KM3 Servo Tuning Problem

[please no smoke]

I have been trying to get my new (junk) machine running. I replaced the servo control board and have been trying to tune the Servomate drive. I was able to tune the y and z, but during x tuning and moving the table in x to adjust the sig voltage, the table would start vibrating back and forth like a jackhammer. It would eventually throw a yellow lite on the servo mother but it wouldn't stop until I e stopped it or moved the table a ways. Table will still kind of move even with the oscillating. Sometimes it does it, sometimes not, but enough to mess with my tuning procedure. What the heck? Is it from the motor/ encoder? The servo mother unit? Servo control board? I'm so close but so far still :-[

[bloke]

For a machine with Ultimax (twin screen) control:
You have the Tach. and Sig. pots wound too far CCW. Wind the Tach. pot fully CW then back eight turns. wind the Sig. pot fully CW then back about five turns. Power up the servos and put your meter on DC volts and measure the voltage at the brown and orange wires on the edge of the amp being checked.
Jog the axis forward and backwards at 40IPM and adjust the Sig. pot for 0.8v in both directions (use the Bal. pot to even things up about centre i.e 0.79v one way and 0.81v the other can be balanced to get 0.8v both directions).
If there is not enough adjustment on the Sig. pot, wind the Tach. pot CW one turn and try again. When you have 0.8v in both directions, wind the Gan. pot CW until the axis just becomes unstable then back it off 3 turns.
Rinse and repeat for the other two axes.

If the machine has a BX (single screen) control you'll need to jog at 25 IPM and set the Sig. pot for 0.65v

[please no smoke]

Tried what you said but still has issues. I had been using the tuning instructions from AMTS (hurcostore.com) but even when I did as you said the x would still oscillate. If I turned the sig far CCW i could get it to stop but when I would jog it it would be shaky and then start oscillating again. I swapped the y amp board in and it still acted the same. Also, if I try to jog the y, or z I get a motion error and an e stop. Something is not right.

[bloke]

Aha. Sounds like you have a fault with the tach in the motor or the wiring from the tach to the servo amp. What type of motors do you have?

[please no smoke]

Would that make the y and z decide not to move as well. The servos are ElectroCraft E252.

Thanks

[bloke]

The servos can refuse to move if the balance pot is waaaaayy out of adjustment on any one axis. I know I've asked the type of motors but are they black with a multi-pin connector or do they have a cover box over them? Also, does this have a single or twin screen control?

[please no smoke]

They are the old round black on black ones with a small connection box and a multi pin cable.

[bloke]

If you power up the servos and put your meter leads in the brown and orange wire terminals (set it to DC volts), measure the voltage without moving or attempting to move an axis. This should read 0v. If it doesn't, adjust Bal on the amp you are measuring to make the reading as close to 0v as you can get. This will put you in the ballpark.
Then adjust the Sig., Tac. and Gan. as above.

[please no smoke]

Thanks. I will go try.

[please no smoke]

Still not working. As soon as I power the machine, and before I enable and axis it starts. Then if I am lucky one of the times I reset it it will stop, but as soon as I move the axis, the oscillating starts. The adjustments only make a slight difference. I have my meter coming off the 8, and 9 pins on the servo control board which was what the other instruction said. i was not sure which brown and yellow you were talking about. There is a set on the wire that ties all three boards. I now only have the x and z boards connected.

[bloke]

The servo amps have a connector at the bottom of each board. A cable is plugged in that goes to the terminal strip. On each cable, there is a brown and an orange wire. meter between these on each axis.
Due to the instability of the amps, it may be best to only run one axis at a time by unplugging the other two amps.
Set the first amp up then unplug it. Move to the next one and set that up.
If you find one is tricky to set up, move it to an axis that will run and set it up there. I will be easier to find what is causing the oscillation that way.

[Al_The_Man]

If you have an older analogue drive with trimpots and tach feedback it is far better to test and adjust by removing the CNC control loop.
This is the analogue signal from the controller.
This is known as tuning the inner loop, otherwise if there is gross error in the drive, the CNC is trying to correct it.
If you remove the analogue input signal and connect these terminal together, the motor should not be active, if the motor moves it is either the loss of tach feedback, wrong tach polarity, or balance pot is way off.
If the tach is proved out by DC output voltage then you should see a difference with the balance pot to zero the motion at this point.
A good test in aligning these type of drives is to use a +-9v battery box in to the analogue input after you have adjusted the balance, gain and tach pot to see if the drive moves the motor smoothly.
Al.