Fanuc 21i Spindle Torque Control/Limiting?

I have a lathe with a 21i and the spindle has way more torque than I ever use.
Load meter shows only a few percent while turning parts but spikes to 150% when staring from a dead stop to any speed over 800RPM

Pulls a lot of power to spin up and stop the chuck. Kind or like flooring the gas pedal when the light turns green or slamming on the brakes instead of a more controlled stop.

Spindle spins freely by hand.
Maintenance records show new bearings installed a year ago.

Seems wasteful and I have limited power supply so I have to be careful what all is running.
Its a pain to modify the programs to ramp up and down in stages

I would like to find out if there is a way to control ramp up and deceleration speed?
Kind of like a soft start or torque limiting

What you're describing is normal. I've seen spindle load meters spike and then float back to a very low level once the spindle is turning. This on both lathe or mill.

If you want a "soft start" you should program it in. First give it a 500 rpm, then go to 1000, then etc..

Parameters 1600-1699 should control accel/decel. I have never personally played with them but it's worth a look. If you find a way I would be interested to learn what worked from you.

You also could write a little macro for it and then just copy/past it in as needed. It could be used for acceleration and deceleration. Something like:

#100=0 (STARTING RPM)
#101=4000 (DESIRED RPM)
#102=200 (RAMPING INCREMENTS)(ENSURE #101 IS DIVISIBLE BY #102)
#103=.1 (DWELL BETWEEN INCREMENTS IN SECONDS)
WHILE[#100LT#101]DO1
#100=#100+#102
G97S#100M3
G4U#103
END1
...
(YOUR PROCESS HERE)
...
#100=4000 (STARTING RPM)
#101=0 (DESIRED RPM)
#102=-400 (RAMPING INCREMENTS)(ENSURE #101 IS DIVISIBLE BY #102)
#103=.15 (DWELL BETWEEN INCREMENTS IN SECONDS)
WHILE[#100LT#101]DO1
#100=#100+#102
G97S#100M3
G4U#103
END1
M5


Good luck!

Redd

EDIT: For deceleration it should be a minus value on the ramping increments, I underlined the location.

You will have to get the 21i parameter manual.
You can change the acceleration type and rate. I tried this as a work-around for belt slippage due to coolant getting on them. On a 0iF, so the parameters might be different.

Just be aware that it applies to CSS also.

DouglasJRizzo said:

What you're describing is normal. I've seen spindle load meters spike and then float back to a very low level once the spindle is turning. This on both lathe or mill.

If you want a "soft start" you should program it in. First give it a 500 rpm, then go to 1000, then etc..

Click to expand...

Thanks guys
I have used this step up process and it works good
Just thought I could find a machine control fix and eliminate this extra process
Talked to Fanuc late yesterday and they said they would need to come out and tune? Big Dollars $$$$$$$$
Not a big wiz with controls although I have made similar changes to other brands of controls but never on a Fanuc
From a production efficiency stand point one would thing this would be a common adjustment
If you were running a small diameter collet chuck you could increase acc/dec rate as the rotating mass is less and vice versa for running a large chuck/part.
I am not suggesting one would be making daily changes to these parameters but for a machine that will be running production for extended or permanent time frame it makes sense.