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  1. #1
    Join Date
    May 2009
    Posts
    6

    Unhappy G41 and G42/40 explanation

    hi ,guys my question is: is there a problem if I activate cutter comp. on a z movement and I am not sure if it only work on the G1 line and if it matters if G40 would be in the las cutting movement or is nessesary to put g40 only onthe exit movement.I have been experienced problems like alarms and tapered surfaces where i nedded straight movements . any tips or insights would be fine ,thankyou for your time and help.

  2. #2
    Join Date
    Dec 2003
    Posts
    24220
    Do you mean you want to compensate the Z movement? G41/G42 is diameter compensation, G43/44 is tool length comp.
    The general rule AFAIK is the G41/G42 has to be implemented at least 1 block ahead at a distance of Tool radius minimum.
    I am not a machinist so I may not be getting the gist of what you are looking for.
    Al.
    CNC, Mechatronics Integration and Custom Machine Design

    “Logic will get you from A to B. Imagination will take you everywhere.”
    Albert E.

  3. #3
    Join Date
    Jul 2005
    Posts
    12177
    It depends on your machine.

    G41/G42 does not apply to the Z axis it is normally only X and Y that can be compensated.

    As Al says normally you need to do the move that starts compensation ablock ahead of the first feed motion that is compensated, and also cancel compensation after having moved away from the compensated tool path. In other words start compnesation before any cutting and then complete all the cutting and move away a small distance before cancelling compensation.

    On some machines it is possible to have a Z move in the same block that the X, Y compensation is set but I think some machines will not allow this.
    An open mind is a virtue...so long as all the common sense has not leaked out.

  4. #4
    Join Date
    Dec 2008
    Posts
    3137
    It all depends on what plane you are in when applying comp.

    If G17 is active then comp is taken only in the XY plane, likewise for G18 = XZ, and G19=YZ . Most machines cannot change planes with comp active.

    Common practice is to start and finish compensation on a move involving the active plane's axes. This ensures that any following moves do not give un-expected results.

    eg.
    G17 G41 D1 Z-.1 F.1 (is not the best method)
    G0G40Z2. (may move the XY on some machines)

    more common
    G1 Z-.1 F
    G17 G41 D1 X Y F
    ..
    G40 G1 X Y
    G0 Z.2
    or
    ..
    G40
    G1 X Y
    G0 Z.2

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