Set up using AMC AB15A100 drives, brushed DC motor Prototrak Plus with Encoders

Todd, thanks, I will work on all back to factory settings & Pots 1, 3 and the SW2 switches only.
The o-scope, does it need the current probe that matches the o-scope? That was the hang up earlier I believe. When testing with the o-scope will the motors need to be on the machine?

Many thanks

Edit: One thing that is strange is as power fades from the power supply (by watching the red LEDs fade from drives) if you were moving the table quickly, as the power go out the motors feel like they are generating electricity. If you crank table after LEDs go out they will light red again as I crank the table ie. spin motors.

According to this paper from AMC the current probe is recommended but not required.
 

Your drive has the current monitor output pin (pin#8) to use with the o-scope to monitor the current instead of using the current probe on the motor lead.

But be sure to read the above carefully, (and have whomever helps you read it to.)  There is some risk to both your drive and motor if the current loop is improperly tuned. 

When tuning the current loop it is recommended that the motor is not connected to a load. You could leave it on the machine, but simply remove the drive belt.  The motor could respond violently and unpredictably when sent the signal from the signal generator. 

Don't forget to power off the power supply to the drives when making changes to the SW3 switches.

All that said, at this point you are not even sure if you need to mess with the current loop.
 

Todd, thanks, I am going to need to take it to someone, I believe that I should send drives back to A-M-C & pay to have them checked so that the servo guy or whoever knows the drives are working proper. When I used a sw3- setting that was not on the table is when I believe damage may have occurred.

Many thanks

I don't think there are any possible SW3 combinations that are not in the table, other than possible combinations using SW3-10. If SW3-10 is turned on then all of the other possible SW3-6-9 settings are irrelevant, because SW3-10 simply bypasses all of the current loop capacitors so they are not used. This wouldn't cause any direct damage, other than the possibility of overheating the drive and hurting it because of an over current due to poor tuning. I don't think this happened because if you had, first you'd smell it, 2nd the drive wouldn't work at all any more.

I also just noticed that they suggest that the shaft of a DC brush motor be locked when tuning the current loop. This sounds a little scary. If you do it be sure to use a relatively small input for the signal generator test, so you don't burn anything up.

Todd, I found a single wire that looked like not fully under screw, this is where 2 wires are under a single screw. The traces are better. All units are same. This is best yet. settings are SW2=.047; SW3(1TO5)=320; SW3)6TO10)=.0047; POT1= 11.25; POT3= 7.375 FEED 20.0"/MIN.
This trace is not so good, I have tried every other SW3 (1TO5) (example:started at 10 go to 320 (k omega). I tried only (.0047) in SW3 (6to10). Non of the traces are close to earlier traces like on pages 17 to 18.

Many thanks, suggestions welcomed.

Todd, thanks! This morning I have started with factory settings on SW2 & SW3, then only changed SW3, 1 switch at at time ,going from "on" to "off", so just this change. The file name are the settings, example: p1 8.5 p3 5.0 s2 f s3 f fd 20.0 is Pot1=8.5, Pot3=5.0, SW2=factory (.047), SW3=factory (.0147), feed 20.0"/min. The traces show purple (shows as white) trace as close to red trace using Pot3 (CCW makes trace go lower on screen) and still have motor move when commanded. The setting for Pot3 shows the lowest setting, but also as close to red trace and have motor move. The motor is slow to move on start, go up on pot3 & motor more responsive, but trace goes away from red trace.

The pics are just sw3-6 to 10, 1 switch at a time.

Suggestions are welcome.
Many thanks

 

Many thanks for all the great help. I offer my sincere apologies for causing some much work for the forum & members with trivial matters I seek. I have swapped x axes motor with y axes motor, went through the same set of settings as described above post, very little difference in trace, all look like the original x axes motor. I will post one pic.

I would talk about motors (I believe they are ok) but I have had the original x motor pick up quickly to speed (I have no way of knowing it was 60"/min) when reached cruse, would hold for only a second, the rate of speed would drop (you could here motor slow some) and it would pick back up, moving quickly, before joint error out.

Edit: What it the part the brakes on DC brush style servo motors? Is it the start part of motion that stops first? The copper commutator (bright & shinny, no burnt places) looks good in both motors, brushes are over 1/2" long. Where should I be looking?

Many thanks

Edit: I am open to buying oscilloscope, from earlier post [30 Jun 2022 16:11 #246286] use pin 8 on drive. What I see in the used o-scope have a wide range of Mhz.

What range or way to know the o-scope I am looking at will work for the application. Some new scopes are very reasonable. What brand name is preferred, if I buy used?

 

The last one is by far the best one but it is still pretty awful. I'm not sure we are learning much blindly flipping the SW3 switches.

What I'm seeing there is a very slow response, then a long slow over shoot period, then that bump on the end is the drive finally settling for a moment before decelerating.

I think you need to concentrate on tuning with SW2 and pots 1 and 3. I'm not sure I've seen your results of trying to do this with the new power supply.

Are you sure SW1 switch 1 and 3 are in the off positions?

Todd, thank you. SW1 settings are all OFF. What I have found with Pot 1 is a faint noise will start at about 11.0 turns CW, if you go .5 turn more the noise is louder & a vibration starts in the motor. The A-M-C power supply does not have a fan, that fan noise was always louder than the faint noise of the motor before vibration. Currently, Y axes motor is in the x axis for testing to see if motor is the issue & that is the Y in the file name.

After testing a lot of different settings, Pot 1 does not vary much from one SW setting to another SW setting. I can appreciate that if 1 turn is too course of increment & I went past the preferred setting. After re-reading your post you may feel that the 1.0 increment is too course, I passed by the spot that was correct?

If I increase Pot 1 the vibrations get larger, I usually back off 3 turns. Some of the traces I have reduced the 3 turns to as much as 1, it seemed to help at the start. I can revisit this, try to reduce the 3 turns associated with Pot 1 & adjust (CCW lowers purple trace) Pot 3, so purple trace matches red trace all at 20"/min feed & FF1 set to 1.0.

I power down the power supply each time I change SW3 (or any SW-) settings.

Is it necessary for the LED to be out completely, so absolutely no residual power is remaining, before changing SW settings?

Many thanks

I can't answer to the ramifications of switching switches before the power led is fully extinguished. That would be a question for AMC.

As to pot 1 I think the recommendation for turning it back 3 turns is to find a good starting point for tuning. From there turn it up in increments testing between looking for improvements until either overshoot and oscillation become a problem (SW2 switches can be used to reduce the overshoot) then reduce to the best result. You should be able to see oscillations beginning on the scope before they become audible. You are looking for a nicely shaped trapezoidal velocity trace, then use pot3 to scale it properly