Core XY with dual gantries using a duet wifi



  • Hi,

    Just toying with an idea, I'd like to build a D-bot coreXY with dual moving gantries (but only one at a time actually moves). The idea would be to have a E3d aero (or something) for most use incl flexible printing so the form and mass is minimalised to keep the speed up, but then have a e3d chimera or even a e3d kraken for "complex" items on the second gantry where I need supports or maybe multicolours. So the idea is one or other would be parked at opposite end of the axis while not in use. (dont ask about the belt layout its mind boggling and probably just a crazy idea for later on, or just plain crazy and will never work/happen!

    So the duet wifi would have to power 2 pairs of X and Y steppers and potentially 3~5 extruders by clicking the tool to use? is this possible to link up? Could the software handle such a config? if not well the idea is dead.

    Looking at the hardware…......duet5x addon this would run 3 of the nozzles on the kraken and the two extra X and Y steppers, the base duet wifi board has a spare extruder stepper for the last kraken nozzle so physically it looks like it can be done?

    I'd need 3 pt100 daughter boards to run 5 sensors, that seems Ok as well?

    Has anyone tried this sort of architecture/config? or maybe its just better to go to a Delta (or something else) with a kraken on it? or maybe just build 2 printers, LOL...


  • administrators

    Dual (or greater) movement axis are supported in cartesian printers. have a look at this:

    https://duet3d.com/wiki/Configuring_multiple_independent_X-carriages_on_a_Cartesian_printer

    So a setup like the BCN Sigma or the IDEX bigbox works well. The issue with CoreXY, as you have pointed out, is that you need to use two sets of axis, XY and UV for example. That makes it mechanically more complicated for a start.

    I think it would be a better solution to use an IDEX configuration where the X carriage had the Aero and your U carriage had the Chimera/cyclops/Kraken/Diamond hotend. This is mechanically much simpler and already supported in firmware. This also has the advantage that you can do "ditto printing" (printing the same object with both hotends at the same time) as long as you level the hotends.



  • Hmm yes this might be simpler, except with 2 moving heads on the moving gantry the mass goes up so maybe not. I might as well just fit a kraken on 1 gantry and be done with it.

    http://www.thingiverse.com/thing:2073946



  • So just to be clear for stupid ppl like me, the duetwifi can with the present firmware support 2 moving gantries as X and U as a core XY - IDEX?



  • So in terms of high level architecture / outcome is a IDEX a good way forward or is a delta carrying 4 heads going to give the better solution?


  • administrators

    @gzcwnk:

    So just to be clear for stupid ppl like me, the duetwifi can with the present firmware support 2 moving gantries as X and U as a core XY - IDEX?

    No, some firmware work would be needed to define which motors control the U axis.


  • administrators

    @gzcwnk:

    So in terms of high level architecture / outcome is a IDEX a good way forward or is a delta carrying 4 heads going to give the better solution?

    Personally i would avoid the issues caused by multiple nozzles, by using a Diamond hot end instead of a Kraken. If you want a separate extruder for support material, then IDEX.



  • @dc42:

    Personally i would avoid the issues caused by multiple nozzles, by using a Diamond hot end instead of a Kraken. If you want a separate extruder for support material, then IDEX.

    You can also use a different material for supports with a Diamond hot end.


  • administrators

    @deckingman:

    @dc42:

    Personally i would avoid the issues caused by multiple nozzles, by using a Diamond hot end instead of a Kraken. If you want a separate extruder for support material, then IDEX.

    You can also use a different material for supports with a Diamond hot end.

    Doesn't support filament usually need a different extrusion temperature?



  • @dc42:

    @gzcwnk:

    So just to be clear for stupid ppl like me, the duetwifi can with the present firmware support 2 moving gantries as X and U as a core XY - IDEX?

    No, some firmware work would be needed to define which motors control the U axis.

    That said, if someone would be willing to solve the mechanics of a dual coreXY and actually build it, would it be interesting to create firmware support for that?

    Like gczwnk said, it would allow for very low moving mass and independent extruders. If we look at current independent extruder systems the Y-axis gets very heavy very fast. As an extreme (and also what I would like to run), imagine dual independent direct drives. On a dual coreXY the moving mass on Y could be something as low as 250g, whereas on a current system we would most likely approach 1kg πŸ™‚


  • administrators

    Yes, it would be interesting to support 2 moving gantries. In effect, each tool would be a separate CoreXY machine except that they would share the Z axis. We'd need to map the Y axis to the V axis on the second tool, and define the U and V positions as being defined by the U and V motors in the same way as X and Y. It doesn't sound difficult.



  • @dc42:

    @deckingman:

    @dc42:

    Personally i would avoid the issues caused by multiple nozzles, by using a Diamond hot end instead of a Kraken. If you want a separate extruder for support material, then IDEX.

    You can also use a different material for supports with a Diamond hot end.

