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VF2 Servo Fault Error 161

WNYsteel

Plastic
Joined
Jun 1, 2010
Location
Buffalo, NY
I have a 1996 Haas VF2 and the x-axis faulted on an error code 161, which basically means the motor is being overloaded or grounded out. The table is not blocked and can easily be moved by spinning the ball screw. So, I removed the x-axis motor and found the connector box packed with black dust. I'm assuming this is from the brushes. When I spin the motor is sounds a bit scratchy coming from the rear of the motor near the resolver.

My questions are: should I just clean the motor up and re-install it, or am I asking for trouble by doing this? Is this black dust likely the cause of my problems making an internal short? Is this motor a hard unit to re-assemble?

Thanks in advance.
 
I would take all of the brushes out and blow it out really well and give it a try. Mine had three caps on the back of the motor that you simply un-screw to remove the brushes.

I had encoder go out a couple of years ago and one of the first things the tech checked was dust from the brushes.
 
Any DC motor is going to sound "scratchy" because of the brushes. If the motor is free, you need to simply test resistance across the two leads and both to ground. If that checks out, you are likely looking at an amp problem. I don't care what the service code is, that only offers direction. What can and will happen is the control sends command to the amp, the only way it knows it is working is by movement of the encoder in the motor. If that does not move, it think it is binding up which in fact the amp did not send anything to the motor. Make sure to check the fuse in the amp as well. If it pops it, I might try one more, if that pops, you have issues and I would then disconnec the leads connecting the amp, If those leads are not showing a short in the wiring, you likely have an amp issue.
 
Thank you for the replies. I cleaned the motor and checked the stuff viper suggested. Everything was good to go so I reassembled the machine minus the way covers. The table was all the way to the right on startup. The zero return was going perfect, but when th x axis got almost to zero I got the same fault again. I could spin the ball screw by hand so it wasn't stuck. I again moved the table all the way to the right and the zero return on startup yielded the same results. Is there a chip on something?
 
No, I seriously doubt you have amp or motor troubles. First thing I would look at is your limit switches. IIRC, hit the parameter button 2-3x and you will see a list of XYZAB switches and their current condition. WITH E STOP ON, roll the way covers back and actuate them and you will see them change state.

It may also be that you are hitting the hard stop because the switches are not working. I found a big design issue with mine where chips were allowed to get into the connector in the back near the oiler and was shorting the switches.

Start there and keep an eye on the fuse on that amp to be sure. IIRC, they will light an LED when the fuse is blown.
 
Cables

If you do not notice a push-back ( the rubber will push the table once the drive quits) at the homing it might be your X axis cable.

If you remove the front Y axis way cover you will find your X axis cable sloshing around in the coolant. The best thing to do is to use a "megger" on the cable after you remove it. What happens is as the cable is moved in one way or another it will short out. On an old machine like this the rubber gets hard and cracks.
If it is not the limit switch, hopefully it is , do not try to run the machine any more, you can short the motor, cable and drive, a big pile of cash, we have all done that ! The biggest fear is fire, eventully you will smell smoke!

I find the drives work or they do not, the motors work or they do not, cables are always intermitant but they can do the most damage and when you see how the cable drags down in the coolant I would be real suprised if the first words out of your mouth is "W.T.F."

Oh yea, check and clean your brushes once a year or two but remember at some point you are going to blow out the motor and it is going to short out the motor.

Good luck!

Mike
 
Ok, I'm back and running now so I want to close the loop here with what I learned. I tried everything suggested above and also some stuff that the service tech suggested over the phone, but nothing was working. The home switches were correctly switching from zero to one as could be observed from the parameter screen, the motor cables checked out ok (although they're old so likely need replacing), the ball screws spun freely, I cleaned all the chips from under the way covers, cleaned the black brush dust from the motor, and still I got the same fault. During my trouble shooting process I moved the X axis all the way to the right. This is when I discovered the one thing about the fault that was driving me nuts. During the zero return sequence from this table position the X axis would move the table all the way back to the left like it is supposed to do, then it would hit the home switch and give me the fault code. So to me it appeared that the motor was capable of moving, but I didn't understand what was happening once it hit the home switch.

I called in the service tech...he said it was an interesting problem that he hadn't encountered before. he turned some parameter off so he could jog the axis without having the zero return. he could jog the axis to the left, but everytime he tried jogging it to the right he got the fault. His trouble shooting was simple, but effective. He checked the motor cables then swapped the X and Y axis drives. The issue followed the drive. Mystery solved for me.

I wanted to write as much as I knee here as to document it for others to learn from.

One last tis bit of info. I used the A axis drive for the X axis. The tech told me I couldn't do that but he didn't know why. I don't use the A axis so I really wanted to steal this drive. I carefully went through each component on the drive board and learned that the only difference was two resistors. I un soldered them from the X axis board, soldered them onto the A axis board and everything is currently running good.

I'm still curious as to why the drive went bad in the first place. I would assume if the cables were bad that I would blow a fuse. If anyone has any thoughts about that please share them.
 
If you read my first post, I explained that if the control tells the amp to go and it doesn't, it is seen by the control as bind or an overload condition when in fact, the amp just did not say go. I should have explained to simply swap the wires around so use a different drive card to see if the problem followed the card. I never got any info about the machine.

I do not know about using the A amp in the X because I am not sure what you have but I know some of the As are setup for DC rotaries but in your case with most likely DC servos, I am not sure of the issue here. I would be real curious to see the values of the resistors you swapped. they could have been bleed resistors, calibration resistors, dunno. guess the good part is things are working and you did exactly what I would have but I might have troubleshot the amp and repaired it. Not too much going on there.
 








 
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