Multiple Z axis and complex tools, possible?



  • English isn't my native language, so please forgive me for wrong spelling and grammar. I'll try my best.

    I'm designing a custom 3d printer who would be a step forward from other that has become real and it's sucessfull working (w/marlin fw). It's a commercial product in fact.

    My design it's esentially a cartesian printer with a fixed bed, similar to a CNC router grantry, because there must exist a lab balance under the printbed, and an X carriage populated with 3 "extruder" tools.
    The tools could have different shapes, sizes and lenght, and should need to rise up indistinctly the idle tools while one of them is printing. I was thinking if assign a Z axis to each tool with a their Z probe (so i'll get 3 Z axis and 3 Z probes), or a common Z axis with a Z probe and three actuators (pancake stepper motors) to rise up the idle tools. Also I could need to have E-Endstops (min/max) in each tool for reference positions (E-home).

    It's possible to get one X axis, dual motor Y axis, and three Z axes plus 3 "extruder" motors with a Duet3, plus extension board(s) and CAN-FD tool boards on each tool? Too much?

    My concerns it's with the huge number of motors/axis and single/multiple Z probings with RRF and Duet ecosystem who I don't know so much. Tried before with Marlin (32bit 2.0.x) unsucessfully, not enough options and power also lack of controllers (ST

    In your expert opinion, which approach would be more appropriate? Is it even possible to wire and run this scheme?

    Thank you in advance.


  • Moderator

    You could use a stepper motor as a seperate linear axis (not necessarily Z) but call it U etc. You could then use the tool change files to command that axis to raise and lower the tool itself.


  • administrators

    Yes that should be possible. You can only have one Z axis at any one time, but you can switch Z to be different motors using the M584 command. Or (and probably better) you can have a single Z axis, and use axes U, V and W to raise and lower the tools. You can hide the additional axes except when doing a tool change.

    Duet 3 main board gives you 6 stepper motor outputs, after than you can add 3-driver expansion boards, and tool boards. The Duet 3 firmware build limits are currently:

    26 stepper motors (6 on main board + 20 on CAN-connected expansion and tool boards)
    10 axes (to be increased to 15 soon)
    16 extruders (with a limit of 20 axes + extruders)
    56 temperature sensors
    32 heaters
    4 Z probes
    16 fans
    32 GpOut ports
    16 GpIn ports
    2 CNC spindles

    We've tested up to main board + 3 expansion boards + 3 tool boards, but plenty more should be possible.

    HTH David



  • Ok, understood.

    Thank you @Phaedrux and David @dc42 for your advice. We'll go for the necesary hw to begin testing in our lab when boards back to stock in the shop. F**K coronavirus!

    Another question arise on our planning meetings it's if Can-FD "printheads" could been switched in hotswap manner or can be damaged, and also if could been set a unique "Tool ID" to recognize them back seamlessly (by software or pogo-pins detection, for example). I couldn't see anything like that nor in gcode nor in firmware documents reviewed, may requiring a new module development for tools management.

    Best regards,
    Marcos


  • administrators

    @Marcossf said in Multiple Z axis and complex tools, possible?:

    Another question arise on our planning meetings it's if Can-FD "printheads" could been switched in hotswap manner or can be damaged, and also if could been set a unique "Tool ID" to recognize them back seamlessly (by software or pogo-pins detection, for example). I couldn't see anything like that nor in gcode nor in firmware documents reviewed, may requiring a new module development for tools management.

    I can see two issues with hot-swapping print heads:

    1. When you first apply power to a tool board, there is a large current surge because of of the VIN capacitors charging. You could mitigate that using a NTC thermistor in series with each tool board VIN pin.

    2. Currently, RRF does not expect tool boards that have registered with the main board to go offline. We have not implemented a firmware hot-swap facility because there is a patent (currently owned by Stratasys AFAIR) covering hot-swappable tools connected via a CAN bus with pogo pins or similar.



  • Thank you very much indeed @dc42 David.


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