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GRBL and a polar machine

Discussion in 'Control Software' started by ChrisSmith, Dec 10, 2018.

  1. ChrisSmith

    Builder

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    I am billing a sand plotter - it has a couple of stepper driving a rotary table and a concentric rack and pinion. I have been playing around with a RAMPS board and GRBL which is an easy way to run the steppers. I am
    I am billing a sand plotter - it has a couple of stepper driving a rotary table and a concentric rack and pinion. I have been playing around with a RAMPS board and GRBL which is an easy way to run the steppers. I am going to drive the whole thing from a PC so I can convert XY coordinates to polar but am have a real issue working out homing and the fact that the X (rotary) axis is effectively unlimited. Was thinking that I could just watch for the X axis crossing zero and then reset to GRBL X coordinates to 0.

    Has anyone done anything like this? Any hint on setting the coordinates?


    Thanks


    Chris
     
  2. David the swarfer

    David the swarfer OpenBuilds Team
    Staff Member Moderator Builder

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    'home is where you turn it on' is probably the easiest.
    in other words, no home switches and homing not enabled in GRBL.
    thus the machine coordinate system (home) is defined as wherever GRBL booted, which can happen at power on, when the PC GUI connects, or due to a reset switch push.

    after boot you can fine tune the 'part zero' and use the GUI 'set zero here' buttons to set the Work Coordinate system so wherever you need it.
    If you do not turn soft limits on you will then be able to move the machine in any direction with only the internal GRBL number format limit as the limit. IIRC this is 32 meters of travel. if you cannot do your sand plot in that space then you are probably doing something wrong (-:
     

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