fanuc ot g96 overspeed

[Daniel Boone]

I have a lathe with fanuc ot and it does not seem to correctly be reading the diameter of the stock correctly and when in g96 constant surface speed it tends to overspeed or alarm out. Any ideas? Thanks

[kcho]

you must use g50 S**** so you can limite the spindle speed.

[Daniel Boone]

I do use g50 and it still errors out.

[kcho]

Please give us more data about your machine, spindle amplifier type, cnc type, iso program....

[sinha_nsit]

Try invoking G96 after bringing the tool near OD of the workpiece. And cancel it before sending the turret to home position.

[dcoupar]

post your program, please

[EECENOD]

THE PROGRAMMING LOGIC OF G96SXXXX MEANS NOT SPEED BUT SURFACE FEET
THAT IS IF I PROGRAM G96S600 AT A SPECIFIED RADIUS FROM CENTERLINE THE
SPINDLE WILL ATTEMPT TO MAINTAIN 600 SURFACE FEET..... AT .0001 FROM CENTERLINE
VECTORING THAT OUT WOULD RESULT IN MILLIONS OF RPM.

[dcoupar]

Originally Posted by EECENOD THE PROGRAMMING LOGIC OF G96SXXXX MEANS NOT SPEED BUT SURFACE FEET THAT IS IF I PROGRAM G96S600 AT A SPECIFIED RADIUS FROM CENTERLINE THE SPINDLE WILL ATTEMPT TO MAINTAIN 600 SURFACE FEET..... AT .0001 FROM CENTERLINE VECTORING THAT OUT WOULD RESULT IN MILLIONS OF RPM.

EECENOD,

This is already established. The G50 Snnnn should limit the RPM to nnnn, but it's not, hence the reason for Daniel Boone's original post.

[dcoupar]

Originally Posted by Daniel Boone I do use g50 and it still errors out.

Any possibility that your control is set up to use G-code system B or C, which use G92 Snnnn to specify the maximum RPM during G96 mode?

[Al_The_Man]

Is there a possibility the spindle encoder is giving problems or where driven from a small timing belt, belt slip or failure could be the problem.
Al.

[cncserveng]

Its not just overspeed, underspeed can cause issues also.

you need to set min and max speeds, i.e. P 200 Q2000.

Have you tried G92 ?

[dcoupar]

Originally Posted by cncserveng Its not just overspeed, underspeed can cause issues also. you need to set min and max speeds, i.e. P 200 Q2000. Have you tried G92 ?

In all my years of programming Fanuc controlled lathes, I've never seen a command to set minimum RPM. Please explain the use of P200 and Q2000 to set min and max speeds.