Considering this 4 axis CNC w. 3polar axes



  • Hey guys, this is my first post, and inevitabely kind of a shot in the dark.
    There is a dental style "chairside" CNC mill for sale in my area. See link for some info:
    https://www.machinedesign.com/mechanical-motion-systems/article/21833590/belleverman-rotary-stages-usher-in-chairside-dental-crowns
    The machine has an envelope of 40x40x40mm, and obviously I wouldn't be machining much dental crowns with it 🙂

    The challenge I have on hand is that the machine has 3 polar axes and 1 cartesian, and I would need a firmware which can handle this. Next challenge would be me learning to tweak the firmware to work...

    I found this link, explaining how duet can be set up with polar coordinates, which in turn led me to this forum:
    https://duet3d.dozuki.com/Wiki/ConfiguringRepRapFirmwarePolarPrinter

    The tutorial leads you through how to set up one axis as a polar axis, but will the firmware handle 3? Plus 1 cartesian?

    The printer comes with a Delta Tau Clipper controller board, but the license for this alone is as expensive as the mill, so that is kind of out of the question...


  • administrators

    I am guessing that the milling head on the right moves in a left-right direction. If so then I suggest you treat that as the Z axis, to make it like a conventional milling machine with a tool that is lowered on to the work piece.

    To handle the other axes, one option is to generate GCode designed for rotary axes. Then you can set up the other axes as standard Polar or even Cartesian.

    If you want to add new kinematics so that you can send it standard XYZ GCode, there is a brief guide on how to do this at https://github.com/Duet3D/RepRapFirmware/blob/dev/AddingNewKinematics.md.

    HTH David



  • Hi David,
    Thank you, I really appreciate your answer ! It seems to me like you don't see any problems at all.. For a beginner like me though, it generates a couple follow-up questions.

    1. Sending polar gcode; Is this a matter of finding a CAM tool that supports designating polar axes to the tool paths, and that generates gcode accordingly? If so, would you consider this or cartesian gcode the most professional and hassle free, once I get going?

    2. Will the duet also handle the 4th axis, called indexer in the article ?

    3. Would you recommend a controller software for controlling the CNC and sending gcode to Duet?

    I apologize for any questions that doesn't make any sense.

    By the way, does any co troller software that works with Duet work with spi dle motor control, that is controlling the on/off and rpm of the spindle motor ?

    Thanks again,
    Edward


  • administrators

    I have no direct experience with CNC machines, so i can't answer your questions #1 and #3. Others on this forum may be able to answer them.

    Regarding question #2, RepRapFirmware supports up to 10 axes (soon to be up to 15) depending on which board you use.

    RRF supports CNC spindle control commands.


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