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Z axis calibration

Discussion in 'CNC Mills/Routers' started by tommy arno, Aug 2, 2017.

  1. tommy arno

    Builder

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    I have the ox cnc machine, how accurate can I expect the Z axis to be? and how do I calibrate it?
    when I run a job the first cut always seems to be deeper than the 1mm stepdown I enter in fusion.
    I tested it buy using a pencil in place of a bit, putting it on the board and then jogging up by 1 mm, the distance it jogs up by seems to be slightly more than 1mm maybe 1.1 or 1.2, this amount of inaccuracy I could deal with, but if I then set this new position as my work zero, then run the job the first pass seems to be slightly into the material by about 0.4-0.6mm whereas it shouldn't really touch the surface considering it is jus over 1mm away and the step down is 1mm
     
  2. Joe Santarsiero

    Joe Santarsiero OB addict
    Staff Member Moderator Builder

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    Hi Tom. Please include the controller and software you are using.
    Thanks

    Joe
     
  3. David the swarfer

    David the swarfer OpenBuilds Team
    Staff Member Moderator Builder

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    You have calibrated it, right?
    HOWTO Calibrate your CNC Machine for MACH3 or GRBL

    The leadscrew should be pretty close to 0.01mm per step or a multiple of that, depends on your microstep setting.
    You can figure out the theoretical steps/mm here GRBL settings calculator and then do the calibration to fine tune it.

    Then, backlash, and how it affects how you set Z=0
    if you bring the bit down till it touches the material by the merest hint, then you should be good.
    if you come down too far and touch the surface you can get a situation where the Z is using up some backlash with the bit resting on the surface. This can give you a 'too deep' first pass.

    I like the paper method, laser printer paper is very consistant in thickness, so you can be assured of a good setting every time, so long as YOU use the correct technique, and do the same thing everytime.
    Machine Tools: Mill Tips & Techniques

    Have you cut the waste board flat?
     

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