    Doesn't support filament usually need a different extrusion temperature?

    Yes but that's not a problem. Just use different active and standby temperatures for each tool. Of course one has to set the mix ratios to 100% for each tool(filament). It's just the same as having separate nozzles. If the "inactive" tool isn't extruding, there won't be any oozing/mixing (well not noticeably). Also, I think E3D's scaffold is best printed at 215 so you could probably print PLA and Scaffold at the same temperature - haven't tried it though.

    Edit. I have printed something in PLA at 195 with a "T Glass" window printed at 235 with the Diamond - worked fine.



  • @vvonplaten:

    That said, if someone would be willing to solve the mechanics of a dual coreXY and actually build it, would it be interesting to create firmware support for that?

    Like gczwnk said, it would allow for very low moving mass and independent extruders. If we look at current independent extruder systems the Y-axis gets very heavy very fast. As an extreme (and also what I would like to run), imagine dual independent direct drives. On a dual coreXY the moving mass on Y could be something as low as 250g, whereas on a current system we would most likely approach 1kg πŸ™‚

    For info, I run a Diamond hot end on a coreXY which alone weighs 250gms. I've lightened the axes a bit by going from dual X rails to a single rail but I'm not happy with the stiffness (or lack of) so I'll be reverting back to dual rails. So the total X carriage with fans and the Diamond hot end etc weighed 690 gms (without the 3 off extruders). The Y axis including the X rails but without the X carriage weighed a further 1,210 gms giving a total Y axis weight of 1,900 gms. On top of that, I have 3 extruders suspended above the centre of the bed with a counter balanced pulley arrangement. Although the weight is counterbalanced, they still have to be dragged around. Despite all that, I still print at 90 mm/sec no probs, with non print moves of up to 300 mm/sec. Although I'd like to reduce the weight if possible, I have to say that I've never had a problem with ringing - I think it's all just too heavy and stiff to resonate.:)



  • Well to do a dual gantry, I assumed there would be 4 steppers, one for X and one for Y for gantry1 and then one for U and one for V for the gantry2.

    With a d-bot design using openbuilds 2040 and some 3d printing it wouldnt cost much to make such a test setup. Not sure if it achieves anything NET good, mind you it would look cool πŸ˜„



  • @dc42:

    @gzcwnk:

    So just to be clear for stupid ppl like me, the duetwifi can with the present firmware support 2 moving gantries as X and U as a core XY - IDEX?

    No, some firmware work would be needed to define which motors control the U axis.

    Um so it would be 2, actually U and V? I sort of assumed the gantries and belts and steppers would be totally independent of each other.



  • I’m currently (slowly) building a dual carriage core-xy printer. The kinematics were described in http://forums.reprap.org/read.php?397,737863 over at reprap forum and David wrote a bit about what would need to be implemented in firmware.
    Would love to see the Duet/RepRapFirmware support it!



  • I'm struggling to get to grips with this idea. From what I can ascertain, to keep the axes on the same plain, they share a common Y but have different X axes. This means that the X axis must be very wide and /or one would lose a lot of travel. So, the only advantage I can see over simply fitting two hot ends to a single X carriage is that there would be a weight saving on one of the X axes. However, the Y carriage would still have to move both the X axes so the Y axis weight will be the same. Therefore any speed advantage would be limited to pure X moves which is unlikely to have much of an impact on the total time it takes to print something. It seems a lot of complexity for very little practical gain or have I missed something?



  • Well, you do have 4 steppers contributing to z-axis movement and 2 for x-axis. Although you have to move shafts and the two hotends for z-axis movement and only a hotend for x-axis. Differences in z offset of the two hotends should not be a problem using two carriages and you could use two very different hotends if you find that useful.



  • @dc42:

    Yes, it would be interesting to support 2 moving gantries. In effect, each tool would be a separate CoreXY machine except that they would share the Z axis. We'd need to map the Y axis to the V axis on the second tool, and define the U and V positions as being defined by the U and V motors in the same way as X and Y. It doesn't sound difficult.

    Yes, that is exactly what I'm thinking of! Time to start setting it up in cad then! πŸ™‚



  • Ahh.. two gantries, I was thinking one gantry (shared Y and Z and independent X). I’m too preoccupied with what I’m building so I missed that part, sorry πŸ˜‰



  • @vvonplaten:

    @dc42:

    Yes, it would be interesting to support 2 moving gantries. In effect, each tool would be a separate CoreXY machine except that they would share the Z axis. We'd need to map the Y axis to the V axis on the second tool, and define the U and V positions as being defined by the U and V motors in the same way as X and Y. It doesn't sound difficult.

    Yes, that is exactly what I'm thinking of! Time to start setting it up in cad then! πŸ™‚

    I still can't get my head around the mechanics of how this would work. I can't see how you could have the gantry's on the same plane without one interfering with the other. Unless, the gantry's are stacked one above the other? But then you'd have to somehow deploy one hot end to move in Z by the thickness of one of the gantry's. I just can't picture it in my mind - be interesting to see a design.

