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z clearance in go to (home) function

Discussion in 'CNC Mills/Routers' started by donald k wilson, Dec 11, 2021.

  1. donald k wilson

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    Hi all,
    I'm running into an interference problem with the z clearance heights in the go to xyz zero or home function in openbuilds control. Both home commands put z travel at about 1/4" above the table or z zero and depending on where my toolpath ends in relation to my part I cant run the home function because the bit will nosedive into the piece. I need to raise z clearance to about 4". Is this possible and how might it be accomplished?
    Thanks in advance, great site and products, dkw
     
  2. donald k wilson

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    a little more info, I've resorted to doing a 3 step process to go home, raising z to 4" then sending x and y home separately with their individual buttons.this works fine just not as efficient.
    thanks, dkw
     
  3. sharmstr

    sharmstr OpenBuilds Team
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    It could be a few things. Lets start with "home function". I'm assuming here you mean the "Home All" button. If so, it sounds like your machine isnt moving in the correct direction. Z+ should move the spindle up. If not, correct that by inverting the direction in the grbl settings. If, on the other hand, it is going in the correct direction, then maybe you dont have limit switches. Using the Home All button in control requires limit switches. If you dont have limit switches, then disable them in grbl settings. This will disable the Home All button since you cant use it.

    Now on to "GOTO xyz zero". There are three options there. The first one uses your work coordinates. If you set your work Z zero to your spoilboard, then it will for sure hit your stock. Its only going to raise up to (or move down to) 5mm above Z 0. Dont use it unless Z zero is on top of your stock.

    The second option uses Machine Coordinates Z zero and Work X and Y zero. This requires that you home your machine. If you dont have limit switches, then you can fake homing using the procedure here: How to 'Fake the home'

    The third option use Machine Coordinates for X, Y and Z. This requires limit switches and that you've homed your machine.
     
  4. donald k wilson

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    Thanks for the insight. I am making incorrect assumptions about how the go to xyz zero path functions. a couple of adjustments to how I am setting up my work and table planes should solve the problem. On to the next crash and burn...
     
    sharmstr likes this.
  5. David the swarfer

    David the swarfer OpenBuilds Team
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    OBControl does indeed do a G0 Z5 during a 'gotozero' sequence. Drives me crazy....
    it should be a much safer
    G21 G90
    G53 G0 Z-5
    G0 X0 Y0
    G0 Z5 ; optional - i would leave it off
    But the button will be disabled because hard limits are disabled. A false assumption. Very few people can get away with not hard homing or faking the home, so G53 moves are (close to) always valid, and if they cause a crash, we can recommend some OB limit switches to solve it (-: (but the user still has to home, so we cannot solve everythign with software and llimit switches)
    [/QUOTE]
     
  6. Peter Van Der Walt

    Peter Van Der Walt OpenBuilds Team
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    The menu item was added to please you
     
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