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Restore coordinates without homing?

Discussion in 'CNC Mills/Routers' started by qbota, May 31, 2023.

  1. qbota

    qbota New
    Builder

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    LEAD 1515 here. Normal procedure:
    1. homing (hardware: with end-switches)
    2. manually move to the place where work-piece "starts"
    3. set zero on x,y,z
    4. work.
    5. power off everything.
    Lets say that machine finished work on x=500, y=500, z=0.

    Next day I want to continue work. Note that work-piece is exactly in the same place, not touched.
    I turn on everything and Blackbox reports some crazy coordinates like X=1258, Y=1123, while I would expect it to report: X=500, Y=500.

    So I do homing and after homing is finished, things get better: Blackbox gives mi proper coordinates with respect to zeros set day before!
    In other words:
    Usually my work piece starts at about 50,90 from physical machine zero. After homing crazy coordinates becomes nice perfect -50,-90, so I'm ready to go, perfectly calibrated.

    Question:
    Is there any way to avoid homing every time machine is re-powered? A way to tell machine: "trust me, you are where we finished yesterday".
    I mean, machine somehow knows that physical 0,0 is actually my -50,-90 which I set a day before right?

    I know that I can write down coordinates on finish and enter them manually after power-on but then homing is actually easier to do. Looking for some easier magical way to get X=500,Y=500 without need to drive machine all the way to the corner.
     
  2. David the swarfer

    David the swarfer OpenBuilds Team
    Staff Member Moderator Builder Resident Builder

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    Homing does it all for you!
    The setXzero/SetYzero etc buttons set offsets from home, which the controller remembers.
    When you turn the controller on it sets machine 0,0,0 as the current position, but since we (you, me and the machine controller) don't know where it is now, the offsets to the work are NOT valid.
    Homing sets the machine coodinates to 0,0,0 at the home position, now the controller knows where its world starts, and the offsets to the workpiece ARE valid.
    This is what homing is for! (and is the only way to change the machine coordinates after power on)

    You can shorten the time that homing takes by creating a macro for yourself that you use before powering off.
    This macro must move the tool to near the home position so that the homing routine does not need to move far to find the home switches.
    Something like this will work for a machine with home switches at right, far, up (industry standard home at + ends of travel)
    Code:
    G17 G90 G21  ; awlays set the modes we want
    G53 G0 Z-10   ; raise Z to safe height but don't hit the switch
    G53 X-10 Y-10 ; move to just short of the X and Y switches
    
    since your machine appears to have home in a diferent corner, adjust the values for X and Y to suite your machine.

    (note: my machine has no home switches and I 'fake the home' by always parking it at machine 0,0,0, or after a crash, manually move it to the proper corner and reset the controller to make it set the MCS to 0,0,0 at that position. This works perfectly for resuming a job after a power failure or other problem)
     
    Christian James likes this.

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