? A picture or sketch would help my understanding if that is possible.

  • Almost sounds wise to use a larger diameter PTFE tubing for the longer run and then standard size for the shorter run. The idea being the longer run with the larger diameter will have less surface area contact and less friction. I'm assuming this is to keep out moisture, dust, dirt, etc.


  • The issue i was having is I'm using cable chain with a fairly tight bend radius so we needed assistance across the length due to slippage and the issue with using the larger diameter tube is fitment within our chain although we may heed the advice and give it a try if the new solution fails to work please bare in mind the main reason for having an extruder closer to the hot end is for flexible filament while using the kraken so no room for direct extruder above the hotends unfortunately.

    dirt and debris should not be an issue in the tube due to a two stage filament wipe

    i will update when I'm with the printer thanks guys for the feedback/advice all duly noted


  • Post a picture of the printer some time if you can. I might have a suggestion but I'd need to visualise the layout.

  • @deckingman:

    Post a picture of the printer some time if you can. I might have a suggestion but I'd need to visualise the layout.

    Yah a picture certainly would help.


  • Right guys I'm just getting the motor to rotate but i get buzzing sound and when i put a bit of force against it rotating it skips back and forth in direction until it recovers and continues in correct direction tried turning up the amps

  • Small update when i use the smaller length wired motor on the same drive output it behaves as normal

    could this issue be the wire ? because i have small gauge wire to thicker then thiner stepper wire again ?

  • administrators

    The behaviour is consistent with an intermittent connection (beware that can also blow a stepper driver).

    I would replace the connection to the motor that is misbehaving with a single run of wire.

  • Ok tony i will do a continuity test tonight for all wires

    Also notice that when they are both connected the one with the trouble just buzzes and the other one is unaffected

    If someone could send a picture of the duet with the drives numbered from above say what the stock z is numerically

  • Done the continuity test and all 4 wires test fine and no weird resistance between coils so I'm kinda stumped when i get home i will upload picture of the gantry

  • Perhaps one pair of wires flipped ? You said the motor moves at times…so odd. If one phase is wired backwards you can get that just buzzing sound with no movement. Actually it's more like a grinding noise most of the time.


  • A picture or sketch of your configuration would be extremely helpful, as posted above. Show interesting but can't visualize the reason for needing to layout components in the manner described. So yes, please post picture whenever possible and hopefully thereafter we'll be able to help out further.

    Hoping everyone is having a nice day!

  • How do you upload pictures on here not used to this forum format ?

  • @CLA:

    How do you upload pictures on here not used to this forum format ?

    Try putting it on google drive or dropbox or some such, then post a link.

  • excuse the untidy wires etc still plenty of messing about before tidy up

  • Let me help out a bit with the images.

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