[rlarios]

Hi there!



Matsuura MC1000 with Fanuc 12 installed.


Problem: It all started a few weeks ago with AC input A 30A fuse blown along with its 1.3A alarm fuse on Y-axis servo. Fuses were replaced and machine resumed operation. The following day, 30A fuse on AC input 1 blew along with its alarm fuse. This time, an Ohm meter was used to test for possible shorts at AC input on load side of contactor only to get infinity readings. Motor insulation was megged and readings were high enough to consider it still good. Fuses were replaced again and machine continued operation.


Machine operator said that -right before a fuse blew- the machine ran properly, until a G00 command was executed with Rapid Traverse Override set at 100%. Operator reduced this setting to 50% and machine operated well for a couple of weeks, then another fuse blew. As the shop had a lot of work to do, the operator continued replacing fuses until he finished all pending work.


In the meantime, I had been reading this forum's posts about the subject. Once the machine was released for maintenance, I started checking the ball screw thinking that maybe motor had too much load but ball screw could be turned by hand with motor still in place -not an easy task with all that lube on the screw-. Motor was removed for maintenance and it was noticed that insulation resistance had reduced to 0.069 M Ohm. Motor was sent for repair and once it came back, insulation resistance was 139 M Ohms. Motor is Gettys Fanuc Model 20.


Motor was re-installed and after machine had been turned on for testing, the operator ran the motor in manual mode and then, another fuse blew. This time I was puzzled as motor insulation resistance before repair was lower than what I had read on DC Spindle maintenance manual which made it appear that the motor was the problem. I have no maintenance manual for this VMC.


Anyway, using some older postings in this forum as a reference, I tried to see that maybe fine tuning was required for firing angles on SCRs. By the way, in a very good posting about a "New Control on Fanuc DC Servo" by user LeRa, several users mentioned pin outs of connectors of this very same DC drive:


http://www.cnczone.com/forums/servo-...-dc-servo.html


They even mentioned to have shared schematics via PM, although, the posting was not related to my specific problem it has very good information.


On the other hand, another user named moldmker posted:


http://www.cnczone.com/forums/fanuc/...fuses-6mb.html


Which describes a problem very similar to mine. As my fuses blew only when Y-axis motor ran, and following the instructions given on this post, I decided to swap drives using X-drive as Y and vice-versa. All potentiometers were set almost exactly the same with jumper settings the same as well, except, the original Y servo had S21 shorted and original X servo had it open. I moved this jumper to have both drives correspond to original settings. I have to point out that original X servo drive has an onboard power supply that also feeds the original Y drive which doesn't have onboard power supply. I even swapped incoming AC power -being careful with phase sequence and the whole nine yards- which is same voltage but coming from different taps from transformer at bottom of cabinet. Motors leads were swapped as well.


My intention was to see whether the problem either went with the drive or stayed with the motor. However, right after pressing power-on button, machine showed a "not ready" message along with error 400 which according to operator's manual, is a servo overload. As I had also swapped CN1 connector and thinking that maybe a wire had come loose, I removed both CN1 connectors hoods but wires were still in place. I put hoods back on and hooked up CN1 connectors to where they were supposed to go and still got same error.


Fearing that I had made things worse, I decided to swap drives back the way they were originally. I had the operator press power-on button and the machine came on with normal X, Y, Z screen, he released the e-stop button and as soon as he pressed power-on button again, we heard a contactor noise at the back and screen displayed error 401 which had been the error shown every time a fuse blew. Upon checking servo drive again, sure enough, an input 30A fuse on line A was open along with its alarm fuse. This is the first time a fuse blows with motor NOT being told to move. I checked SCRs and they are not shorted, so far.


The strange thing is that every time a fuse blew, it was line A, next time line 1, and then line A and so on, but line 2 input fuse has not blown a single time. This last fuse the blew was line A's, and the time before, was line A fuse as well.


Anyway, can anybody help with either schematics, fine tuning procedures or a maintenance manual for this A06B-6045-H005/H006 servo drive? I've been checking on eBay for these drives and they are not cheap.


Thank you in advance for your attention to this and any help you may provide.


rlarios

[rlarios]

Well, not having a manual this was tough. In order to make sure the drive was bad and no mechanical load was the problem, we had to remove the motor and tested it this time sitting on a wooden pallet. Fuses still blew. I ventured again to switch drives and by fluke made the motor work using X-axis VCU to drive Y-axis motor. This clearly told me that the drive was the problem. We managed to get another VCU from a vendor and again, error 400 was shown.

After following the wiring trying to find the source of the Over Load, I found that X-axis VCU had a connection to a temperature switch inside the transformer that fed power to this VCU. The new VCU doesn't have a power supply, so there was no incoming AC power to feed it. There is a jumper setting S21 that (which I found out after struggling for a couple of hours) has to be shorted on the VCU that has no power supply, and open on the VCU that has a power supply. I was under the impression that this S21 jumper had to do with motor type hooked up to VCU.

Anyway, to make a long story short, the problem was fixed, machine was ready but it still had to have Y-axis' Zero Return set. After having someone else set up Zero Return setting, machine is back on its feet.

The question remains, any idea on where to get a maintenance manual for VCU A06B-6045-H005/H006? Could anyone of you guys at least point me in the right direction by saying what Fanuc maintenance manual to look for? I have found several maintenance manuals on eBay but they are not specific regarding what VCU they are for. I have asked questions to sellers and so far have gotten no answers.

I appreciate any light you could shed on this.

Thanks.

rlarios