[Karl_T]

I have fought a vibration on and off with my galil card driving AMC servo amps for years. Tried everything i could think of. Its been an anoyance until today. I had to shut down the machine and work on the problem before making more parts.

Before today, the vibration would only occur when the machine was sitting still. it would be a buzzing sound and you could put your hand on the servo and feel it making very small moves back and forth rapidly. Over time I've seen the issue on all four axis. An Estop (issues MO) and reset (issues SH) always calmed it right down.

Today, my knee started vibrating (axis 4) under motion and its more severe. I (of PID) is 0 on this axis. I changed it to 10 and the frequency was much lower but the amplitude was MUCH higher. I shut it down after one second.

Tommorrow morning, I'll take the servo apart and look for mechanical issues and test without the belt to the load on.

I could sure use other ideas.

Karl

[Al_The_Man]

I assume they are used in Torque (current) mode and the gain pot is fully CCW?
I have never really had a problem with the AMC.
Al.

[Karl_T]

I assume they are used in Torque (current) mode and the gain pot is fully CCW?
I have never really had a problem with the AMC.
Al.

Yes and yes. Also a pot to adjust drift. AMC has a GREAT manual on setup, I've read and followed it MANY times chasing this issue. There's so little here and its so simple, I've just about ruled this area out.

You're just about the only expert on this area. I hope you have some other ideas.

Karl

[Al_The_Man]

I have never really had a problem with the Galil and AMC, I often have tuned them manually rather that the tuning s/w, if the load exceeds the capability of the motor, or there is a back feeding load at rest it can sometimes cause a problem, as in heavy vertical Z axis etc, or in your case the knee could be the cause?
This is where the importance of a tuned counterbalance in a Z axis makes a difference.
In the case of my Excello Knee, the servo positions and is then disabled and the brake engaged, so the servo is not constantly active.
Al.

[Karl_T]

I have never really had a problem with the Galil and AMC, I often have tuned them manually rather that the tuning s/w, if the load exceeds the capability of the motor, or there is a back feeding load at rest it can sometimes cause a problem, as in heavy vertical Z axis etc, or in your case the knee could be the cause?
This is where the importance of a tuned counterbalance in a Z axis makes a difference.
In the case of my Excello Knee, the servo positions and is then disabled and the brake engaged, so the servo is not constantly active.
Al.

It is my heavy knee giving trouble. First trial will be to disconect the load.

I tried disabling the knee (MO) and applying the brake, but the galil card keeps giving me an error telling me the motor is off. This would be a GREAT quick work around if I could figure out how to stop the error message.

Karl

[Al_The_Man]

I take it you did use the MO and SH for the specific axis?
MOZ off & SHZ must be turned on before commanding any motion on that axis.
I don't see how this would not work?
An alternative, which should not be necessary, would be to try turning the amp command to zero by the TL,,0 command, the correct TL would be have to be re-entered when the brake comes off.
Al.

[Karl_T]

This was the exact "COMMAND MOD". (COMMAND tells Camsoft its a direct galil command)lls I immediately get an error comming from Galil, "cannot move motor 4 is off". Guess there must be some sort of "off on error trap". NOTE: I have Camsoft standing between me and the card, its the HMI.

I'll try the other suggestion this evening. Unfortunatly, i still work for a living

Karl

[Al_The_Man]

I have not used Camsoft for some years, but there must be a way to turn one motor off and it should not error, as long as you do not command a move for that particular axis?
Al.

[Karl_T]

I just fell on the PL command, huge improvement. Do you know anything about the NF and NZ commands? I need more info than in command reference.

I'm convinced this is just a servo tuning problem. I have a HUGE mass to move and The numbers WSDK gave me don't work. Mechanically the system looks great.

Karl

[Al_The_Man]

Never used the NF or NZ, only GN.
You could also be slightly undersized, motor-wise?
The problem with a counterbalanced system such as this when the motor is kept active, the load can change at rest due to part weight and tool down pressure etc.
Al.

[Karl_T]

I don't know GN don't see it listed in Galil command reference.

servo is what i had, eBay special. Reliance Electric model E675 1/3 Hp. I belted it down 8:1 to a 0.200" lead ball screw.
These motors are 120VDC nominal, 2.6A cont., 15A peak. They have a torque constant of 5.75 lb-in/A, and back EMF constant of 68 V/krpm.
Have idea how this compares tosizing calcs.

After playing more with the PL command, the knee isn't bothering at all, today.

Now, today, the "Y" axis is buzzing at stop. Like I said, seen this on all axis and it comes and goes.

I'd sure like to get the bottom of this issue. its been an annoyance for years.

Karl