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  1. #1

    Join Date
    Nov 2008
    Posts
    16

    how does G92 work

    have romi lathe with fanuc otc. found g92 to limit max speed but how is it cancelled and can it be set differently for other tools or operations with same tool?

  2. #2

    Join Date
    Jun 2005
    Posts
    218
    Quote Originally Posted by tony y View Post
    have romi lathe with fanuc otc. found g92 to limit max speed but how is it cancelled and can it be set differently for other tools or operations with same tool?
    G92 is used with constant suface speed (G96 )as a max speed limit. Or as a work shift .

    Lets say you you have a 6 inch dia. part to face and you want to use constant surface speed( CCS) of say 400
    The means that 400 feet of metal will be cutting at any diameter. So the spindle speeds up
    as the tool gets to X0.
    Now if your machine has a max spindle speed of 6000 rpm and the tool gets close to x0 the machine will speed up to
    6000 rpm. Now this can be very dangerous if the part over hangs the chuck jaws a few inches the part can come out at this high of speed.
    So you want to limit the speed or clamp it to a safer maximum speed say 2000rpm. Thats what G92 does limits the maximum speed.
    .
    I put the G92 after the tool change. Before I turn the spindle on.




    T0101(face tool )
    G92 S2000 (clamp speed)
    G0x6.1
    G96 S400 M3 (Spindle starts)
    Z0
    G1 X0 F.005

    So what I have here is a clamp speed of 2000 rpm
    and a constant surface speed of 400
    so when the machine starts up and the tool is at 6 inchs
    the spindle rpm is 254 as it cuts and gets closer to center it speeds
    up to a maximum 2000 rpm.


    If you want to cancel the G92 just take it out of the program or use G97
    .
    Here is a video of a part sticking out way to far and not using the proper clamp speed .
    Notice the spindle keeps speeding up.
    http://www.youtube.com/watch?v=nzb-i7-fuq8


    Tim

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