Fanuc Servo Alarm

[herbmarkovit]

Removed the Z axis DC servo motor from the Kitamura Mycenter 1. This is definitely not a mechanical problem. Within 10 seconds after "power-on" the servo starts to run for about 10 seconds than the brake comes on & I get a Z31 & Z32 alarm.

The Z axis servo is a 10M and the X & Y are 5M servo's. Swapped the encoders linked to the rear of the aramture. The symptoms are the same.

Swapped drive axis PCB's (A20B 0009-0320), they are the same except for jumpers. The symptoms are the same.

I then swapped the feedback & command cables going into the Control Motherboard. The symptoms changed. I now got Z21 & Z22 alarms. This, I believe indicates the the problem is somewere between the drive and the servo.

Does anybody have any more ideas? Could a broken wire in the feedback cable cause this problem? Are any feedback signals sent back to the drive module? It appears that the servo should come on at power on long enough for the encoders to relay a few pulses? I dont have any more parts to swap and I am running low on ideas. By the way, I now have a Web Site: www.benchrestjoystick.com. At least my other CNC works.

[Al_The_Man]

If you have concluded definately that it is OK mechanically, another point to check is the tuning parameters, do you have the parameter list? Check for comparison between Z and the other axis, They may not be identical, but usually are close.
I recently had a customer that had a similar problem on a 6M, as soon as the Z axis was moved it would fault, I checked the parameters and the Z CMR parameter had a large -value instead of positive. I am sure that no one in the plant knew where the parameter overide switch was to tamper with them, I assumed that somehow the register got overidden by sporadic noise or other means. Restoring the parameter cured the problem.
There are just a few parameters that apply to the servo on the 3M
Al.

[HillBilly]

On the 3M mother board there are frequency to voltage convetors for each axis that makes a tachometer signal from the encoder that is in turn sent to the velocity control unit for that axis. So yes a broken wire here will cause a run away situation.

Darek

[hangslot]

Also check the Automatic Drift Compensation parameter.
I once seen one with a value of 99999999.
Just make it zero and see what happens.

[herbmarkovit]

This has been a long process. Thanks to Hank at Fanuc America my Kitamura CNC is now running in MANUAL mode. There were 4 problems that Hank helped solve during a long phone conversation.

(1) the overload breaker activated because the brake was dragging. Corrected this previously by adjusting the pressure plate in the servo. (2) Parameter #61 wrong due to automatic drift compensation. Corrected per Hank. (3) Servo would turn on at start up. WIRING ERROR! Corrected per Hank by swapping + & - feedback signals to "Z" axis PCB. and the most difficult (4) The internal thermostst in the "Z" axis servo was bad the resistance was low enough for the servo to turn on a few times but after that the resistance would increase and present an open to the circuit. Corrected Per Hank, replaced thermostat.

The relationship between problems 1 & 4 made this repair exponentially more difficult. This is what anybody can run into by purchasing a machine that did not operate because of a minor problem. In this instance the price is right.

There is still a PROBLEM in AUTO. The X & Z axis will not ZERO out. I will work on this next week. I am thinking that 1 or more parameters maybe wrong???? Anu Suggestions?

[Al_The_Man]

Originally Posted by herbmarkovit There is still a PROBLEM in AUTO. The X & Z axis will not ZERO out. I will work on this next week. I am thinking that 1 or more parameters maybe wrong???? Anu Suggestions?

Do the axis move? Do they reach the zero LS? What happens when you try and zero?
Al.

[herbmarkovit]

Thank you for your reply Al; It has been a long week.

All Axis (X, Y, & Z) move to Zero. The Y axis will zero with light on. The X & Z axis get OVERTRAVEL alarms. The X & Z axis stopping positions always vairy a little (Z machine position always around 2.5). I do not see the zero light illuminate and do not see a slow down near the zero position.

I can program a move for either the X or Z axis and they will move to position, but without zero referencing all the axis I can not get the tool changer to operate or for a program to function.

[Al_The_Man]

Use the diagnostic page to look at the slow down limit sw's. On most models the first diag. page is the inputs, try tripping the switch manually and see if a input bit registers, if you have the book it will tell you the inputs.
Also try homing and trip the switch prematurely by hand and see if it home's out ok.
Al.

[herbmarkovit]

I recieved this from JR this morning:

Fanuc controls only. Turn the control power off. Power on the control pressing letter (P) and the cancel (CAN) key and keep them depressed until the CRT Display comes up plus an additional 5 seconds. Then release P and Cancel keys . (Do not hold in any other keys or risk loosing parameters, programs and more) Once powered up fully perform Zero Return. This procedure bypasses the soft limit, and will reset after completing a zero return. If the axis overtravels again after decelling, more than likely you have a bad Zero return Switch if its not an absolute pulse coder.
__________________
JR Walcott
Georgia Machine Tool Resources, LLC

All Axis Zero Returned and the lights came on.

Thank You all again
Herb
www.benchrestjoystick.com