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 hardwareโ€ฆ......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 ๐Ÿ™‚


  • 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 ๐Ÿ™‚

    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 ๐Ÿ˜„



  • @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.



  • Iโ€™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! ๐Ÿ™‚



  • Ahh.. two gantries, I was thinking one gantry (shared Y and Z and independent X). Iโ€™m too preoccupied with what Iโ€™m building so I missed that part, sorry ๐Ÿ˜‰


 

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