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mm to inch?

Discussion in 'General Talk' started by Les Adams, Jan 9, 2023.

  1. Les Adams

    Les Adams New
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    Just finished building a custom small mill and set it up with c beam parameters. Azis run in the proper directions but doesn't seem to cut inch size from the G code. Also cuts are reversed from sim drawing on only one axis? Thanks, Mark, for your last help.
     
  2. Giarc

    Giarc OpenBuilds Team
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    Which axis are the cuts reversed. Is it the Y? On a Cbeam type machine when you jog the Y axis in the positive direction, the the moving work area should move towards you. As for not cutting inch size, is it slightly less or more than an inch where maybe the machine needs calibration, or is the Gcode coming out set for mm. If there is a G21 in the beginning, it is in metric. Maybe you should post your Gcode file so we can look at it.

    Metric Example:

    upload_2023-1-9_18-48-36.png
     
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  3. David the swarfer

    David the swarfer OpenBuilds Team
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    Every Gcode file MUST have a units specifier. G20 for inch, G21 for mm.
    If your postprocessor is not emitting such a code, then it needs to be fixed soonest.
    Then one of your axes is reversed.

    The conventional axis directions are for 'tool motion relative to the work'.
    So if it has a moving table the table will move 'opposite' so that the tool moves correctly.
    If is has a gantry, then the tool motions are obvious.
    You loaded the c-beam parameters, and the c-beam machine is a moving table in Y machine, so that axis will be naturally reversed in the parameters.
     
  4. Les Adams

    Les Adams New
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    Thanks friends. The G code is showing inches but the cuts are about half the size they should be. The reversal is as seen in the sim picture . cut is reversed from the computer view. will check the motor settings. Have sphynx and cuts are perfect with same G code?
     
  5. David the swarfer

    David the swarfer OpenBuilds Team
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    Then you need to calibrate, use the wizard in CONTROL to set the steps/mm correctly.

    An inch/mm mismatch would cause too small or too big by a factor of 25.4, half size is a steps/mm problem which the calibration will solve.
    more info HOWTO Calibrate your CNC Machine for MACH3 or GRBL
     
  6. Peter Van Der Walt

    Peter Van Der Walt OpenBuilds Team
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    Also more info:
    Follow onscreen instructions
     
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