    I am in fact working on a stacked gantry design but that's a just a way of trying to mount 3 extruders above a diamond hot end whilst keeping the footprint small and the Bowden tubes short. In this case, both gantries will be active at the same time and the second gantry would probably be passive - i.e. linked to the lower gantry but without any motors or belts of it's own.


  • administrators

    I presume you would part park one gantry at one end of the Y axis while you use the other one. Just as on an IDEX machine you park one X carriage at the end of the X axis while you use the other one. The printable length of the Y axis for each head would be reduced by the amount of space taken up by one gantry, and the printable length accessible to both heads would be reduced by the amount of space taken up by both gantries.



  • @deckingman:

    @vvonplaten:

    @dc42:

    Yes, it would be interesting to support 2 moving gantries. In effect, each tool would be a separate CoreXY machine except that they would share the Z axis. We'd need to map the Y axis to the V axis on the second tool, and define the U and V positions as being defined by the U and V motors in the same way as X and Y. It doesn't sound difficult.

    Yes, that is exactly what I'm thinking of! Time to start setting it up in cad then! πŸ™‚

    I still can't get my head around the mechanics of how this would work. I can't see how you could have the gantry's on the same plane without one interfering with the other. Unless, the gantry's are stacked one above the other? But then you'd have to somehow deploy one hot end to move in Z by the thickness of one of the gantry's. I just can't picture it in my mind - be interesting to see a design.

    I am in fact working on a stacked gantry design but that's a just a way of trying to mount 3 extruders above a diamond hot end whilst keeping the footprint small and the Bowden tubes short. In this case, both gantries will be active at the same time and the second gantry would probably be passive - i.e. linked to the lower gantry but without any motors or belts of it's own.

    Like dc42 said, I'm thinking of dual gantries. A bcn3d sigma for example uses one Y-gantry where two X-carriages live. Imagine instead two independent Y-gantries with one X-carriage each. Each gantry+carriage is controlled by its own set of steppers.



  • @dc42:

    I presume you would part park one gantry at one end of the Y axis while you use the other one. Just as on an IDEX machine you park one X carriage at the end of the X axis while you use the other one. The printable length of the Y axis for each head would be reduced by the amount of space taken up by one gantry, and the printable length accessible to both heads would be reduced by the amount of space taken up by both gantries.

    Yes that was the idea, ie parking a complete gantry each end was forming in my mind. The original Dbot is a 300(x)x300(Y) corexy printer but its made from openbuilds 2040 so its easy to re-dimension (cut). My original idea was to build something big enough to print my own storm trooper armour parts in one piece (to save glueing) for that I need 500~550mm in one dimension of X or Y and 450~500mm high and then maybe cut it back to something more physically manageable later if need be.

    Being lazy the 2040s come in 1500mm lengths so I just chopped up 2 lengths and ended up with 4 x 750mm pieces and did the same for Z and there is the frame https://ibb.co/dtCE35. I just added the HGR15 Linear rail on top yesterday giving an absolute max stoke of 670mm, or around 600mm~630mm NET stroke. So the linear rails came with x2 boggies each anyway so I have added these both to the top rail since two were spare. https://ibb.co/bKvqbQ The second gantry will cost me 75~100mm at most if I hand and overhand them so on Y so I think I'm still OK for 550mm, Worst case I have to buy a bit more 2040 (4 x 1m), about $40US worth, that is not going to break the bank.

    So structurally I am set, linear rail I am set, next and biggest nightmare is somehow running 2 sets of belts, hello fusion 360 and some evenings not to hard, its the multi-dimensional curves that drive me nuts. The last part will be the firmware to allow it to work. Would there be anything else Ive missed?

    As an aside unlike the wanhao pile of crap mainboard that lasted 3 months (that would have cost me $165US to replace and they are dying like flies due to bad relays) v the duetwifi at $200US has well proven itself, its quiet and the web gui is just nice.



  • Hello im also thinking of dual extruders πŸ™‚
    i like this ide
    http://www.thingiverse.com/thing:1446731
    that way you dont need extra steppers motors
    only need a way to power 2 magnets in the tool change script
    is there a way to send a signal to the magnet to turn on/off

    for example the tool script will do something likt this
    ->move left turn of magnet #1 (park extruder1)
    ->move right turn on magnet #2 (get extruder2)
    ->print

    here is the magnet
    https://www.aliexpress.com/item/16-25-Holding-Electric-Magnet-Lifting-2KG-20N-Solenoid-Sucker-Electromagnet-DC-6V-12V-24V-Non/32763680868.html?spm=2114.13010208.99999999.262.V23JLP

    see here
    https://www.youtube.com/watch?v=FiTmRHkiEUg

    sounds simple … πŸ™‚


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