Servo tuning for beginners..........CNC4PC components

[bhdavis1cnc]

I've got the new CNC4PC components built into the new control for my old 3-axis Precix CNC router. Servos will spin so I'm ready to do the tuning. I've watched a number of videos on PID tuning and spoken with Arturo from CNC4PC to get me going. As can be expected though I'm struggling a bit as I've never done this before.

It was suggested that I disconnect the LAN cable from the C78 card to the CNCdrive DG4S servo drive. However when I do this Configuration3 PID screen is grayed out. So I'm working with the drive connected to the C78.

It was also suggested that I start with the output power to the servo removed and leaving only the encoder connected. This however gives me no sine wave track on the Configurator3 PID sine wave screen after downloading a setting to the drive and hitting the ANALYZE button. So for now I've removed the drive belt from my Y-axis servo so it can spin freely. That is where I'm starting the process.

So I have the MAIN connector from the C78 to the DG4S installed, and I have the 48v DC power cable output to the servo connected to the DG4S drive.

With this setup I started with 100,0,5 for my Ap, Ad and Ai settings. This will make the servo rotate and give me a sine wave reading. If I reduce the Ai to 0,1 or 2 I get no servo rotation.

The servo drive belt is removed from the machine axis I'm working on so the servo motor is free to spin with no machine movement. Once I have this axis tuned so the motor is running relatively smoothly I can reconnect for final tuning under load.

Bottom line here is I really don't know what I'm doing. I already thought I damaged something once and fortunately it was only a blown 5a fuse that I have protecting each drive.

So, basic questions:

1) Should I be doing this with only the encoder connected to the DG4S or do I need the servo motor powered to run when commanded?
2) Am I taking a chance on damaging the servo motor or drive if the motor is 48vdc powered or not?
3) If an attempted setting does not make the servo spin is that an incorrect setting just because the motor didn't spin? Some of the cleanest PID screen sine wave results (straightest line up by the top horizontal line on screen) happen with setting that don't make the motor spin.

I have developed a really base level of understanding of the PID relationship and the Configurator3 software but find I'm throwing darts at the target with a blindfold on.

Any guidance would be much appreciated.

Thanks,
BH

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