Fanuc 21i-TA Control Issues...

[mwbishop71]

I have a OmniTurn GT-27 Lathe with a Fanuc 21i-TA controller that refuses to hold the machine axis positions after powering down. The machine's power and servo modules were both recently repaired, and the machine appears to be operating normal. I have checked the servo module's backup battery and it also seems to be working properly. It seems to me that the machine zero problems may be related to a faulty parameter setting somewhere... Does anyone have any input as to which parameter may be causing this problem?

[cnc2149]

The symptom you describe can occur if the absolute encoders become out of synchronization due to disconnection, maintenance, etc. Use the following procedure to completely re-establish the abs pulse coder. Don't get in a hurry and bypass any of the steps.

1. Set 1815.5 (APC) = 0, 1815.4 (APZ) = 0, 1860=0, 1861=0 for the given axis
2. Power down
3. Power up
4. Set APC=1
5. Power down
6. Power up
7. Home the absolute axis. This can be accomplished with either manual referencing (if they have home switches), dogless (if they have the DLZ parameter enabled), double-bump torque method, or by MDI setting. Go with the method recommended by the machine tool builder. APZ should be 1 when completed. New values will automatically be loaded into par 1860 and 1861.

[mwbishop71]

Thank You, cnc2149:

I tried resetting the X and Z soft limits prior to posting my problem. Maybe I made a mistake somewhere during the procedure. I'm going to try again following your steps, and see what happens...

[mwbishop71]

Okay, I tried going through the steps to synchronize the encoders and I keep getting a 090 reference return incomplete alarm when I try to zero out the machine. If I jog the X and Z axis back and forth before attempting to zero out the machine, the machine will zero return but it's nowhere near where I set it. Also, I checked the 1860 parameter after restting the APC parameters and the values did change...

[angelw]

Originally Posted by mwbishop71 Okay, I tried going through the steps to synchronize the encoders and I keep getting a 090 reference return incomplete alarm when I try to zero out the machine. If I jog the X and Z axis back and forth before attempting to zero out the machine, the machine will zero return but it's nowhere near where I set it. Also, I checked the 1860 parameter after restting the APC parameters and the values did change...

Try the following:

1. Power ON the control.
2. Manually move (Jog, Hand Wheel) all axes to their respective reference marks.
3. Once 2 above is done, select MDI MODE, set PWE to 1, and search for parameter #1815.4.
4. Toggle bit #4 from 1 to 0, and then toggle back to 1 again.
5. Set PWE back to 0
6. Power OFF control, and power ON again.
7. Select JOG mode and JOG all axes in both + and – directions, and leave each one off their marks.
8. Select REF RETURN, and perform REF RETURN.
9. Verify that the axes all return to the specified marks.
10. Finished.

Regards,

Bill

[mwbishop71]

angelw:

After following your instructions, I find that the zero return function works correctly. But, I am still having the same problem with the machine holding the machine zero after turning off the machine. What happens is... everytime I turn the power off and on, the machine resets the machine zero position to wherever the carrage stopped when the machine was shut down. As you can imagine, this can create a very dangerous situation when the machine is restarted. Fortunately, I know what is going on and I am the only person programming and operating the machine, but the fact remains that it shouldn't work like that...