Printer architecture



  • Hi!

    I'm currently building a 3D printer with a duet board. I will have a five filament PLA diamond hotend and a PVA extruder. I will need more extruders and hotends later so I need something with evolution possibilities. I'm currently a bit lost when thinking about what architecte to use. Carthesian? Delta? CoreXY? I dont like to have a moving bed so do you have any idea about the most adapted architecture and why?

    Thanks.



  • Where do I start? I guess you ought to take a look at my blog which is linked in my signature. You'll find that especially useful if you are thinking of going for the 5 colour Diamond.

    Not sure that understand what you mean by "five filament PLA hot end and PVA extruder". You'll need 5 extruders in any case.

    A couple of things to bear in mind. The hot end is heavy - very heavy, and also big - very big. Direct drive extruders would make it impracticably heavy and big so Bowden tubes or flexible drives are the way to go. IMO a Delta would not be the best choice due to the weight and size of the hot end as well as the effect that 5 Bowden tubes might have on effector tilt. Cartesian or CoreXY - either would work but having a bed that is stationary or only moves in Z is easier with CoreXY IMO. Because of the mass that you will be throwing around, the frame needs to be substantial and rigid. Due to the size of the hot end, you need to make the frame overly large to accommodate your desired X and Y travel. This means that if you mount the extruders on the frame, then the Bowden tubes will be very long which is not desirable. See my blog for my solution but it's not cheap to implement.



  • I will need 6 extruders, 5 for the fullcolor diamond hotend and one for the PVA, they will be on two different heads.

    I think I will go toward a coreXY architecture but what's the n'est between a stationary bed or an X-moving bed?

    Also, I saw somewhere that you can use the same driver for multiple X motors. Is that true?


  • administrators

    Definitely go with Cartesian or Corexy. Given the size of your hotend assembly I assume you are going to have a large build area ( how big?) As the build area grows having a moving (in X or Y) becomes less and.less.of a good idea.



  • @PtitLu:

    I think I will go toward a coreXY architecture but what's the n'est between a stationary bed or an X-moving bed?

    Take a look at this on my YouTube channel https://www.youtube.com/watch?v=vG1WqijJ634. I doubt very much if that would be possible on a bed that moves in X.



  • Initially I was planning a 300x300x400 build area, maybe more if I can. I will go to corexy.
    Do you know if it's realy possible to have multiple X motors for the same driver?



  • @deckingman:

    Take a look at this on my YouTube channel https://www.youtube.com/watch?v=vG1WqijJ634. I doubt very much if that would be possible on a bed that moves in X.

    Do your bed moves in Z?



  • @PtitLu:

    Do your bed moves in Z?

    Yes. It's easier than moving the CoreXY (especially when you have two CoreXYs stacked one above the other as I now do - https://somei3deas.wordpress.com/my-corexy-printer-build/5-colour-upgrade/)).



  • @PtitLu:

    Do you know if it's realy possible to have multiple X motors for the same driver?

    If it's CoreXY then both motors contribute to movement so I don't understand why you wound want multiple motors for X alone. Unless of course you mean multiple X axes in which case you need to look at IDEX designs -(possible but not easy with CoreXY).



  • My question is "is it possible to have multiples motors for one axis if there is a lot of weight and is it possible to use only one driver for all of them?"



  • @PtitLu:

    My question is "is it possible to have multiples motors for one axis if there is a lot of weight and is it possible to use only one driver for all of them?"

    Yes you can do that but it's not necessarily going to gain you anything.

    Also, even with a massively heavy hot end such as the Diamond 5 colour, a single Nema 17 is more than adequate in practice.



  • OK, that's good to know. Maybe it will ne usefull for the Z axis.
    I saw you use direct extruders with your diamond, is it possible to use bowden to reduge the weight or it's a bad idea?



  • @PtitLu:

    OK, that's good to know. Maybe it will ne usefull for the Z axis.
    I saw you use direct extruders with your diamond, is it possible to use bowden to reduge the weight or it's a bad idea?

    Look again, they aren't direct and I do use Bowden tubes. However, because my frame is 600mm square, if I'd mounted the extruders on the frame, I'd have had Bowden tubes about a metre long which in my opinion, would likely cause all sorts of problems. So I've mounted the extruders close to the hot end. Initially, they were slung on a sort of counter balanced arrangement, later I mounted them on their own carriage but passively driven, then finally I made the carriage actively driven so effectively I have two CoreXYs, one above the other. The Bowden tubes are only about 200mm long.

    Rather than use multiple motors and a single driver chip, the other thing you can do is map multiple motors, each using their own driver to a single axis and each one receives identical signals. That is how my double CoreXY is driven. So X uses drives 0 and 3, Y uses drives 1 and 4 and Z uses drive 5. As far as the electronics are concerned, it is a single CoreXY but in practice the upper CoreXY which holds the 5 extruders exactly mimics the movement of the lower CoreXY which holds the hot end.



  • OK so that's why you have two things moving. There's just a thing I don't understand, have you two Y motors on each corexy (see the image)? Lastly, how many Z motors do you have?



  • Yes, correct (sort of). On a CoreXY and with Duet electronics, the motors are still referred to as X and Y. However, if just one motor turns, the carriage will move at 45 degrees - so in both the X and Y directions. To get movement in just X or just Y, you drive both motors. See here http://corexy.com/theory.html.

    Technically the motors should be called alpha and beta or delta A and delta B rather than X and Y (sorry can't off hand find the correct symbols on my keyboard).

    In the image above, the lower left and right motors are delta a and delta b for the hot end CoreXY and the upper left and right motors are delta a and delta b for the extruder CoreXY.

    I have a single Z motor which drives 3 lead screws via a continuous belt. The Z motor is fitted under the plate bottom front of the image.

    That's the 5 stepper drivers on the Duet main board. I have a Duex 5 expansion board for the 5 extruders so that's me maxed out for steppers until the next generation board comes out.



  • Is there any major differences betweens multiple motors on the same driver and map different motors? I need 6 extruders so I can't have two ∆a and ∆b motors.


  • administrators

    You can use an two more external drivers on the CONN_LCD header with recent firmware

    That would allow you to drive your 6th extruder.



  • @PtitLu:

    Is there any major differences betweens multiple motors on the same driver and map different motors? I need 6 extruders so I can't have two ∆a and ∆b motors.

    I'd have thought that in simple terms a driver chip is capable of providing x amount of power so if you use two motors, each one would only have half the power of the driver chip available but I'm not sure if it works that way. No doubt someone with more knowledge than I will step in and correct me. Having said that, the driver chip may still be capable of supplying sufficient power for your needs to two motors. Before I instigated the second CoreXY mechanism, I had the extruders mounted on a carriage in such a way that they were passively "dragged around" by the hot end, so effectively one set of driver chips was supplying sufficient power to move both the hot end and the extruders (but I only had 3 extruders at that time, not 5).



  • Something else has just occurred to me. Are you intending to use both heads at the same time or are you planning on having a carriage that will take either head and swap between them that way? If it's the former, then you'll have a large offset between the nozzles because the heat sinks on the Diamond are angled out at around 22 degrees forming a circle of about 75 mm in Diameter. So depending on what the second hot end is, you'll have to allow around 50mm for the lost axis travel. If you don't need to use them concurrently, then you physically swap between them and use one of the 5 Diamond extruders for the other hot end.



  • I will use both heads at the same times, one for the main structure in PLA, and one for the support material in PVA.


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