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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?
G92 is used with constant suface speed (G96 )as a max speed limit. Or as a work shift .
Originally Posted by tony y
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)
G96 S400 M3 (Spindle starts)
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.
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