Multiple Z Axis Possible?

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  • February 2, 2016 at 12:06 pm #9322
    mrwildbob
    Member

    In my CNC build, my goal is to make a fully automated machine. I was wondering if it was possible to have multiple Z Axis. Axis Z1 would have a spindle for engraving and axis Z2 would have a spindle for drilling holes as well as an offset stepper motor geared down to cut threads using a tap.

    The TinyG has 4 motor ports but is capable of doing 6 axis. To get the other two ports can I use another TinyG or gShield and connect them together (master/slave configuration)?

    thanks

    boB

    February 2, 2016 at 6:58 pm #9324
    cmcgrath5035
    Moderator

    The TinyG has 4 motor ports but is capable of doing 6 axis. To get the other two ports can I use another TinyG or gShield and connect them together (master/slave configuration)?

    In theory you can have master/slave tinyG’s (not GShield here).
    I have not seen anyone talk about it, which begs the question of how well it might work.

    You might want to peruse tinyG2,

    With a Due you can fully decode 6 axis motion, but you would have to come up with custom motor drivers.

    I am not at all sure how you would implement two Z xais setups mechanically, a ‘simple solution’ would be to have different config files, one that assigned motor 4 to Z1 and Motor 5 to Z2.
    Challenges that remain are only one set of spindle control ports (PWM ports) and finding something to generate Gcode for it.

    February 3, 2016 at 11:50 pm #9328
    mrwildbob
    Member

    Last night when I was in bed, I had an idea.

    My CNC machine is not your typical machine. It will only have one purpose. My axis assignment is based on the orientation of the part to be worked, so it might not sound correct but the Z axis is a conventional Z axis. As far as the mechanics, I will make two Z axis back to back.

    After starting the job the machine will position the Y axis to a specific location. Then Z2 axis will drill a hole, then move the Y axis to the next position and tap the hole for a setscrew. Z2 will go back home, then Y axis will move to the final position for engraving. The Z1 axis will then engrave the part with the design. When the job completes, all axis return back home and wait for the next part.

    My solution: Use a TinyG and gShield and create a hybrid machine using two independent controllers. They don’t even need to know the other is there. At each process, I only need to talk to one controller at a time. The TinyG would control the X, Y and Z1 axis and the gShield would control the Z2 axis and tapping stepper only. Since the Z2 axis is just a drill and a tap, I can setup the python script to send the first instruction to move the Y axis to the correct location and wait there. Then the script will send the next gcode commands to the other controller and drill and tap. When those commands are done, control is back to the TinyG and it will finish the job with the engraving. I know this setup sounds weird, and it is, but I am focusing more on automation at this point. I plan to hand code most of the gcode anyway or create parts using a program and then modify for my needs. As far as spindle control goes, both spindles have controllers with pots on them. I could set the speed with them and forget about the PWM. I will use a relay board to turn on the spindles.

    Once I get all this figured out and built, I am going to document and possibly make a video.

    boB

    February 4, 2016 at 5:29 am #9330
    cmcgrath5035
    Moderator

    Sounds feasible and very reasonable approach for someone able to glue it all together with the right code.
    Good luck with your project.

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