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  1. #1
    Join Date
    Jan 2025
    Posts
    1

    HELP ILLIGAL G72

    i have been trying to run a g72 for a back rad on my romi g20 Fanuc 21i-t every time u run it it says illigal g71-g71 have tried a few different things with the same result not sure what's wrong as never done this before
    N4(BACK RAD ROUGH)
    G28U0
    G28W0
    T0404
    G97S1000M3
    G0Z-29.0
    X53.0
    G1X30.7F.12
    G0X53.0
    Z-19.0
    G72U0.7R0.5
    G72P104Q105U.2W.1F.1
    N104G1X50.8F.1
    G3X30.8Z-29.0
    N105G0X55.0
    G28U0
    G28W0
    M1 any help would be appreciated

  2. #2

    Re: HELP ILLIGAL G72

    Quote Originally Posted by Doink View Post
    i have been trying to run a g72 for a back rad on my romi g20 Fanuc 21i-t every time u run it it says illigal g71-g71 have tried a few different things with the same result not sure what's wrong as never done this before
    N4(BACK RAD ROUGH)
    G28U0
    G28W0
    T0404
    G97S1000M3
    G0Z-29.0
    X53.0
    G1X30.7F.12
    G0X53.0
    Z-19.0
    G72U0.7R0.5
    G72P104Q105U.2W.1F.1
    N104G1X50.8F.1
    G3X30.8Z-29.0
    N105G0X55.0
    G28U0
    G28W0
    M1 any help would be appreciated
    You are using G3 (arc move) in N104 (G3 X30.8 Z-29.0), which could be problematic in a G72 cycle.
    G72 requires only linear moves (G1, G0)—no arcs (G2/G3). Try breaking the arc into small linear moves.
    http://cncmakers.com/cnc/controllers/CNC_Controller_System/CNC_Retrofit_Package.html

  3. #3
    Join Date
    Dec 2012
    Posts
    410

    Re: HELP ILLIGAL G72

    Nope,

    ARC's are no problem for G71/G72, this is actually G71 code not G72.

    1st: - when you want G72 change G72 U0.7 R0.5 to G72 W0.7 R0.5 ... U is for G71 / W for G72 !!
    2nd: - first move in line after G72 is a Z-move, not X, N104 G1 Z___ F.1
    3rd: - add a R-value to your G3 X30.8 Z-29.0 R___ !!

    regards.

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