tuning out hydo counterbalanced head (servo)

[howling60]

hello there all,

The background:
I'm in the final stages of getting a Cincinatti Milacron 10hc-2500 mill retrofitted with new controls and servo drives. The machine, weighs in somewhere in the neighborhood of 40k lbs. I am driving the 3 axis with Servodynamics amplifiers, and 221 in-lb servomotors, controlled by a galil/camsoft interface.

I have been able to get my X and Z axis tuned out, no problem, however, when i move onto tuning out the Y axis (spindle, plus a tool changer that travels with the head), I am running into issues. The head and tool changer are counterbalanced using a pair of hydraulic rams. While moving the Y axis up/down, no matter how i set my P,D, constants, i listen to the entire axis "chattering" as it moves.

I tried altering the pressure at which the hydraulics were set at, and it seemed to make a difference in performance, however I am starting to feel like i'm running in circles tuning this out.

If anybody has ANY experience, or ideas on how to approach this problem best, i would highly appreciate it! Thanks In Advance!

-Nate

[MetLHead]

Nate,

If you have one, try running the axis with a battery box. This will help you isolate the problem to either the control loop or the axis/drive setup. If the axis runs smooth under battery box control then the problem is most likely your control tuning. If it is still jerky, you probably have to adjust the drive gains. Try to get the drive/axis running smooth before running it with the control. Since this is a retrofit, you probably haven't changed any of the hydraulic settings (other than the counterbalance pressure). This type of counterbalance usually cannot be pushed much faster than the original design intended. So if the original control ran the axis at 100IPM, you probably won't get much more than that after the retrofit. This is simply a matter of how fast you can move the oil into and out of the cylinder.

Regards,
Scott

[howling60]

Originally Posted by MetLHead Nate, Since this is a retrofit, you probably haven't changed any of the hydraulic settings (other than the counterbalance pressure). This type of counterbalance usually cannot be pushed much faster than the original design intended. So if the original control ran the axis at 100IPM, you probably won't get much more than that after the retrofit. This is simply a matter of how fast you can move the oil into and out of the cylinder. Regards, Scott

it's funny, we're actually running the axis at 100 ipm slower than the original specs

I did just obtain some help on the servo tuning from camsoft, hoping it might help out on the counterbalance issue...

thanks alot for the ideas, i do appreciate 'em... any other ideas, let them fly!

-nate