Fanuc Alarm 401

[tsteele]

Having successfully fixed the issue with the tool changer, I have now uncovered an issue with the drives on my Triac Fanuc. I have wiped the controller memory and carefully input all of the parameters again, but the alarm persists. When the controller is started up the green DRDY led on the axis drives board briefly comes on and then goes off, accompanied by the sound of a contactor pulling in/out. The controller displays 401 SERVO ALARM (VRDY OFF) and 420 SERVO ALARM Y AXIS EXCESS ERR. The diagnostics parameters 720-722 all read zero.

Any suggestions on what to check out would be much appreciated.

[Martin]

Do any of the axis jump at this point?

You may have rouge values in the parameters. I think it's around the 550's but if you do a search on the forum you should be able to check exactly which should be zero.

I presume you have set diagnostic 453 bit 1!

[tsteele]

Hi Martin, none of the axes jumped at that point as far as I can remember. I have the original list of the parameters for the machine and I will recheck the all the 500 parameters again just to be sure. Good point on the 453 diagnostics, there's a good chance I may not have set that to 1. I check everything out when I get home this evening.

Many thanks for the suggestions.

[tsteele]

I checked the 500 series parameters and they look okay. The only one I am uncertain about is 508, which is labeled in the list as P-------- and there is no other information on it. 508 is currently set to 0. The other parameters listed as P-------- in the parameters sheet, have values assigned to them on a separate sheet which came from Denford. This lists those parameters and the 400 diagnostic parameters. I set 453 diagnostics to 1 and it flips back to 0 immediately (this I believe may be normal behaviour?). On restarting the machine the same 401 alarm occurs and the 720-722 diagnostics parameters are all zero.

I also checked the axis on startup very carefully and it does appear that there is a small movement as the DRDY led goes on and off. This is in the order of a few tenths of a millimeter and I that is why I missed it before. Any thoughts on other things I should check?

Trevor

[tsteele]

Hi all. I've been experimenting over the weekend to see if I could get the Triac to run without the 401 alarm and some progress has been made. I have worked on the assumption that I would try changing parameters before looking too deeply into the electrics and electronics which are not my strong point. The results so far are:

Tried the motor parameters from the Fanuc parameters manual, as some were different from the Denford ones. Still 401 alarm on startup.

Set 8n21 to -128 and 8n43 to 100 which is what the machine came with. I realize these are not correct, but thought I would try just in case. Machine switched on and zeroed without any errors but jogging in 1mm increments, only moved it 0.25mm.

Set 8n21 to 0 and 8n43 to 100. Alarms 401 and 410.

Set 8n21 to -128 and 8n43 to 267. Machine started but servos were VERY noisy.

So the only combination working so far is the one the machine came with. I decided to try an arbitrary CMR value to see if I could get the machine moving the correct distances, so set 35.7 to 1 and 100 to 103 to 16. The result was the correct movement, but the axes would trip out on rapids with a 4n1 axis excess alarm. Set parameters 504 to 507 to 16666 and all except the z axis were happy. z axis still tripped moving in a +ve direction, but okay in -ve. Setting the maximum feed for rapids to 2000 mm/min seems to have solved this. The feedrates seem a bit slower than programmed, but I'm not really surprised considering all the changes made.

Now I'll be the first to admit that this is two or more wrongs making a right, so if anyone has any suggestions I would be very grateful for their views and comments. Ideally it would be great to have things working with the original parameters.

Best regards

Trevor

[tsteele]

Just to report back on the final settings which now work for my machine, in case they may help anyone else.

The following parameters are set:
4 to 7 set to 100
35.7 set to 1
100 to 103 to 4
504 to 507 set to 8333 (the original setting),
518, 519, and 521 set to 5000
520 set to 3000.
8n21 to -128
8n43 to 100

After much reading up on various other issues all of which were dealt with on this forum, I am finally up and running. Thanks to all who contribute to the forum your help is greatly appreciated.

Below is a picture of the first job done using the Triac.

Foresight.jpg (61.01 KiB) Viewed 7146 times

[tsteele]

Finally got around to looking at the z axis issue where the drives were tripping out during rapid moves. Very careful realignment of the ball nuts has now solved this problem. The machine can now run at 5000mm/min in all three axes.