Servo Drive problem

[Pat Larkin]

I am having a problem with the X axis servo drive on our Rover 20. When the router/drill head is meant to start slowing down to start machining something (or to come to a home position), the router shuts down entirely. We have been in touch with Biesse and it sounds like the problem is with the servo drive, specifically with a brake capacitor (or something similar) overheating. The servo shows an A40 or A41 alarm when the router shuts down. They gave us a contact for someone that repairs servos. We had it and the X axis motor checked out, but they could find no problems with either. I can't help but think that they were not able to test it properly. They tested the servo and motor in their shop and everything worked, but when the command to stop the motor was given, it was only stopping the motor (without the weight of the Router/drill head assembly). I assume the added weight is overheating a defective capacitor.

Just wondering if anyone has any ideas on how to test this properly, or how to pinpoint the faulty circuits.The Biesse technician actually ordered a new servo drive and motor, but it turns out it is the wrong Servo and the one we need is not in stock in North America or Italy. Our Rover is a 1999 or 2000 model which we purchased new and has seen fairly light duty. Biesse is trying to find a solution, but I wonder if anyone here has any ideas.

Thanks, Pat

[Paul Grothouse]

That's a tough one. Depending on your machine can you switch the Y and X motors, see if the issue follows the motor. If it doesn't then you know it's not the motor. I would check your voltage and amperage as the issue is occurring, make sure your not getting a pull down.

Can you home the machine? If you can't it might be an encoder, I had this occur.

When you say shut down entirely the spindle stops and everything or just the drive? Does the inverter shutdown? Can you jog the machine around, does this only happened when you are running a program?

Please elaborate more on the conditions of what is happening.

[Pat Larkin]

I thought about switching the Servo drives, but the X and Y are different (as are the motors). We ordered a new motor with the Servo and it is now installed with no change, so we are pretty sure the problem is with the Servo. I'm not sure what you mean by pull down, but the voltage has been tested to be sure the servo is receiving the proper power. We can zero the machine and we can jog it around as normal..we can also run it sometimes at 30% travel speed. We were able to run it at 50%, but that lasted a day. We were told the problem would just keep getting worse. The problem has only occurred when running a program.
The spindle stops, vacuum pump stops and the router head starts to drop (since it's no longer under power). The router/drill assembly is still in motion when it dies and the machine/computer must be rebooted to try again.

[Paul Grothouse]

"New motor, but still have the problem, it must be the servo," The motor is the servo, the servo invertor or "drive" feeds the power to the servo. Usually invertors/drives on the larger machines (like Beisse) are pretty smart, and pass errors pretty directly when something is wrong. What are the A40 and A41 errors defined in your manual as?

When I say pull down, you monitor each of the three lines, one at a time for voltage drop, or amperage peak, when the problem occurs. If you do see a change, you know you are shorting to ground or something serious (but rare) is going on in your invertor.

I hate to say it, because it's usually the worst possible problem to find. Sounds like a bad wire or a wire that has failing insulation, that only jumps to ground when a lot of current is applied.

Can you jog the machine in rapid mode. Push it up to full speed, you may have to pass an M code to the machine to get full transfer speed. Turn on the spindle to your machining speed. Then jog the machine back and forth, back and forth, back and forth on the axis in question, see if you can make it happen. If that doesn't work, start transitioning the other axes at the same time. Put the machine through it's paces MANUALLY. If you can't repeat it in jog mode, I would highly doubt it is not a hardware issue. It may be an issue with your code. It is rare that you will have a hardware issue that does not occur when jogging the machine, but only when running a program.

If you cannot recreate the issue, please upload an NC file of one of your programs. If you know which line the program fails on, that would also be helpful.

[Cody Woodman]

We have had the same problem crop up on our Biesse Rover 20 "Y" axis servo (motor or controller [?]) and the machine fails at the start of a program at manual override as low as 20%.
It will reset (albeit at the slowest possible speed) but when the machine launches into action from rest position it throws the error predictably; Y axis servo controller reports current overvalue, could this be the braking capacitor failing instead of the servo or controller?
Did you resolve your problem successfully without replacing the controller?

We are in Thailand where parts and service are hard to secure and would greatly appreciate hearing how you resolved your Rover 20 problem.
TIA