Gecko 320x faults over certain speed

[AndreasT]

Hi!

New here and is just about finishing my zx45 cnc conversion.

I have a problem with my setup:

Gecko 320x
PMDX - 126 BOB
Keling 850oz/inc servo.
AMT 102 encoder with 500cpr setting
Smoothstepper
Mach 3

When i jog any of(x,y,z) in positive direction I can achieve ~2450rpm for the servo motor, above that my gecko 320x faults. This is done with servo free at the table.
When I jog in the other direction i can only obtain 2300rpm until the gecko faults. This is done with 800 step (500cpr encoder, 1:2 pulley ratio, 5mm pitch screw)

So why is this happening? The servo should do 4200rpm (18.75V/100rpm) according to keling.

/Andreas

[Bubba]

Andreas,
You don't state the voltage your using to feed the servos. But if you read the specs, the max rpm is 4000 rpm, and the Ke is 18.75 V/(should read 1000rpm).
To achieve 4000 rpm, you need 18.75*4000/1000 or 78.75 volts which is very close to the limit of the gecko.
Obtaining ~2300 rpm would indicate a voltage of ~43V unless I have missed my math.
Tuning could also be a problem if you have the correct voltage.
Just my thoughts.

[AndreasT]

Hi!

Have a antec power supply of 72V.
I understand i can´t get 4200rpm but atleast 3500rpm from that voltage supply. Also wonders why it differs 100rpm depending on the direction of the servo.
Using std 11´o clock setting for the 320x right now, possible error?

[Bubba]

Andreas,
Possible, but I don't have any X variety of the 320's.

Have you also set the max speed in your configuration files. Again, I am not familiar with the smoothstepper and dangerous around Mach!

As for the difference, I don't know.

[AndreasT]

Hi!

Yes i have set the maxium speed above this when i tested.
Did some testing and from what i can see, the gecko 320x warns first that the encoder is out of limit 256step and the fault.

Accordingly to the manual it could be one of these error:

1) The loop settings are severely under-damped and the motor breaks out into oscillation.
2) Excessive motor load due to acceleration or workload.
3) The speed command in excess of what the motor can deliver.
4) The current LIMIT is set too low.
5) The power supply current is insufficient for the demand.
6) The power supply voltage is below 18 VDC.
7) The motor is wired backwards, is broken or disconnected.
8) Encoder failure.

[Bubba]

Hi,
I just happen to think, there have been people that have had a problem with the AMT encoders where the part mounted on the shaft is not rigid. Some have even gone so far as to glue that part on. If it is loose, it could be giving false signal to the encoder circuitry?

[AndreasT]

Hi!

Thanks for the tip, will try put on some rtv silicon later today. But i don´t think it will help since i "only" using 500cpr setting. From what I have read this problem occurs mainly when using higher cprs above 1000, but will give it a try.

Tested with 1000cpr setting, then it only did 120rpm and wih 250cpr setting I was able to get 3500rpm easy.
So this problem is related the step pulses. Just now I´m running mach 3 demo version with smootstepper.
Am I limited to a 25kHz even with smootstepper?

/Andreas

[Bubba]

Andreas
Sounds like your on track to solve the real problem. As for the limitation, I don't have a clue. I don't use either Mach or Smoothstepper.

I had hoped that someone more knowledgeable than I would jump in with better answers.

[Bubba]

OOPs

[AndreasT]

The silicone didn´t help :/
Have a voltage of 67.2V to the geckos, and when the faults occurs it reads 47.7V. Running out of ideas, anyone else have an idea?

[judleroy]

Sounds like your encoders are not tracking correctly. If you get off count your drive will fault. Are you using good shielded encoder cable? Check the gecko site for there info on adding resistors to your encoders. This may help. Good luck.
Judleroy

[AndreasT]

Hi!

I'm using 24awg rs232 5wire with shield. The shield is connect to frame ground close to gecko drive. Good enough?