Problem with servo motor on Haas VF0

My friend has a '98 VF 0. Alarm code 175 came up when the machine was turned on, this code indicates that there is a short in one of the AC motors in one of the drives or tool changer. The operators said the X axis was making a noise over the last two weeks so I took off all the way covers to examine the drive motor what I found was a lot of black dust from the motor in the cover where the electrical connections are made on the motor/servo.

We ordered from Haas a new motor assy. which includes the servo and the cable. We installed the new part and cable now when the machine is turned on we get another alarm code 182 which is "cable from X axis encoder does not have valid differential signals". I swapped the X & Y connections & the alarm code then moves to the Y axis. Code 175 doesn't come up now.

I think the problem is with the new motor assy.


We have called Haas in Conn. for a service call & we are still waiting!

Any thoughts from you guy's would help.

Thanks,

Jackmo

Can you swap the cables? I have gotten a bad cable before, perhaps the wrong pin configuration. Not sure what alarm it gave though. Good luck.

Do as Jerry said --
at the motor end move the X axis cable to a different motor possibly Z. Keep the X cable plugged into the X drive.

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I am recluctant to remove the cable from the motor end because it came with the assy. & if it is bad I might cause a problem if we have to return it, also it is all installed in the machine & it was a real PITA to install!!

I don't understand what " differental signals" mean??

Jackmo

Differential signal is where you use two wires for the signal neither of which is ground. When one line is high relative to ground, then the other is low, and vice versa. The difference voltage between these two lines determines the logic state. This is a more noise immune system compared to a signal that is high or low relative to common (ground).

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Not enough information to give a definitive diagnosis but . . .


Invalid "differential signals" could mean any number of things.

Most commonly if referencing an encoder it means that the differential A and A/ (or B and B/) are out of phase with the rotation of the motor. In effect, the motor is rotating Clockwise, but the encoder is telling the drive that it is turning Counter Clockwise.

This can be corrected by swapping any two motor leads or by swapping A and A/ -or- B and B/

Less commonly if referencing a resolver - the Sin and Sin/ signals could be swapped or again, you can swap any of two motor leads.

One way to gain clarity is to simply move the axis by hand and see if the displayed position is moving in the right direction. If you push the axis in the positive direction does the position go positive? If not - you need to swap A and A/

If the display accurately follows the manual positioning of the axis - then likely you need to swap any two motor leads.

If manually positioning the axis shows no results - you have a bad encoder or cable.

I have had very good treatment from the haas boys at the factory 1-800-331-6746 usualy a short wait to speak with a tech.

kustomizer,

We have to deal with the dealer in Conn. and they usually are very good but this time they are really dragging their feet, not even returning our calls.

Maybe they are not happy because we installed it ourselves but we bought it from them at $1600.00!!

Thanks for all the replies.

Jackmo

I'm puzzled by the black dust. I had a '92 VF-0 X axis motor give a ground fault alarm and it turned out that the brush dust had accumulated to the point where it was conducting to ground. Where would black dust come from in an AC motor?

Bad motor / encoder, unit was right from Haas factory.

Thanks for all your help.

Jackmo

Mike K:

92 year machines and until about 96 used brush type DC servo motors. I believe that the specification was that a shunt resistance to ground (motor frame) less than 1 megohm was a problem. Below this was likely to damage the motor controller.

After about 96 HAAS changed to brushless servos. With these you have a substantial noise problem that may affect RS232 communication. Our I232 Isolator System solves this problem, and gives you high baud rate at long cable length.

We have one customer with two VF3s side by side. One machine has brush type servos, and the other brushless. On the brushless machine it was impossible to send or receive programs with the servos on at any baud rate. Thus drip feed was impossible. No problem drip feeding with the brush type machine. After installing our I232 System to the brushless machine the communication in drip feed mode (DNC) at 115.2 kbaud and 100 ft of cable was error free.

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That's interesting that the AC motors are noisier than the brushed motors. I would have thought the reverse. Learn something every day!

When we had the problem with brush dust, I pulled the motor, disassembled it and put everything but the bearings in the ultrasonic cleaner. Put it together with new brushes and it's been working ever since.

Jackmo, we too have to "buy" stuff from our dealer but the service guys at the factory are very helpfull and are there are 7:30 am pacific time I am quite sure if you call they will talk you thru the diagnosis and the cure, fact is I got so mad at my dealer a few years back I called the factory in a rage and ended up going down and taking the same service course as the dealers boys take, they gave me all the service books on everything they made at the time ( about 350 lbs of books ) several special tools, fed me lunch every day for the two weeks I was there, and got me a half off deal in a hotel for the time I was there. The dealer is not always helpfull but the factory has a bunch of good guys just waiting for you to call.