Rotary Table Tuning Problems

I have been trying to tune a rotary table for 3 months of evenings and weekends but can't figure out what is wrong.

This is on a Mori Seiki MVJR (20"X) and the rotary table is a Tsudakoma 200mm table

I have it to the point that is will move.but can't do much better than that.

The main symptoms are:

1. When I do "Touch Off 0.0" the readout in Axis says about 0.050 degrees
2. When I use the hand-wheel to move it in one direction it can move slowly in one direction but it growls.
3. When I use the hand-wheel to move it in the opposite direction it move very very slowly but if I try to turn it fast at all, it bucks and gets a following error. When the following error happens the motor lurches back the opposite way a few table degrees. Each time I turn the servos back on, it repeats the lurching and errors out again. If I repeat turning on the servos 3 or 4 times, they will stop lurching. But then I am back where I started.

I have tried settings
P from 1 to 100
I 0 to 10
D 0 to 2
Min Ferror can't be less than 0.1 or it erors out with following error

Basically tried 100's of combination of tuning values for all variables but nothing seems to help much.
I can find setting that will make it worse,, just not better.

I tried reversing the tachometer leads, that didn't make any difference, maybe the tach isn't working at all?

I have run out of ideas to try, short of buying a new motor.

If you have any ideas, please let me know.

Here is a picture of what it looks like. It is balanced within the drag of the bearings. If I loosen the backlash, I can rotate it either way by hand.

Thanks, I will try the small P values tonight.

I didn't understand what you meant by "Do this with a direct command," can you tell me how to do that?

With regards to testing tuning variables, I have wondered which ones negative values are valid for.
Do you know if negative values are valid for: P,I,D, etc?

OK could you tell me what you mean by a direct command?
Do you mean a G1 instead of turning the hand wheel?

OK, I didn't know how to do that with a command so I removed the motor and connected it to a variable voltage power supply.

The supply goes from 0-25 volts and that turned the motor from 0 to about 250 RPM (by eye). With all the resistance drag I could put on it squeezing the shaft at 200 RPM it got to 5 amps and worked smoothly in both directions. I guess the motor is OK. That is a relief.

I measured the tachometer voltage while it was still connected and it was constant voltage about 0.3 volts.even when it is sitting still or running at 250 rpm..

I disconnected it and found the voltage varied as expected with change of RPM.
I will try to see what the voltage is on other tachometers and if they have a range of 0-7 like I expect, then I will try to find out why this one in not working that way.

Thanks for your help. It was good to remove the motor, Now I see how to tighten the backlash a little more than was possible before; that was on my to-do list anyhow.

Thanks, that is a useful testing strategy, I didn't know how to do that..