410 Y axis(2) position error

[charlie]

Hi all,

My Y-axis isn't working properly. 4axis VMC. DC servos all round (SEM brand). M400 control circa year 2000.

I powered down my machine for the first time in quite a long time on Sunday. I wanted to open the control cabinet to check if the VFD had a load output as I'm considering upgrading to an Allin1DC board (and spindle load monitoring is a feature). This involved opening the cabinet, removing the faceplate from the front of the VFD, replacing it and closing the cabinet. I would have also inevitably bumped or touched a few cables but I certainly didn't hang from any of them! I proceeded to power it back up and perform the homing sequence as per normal. This is when I received the following error as soon as I hit cycle start (to initiate the homing sequence): 410 Y-axis(2) position error

I'm able to:

• start & stop the spindle

• jog all other axes (including the 4th axis)

• attempt to jog the y-axis. Note, when I attempt to jog by any means, (inc/non inc on the console, or via the mpg) the servo jumps about 3.5 revs very quickly - as if it's receiving full power - and then stops and displays the aforementioned error. It jumps in the same direction regardless of the direction of the jog attempt

I'm not able to:

• complete the homing sequence

• perform an auto tune

What I've tried:

• physically swapped the x-axis and y-axis servos. Result: error remains & repeats on the y-axis. The x-axis runs fine with what was the y-axis servo. Conclusion: encoder and motor are fine. Returned servos to original axis

• swapped the X and Y power terminals at the drive & the X and Y encoder cables at the PC. Result: error remains, but now physically presents on the x-axis. Physical Y-axis (virtually, this is now X, and shows as motion in x on the DRO) now behaves normally. Conclusion: Power and encoder cables are fine. Returned wiring to normal.

At this point, I'm suspecting that either the drive is toast or something deeper is going on that's beyond my basic knowledge.

Further info:
- when in the PID menu, the Y-axis counts smoothly in both directions when the servo pulley is turned by hand. I did this check with the e-stop engaged AND also with it disengaged. I would have expected the servo to fight when disengaged hower this may not be the case when homing isn't complete.
- the drive has a row of red LED's labelled by axis letter. As I jog each axis in turn (omitting y) these lights go out one by one. When I jog y, they all re-illuminate.

Any help or suggestions would be much appreciated. I have done an extensive search of the 410 error, but nothing quite aligns with the symptoms that I’ve observed.

Report and images attached and inline.

[cnckeith]

hello. position error description on page 339 of the mill operator manual.
https://www.centroidcnc.com/centroid_di ... -v4.14.pdf

Tech Bulletin covering position errors.

https://www.centroidcnc.com/dealersuppo ... ads/26.pdf

[cncsnw]

It sounds very much like you have isolated the problem to the servo drive, Y axis power section.

You should contact Centroid about sending the drive in for repair-and-return, or for swapout with a refurbished unit.

[cnckeith]

support@centroidcnc.com or call 814 353 9256 press 4 mon-fri 9-5 EST

[charlie]

The new drive is on its way. Hopefully solves the problem!

[cncsnw]

There is a possibility that the MOSFET failure on the servo drive was caused by progressive breakdown of the motor.

Look up Tech Bulletin 155 and take a close look at the motor resistance -- especially the resistance between the power leads and chassis ground.

[charlie]

Ok will do - thanks!

[charlie]

There is a possibility that the MOSFET failure on the servo drive was caused by progressive breakdown of the motor.

Look up Tech Bulletin 155 and take a close look at the motor resistance -- especially the resistance between the power leads and chassis ground.

Just checked the servo that was on the faulty axis. All checked out ok. 1.7 Ω motor resistance and open loop to ground. Applied 12V DC direct to the motor and it spun at a few hundred RPM.