G320 not singing?

[Chris64]

OK...so I finished connecting 1 axis. It's an 80vdc servo motor.

The first time I powered it up, then enabled axis, finally reset the err (with gains and limit turned really low) it made a singing type of sound but it changed in pitch and then went into fault state after about 1-1.5 seconds. It seems logical that either the encoder or the motor was wired backwards. I reversed the encoder and that seemed to do the trick as far as it going into fault mode.

Now the problem is I don't get any singing at all.

I turned the current up to full, then slowly turned the gain up but nothing changed.

BUT - if I go over to the hand dial and give it a twist, it fights me and tries to correct itself...that said, it doesn't do a very good job. It seems that I can fight it enough to make it change it's current position and it will stay in the new position instead of returning to the original position. Besides, a 1/2 HP servos geared 1/4 - there should be no way I could turn it at all. When I turn it, it doesn't go into fault mode.

Any thoughts on this?

[Chris64]

OK...just a follow up. My first test was with no computer connected...just trying to get the singing started. Also...this CNC system had a distinctly loud singing prior to the conversion so i don't think it's just too quiet to hear. Since the singing pitch is probably defined by the encoders, I would expect it to sound different, but not completely silent. I'm using USdigital SMS500 500 line encoders. I'm using sheilded wire (grounded at one side only), but it's running inside the same 3/4" flex conduit as the motor wires

Since then, I decided to go ahead and connect the computer and see if I could make some motion happen (and perhaps see an improved motor action). Well, it moves, but not very well. It appears to be very jumpy like a stepper motor when skipping. Even when just holding a single direction.

Are these normal symptoms of a Gecko/mach setup that's just not tuned? It seems too out of whack to be just poorly tuned. My attempts to adjust it didn't seem to improve things much.

Right now I've tested it with current limit turned to full but it seems like it's just not getting enough power. If the limit is below halfway it will trip the fault. I did meter the motor supply while it's going and changing directions to confirm that it's not losing power, but it's holding a strong 80vdc no matter what action the motor is taking.

[Chris64]

And the power wires are very short...maybe 12"

They do have an in-line fuse on them, but I wouldn't think that would be causing much power loss.

[Torchhead]

Gain pot determines "stiffness". Dampening pot stabalizes the loop so it doesn't break into oscillation.

Tuning in MACH and on the drives for a given motor configuration is essential. If you have the acceleration set too high for the drive settings it will fault.

Motion should be nice and smooth. Motors will sing slightly. If they don't the dampening may be too high and they can get spongy

This is not a problem of the motors not getting enough power. It's probabaly all tuning...both in MACH and on the Gecko's. An inline fuse drops millivolts...not even enough to consider.

Tom Caudle
www.CandCNC.com

[Chris64]

Thanks for the reply (I'm a Corel DXF client too).

I still am not getting any singing...despite what i've tried. I've been working on the yahoo message board with a bunch of people trying to help me out. My biggest problem was grounding the shielding to the table (brain fade). I'm sure that the sliding surface caused some strange interference. I disconnected it so it's only grounded in the cabinet and all the strangeness went away. I tuned it in pretty good last night so it moves OK. I'm still not really in awe of it's fast movement (fast, but not quite rapid). It appears to have a bit of a hesitation/uneasiness. At rapid it's smooth and anything under 20 IPM it's nice...which is where I'll be most of the time. It's holding power is great.

I think I still have a little tuning to go, but I'm probably 98% of the way there. My 3 phase may just be too loud for me to hear the singing...but it used to be so loud I considered ear protection - no joke.